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Sökning: L773:1946 3936 OR L773:1946 3944

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1.
  • Aghaali, Habib, 1981-, et al. (författare)
  • Performance Sensitivity to Exhaust Valves and Turbine Parameters on a Turbocompound Engine with Divided Exhaust Period
  • 2014
  • Ingår i: SAE International Journal of Engines. - : SAE. - 1946-3936 .- 1946-3944. ; 7:4, s. 1722-1733
  • Tidskriftsartikel (refereegranskat)abstract
    • Turbocompound can utilize part of the exhaust energy on internal combustion engines; however, it increases exhaust back pressure, and pumping loss.  To avoid such drawbacks, divided exhaust period (DEP) technology is combined with the turbocompound engine. In the DEP concept the exhaust flow is divided between two different exhaust manifolds, blowdown and scavenging, with different valve timings. This leads to lower exhaust back pressure and improves engine performance.Combining turbocompound engine with DEP has been theoretically investigated previously and shown that this reduces the fuel consumption and there is a compromise between the turbine energy recovery and the pumping work in the engine optimization. However, the sensitivity of the engine performance has not been investigated for all relevant parameters. The main aim of this study is to analyze the sensitivity of this engine architecture in terms of break specific fuel consumption to different parameters concerning the gas exchange such as blowdown valve timing, scavenging valve timing, blowdown valve size, scavenging valve size, discharge coefficients of blowdown and scavenging ports, turbine efficiency, turbine size and power transmission efficiency. This study presents the sensitivity analysis of the turbocompound DEP engine to these parameters and defines a set of important parameters that should be examined in experimental studies.
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2.
  • Bergman, Miriam, 1978, et al. (författare)
  • CFD-Based Optimization of a Diesel-fueled Free Piston Engine Prototype for Conventional and HCCI Combustion
  • 2008
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 1:1, s. 1118-1143
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents results of a parametric CFD modeling study of a prototype Free Piston Engine (FPE), designed for application in a series hybrid electric vehicle. Since the piston motion is governed by Newton’s second law, accounting for the forces acting on the piston/translator, i.e. friction forces, electrical forces, and in-cylinder gas forces, having a high-level control system is vital. The control system changes the electrical force applied during the stroke, thus obtaining the desired compression ratio. Identical control algorithms were implemented in a MATLAB/SIMULINK model to those applied in the prototype engine. The ignition delay and heat release data used in the MATLAB/SIMULINK model are predicted by the KIVA-3V CFD code which incorporates detailed chemical kinetics (305 reactions among 70 species). Since the piston motion and frequency, the rate of heat release and the initial in-cylinder conditions all affect each other, while predicted using different modelling tools with no direct coupling between them, an iterative procedure was used among models describing:1. Piston dynamics governed by Newton’s second law including a high-level control system (using MATLAB/SIMULINK)2. Combustion processes (using KIVA-3V)3. Intake and exhaust system dynamics (using the GT-POWER module of the GT-SUITETM)Effects of varying parameters such as compression ratios, power supplied to the compressor, fuel injection timings and injection pressures have been studied in both conventional diesel and HCCI modes, the target being to identify optimal conditions for the combustion process in which the engine can be operated highly efficiently with very low-emissions.
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3.
  • Binder, Christian, 1988-, et al. (författare)
  • Heat Loss Analysis of a Steel Piston and a YSZ Coated Piston in a Heavy-Duty Diesel Engine Using Phosphor Thermometry Measurements
  • 2017
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 10:4, s. 1954-1968
  • Tidskriftsartikel (refereegranskat)abstract
    • Diesel engine manufacturers strive towards further efficiency improvements. Thus, reducing in-cylinder heat losses is becoming increasingly important. Understanding how location, thermal insulation, and engine operating conditions affect the heattransfer to the combustion chamber walls is fundamental for the future reduction of in-cylinder heat losses. This study investigates the effect of a 1mm-thick plasma-sprayed yttria-stabilized zirconia (YSZ) coating on a piston. Such a coated piston and a similar steel piston are compared to each other based on experimental data for the heat release, the heat transfer rate to the oil in the piston cooling gallery, the local instantaneous surface temperature, and the local instantaneous surface heat flux. The surface temperature was measured for different crank angle positions using phosphor thermometry. The fuel was chosen to be n-heptane to facilitate surface temperature measurements during non-skip-fire, thermally stabilized operating conditions. Assuming one-dimensional heat transfer inside each piston, the local instantaneous surface heat flux was calculated using the heat transfer rate to the oil in the piston cooling gallery and the surface temperature measurements. The results from this study show that the surface temperature variation is similar for both pistons. The instantaneous heat flux during combustion is however significantly greater for the steel piston than the coated piston. The heat release analysis also indicates that combustion is slower for the piston with the yttria-stabilized zirconia coating.
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4.
  • Boden, Hans (författare)
  • IC-Engine Exhaust and Intake System Acoustic Source Characterization
  • 2014
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 7:3, s. 1579-1584
  • Tidskriftsartikel (refereegranskat)abstract
    • The paper gives an overview of techniques used for characterization of IC-engines as acoustic sources of exhaust and intake system noise. Some recent advances regarding nonlinear source models are introduced and discussed. To calculate insertion loss of mufflers or the level of radiated sound information about the engine as an acoustic source is needed. The source model used in the low frequency plane wave range is often the linear time invariant one-port model. The acoustic source data is obtained from experimental tests or from 1-D CFD codes describing the engine gas exchange process. The IC-engine is a high level acoustic source and in most cases not completely linear. It is therefore of interest to have models taking weak non-linearity into account while still maintaining a simple method for interfacing the source model with a linear frequency domain model for the attached exhaust or intake system. The use of source characterization in acoustic design of mufflers is also briefly discussed.
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5.
  • Båstedt, Peter, et al. (författare)
  • Subcooled Flow Boiling in High Power Density Internal Combustion Engines I: Thermal Survey Measurement Campaign
  • 2022
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 16:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Nucleate boiling occurs inadvertently in the coolant jacket of high power density internal combustion engines, especially in vicinity of regions experiencing high thermal loads. Occurrence of boiling can be beneficial and be an efficient way to improve heat transfer locally near hot spots, but excessive boiling can be detrimental to structural integrity of the engine. While most of the efforts to understand boiling have been focused on experiments in simplified geometries, this article presents results from thermal survey measurement on a production engine. The purpose of the measurement campaign is to understand the intensity and extent of nucleate boiling occurring in different parts of the engine coolant jacket. This is achieved by sweeping across different input parameters, such as engine operating load point, cooling system operating pressure, coolant flow rate, and coolant inlet temperature. Different boiling regimes are encountered in different parts of the coolant jacket. A wide database of local solid temperatures measured at several critical locations is obtained and these results are interpreted in line with the underlying physics of subcooled flow boiling. The database not only helps to understand the boiling phenomenon occurring in engine coolant jacket, but is also used to calibrate a numerical boiling model.
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6.
  • Chartier, Clement, et al. (författare)
  • Air-Entrainment in Wall-Jets Using SLIPI in a Heavy-Duty Diesel Engine
  • 2012
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 5:4, s. 1684-1692
  • Tidskriftsartikel (refereegranskat)abstract
    • Mixing in wall-jets was investigated in an optical heavy-duty diesel engine with several injector configurations and injection pressures. Laser-induced fluorescence (LIF) was employed in non-reacting conditions in order to quantitatively measure local equivalence ratios in colliding wall-jets. A novel laser diagnostic technique, Structured Laser Illumination Planar Imaging (SLIPI), was successfully implemented in an optical engine and permits to differentiate LIF signal from multiply scattered light. It was used to quantitatively measure local equivalence ratio in colliding wall-jets under non-reacting conditions. Mixing phenomena in wall-jets were analyzed by comparing the equivalence ratio in the free part of the jet with that in the recirculation zone where two wall-jets collide. These results were then compared to φ predictions for free-jets. It was found that under the conditions tested, increased injection pressure did not increase mixing in the wall-jets. Comparisons with free-jet predictions further indicated that mixing in wall-jets is less effective than in free-jets for identical conditions and downstream distances. The confined nature of the wall-jet in the optical engine is suspected to be the reason for these observations. A rapid leaning-out of the jet after end of injection was observed for all cases, but this enhanced mixing was not transmitted to the wall-jet.
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7.
