| 1. |
- Giramondi, Nicola, 1991-, et al.
(författare)
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CFD-Driven Preliminary Investigation of Ethanol-Diesel Diffusive Combustion in Heavy-Duty Engines
- 2019
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Ingår i: SAE Technical Paper Series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- The introduction of renewable alcohols as fuels for heavy-duty engines may play a relevant role for the reduction of the carbon footprint of the transport sector. The direct injection of ethanol as main fuel and diesel as pilot fuel in the engine combustion chamber through two separate injectors may allow good combustion controllability over the entire engine operating range by targeting diffusive combustion. Closed-cycle combustion simulations have been carried out using AVL FIRE coupled to AVL TABKIN for the implementation of the Flamelet Generated Manifold (FGM) chemistry reduction technique in order to investigate the influence of the injection system geometry and the injection strategy of pure ethanol and diesel fuel on ignition characteristics and combustion at different operating conditions.
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| 2. |
- Giramondi, Nicola, 1991-, et al.
(författare)
-
Combustion Characteristics, Performance and NOx Emissions of a Heavy-Duty Ethanol-Diesel Direct Injection Engine
- 2020
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Konferensbidrag (refereegranskat)abstract
- Diffusive combustion of direct injected ethanol is investigated in a heavy-duty single cylinder engine for a broad range of operating conditions. Ethanol has a high potential as fossil fuel alternative, as it provides a better carbon footprint and has more sustainable production pathways. The introduction of ethanol as fuel for heavy-duty compression-ignition engines can contribute to decarbonize the transport sector within a short time frame. Given the resistance to autoignition of ethanol, the engine is equipped with two injectors mounted in the same combustion chamber, allowing the simultaneous and independent actuation of the main injection of pure ethanol and a pilot injection of diesel as an ignition source. The influence of the dual-fuel injection strategy on ethanol ignition, combustion characteristics, engine performance and NOx emissions is evaluated by varying the start of injection of both fuels and the ethanol-diesel ratio. The results are compared against two baselines, i.e. conventional diesel combustion and dual-injections of diesel. Diesel substitution ratios above 80% on an energy basis are investigated, as the objective is to minimize diesel consumption while keeping stable and complete ethanol combustion. A minimum separation between ethanol and diesel injections is found to be necessary in order to limit the degree of premixing of ethanol at high load and avoid partial ethanol misfire causing combustion instability at low load, respectively. At low load, shortening the ethanol-diesel injection separation causes an increase in HC and CO emissions leading to lower combustion efficiencies. At high load, NOx emissions grow at higher degrees of premixing of ethanol. A slight reduction in NOx emissions occurs when increasing the relative amount of ethanol injected. Higher gross indicated efficiencies are observed for the ethanol-diesel cases compared to conventional diesel combustion. In conclusion, stable mixing-controlled combustion of ethanol is achieved with minimal diesel pilot quantities within a broad engine load range.
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| 3. |
- Giramondi, Nicola, 1991-
(författare)
-
Diffusive Combustion of Ethanol in a Dual-Fuel Direct Injection Compression Ignition Engine
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The impact of climate change due to global warming necessitates rapid and extensive measures to enhance the sustainability of the energy and transport sectors. In this context, there are large environmental and societal benefits to be gained by replacing diesel with renewable fuels for road freight transport. This solution may facilitate and expedite the transition towards fossil-free, carbon-neutral transport, while the electrification process takes shape. Short-chain alcohol fuels have favorable properties for the enhancement of engine performance and the abatement of pollutant emissions, however, they necessitate ignition aid systems in compression ignition engines. The present research investigates a novel concept of dual-fuel combustion for heavy-duty compression ignition engine applications by means of engine tests and three-dimensional combustion simulations. This concept involves the direct injection of pure ethanol as main fuel through a centrally mounted injector, and minimal quantities of diesel as pilot fuel via a separate injector. The objective is to achieve diffusive combustion of ethanol in a process analogous to conventional diesel combustion throughout the entire engine load range, with a higher thermal efficiency and lower pollutant emissions. Single-cylinder engine tests were carried out to evaluate the influence of combustion characteristics and performance with respect to dual-injection strategy, engine load, ethanol ratio and configuration of the diesel pilot injector. The characteristics and performance of ethanol-diesel direct injection compression ignition (DICI) combustion were compared to two sets of baselines, that are conventional diesel combustion and dual-injections of diesel via the main and pilot injector in the same proportion as in the dual-fuel test points. At low load conditions, increasing the separation between the diesel pilot and ethanol main injection enabled the achievement of diffusive combustion of ethanol, avoiding combustion instability and partial misfire thanks to minimal quantities of diesel injected. At high load conditions, a minimum main-pilot separation was instead required to limit the degree of ethanol premixing at ignition. Using a diesel pilot injector having a lower number of sprays with a wider hole diameter promoted a more robust ignition of ethanol, while also causing a reduction of engine performance. Parallel to the experimental work, three-dimensional combustion simulations were carried out in order to investigate the interaction between diesel and ethanol sprays during ignition at various engine operating conditions, from low to full load. At the operating conditions investigated during engine tests, the ignition of a subset of ethanol sprays was locally triggered by the contact with the products of diesel combustion. Subsequently, ignition propagated towards the neighboring ethanol sprays, until reaching the furthest ones from the diesel pilot injector. The coupling between experimental and numerical results highlighted the noteworthy predictive capability of the adopted combustion model with respect to the ethanol combustion characteristics. In conclusion, the present research work provides a solid starting point for future studies on diffusive combustion of alcohol fuels in compression ignition engines. The structured knowledge built in the course of the doctoral project lays the foundation for the development of a fuel-flexible engine for heavy-duty applications.