  • Clasén, Kristoffer, 1992, et al. (författare)
  • Influence of Trapped Residual Gasses in Air-Diluted Spark Ignited Combustion
  • 2022
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 15:6, s. 849-881
  • Tidskriftsartikel (refereegranskat)abstract
    • Homogeneous air-diluted spark ignition is one advanced combustion concept that is recognized for its potential of efficiency improvement which can be utilized in the next generation, affordable, light duty propulsion systems. However, cyclic dispersion and high load end-gas autoignition of diluted combustion remains a challenge, preventing necessary nitric oxide emission suppression which in turn obstructs market penetration. It is well known that trapped residual gasses in the cylinder influence the cyclic dispersion of combustion by contributing to the total amount of charge dilution which influence the total mean flame speed and thereby the combustion sensitivity to cyclic perturbations. However, the amount of trapped residual gasses in the cylinder is difficult to measure and therefore its influence is complicated to assess. In lean combustion research, the presence of residual gasses is often acknowledged, but few studies have investigated the influence of a combined dilution of residual gasses and air. This paper aims at assessing the influence of trapped residual gasses on lean combustion through combining engine experiments with 1D-computer simulations using a three-pressure analysis. A three-pressure analysis utilizes experimentally acquired data such as crank angle resolved port- and cylinder pressures to minimize the scope of discretization and predictability of the model, to improve accuracy. The experimental results were replicated in the simulation and quantities, such as residual gas fraction and total trapped in-cylinder mass, were estimated. From the performed engine experiments and corresponding simulations, it has been concluded that residual gasses have a substantial influence on combustion. The total dilution, the blend of residuals and air, is highly correlated to NOx emissions at all investigated operating conditions. Additionally, at low loads, the total dilution correlates with the dilution stability limit, rather than air-dilution solely. At high loads, residuals contribute little to the total dilution, but has been linked to increased propensity of knock.
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8.
  • Dahl, Daniel, 1982, et al. (författare)
  • Valve Profile Adaptation, Stratification, Boosting and 2-Stroke Strategies for Raising Loads of Gasoline HCCI Engines
  • 2012
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 5:3, s. 13-1045
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of high efficiency powertrains is a key objective for car manufacturers. One approach for improvingthe efficiency of gasoline engines is based on homogeneous charge compression ignition, HCCI, which provides higherefficiency than conventional strategies. However, HCCI is only currently viable at relatively low loads, primarily becauseat high loads it involves rapid combustion that generates pressure oscillations in the cylinder (ringing), and partly becauseit gives rise to relatively high NOX emissions.This paper describes studies aimed at increasing the viability of HCCI combustion at higher loads by using fullyflexible valve trains, direct injection with charge stratification (SCCI), and intake air boosting. These approaches werecomplemented by using EGR to control NOX emissions by stoichiometric operation, which enables the use of a three-waycatalyst. Experiments were carried out using a single-cylinder engine of passenger car size running on gasoline andcontrolled with negative valve overlap. By adapting the valve profiles (lift, duration and phasing) for high loads, a fuelsaving of 3% at constant load or a load increase of 6% could be achieved for lean HCCI compared to those obtained usingcamshafts that were not adapted for high load operation. Further, using intake pressures up to 180 kPa provided almostlinear increases in load for lean HCCI, stoichiometric HCCI and stoichiometric SCCI. However, lean SCCI did not profitfrom boosting because the charge became too lean and stratification lost its effect as a ringing inhibitor. At intake pressuresexceeding 140 kPa, stoichiometric HCCI operation becomes redundant since NOX ceases to be a limiting factor.Additionally, promising results were obtained in initial tests of two-stroke operation, which yielded higher maximumloads, lower fuel consumption and lower NOX emissions than the other strategies.
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9.
  • De Abreu Goes, Jesus, 1989, et al. (författare)
  • Correlation between Vehicle- and Rapid- Aged Commercial Lean NOx Trap Catalysts
  • 2017
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 10:4, s. 1613-1626
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Even though substantial improvements have been made for the lean NOx trap (LNT) catalyst in recent years, the durability still remains problematic because of the sulfur poisoning and sintering of the precious metals at high operating temperatures. Hence, commercial LNT catalysts were aged and tested in order to investigate their performance and activity degradation compared to the fresh catalyst, and establish a proper correlation between the aging methods used. The target of this study is to provide useful information for regeneration strategies and optimize the catalyst management for better performance and durability. With this goal in mind, two different aging procedures were implemented in this investigation. A catalyst was vehicle-aged in the vehicle chassis dynamometer for 100000 km, thus exposed to real conditions. Whereas, an accelerated aging method was used by subjecting a fresh LNT catalyst at 800 °C for 24 hours in an oven under controlled conditions. Engine dynamometer studies were performed with a Volvo mid-sized diesel engine with the purpose of testing the NOx storage and reduction performance, as well as the THC and CO conversion activity of the catalysts under controlled conditions. The aged catalysts activity was shown to be significantly degraded, mainly at low working temperatures compared to the fresh LNT, and one reason for this could be limited NO oxidation. In addition, the oven-aged sample was found to be well correlated to the vehicle-aged catalyst. On top of that, several vehicle emission cycles were carried out in the vehicle chassis dynamometer with a 2.0 l Volvo XC90 diesel vehicle in order to study the catalysts performance under real driving conditions and monitor the gradual deterioration of the vehicle-aged catalyst during the vehicle aging testing.
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10.
  • Doornbos, Gerben, 1987, et al. (författare)
  • Knock Phenomena under Very Lean Conditions in Gasoline Powered SI-Engines
  • 2018
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 11:1, s. 39-54
  • Tidskriftsartikel (refereegranskat)abstract
    • Homogeneous lean operation is a well-known strategy for enhancing the thermal efficiency of SI-engines. At higher load points the efficiency is often compromised by the need to suppress knock. Experiments were performed to determine the knock characteristics of SI engines using homogeneous lean operation at λ values of up to 1.8 with various hardware configurations that are commonly used to increase the lean limit. Changing λ altered the eigenfrequencies of the combustion chamber and the highest energy excitation mode. Increasing λ from 1.0 to 1.2 increased the knock tendency and led to an earlier knock onset. However, further increases in λ significantly reduced the knock tendency and retarded the knock onset. The knock signal energy increased for higher λ values and constant knock tendencies. The differences in knock characteristics between the various λ values became more pronounced upon raising the intake temperature from 40 °C to 90 °C. The trends in knock tendency and knock onset largely parallels that observed for engine out NOxemissions and thus the NOxconcentration in the internal EGR. The increased knock signal energy under lean conditions is partly attributed to the change in eigenfrequencies in the combustion chamber.
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11.
  • Ehleskog, Malin, 1980, et al. (författare)
  • Effects of High Injection Pressure, EGR and Charge Air Pressure on Combustion and Emissions in an HD Single Cylinder Diesel Engine
  • 2009
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 2:2, s. 341-354
  • Tidskriftsartikel (refereegranskat)abstract
    • When increasing EGR from low levels to a level that corresponds to low-temperature combustion, soot emissions initially increase due to lower soot oxidation before decreasing to almost zero due to very low soot formation. At the EGR level where soot emissions start to increase, the NOx emissions are low, but not sufficiently low to comply with future emission standards and at the EGR level where low-temperature combustion occurs CO and HC emissions are too high.The purpose of this study was to investigate the possibilities for shifting the so-called soot bump (where soot levels are increased) to higher EGR levels, or to reduce the magnitude of the soot bump using very high injection pressures (up to 240 MPa) while reducing the NOx emissions using EGR. The possibility of reducing the CO and HC emissions at high EGR levels due to the increased mixing caused by higher injection pressure was also investigated and the flame was visualized using an endoscope at chosen EGR values. In addition, flame temperatures and soot volume fractions were determined using two-color pyrometry.A single-cylinder heavy-duty direct injection diesel engine equipped with an electronically controlled unit injector with variable needle opening pressure was used in the investigations, with geometry based on the Volvo D12C production engine but with the compression ratio reduced from 18.5 to 14.The results from the studied cases showed that increasing EGR from 0 to 30% reduces both soot formation and oxidation resulting in higher engine-out soot emissions. Also, an increase in NOP for a case without EGR was found to give both high soot formation and high soot oxidation, resulting in reduced engine-out soot emissions. When EGR was added, increased NOP resulted in increased soot oxidation and thus in lower engine-out soot emissions. An increase in NOP was also found to reduce HC and CO emissions at high EGR levels.
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12.
  • Eismark, Jan, 1962, et al. (författare)
  • Role of Piston Bowl Shape to Enhance Late-Cycle Soot Oxidation in Low-Swirl Diesel Combustion
  • 2019
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 12:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Late-cycle soot oxidation in heavy-duty (HD) diesel engine low-swirl combustion was investigated using single-cylinder engine and spray chamber experiments together with engine combustion simulations. The in-cylinder flow during interactions between adjacent flames (flame-flame events) was shown to have a large impact on late-cycle combustion. To modify the flame-flame, a new piston bowl shape with a protrusion (wave) was designed to guide the near-wall flow. This design significantly reduced soot emissions and increased engine thermodynamic efficiency. The wave’s main effect was to enhance late-cycle mixing, as demonstrated by apparent rate of heat release after the termination of fuel injection. Combustion simulations showed that the increased mixing is driven by enhanced flow re-circulation, which produces a radial mixing zone (RMZ). The leading edge of the RMZ extends toward the center of the piston bowl, where unused ambient gas is available, promoting oxidation. The wave also enhances mixing in the trailing edge of the RMZ when it detaches from the wall, accelerating the burn-out of the RMZ. This flame interaction effect was isolated and studied further using a new optical setup in a spray chamber with a 2-hole nozzle fuel injector. A conceptual model relating piston bowl geometry to soot oxidation efficiency was developed to explain late-cycle soot oxidation in low-swirl HD engines.
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13.
  • Eismark, Jan, 1962, et al. (författare)
  • Role of spray chamber experiments in understanding flame-flame interaction events in heavy-duty diesel engine combustion.
  • 2018
  • Ingår i: SAE International Journal of Engines. - 1946-3944 .- 1946-3936.
  • Tidskriftsartikel (refereegranskat)abstract
    • Combustion in spray-controlled heavy-duty (HD) engines is characterized by gas-phase interactions between the ignited fuel jets (flames) and piston walls rather than liquid fuel impingement on the walls. In the research on HD engine emissions and fuel consumption, enhancement of mixing late in the combustion cycle is important. Mixing late in the cycle depends on development of the flow field in the cylinder, which in turn is affected by phenomena such as turbulent flow near a stagnation point during jet-wall impingement, wall-jet development along the piston walls and flame-flame interactions. Optical diagnostics in single-cylinder engines and combustion computational fluid dynamics (CFD) simulations are well-known methods for studying in-cylinder flow events. Detailed optical experiments conducted in high temperature/high pressure spray chambers (SCs) with single-hole fuel nozzles are now widely used for generating validation data for modeling a freely developing single spray. However, to date, very few SC setups have included flame-flame interactions. In this paper, a new SC setup is presented comprising a HD double-hole nozzle and different wall geometries. The setup enabled detailed optical analysis of the aforementioned interaction events. Imaging of soot luminosity, OH chemiluminescence and laser soot shadow imaging were used to compare late-cycle mixing in a conventional bowl geometry with a new piston type able to lower soot emissions considerably (referred to as a wave piston). Together with combustion CFD simulations, the new experimental setup yielded useful results for understanding flame-flame interaction effects on late-cycle mixing in HD engine combustion.
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14.
  • Ericsson, Gustav, 1979-, et al. (författare)
  • Optimizing the Transient of an SI-Engine Equipped with Variable Cam Timing and Variable Turbine
  • 2010
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 3:1, s. 903-915
  • Tidskriftsartikel (refereegranskat)abstract
    • As the engines of today decrease in displacement with unchanged power output, focus of today's research is on transient response. The trend of today is to use a turbocharger with high boost level. For SI-engines a regular WG turbocharger has been used, but in the future, when the boost level increases together with higher demand on the transient response, a Variable Nozzle Turbine (VNT) will be used together with Variable Valve Timing (VVT). As the degree of freedom increases, the control strategies during a transient load step will be more difficult to develop. A 1D simulation experiment has been conducted in GT Power where the transient simulation was "frozen" at certain time steps. The data from these time steps was put in a stationary simulation and the excessive energy was then bled off to obtain the same conditions for the engine in the stationary simulation as if the engine where in the middle of the transient. This method allows a faster and easier way to obtain a good control strategy for the VNT turbine and the VVT during a transient load step. The method can be used to find VNT/VVT settings strategies for the transient control with a good and robust result.
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15.
  • Eriksson, Lars, et al. (författare)
  • Calculation of Optimal Heat Release Rates under Constrained Conditions
  • 2016
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 9:2, s. 1143-1162
  • Tidskriftsartikel (refereegranskat)abstract
    • The work extends a methodology, for searching for optimal heat release profiles, by adding complex constraints on states. To find the optimum heat release profile a methodology, that uses available theory and methods, was developed that enables the use of state of the art optimal control software to find the optimum combustion trace for a model. The methodology is here extended to include constraints and the method is then applied to study how sensitive the solution is to different effects such as heat transfer, crevice flow, maximum rate of pressure rise, maximum pressure, knock and NO generation. The Gatowski single zone model is extended to a pseudo two zone model, to get an unburned zone that is used to describe the knocking and a burned zone for NO generation. A modification of the extended Zeldovich mechanism that makes it continuously differentiable, is used for NO generation. Previous results showed that the crevice effect had a significant influence on the shape for the unconstrained case where a two mode combustion was seen, one initial pressure rise and one constant pressure phase. Here it is shown that it still has a significant influence on the appearance until the maximum pressure limit is reached and becomes the dominating constraint. In the unconstrained case no conditions had combustion before TDC all started after, but when limitations are considered and come into play the combustion can now start before TDC to avoid excessive losses during the expansion. When introducing constraints on the NO formation through the extended Zeldovich mechanism the combustion takes the shape of a three mode combustion, one initial rapid burning, one later rapid burning and a constant pressure phase. In summary it is shown that the methodology is able to cope with the introduced constraints.
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16.
  • Eriksson, Lars, et al. (författare)
  • Computing Optimal Heat Release Rates in Combustion Engines
  • 2015
  • Ingår i: SAE International Journal of Engines. - Warrendale : SAE inc.. - 1946-3936 .- 1946-3944. ; 8:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The combustion process has a high impact on the engine efficiency, and in the search for efficient engines it is of interest to study the combustion. Optimization and optimal control theory is used to compute the most efficient combustion profiles for single zone model with heat transfer and crevice effects. A model is first developed and tuned to experimental data, the model is a modification of the well known Gatowski-model (Gatowski et.al 1984). This model is selected since it gives a very good description of the in-cylinder pressure, and thus the produced work, and achieves this with a low computational complexity. This enables an efficient search method that can maximize the work to be developed. First, smooth combustion profiles are studied where the combustion is modeled using the Vibe function, and parametric optimization is used to search for the optimal profile. Then, the most efficient combustion process with a completely free combustion is studied with theory and software for optimal control. A parameter study is performed to analyze the impact of crevice volume and air/fuel ratio λ. The results show that the losses have a high impact on the behavior, which is natural, and that the crevice effect has a very distinct effect on the optimal combustion giving a two mode appearance similar to the Seiliger cycle.
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17.
  • Eriksson, Lars, et al. (författare)
  • Scalable Component-Based Modeling for Optimizing Engines with Supercharging, E-Boost and Turbocompound Concepts
  • 2012
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 5:2, s. 579-595
  • Tidskriftsartikel (refereegranskat)abstract
    • Downsizing and turbocharging is a proven technology for fuel consumption reduction in vehicles. To further improve the performance, electrified components in the turbocharger arrangements have been proposed, and investigations have shown acceleration improvements, emission reductions, and further fuel conversion efficiency benefits. Simulation tools play an important role in the design process as the interplay between component selection, control strategy, system properties and constraints is very complex. Evaluations are performed with respect to BSFC map, fuel consumption in a drive cycle, acceleration performance, as well as many other aspects. A component-based engine and vehicle model is developed and evaluated to facilitate the process of assessing and optimizing the performance of e.g. engine, charging system, and electrical machine components. Considerations of the execution time and model fidelity have resulted in a choice of models in the mean value engine model family. The turbocharging and electrical system models have all been evaluated using experimental data from engine dynamometer tests and turbocharger gas stand measurements and other dedicated component measurements.
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18.
  • Etikyala, Sreelekha, 1991, et al. (författare)
  • History Effect on Particulate Emissions in a Gasoline Direct Injection Engine
  • 2021
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 15:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Soot formation in internal combustion engines is a combination of complex phenomena. Understanding the formation mechanism that influences particulate emissions can help to make gasoline direct injection (GDI) engines comply with increasingly stringent emission standards. It is generally accepted that the deposition of liquid fuel wall films in the combustion chamber is a significant source of particulate formation in GDI engines. The injection timing, which can help avoid interaction between the pistons and fuel spray, has been identified as the parameter with the greatest influence. Traditionally, the start of injection (SOI) sweeps one can find in the literature are carried out by changing the timing one value at a time. To quantify the influence of SOI, variations in our study were carried out in a novel way using cycle-to-cycle parameter control. Instead of motoring or turning off the engine between different SOI variations, the motor was run continuously with combustion and SOI sweeps carried out online in a series of preprogrammed perfectly deterministic SOI sequences to provide evidence of so-called history effects on particulate number (PN). The variation in SOI produces a change in engine combustion and liquid fuel impingement, leading to a state that acts as a precursor for the next state. The different preprogrammed sequences provided excellent data repeatability between engine runs but very different results, depending on the order in which the SOI timings were set. In-cylinder combustion was visualized with an endoscope connected to a high-speed camera. Two SOI timings were chosen (based on piston deposit level data from stationary measurements) to investigate the history effect of preceding conditions on PN. The results show that the preceding engine states influence PN formation and emission that is established as history effect in the study. The history effect is pronounced and was most noticeable under impinging conditions such as early injection timings like -340 crank angle degrees (CAD). History effect was also found to depend on the duration and SOI of the preceding state. More importantly, the history effect depends on how SOI is varied, which in turn influences PN emissions. In the cycle-to-cycle variation of SOI, PN levels at relatively later injection timing of -250 CAD resulted in similarly high levels at an early injection timing of -340 CAD.