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| 4. |
- Giramondi, Nicola, et al.
(författare)
-
Influence of the diesel pilot injector configuration on ethanol combustion and performance of a heavy-duty direct injection engine
- 2021
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149.
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Tidskriftsartikel (refereegranskat)abstract
- Thanks to its properties and production pathways, ethanol represents a valuable alternative to fossil fuels, with potential benefits in terms of CO2, NOx, and soot emission reduction. The resistance to autoignition of ethanol necessitates an ignition trigger in compression-ignition engines for heavy-duty applications, which in the current study is a diesel pilot injection. The simultaneous direct injection of pure ethanol as main fuel and diesel as pilot fuel through separate injectors is experimentally investigated in a heavy-duty single cylinder engine at a low and a high load point. The influence of the nozzle hole number and size of the diesel pilot injector on ethanol combustion and engine performance is evaluated based on an injection timing sweep using three diesel injector configurations. The tested configurations have the same geometric total nozzle area for one, two and four diesel sprays. The relative amount of ethanol injected is swept between 78 – 89% and 91 – 98% on an energy basis at low and high load, respectively. The results show that mixing-controlled combustion of ethanol is achieved with all tested diesel injector configurations and that the maximum combustion efficiency and variability levels are in line with conventional diesel combustion. The one-spray diesel injector is the most robust trigger for ethanol ignition, as it allows to limit combustion variability and to achieve higher combustion efficiencies compared to the other diesel injector configurations. However, the two- and four-spray diesel injectors lead to higher indicated efficiency levels. The observed difference in the ethanol ignition dynamics is evaluated and compared to conventional diesel combustion. The study broadens the knowledge on ethanol mixing-controlled combustion in heavy-duty engines at various operating conditions, providing the insight necessary for the optimization of the ethanol-diesel dual-injection system.
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| 5. |
- Anton, Nicholas, et al.
(författare)
-
AXIAL TURBINE DESIGN FOR A TWIN-TURBINE HEAVY-DUTY TURBOCHARGER CONCEPT
- 2018
-
Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : ASME Press. - 9780791851005
-
Konferensbidrag (refereegranskat)abstract
- In the process of evaluating a parallel twin-turbine pulse-turbocharged concept, the results considering the turbine operation clearly pointed towards an axial type of turbine. The radial turbine design first analyzed was seen to suffer from sub-optimum values of flow coefficient, stage loading and blade speed-ratio. Modifying the radial turbine by both assessing the influence of "trim" and inlet tip diameter all concluded that this type of turbine is limited for the concept. Mainly, the turbine stage was experiencing high values of flow coefficient, requiring a more high flowing type of turbine. Therefore, an axial turbine stage could be feasible as this type of turbine can handle significantly higher flow rates very efficiently. Also, the design spectrum is broader as the shape of the turbine blades is not restricted by a radially fibred geometry as in the radial turbine case. In this paper, a single stage axial turbine design is presented. As most turbocharger concepts for automotive and heavy-duty applications are dominated by radial turbines, the axial turbine is an interesting option to be evaluated for pulse charged concepts. Values of crank-angle-resolved turbine and flow parameters from engine simulations are used as input to the design and subsequent analysis. The data provides a valuable insight into the fluctuating turbine operating conditions and is a necessity for matching a pulse-turbocharged system. Starting on a 1D-basis, the design process is followed through, resulting in a fully defined 3D-geometry. The 3D-design is evaluated both with respect to FEA and CFD as to confirm high performance and durability. Turbine maps were used as input to the engine simulation in order to assess this design with respect to "on-engine" conditions and to engine performance. The axial design shows clear advantages with regards to turbine parameters, efficiency and tip speed levels compared to a reference radial design. Improvement in turbine efficiency enhanced the engine performance significantly. The study concludes that the proposed single stage axial turbine stage design is viable for a pulse-turbocharged six cylinder heavy-duty engine. Taking into account both turbine performance and durability aspects, validation in engine simulations, a highly efficient engine with a practical and realizable turbocharger concept resulted.