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19.
  • Golovitchev, Valeri, 1945, et al. (författare)
  • Modeling of combustion and emissions formation in heavy duty diesel engine fueled by RME and diesel oil
  • 2010
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 2:2, s. 355-367
  • Tidskriftsartikel (refereegranskat)abstract
    • A comparative study on engine performance and emissions (NOx, soot) formation has been carried out for the Volvo D12C diesel engine fueled by Rapeseed Methyl Ester, RME and conventional diesel oil. The fuel and combustion models used in this paper are the modifications of those described in [1-3]. The numerical results for different load cases illustrate that for both fuels nearly 100% combustion efficiency was predicted; in the case of RME, the cumulative heat release was compared with the RME LHV, 37.2 kJ/g. To minimize soot and NOx emissions, 25-30% EGR levels depending on the engine loads and different injection timings were analyses. To illustrate the optimal engine performance conditions, a special technique based on the time-transient parametric φ-T maps [4] has been used
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20.
  • Gundmalm, Stefan, et al. (författare)
  • Divided Exhaust Period : Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area
  • 2013
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 6:2, s. 739-750
  • Tidskriftsartikel (refereegranskat)abstract
    • In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered. In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency. In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.
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21.
  • Henriksson, Lisa, 1984, et al. (författare)
  • CFD Simulations of one Period of a Louvered Fin where the Airflow is Inclined Relative to the Heat Exchanger
  • 2015
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 8:4, s. 1733-1742
  • Tidskriftsartikel (refereegranskat)abstract
    • This article presents Computational Fluid Dynamics (CFD) simulations of one period of a louvered fin, for a crossflow compact finned heat exchanger, where the incoming airflow was inclined relative to its core. Four inclinations were investigated: 90°, which was when the air flowed perpendicular to the heat exchanger, 60°, 30° and 10° angles relative to the vertical plane. The study included three heat exchanger designs, where two of them had symmetrical louvered fins and a thickness of 19mm and 52mm. The third had a thickness of 19mm and had the louvers angled in one direction. All heat exchangers have been simulated when the airflow entered both from above and below relative to the horizontal plane. Simulations have also been carried out when the airflow entered from the side, illustrating the heat exchanger to be angled relative to the vertical axis. Two air speeds have been investigated for each configuration, where the results were compared to experimental data.The results showed that the airflow characteristics were strongly dependent on the inclination angle. A more inclined heat exchanger generated larger separated areas at the entrance of the heat exchanger core. After approximately six louvers the airflow was fairly similar for all inclinations. The pressure drop over the core was not affected by the direction of the entered airflow. It was also seen that the heat exchanger with the louvers in only one direction resulted in approximately the same pressure drop as the one with symmetrical louvered fins. For a constant velocity in the longitudinal direction within the core, the pressure drop did not varied between the inclinations. Depending on the definition of the heat exchanger arrangement the heat transfer rate was affected. Simulated pressure drop followed the same trend as experimental data, even though the values were over-predicted.
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22.
  • Izadi Najafabadi, Mohammad, et al. (författare)
  • Effects of Injection Timing on Fluid Flow Characteristics of Partially Premixed Combustion Based on High-Speed Particle Image Velocimetry
  • 2017
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 10:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Partially Premixed Combustion (PPC) is a promising combustion concept ,based on judicious tuning of the charge stratification, to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delays of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NOx emissions. Moreover, a proper injection timing and strategy for PPC can improve the combustion stability as a result of a higher level of fuel stratification in comparison with the Homogeneous Charge Compression Ignition (HCCI) concept. Injection timing is the major parameter with which to affect the level of fuel and combustion stratification and to control the combustion phasing and the heat release behavior. The scope of the present study is to investigate the fluid flow characteristics of PPC at different injection timings. To this end, high-speed Particle Image Velocimetry (PIV) is implemented in a light-duty optical engine to measure fluid flow characteristics, including the flow fields, mean velocity and cycle-resolved turbulence, inside the piston bowl as well as the squish region with a temporal resolution of 1 crank angle degree at 800 rpm. Two injectors, having 5 and 7 holes, were compared to see their effects on fluid flow and heat release behavior for different injection timings. Reactive and non-reactive measurements were performed to distinguish injection-driven and combustion-driven turbulence. Formation of vortices and higher turbulence levels enhance the air/fuel interaction, changing the level of fuel stratification and combustion duration. Results demonstrate clearly how turbulence level correlates with heat release behavior, and provide a quantitative dataset for validation of numerical simulations.
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23.
  • Jia, Zhiqin, 1983, et al. (författare)
  • Experimental Investigation of Natural Gas-Diesel Dual-Fuel RCCI in a Heavy-Duty Engine
  • 2015
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 8:2, s. 797-807
  • Tidskriftsartikel (refereegranskat)abstract
    • Studies have shown that premixed combustion concepts such as PCCI and RCCI can achieve high efficiencies while maintaining low NOx and soot emissions. The RCCI (Reactivity Controlled Compression Ignition) concept use blending port-injected high-octane fuel with early direct injected high-cetane fuel to control auto-ignition. This paper describes studies on RCCI combustion using CNG and diesel as the high-octane and high-cetane fuels, respectively. The test was conducted on a heavy-duty single cylinder engine. The influence of injection timing and duration of the diesel injections was examined at 9 bar BMEP and1200 rpm. In addition, experiments were conducted using two different compression ratios, (14 and 17) with different loads and engine speeds. Results show both low NOx and almost zero soot emissions can be achieved but at the expense of increasing of unburned hydrocarbon emissions which could potentially be removed by catalytic after-treatment. CA50 generally occurred before TDC when using a compression ratio of 17. While the CA50 could be shifted to slightly after TDC by increasing the amount of EGR, this would lead to excessive HC emissions. A lower compression ratio of 14 was therefore used to retard the CA50 while maintaining acceptable UHC emissions.
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24.
  • Johansson, Anders, 1985, et al. (författare)
  • Experimental Investigation of the Influence of Boost on Combustion and Particulate Emissions in Optical and Metal SGDI-Engines Operated in Stratified Mode
  • 2016
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 9:2, s. 807-818
  • Tidskriftsartikel (refereegranskat)abstract
    • Boosting and stratified operation can be used to increase the fuel efficiency of modern gasoline direct-injected (GDI) engines. In modern downsized GDI engines, boosting is standard to achieve a high power output. However, boosted GDI-engines have mostly been operated in homogenous mode and little is known about the effects of operating a boosted GDI-engine in stratified mode.This study employed optical and metal engines to examine how boosting influences combustion and particulate emission formation in a spray-guided GDI (SGDI), single cylinder research engine. The setup of the optical and metal engines was identical except the optical engine allowed optical access through the piston and cylinder liner.The engines were operated in steady state mode at five different engine operating points representing various loads and speeds. The engines were boosted with compressed air and operated at three levels of boost, as well as atmospheric pressure for comparison. The fuel used was market gasoline (95 RON) blended with 10% ethanol. The spark plug and injector were mounted in parallel with the intake valves. The gas motion induced by the engine head was primarily tumble motion with a small amount of swirl.Results on particulate emissions indicated that nucleation mode particulates increased with increasing boost. In contrast, agglomeration mode particulates decreased with increasing boost pressure. The combustion was found to consist of a yellow flame in the center of the combustion chamber and a pre-mixed blue flame in the perimeter. The optical studies indicated that the flame area decreased with increasing boost.
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25.
  • Johansson, Anders, 1985, et al. (författare)
  • Reduction of Soot Formation in an Optical Single-Cylinder Gasoline Direct-Injected Engine Operated in Stratified Mode Using 350 Bar Fuel Injection Pressure, Dual-Coil and High-Frequency Ignition Systems
  • 2017
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 10:3, s. 709-721
  • Tidskriftsartikel (refereegranskat)abstract
    • The current trend toward more fuel efficient vehicles with lower emission levels has prompted development of new combustion techniques for use in gasoline engines. Stratified combustion has been shown to be a promising approach for increasing the fuel efficiency. However, this technique is hampered by drawbacks such as increased particulate and standard emissions. This study attempts to address the issues of increased emission levels by investigating the influence of high frequency ionizing ignition systems, 350 bar fuel injection pressure and various tumble levels on particulate emissions and combustion characteristics in an optical SGDI engine operated in stratified mode on isooctane. Tests were performed at one engine load of 2.63 bar BMEP and speed of 1200 rpm. Combustion was recorded with two high speed color cameras from bottom and side views using optical filters for OH and soot luminescence. The results indicated that increasing the fuel injection pressure led to faster burn as well as a reduction in soot luminescence. The ionizing ignition system generated faster initial combustion. Increasing the tumble level reduced the soot luminescence at all injection pressures, but the influence was largest at the lowest fuel injection pressure. The combination of an ionizing ignition system and high fuel pressure was most beneficial for lowering soot luminescence.
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26.
  • Jorques Moreno, Carlos, et al. (författare)
  • Investigation of Small Pilot Combustion in a Heavy-Duty Diesel Engine
  • 2017
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 10:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Factors influencing pilot-injection combustion were investigated using heat release analysis in a heavy-duty diesel engine fuelled with standard diesel fuel. Combinations of pilot-injection parameters i.e. pilot start of injection, pilot mass, pilot-main injection separation, and rail pressure were studied for various operating conditions and combustion phases. An experiment was designed to investigate the factors influencing the combustion of the pilot. For improved injected fuel-mass accuracy, reference data for the injectors were measured in a spray rig prior to the engine experiments. Results show that cycle-to-cycle variations and cylinder-to-cylinder variations influence pilot autoignition and the amount of heat released. Rail pressure and injected pilot mass affect the obtained variance depending on the chamber conditions. The obtained combustion modes (premixed, diffusive) of pilot combustion were found to be a function of the injected mass and rail pressure.
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27.
  • Kabral, Raimo, et al. (författare)
  • A compact silencer for the control of compressor noise
  • 2014
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 7:3, s. 1572-1578
  • Tidskriftsartikel (refereegranskat)abstract
    • Current trends for IC-engines are driving the development of more efficient engines with higher specific power. This is true for both light and heavy duty vehicles and has led to an increased use of super-charging. The super-charging can be both in the form of a single or multi-stage turbo-charger driven by exhaust gases, or via a directly driven compressor. In both cases a possible noise problem can be a strong Blade Passing Frequency (BPF) typically in the kHz range and above the plane wave range. In this paper a novel type of compact dissipative silencer developed especially to handle this type of problem is described and optimized. The silencer is based on a combination of a micro-perforated (MPP) tube backed by a locally reacting cavity. The combined impedance of micro-perforate and cavity is chosen to match the theoretical optimum known as the Cremer impedance at the mid-frequency in the frequency range of interest. Due to the high damping achieved at the Cremer optimum (hundreds of dB/m) it is easy to create a compact silencer with a significant damping (say > 30 dB) in a range larger than an octave. Both simulations and experimental tests of the novel silencer are presented based on a light duty vehicle application.
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28.
  • Kerres, Bertrand, et al. (författare)
  • Analysis of the Turbocharger Compressor Surge Margin Using a Hurst-Exponent-based Criterion
  • 2016
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 9:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Turbocharger compressors are limited in their operating range at low mass flows by compressor surge, thus restricting internal combustion engine operation at low engine speeds and high mean effective pressures. Since the exact location of the surge line in the compressor map depends on the whole gas exchange system, a safety margin towards surge must be provided. Accurate early surge detection could reduce this margin. During surge, the compressor outlet pressure fluctuates periodically. The Hurst exponent of the compressor outlet pressure is applied in this paper as an indicator to evaluate how close to the surge limit the compressor operates. It is a measure of the time-series memory that approaches zero for anti-persistence of the time series. That is, a Hurst exponent close to zero means a high statistical preference that a high value is followed by a low value, as during surge. Maps of a passenger-car sized turbocharger compressor with inlet geometries that result in different surge lines are measured on a cold gas stand. It is demonstrated that the Hurst exponent in fact decreases as the compressor moves towards surge, and that a constant value of the Hurst exponent can be used as a threshold for stable operation. Transient pressure signals of the compressor entering surge are analyzed in order to evaluate the time lag until surge can be detected using the Hurst exponent. Two surge cycles are usually needed to detect unstable operation. However, since the amplitude of these oscillations is relatively small for the first cycles, detection is possible before the oscillations grow into deep surge.
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29.
  • Kerres, Bertrand, et al. (författare)
  • Optimal Pressure based Detection of Compressor Instabilities using the Hurst Exponent
  • 2017
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 10:4, s. 1917-1926
  • Tidskriftsartikel (refereegranskat)abstract
    • The compressor surge line of automotive turbochargers can limit the low-end torque of an engine. In order to determine how close the compressor operates to its surge limit, the Hurst exponent of the pressure signal has recently been proposed as a criterion. The Hurst exponent quantifies the fractal properties of a time series and its long-term memory. This paper evaluates the outcome of applying Hurst exponent based criterion on time-resolved pressure signals, measured simultaneously at different locations in the compression system. Experiments were performed using a truck-sized turbocharger on a cold gas stand at the University of Cincinnati. The pressure sensors were flush-mounted at different circumferential positions at the inlet of the compressor, in the diffuser and volute, as well as downstream of the compressor. Results show that the previously identified threshold value distinguishing between surge and stable operation when the analysis was carried out for a different and smaller compressor can be used also for this much larger compressor. The investigation concerning the sensor locations reveals that pressure sensors at the outlet or shortly upstream the volute tongue give the clearest distinction between fully stable operation and operation close to the surge line. Further investigations show that as currently implemented, the criterion would need a minimum sampling duration of 500 ms and sampling frequency of 512 Hz. An extended algorithm based on distinguishing between a mono- and multifractal pressure signal is shown to have potential as an early warning indicator.
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30.
  • Königsson, Fredrik, et al. (författare)
  • The Influence of Crevices on Hydrocarbon Emissions from a Diesel-Methane Dual Fuel Engine
  • 2013
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 6:2, s. 751-765
  • Tidskriftsartikel (refereegranskat)abstract
    • Emissions of unburned methane are the Achilles heel of premixed gas engines whether they are spark ignited or diesel pilot ignited. If the engine is operated lean, lower temperatures prevail in the combustion chamber and several of the mechanisms behind the hydrocarbon emissions are aggravated. This paper presents an experimental investigation of the contribution from combustion chamber crevices and quenching to the total hydrocarbon emissions from a diesel-methane dual fuel engine at different operating conditions and air excess ratios. It is shown that the sensitivity to a change in topland crevice volume is greater at lean conditions than at stoichiometry. More than 70% of hydrocarbon emissions at air excess ratios relevant to operation of lean burn engines can be attributed to crevices.
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31.
  • Königsson, Fredrik, et al. (författare)
  • The Influence of In-Cylinder Flows on Emissions and Heat Transfer from Methane-Diesel Dual Fuel Combustion
  • 2013
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 6:4
  • Tidskriftsartikel (refereegranskat)abstract
    • In order for premixed methane diesel dual fuel engines to meet current and future legislation, the emissions of unburned hydrocarbons must be reduced while high efficiency and high methane utilization is maintained. This paper presents an experimental investigation into the effects of in cylinder air motion, swirl and tumble, on the emissions, heat transfer and combustion characteristics of dual fuel combustion at different air excess ratios. Measurements have been carried out on a single cylinder engine equipped with a fully variable valve train, Lotus AVT. By applying different valve lift profiles for the intake valves, the swirl was varied between 0.5 and 6.5 at BDC and the tumble between 0.5 and 4 at BDC. A commercial 1D engine simulation tool was used to calculate swirl number and tumble for the different valve profiles. Input data for the simulation software was generated using a steady-state flow rig with honeycomb torque measurements. To measure heat transfer, thermocouples were fitted in the cylinder head and heat exchangers on the coolant circuit and the engine oil. The study shows that swirl has a strong effect on the heat transfer; increasing the swirl from 0.5 to 6.5 increases the heat transfer to the coolant by 50%. With regards to emissions; swirl has the effect of increasing oxidation of hydrocarbons returning from crevices. For this reason a 20% reduction of hydrocarbon emissions can be achieved by increasing the swirl from 0.4 to 3. At high λ of 1.9, combustion is very sensitive to mixing between the gas and the air. The mixing is affected by the turbulence generated over the intake valves. A difference in engine out HC emissions by a factor of two can be achieved by varying the valve lift curve and hence varying the turbulence generated during the intake event. The timing of the gas injection can also improve mixing and achieve similar results. Compared to SI, dual fuel combustion is relatively insensitive to tumble.
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32.
  • Lind, Ted, et al. (författare)
  • Simultaneous PLIF Imaging of OH and PLII Imaging of Soot for Studying the Late-Cycle Soot Oxidation in an Optical Heavy-Duty Diesel Engine
  • 2016
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 9:2, s. 849-858
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of injection pressure and swirl ratio on the in-cylinder soot oxidation are studied using simultaneous PLIF imaging of OH and LII imaging of soot in an optical diesel engine. Images are acquired after the end of injection in the recirculation zone between two adjacent diesel jets. Scalars are extracted from the images and compared with trends in engine-out soot emissions. The soot emissions decrease monotonically with increasing injection pressure but show a non-linear dependence on swirl ratio. The total amount of OH in the images is negatively correlated with the soot emissions, as is the spatial proximity between the OH and soot regions. This indicates that OH is an important soot oxidizer and that it needs to be located close to the soot to perform this function. The total amount of soot in the images shows no apparent correlation with the soot emissions, indicating that the amount of soot formed is a poor predictor of the emission trends.
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33.
  • Llamas, Xavier, 1989-, et al. (författare)
  • Control-Oriented Compressor Model with Adiabatic Efficiency Extrapolation
  • 2017
  • Ingår i: SAE International Journal of Engines. - United States : S A E Inc.. - 1946-3936 .- 1946-3944. ; 10:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Downsizing and turbocharging with single or multiple stages has been one of the main solutions to decrease fuel consumption and harmful exhaust emissions, while keeping a sufficient power output. An accurate and reliable control-oriented compressor model can be very helpful during the development phase, as well as for engine calibration, control design, diagnostic purposes or observer design. A complete compressor model consisting of mass flow and efficiency models is developed and motivated. The proposed model is not only able to represent accurately the normal region measured in a compressor map but also it is capable to extrapolate to low compressor speeds. Moreover, the efficiency extrapolation is studied by analyzing the known problem with heat transfer from the hot turbine side, which introduces errors in the measurements done in standard gas stands. Since the parameterization of the model is an important and necessary step in the modeling, a tailored parameterization approach is presented based on Total Least Squares. A standard compressor map is the only data required to parameterize the model. The parameterization is tested with a database of more than 230 compressor maps showing that it can deal well with different compressor sizes and characteristics. Also, general initialization values for the model parameters are provided using the complete database parameterization results. The results show that the model accuracy is good and in general achieves relative errors below one percent. A comparison of the model accuracy for compressor maps with and without heat transfer influence is carried out, showing a similar model accuracy for both cases but better when no heat transfer is present. Furthermore, it is shown that the model is capable to predict the efficiency characteristics at low speed of two compressor maps, measured with near adiabatic conditions.
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34.
  • Lundberg, Björn, 1982, et al. (författare)
  • New Methodology for Transient Engine Rig Experiments for Efficient Parameter Estimation
  • 2013
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 6:4, s. 1995-2003
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction The diesel oxidation catalyst (DOC) is a well established technology to reduce CO and hydrocarbon (HC) emissions from diesel engines. Strengthened emission standards have made the importance of the DOC even greater in recent years since it plays an indispensible role in enhancing the performance of diesel particulate filters (DPF) and selective catalytic reduction (SCR) by utilization of NO oxidation to NO2. Therefore correct prediction of the DOC performance is very important for simulations of the entire aftertreatment system. When performing kinetic parameter estimation, laboratory scale experimental data is generally used. In laboratory scale it is possible to use essentially any combination of exhaust gas composition and temperature which makes it possible to estimate parameters over a wide range of conditions. However the applicability of these parameters in full scale models is often limited. Parameter estimation on full scale engine rig experiments on the other hand is limited by the exhaust compositions that are possible for the engine to produce. As a result, the fraction of CO is closely linked to the fraction of hydrocarbons and the fraction of NO is closely linked to the fraction of NO2. When switching between two engine operation points it generally takes several minutes before the properties of the emissions have stabilized. This does not only make the experiments time consuming, but it also complicates the transient modeling of the DOC since the changes in inlet properties are far from ideal step functions. In this study an experimental set-up is presented that makes it possible to change the inlet properties of the DOC without changing engine load point which results in much faster transients. The method also makes it possible to change the fraction of NO2 independently of the NO fraction. Method To achieve more controlled and faster changes in the inlet to the catalyst an extra DOC (DOC1) with the possibility for bypass flow and an SCR with urea injection are mounted before the catalyst. The fraction of exhaust gas flow through DOC1 allows variation in the conversion of HC and CO to CO2 and the conversion of NO to NO2. By injecting different amounts of urea the conversion of NO2 and NO to N2 is controlled. The SCR also makes it possible to obtain an inlet composition to the DOC that contains NO2 but is free of NO. Fast changes in inlet conditions are in other words possible and it is also possible to achieve compositions not achievable by only controlling the operation of the engine. Experiments have been performed at several engine conditions and using catalysts with different noble metal loading, lengths and washcoat thicknesses. To achieve high HC and CO concentrations the engine was tuned to run with late fuel injection. Significance A method to carry out engine rig experiments with a wider range of emission conditions makes it possible to more efficiently retune model parameters for a full-scale catalyst from literature data. This should result in faster model development which is of great importance in exhaust gas aftertreatment.
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35.
  • Lundberg, Björn, 1982, et al. (författare)
  • Parameter Estimation of a DOC from Engine Rig Experiments with a Discretized Catalyst Washcoat Model
  • 2014
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 7:2, s. 1093-1112
  • Tidskriftsartikel (refereegranskat)abstract
    • Parameter tuning was performed against data from a full scale engine rig with a Diesel Oxidation Catalysts (DOC). Several different catalyst configurations were used with varying Pt loading, washcoat thickness and volume. To illustrate the interplay between kinetics and mass transport, engine operating points were chosen with a wide variation in variables (inlet conditions) and both transient and stationary operation was used. A catalyst model was developed where the catalyst washcoat was discretized as tanks in series both radially and axially. Three different model configurations were used for parameter tuning, evaluating three different approaches to modeling of internal transport resistance. It was concluded that for a catalyst model with internal transport resistance the best fit could be achieved if some parameters affecting the internal mass transport were tuned in addition to the kinetic parameters. However it was also shown that a model with negligible internal transport resistance still could obtain a good fit since kinetic parameters could compensate for transport limitations. This highlighted the inherent difficulties using kinetic models with high parameter correlation and also showed the importance of using a kinetic model with a structure that is capable of describing exclusively intrinsic kinetics.
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36.
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37.
  • Mahendar, Senthil, et al. (författare)
  • The Impact of Miller Valve Timing on Combustion and Charging Performance of an Ethanol- and Methanol-Fueled Heavy-Duty Spark Ignition Engine
  • 2021
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 14:5, s. 733-748
  • Tidskriftsartikel (refereegranskat)abstract
    • Combustion engines and liquid fuels are likely to continue playing a central role in freight transportation with renewable fuels reducing carbon emissions. Ethanol and methanol are future renewable fuels with a knock resistance that make them suitable for heavy-duty (HD) spark ignition (SI) engines. This simulation work focuses on the potential for improving the efficiency of an ethanol- and methanol-fueled HD SI engine using early intake valve closing Miller valve timing. With Miller valve timing, the expansion ratio and thermodynamic efficiency can be increased while maintaining the same effective compression ratio. However, Miller timing requires increased boost pressure to retain the same trapped air mass and also suffers from reduced in-cylinder turbulence. Unlike previous simulation studies, a validated semi-predictive combustion model was used to resolve the implication of turbulence reduction on burn rate and its impediment in extracting higher thermodynamic efficiency with Miller timing discussed. The observed increase in burn duration adversely affected knock and the overall efficiency benefit from Miller timing. At stoichiometric conditions, a 2-3% increase in brake efficiency was observed with Miller timing by increasing the geometric compression ratio even with a relatively low turbocharger efficiency of 49%. At lean conditions, the increase in burn duration and pumping loss was significant for both fuels demanding a minimum turbocharger efficiency of 55% to gain an improvement in brake efficiency from Miller timing. If the degree of Miller timing is constrained by a single-stage turbocharger, Miller timing showed only a 0.7% point efficiency increase at lean conditions due to the reduced burn rate. If the burn rate can be increased, similar to 2.5% increase in brake efficiency can be achieved using Miller timing leading to over 48% brake efficieny for both fuels thus making the HD SI engine competitive to HD diesel engines.
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38.
  • Mannazhi, Manu, et al. (författare)
  • Soot Oxidation Studies in an Optical Diesel Engine Using Laser-Induced Incandescence and Extinction : The Effects of Injector Aging and Fuel Additive
  • 2021
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 14:5, s. 749-761
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous studies have shown that injector aging adversely affects the diesel engine spray formation and combustion. It has also been shown that the oxygenated fuel additive tripropylene glycol monomethyl ether (TPGME) can lower soot emissions. In this study, the effects of injector aging and TPGME on the late cycle oxidation of soot were investigated using laser diagnostic techniques in a light-duty optical diesel engine at two load conditions. The engine was equipped with a quartz piston with the same complex piston geometry as a production engine. Planar laser-induced incandescence (LII) was used to obtain semiquantitative in-cylinder two-dimensional (2D) soot volume fraction (fv) distributions using extinction measurements. The soot oxidation rate was estimated from the decay rate of the in-cylinder soot concentration for differently aged injectors and for cases with and without TPGME in the fuel. The aged injector produced higher soot concentrations than the new injector at both load conditions. The aged injector also showed higher soot oxidation rates than the new injector at the low load condition. TPGME resulted in lower soot concentrations at both load conditions and faster oxidation rates, especially at mid load conditions.
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39.
  • Muric, Kenan, et al. (författare)
  • A Fast Crank Angle Resolved Zero-Dimensional NOx Model Implemented on a Field-Programmable Gate Array
  • 2013
  • Ingår i: SAE international journal of engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 6:1, s. 246-256
  • Konferensbidrag (refereegranskat)abstract
    • In the automotive industry, the piezo-based in-cylinder pressure sensor is getting commercialized and used in production vehicles. For example, the pressure sensor offers the opportunity to design algorithms for estimation of engine emissions, such as soot and NO, during a combustion cycle. In this paper a zero-dimensional NO model for a diesel engine is implemented that will be used in real time. The model is based on the thermal NO formation and the Zeldovich mechanism using two non-geometrical zones: burned and unburned zone. The influence of EGR on combustion temperature was modeled using a well-known thermodynamic identity where specific heat at constant pressure is included. Specific heat will vary with temperature and the gas composition. The model was implemented in LabVIEW using tools specific for an FPGA (Field-Programmable Gate Array). In order to simplify and implement the model, least-squares-criterion-based polynomial approximations are used that enables the utilization of fast algorithms as well as sub-routines (sub-VIs). The sub-routines can be used to save space on the Field Programmable Gate Array (FPGA) and thus minimizing the risk of potential issues regarding overmapping of the hardware. In this case the interpolating functions are polynomials that only consume addition and multiplication operations. This is suited for the objective in mind due to the fact that the model tailored for an FPGA cannot, in a sufficient manner, handle highly complex calculations nor divisions. The time results obtained during the execution of the model indicates that it is possible to update the NO, at a given temporal state, well below the time corresponding to a crank angle degree. The FPGA NO model was tested against measurement data collected from a Scania engine. The time needed to execute an iteration of the model was approximately 3 μs.
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40.
  • Nezhadali, Vaheed, et al. (författare)
  • Turbocharger Dynamics Influence on Optimal Control of Diesel Engine Powered Systems
  • 2014
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 7:1, s. 6-13
  • Tidskriftsartikel (refereegranskat)abstract
    • The importance of including turbocharger dynamics in diesel engine models are studied, especially when optimization techniques are to be used to derive the optimal controls. This is done for two applications of diesel engines where in the first application, a diesel engine in wheel loader powertrain interacts with other subsystems to perform a loading operation and engine speed is dictated by the wheel speed, while in the second application, the engine operates in a diesel-electric powertrain as a separate system and the engine speed remains a free variable. In both applications, mean value engine models of different complexities are used while the rest of system components are modeled with the aim of control study. Optimal control problems are formulated, solved, and results are analyzed for various engine loading scenarios in the two applications with and without turbocharger dynamics. It is shown that depending on the engine loading transients, fuel consumption and operation time can widely vary when the turbocharger dynamics are considered in the diesel engine model. Including these, have minor effects on fuel consumption and operation time at minimum fuel operations of the first application (~0.1 %) while the changes are considerable in the second application (up to 60%). In case of minimum time operations however, fuel consumption and operation time are highly affected in both applications implying that not considering turbocharger dynamics in the diesel engine models may lead to overestimation of the engine performance especially when the results are going to be used for control purposes.
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41.
  • Nilsson, Tomas, 1983-, et al. (författare)
  • Optimal Operation of a Turbocharged Diesel Engine during Transients
  • 2012
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 5:2, s. 571-578
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent development has renewed the interest in drivetrain concepts which give a higher degree of freedom by disconnecting the engine and vehicle speeds. This freedom raises the demand for active control, which especially during transients is not trivial but of which the quality is crucial for the success of the drivetrain concept. In this work the fuel optimal solution for a turbocharged diesel engine connected to a load which does not restrict the engine speed is derived, analysed and utilized for finding a suboptimal operating point trajectory. We use a Willan s efficiency model for the engine, expanded with a first order delay dependent torque reduction representing the turbocharger pressure, and study different output power transients. The analysis is made with dynamic programming, Pontryagin’s maximum principle and a suboptimal strategy based on the static optimal operating points. We present a method for using Pontryagin’s maximum principle for deriving the optimal operating point trajectory. The time needed for computation was reduced a factor >100 compared to dynamic programming, but this method is only applicable to load cases with steps between different high output powers. We also present a suboptimal method which shows a <1% increase in fuel consumption compared to the optimal, while reducing the time needed for computation a factor >1000 compared to dynamic programming.
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42.
  • Reifarth, Simon, 1980-, et al. (författare)
  • Transient EGR in a High-Speed DI Diesel Engine for a set of different EGR-routings
  • 2010
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 3:1, s. 1071-1078
  • Tidskriftsartikel (refereegranskat)abstract
    • EGR has been proven to reduce NOx emissions from diesel engines significantly and is nowadays widely used in production engines. To reach future emission legislation standards, alternative EGR-routings that deliver higher EGR- rates get into the focus of researchers. As the steady-state emissions are reduced more and more, the emission peaks in transient parts of driving cycles gain importance. Therefore it is interesting to analyze the transient behavior of different EGR-routings. In this work, a 1-D simulation is performed in GT-Power for a 1.9 liter passenger car diesel engine equipped with cooled short-route EGR and a variable geometry turbine. For calibration of the simulation, load transients are measured including the measurement of transient EGR-rates using a fast CO2-analyzer and cylinder pressure to obtain heat-release data. A database with heat-release rates for transient combustion is collected to enable the simulation to run with real combustion data at all points of the transients. The transient EGR-rate as well as the intake pressure are used as criteria to chose the right heat-release rate for a certain cycle. A set of different ways of supplying EGR, namely hybrid EGR, pump-assisted EGR and a reed valve in the EGR- circuit are then implemented in the simulation software and analyzed with respect to transient response and fuel consumption. Another aspect of the analysis is the possibility to control the EGR-rate during the transient. This includes positive load transients with EGR-shutoff as well as negative load transients with need for fast EGR-delivery.
  •  
43.
  • Rinaldini, Carlo, 1975, et al. (författare)
  • CFD analyses on 2-Stroke High Speed Diesel engines
  • 2011
  • Ingår i: 10th International Conference on Engines & Vehicles. - : SAE International. ; 4:2, s. 2240-2256
  • Konferensbidrag (refereegranskat)abstract
    • In recent years, interest has been growing in the 2-Stroke Diesel cycle, coupled to high speed engines. One of the most promising applications is on light aircraft piston engines, typically designed to provide a top brake power of 100-200 HP with a relatively low weight. The main advantage yielded by the 2-Stroke cycle is the possibility to achieve high power density at low crankshaft speed, allowing the propeller to be directly coupled to the engine, without a reduction drive. Furthermore, Diesel combustion is a good match for supercharging and it is expected to provide a superior fuel efficiency, in comparison to S.I. engines. However, the coupling of 2-Stroke cycle and Diesel combustion on small bore, high speed engines is quite complex, requiring a suitable support from CFD simulation. In this paper, a customized version of the KIVA-3v code (a CFD program for multidimensional analyses) has been used to address ports and combustion chamber design of a new project (a 3-cylinder 1.8L engine, with a power rating up to 150 HP). Multidimensional calculations have been supported by 1D engine cycle analyses, using GT-Power.Two types of combustion-scavenging system have been considered, both of them featuring direct injection: a configuration with exhaust poppet valves and another one with piston controlled ports. A development of both projects has been performed through a coupled 1d-3d computational approach.A first set of KIVA calculations has been performed, in order to characterize the scavenging and the port flow patterns of both configurations, considering three different operating conditions, representative an aircraft engine.Then, several combustion simulations have been run, for defining two chambers able to match the project goals (high fuel efficiency, limited in-cylinder peak-pressure). For the two best configurations, the most interesting calculation results are presented in the paper.
  •  
44.
  • Shamun, Sam, et al. (författare)
  • Exhaust PM Emissions Analysis of Alcohol Fueled Heavy-Duty Engine Utilizing PPC
  • 2016
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 9:4, s. 2142-2152
  • Tidskriftsartikel (refereegranskat)abstract
    • The focus has recently been directed towards the engine out soot from Diesel engines. Running an engine in PPC (Partially Premixed Combustion) mode has a proven tendency of reducing these emissions significantly. In addition to combustion strategy, several studies have suggested that using alcohol fuels aid in reducing soot emissions to ultra-low levels. This study analyzes and compares the characteristics of PM emissions from naphtha gasoline PPC, ethanol PPC, methanol PPC and methanol diffusion combustion in terms of soot mass concentration, number concentration and particle size distribution in a single cylinder Scania D13 engine, while varying the intake O2. Intake temperature and injection pressure sweeps were also conducted. The fuels emitting the highest mass concentration of particles (Micro Soot Sensor) were gasoline and methanol followed by ethanol. The two alcohols tested emitted nucleation mode particles only, whereas gasoline emitted accumulation mode particles as well. Regarding soot mass concentration measurements; methanol never exceeded 1.6 mg/m3 while when operating on gasoline this value never descended below 1.6 mg/m3. From this result it can be concluded that the main contributor to PM mass emissions is mainly increasing CMD (Count Mean Diameter) in the accumulation mode size range, but can in diffusion combustion also be caused by a high amount of nucleation mode particles. A probable cause of higher particle number emissions, when running the engine on methanol compared to ethanol, is the corrosiveness of the fuel itself. Except for the ultra-low PM mass emitted from alcohol combustion, it is also possible to alter the EGR concentration with a higher level of freedom without having to consider the NOX - soot tradeoff.
  •  
45.
  • Shwan, Soran, 1984, et al. (författare)
  • Impact of Thermal and Chemical Ageing of Fe-BEA SCR Catalyst on NOx Conversion Performance
  • 2016
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 9:2, s. 1305-1313
  • Tidskriftsartikel (refereegranskat)abstract
    • Emissions of nitrogen oxides (NOx) from heavy-duty diesel engines are subject to more stringent environmental legislation. Selectivecatalytic reduction (SCR) over metal ion-exchanged zeolites is in this connection an efficient method to reduce NOx. Understandingdurability of the SCR catalyst is crucial for correct design of the aftertreatment system. In the present paper, thermal and chemicalageing of Fe-BEA as NH3-SCR catalyst is studied. Experimental results of hydrothermal ageing, and chemical ageing due tophosphorous and potassium exposure are presented. The catalyst is characterized by flow reactor experiments, nitrogen physisorption,DRIFTS, XRD, and XPS. Based on the experimental results, a multisite kinetic model is developed to describe the activity of the freshFe-BEA catalyst. Furthermore, the model can predict deactivation of the catalyst well by decreasing the number of active sites,representing loss of active iron sites due to migration or chemical blockage of the sites. By performing a systematic study of differentdeactivation mechanisms, a deactivation expression for the active sites can be formulated.
  •  
46.
  • Sjöblom, Jonas, 1968 (författare)
  • Combined Effects of Late IVC and EGR on Low-load Diesel Combustion
  • 2014
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 8:1, s. 60-67
  • Tidskriftsartikel (refereegranskat)abstract
    • The increasing demand for improved efficiency of diesel engines requires more advanced combustion solutions. These solutions include the use of variable valve timings in combination with more traditional methods such as EGR, turbocharging and advanced injection systems. By modifying the characteristics of the charge air, further hardware optimization becomes possible. In the current investigation, the effect of late intake valve closing (LIVC) was investigated together with the effect of (external) exhaust gas recirculation (EGR) in a single cylinder heavy duty diesel engine. Different injection timings and injection pressures were investigated. The mass flow of oxygen was kept constant in order to show how the density and temperature of the reactant mixture affect the combustion and emission characteristics. The combustion results showed that if the oxygen mass flow is kept constant, an EGR approach is more efficient than LIVC in lowering fuel consumption due to the effects of increased cylinder gas flow which improves fuel conversion efficiency. It was shown that the ignition delay for a fixed combustion phasing was independent of EGR but could be increased by LIVC. The peak pressure was more strongly affected by EGR due to the larger gas flow but this response can be reduced by means of LIVC. After compensating for combustion timing effects, the reduced peak pressure was mainly attributed to reduced effective compression ratio resulting from the LIVC. The results show how variable valve timing can be used as one important tool to obtain better combustion characteristics and thus enable more efficient powertrains.
  •  
47.
  • Svensson, Erik, et al. (författare)
  • Evaluation of Different Turbocharger Configurations for a Heavy-Duty Partially Premixed Combustion Engine
  • 2017
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 10:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The engine concept partially premixed combustion (PPC) has proved higher gross indicated efficiency compared to conventional diesel combustion engines. The relatively simple implementation of the concept is an advantage, however, high gas exchange losses has made its use challenging in multi-cylinder heavy duty engines. With high rates of exhaust gas recirculation (EGR) to dilute the charge and hence limit the combustion rate, the resulting exhaust temperatures are low. The selected boost system must therefore be efficient which could lead to large, complex and costly solutions. In the presented work experiments and modelling were combined to evaluate different turbocharger configurations for the PPC concept. Experiments were performed on a multi-cylinder engine. The engine was modified to incorporate long route EGR and a single-stage turbocharger, however, with compressed air from the building being optionally supplied to the compressor. Experimental combustion heat release rates and boundary conditions were used to validate a simulation model. This model was then used to compare three different turbochargers: two single-stage turbochargers and one two-stage. The whole speed and load range was covered in the simulations to determine the engine performance. The influence of high EGR rates as well as the effect of charge air and EGR cooler gas outlet temperatures were also investigated. The simulation results showed that the two-stage turbocharger was able to give the highest load over the whole speed range with a brake mean effective pressure of 25.6 bar, whereas the two single-stage turbochargers reached 22.2 and 23.1 bar respectively. The average brake efficiency was 39.3, 39.7 and 40.2 %. It was found that decreasing the inlet temperature is critical for obtaining high loads and system efficiencies. Finally, it was shown that the optimal amount of EGR was dependent on the turbocharger efficiency and cooler temperatures.
  •  
48.
  • Tiikoja, H., et al. (författare)
  • Investigations of automotive turbocharger acoustics
  • 2011
  • Ingår i: SAE technical paper series. - : SAE International. - 0148-7191. ; 4:2, s. 2531-2542
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper an overview of recent experimental studies performed at KTH on the sound transmission and sound generation in turbochargers is presented. The compressor and turbine of the turbochargers are treated as acoustic active 2-ports and characterized using the unique experimental test facility established at KTH. The 2-port model is limited to the plane wave range so for higher frequencies the propagating acoustic power is estimated using an average based on pressure cross-spectra. A number of automotive turbochargers have been studied for a variety of operating conditions systematically selected from the compressor and turbine charts. The paper discusses the experimental procedures including special techniques implemented to improve the quality of the data. Results from a number of experiments on various modern automotive turbochargers including a unit with variable turbine geometry (VTG) are presented. Copyright 
  •  
49.
  • Vasudevan, Sudharsan, 1991, et al. (författare)
  • Subcooled Flow Boiling in High Power Density Internal Combustion Engines II: Numerical Modeling
  • 2022
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 16:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Results from a thermal survey measurement campaign on a four-cylinder Volvo engine was presented in Part I of this article. The focus was predominantly on heat transfer in the engine coolant jacket. This part presents numerical modeling focused specifically on the coolant flow and associated heat transfer in the coolant jacket using computational fluid dynamics (CFD), as a part of a high-resolution complete engine 3D conjugate heat transfer (CHT) model. With local nucleate boiling being an indispensable phenomenon in high power density engines, a dedicated boiling model is essential and is to be used in conjunction with CFD while analyzing heat transfer in the coolant jacket. This article validates a new boiling model with data obtained from the extensive thermal survey measurements, presented in Part I. The new model includes a parameter, based on vapor bubble interactions, that serves as an indication of the transition from beneficial nucleate boiling to high-risk transition and film boiling regimes. This parameter might be used to assess the robustness of new engine designs. The advantages and limitations of the new boiling model are presented and are discussed in detail.
  •  
50.
  • Venkataraman, Varun, et al. (författare)
  • Thin-Wire Thermocouple Design for Exhaust Gas Temperature Pulse Measurements in Internal Combustion Engines
  • 2023
  • Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 16:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Accurate exhaust gas temperature (EGT) measurements are vital in the design and developmentprocess of internal combustion engines (ICEs). The unsteady ICE exhaust flow and thermal inertia of commonly used sheathed thermocouples and resistance thermometers require high bandwidth EGT pulse measurements for accurate cycle-resolved and mean EGTs. The EGT pulse measurement challenge is typically addressed using exposed thin-wire resistance thermometers or thermocouples.The sensor robustness to response tradeoff limits ICE tests to short durations over a few exhaust conditions. Larger diameter multiwire thermocouples using response compensation potentially overcomes the tradeoff. However, the literature commonly adopts weaker slack wire designs despiteindications of coated weld taut wires being robust. This study experimentally evaluates the thin-wirethermocouple design placed in the exhaust of a heavy-duty diesel engine over wide-ranging exhaust conditions for improving both sensor robustness and accuracy of the measured EGT. The assessed design parameters included the wire diameter (51 μm to 254 μm), the exposed wire length, and thewires placed slack or taut with coated weld faces. All taut wires with ceramic-coated weld faces endured over 3 h of engine operation, while similar diameter slack wires (51 μm and 76 μm) were sensitive to the exhaust condition and exposed wire length. Reducing the wire diameter from 76 μmto 51 μm significantly impacted response improvements as evidenced at certain test conditions bya peak-peak EGT increase of 92 °C, a mean EGT drop of 26 °C, and a doubling of the sensitivity ofmean EGT cycle-to-cycle variations to ±12 °C. Increasing the exposed wire length showed less significant response improvements. The Type-K thin-wire thermocouples showed negligible drift, thereby indicating the possibility of using smaller and longer wires built taut with coated weld facesfor improved accuracy of EGT measurements in ICEs.
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