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| 6. |
- Anton, Nicholas
(författare)
-
Engine Optimized Turbine Design
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus on our environment has never been as great as it is today. The impact of global warming and emissions from combustion processes become increasingly more evident with growing concerns among the world’s inhabitants. The consequences of extreme weather events, rising sea levels, urban air quality, etc. create a desperate need for immediate action. A major contributor to the cause of these effects is the transportation sector, a sector that relies heavily on the internal combustion engine and fossil fuels. The heavy-duty segment of the transportation sector is a major consumer of oil and is responsible for a large proportion of emissions.The global community has agreed on multiple levels to reduce the effect of man-made emissions into the atmosphere. Legislation for future reductions and, ultimately, a totally fossil-free society is on the agenda for many industrialized countries and an increasing number of emerging economies.Improvements of the internal combustion engine will be of importance in order to effectively reduce emissions from the transportation sector both presently and in the future. The primary focus of these improvements is undoubtedly in the field of engine efficiency. The gas exchange system is of major importance in this respect. The inlet and exhaust flows as the cylinder is emptied and filled will significantly influence the pumping work of the engine. At the center of the gas exchange system is the turbocharger. The turbine stage of the turbocharger can utilize the energy in the exhaust flow by expanding the exhaust gases in order to power the compressor stage of the turbocharger.If turbocharger components can operate at high efficiency, it is possible to achieve high engine efficiency and low fuel consumption. Low exhaust pressure during the exhaust stroke combined with high pressure at the induction stroke results in favorable pumping work. For the process to work, a systems-based approach is required as the turbocharger is only one component of the engine and gas exchange system.In this thesis, the implications of turbocharger turbine stage design with regards to exhaust energy utilization have been extensively studied. Emphasis has been placed on the turbine stage in a systems context with regards to engine performance and the influence of exhaust system components.The most commonly used turbine stage in turbochargers, the radial turbine, is associated with inherent limitations in the context of exhaust energy utilization. Primarily, turbine stage design constraints result in low efficiency in the pulsating exhaust flow, which impairs the gas exchange process. Gas stand and numerical evaluation of the common twin scroll radial turbine stage highlighted low efficiency levels at high loadings. For a pulse-turbocharged engine with low exhaust manifold volume, the majority of extracted work by the turbine will occur at high loadings, far from the optimum efficiency point for radial turbines. In order for the relevant conditions to be assessed with regards to turbine operation, the entire exhaust pulse must be considered in detail. Averaged conditions will not capture the variability in energy content of the exhaust pulse important for exhaust energy utilization.Modification of the radial turbine stage design in order to improve performance is very difficult to achieve. Typical re-sizing with modifying tip diameter and trim are not adequate for altering turbine operation into high efficiency regions at the energetic exhaust pulse peak.The axial turbine type is an alternative as a turbocharger turbine stage for a pulse-turbocharged engine. The axial turbine stage design can allow for high utilization of exhaust energy with minimal pressure interference in the gas exchange process; a combination which has been shown to result in engine efficiency improvements compared to state-of-the-art radial turbine stages.
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| 7. |
- Anton, Nicholas, et al.
(författare)
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Exhaust volume dependency of turbocharger turbine design for a heavy duty otto cycle engine
- 2017
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Ingår i: Proceedings of the ASME Turbo Expo. - : ASME Press. - 9780791850800
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Konferensbidrag (refereegranskat)abstract
- This study is considering turbocharger turbine performance at "on-engine" conditions with respect to turbine design variables and exhaust manifold volume. The highly unsteady nature of the internal combustion engine will result in a very wide range of turbine operation, far from steady flow conditions. As most turbomachinery design work is conducted at steady state, the influence of the chosen turbine design variables on the crank-angle-resolved turbine performance will be of prime interest. In order to achieve high turbocharger efficiency with the greatest benefits for the engine, the turbine will need high efficiency at the energetic exhaust pressure pulse peak. The starting point for this paper is a target full load power curve for a heavy duty Otto-cycle engine, which will dictate an initial compressor and turbine match. Three radial turbine designs are investigated, differing with respect to efficiency characteristics, using a common compressor stage. The influence of the chosen turbine design variables considering a main contributor to unsteadiness, exhaust manifold volume, is evaluated using 1D engine simulation software. A discussion is held in conjunction with this regarding the efficiency potential of each turbine design and limitations of turbine types.
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| 8. |
- Anton, Nicholas, et al.
(författare)
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ON THE CHOICE OF TURBINE TYPE FOR A TWIN-TURBINE HEAVY-DUTY TURBOCHARGER CONCEPT
- 2018
-
Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : AMER SOC MECHANICAL ENGINEERS. ; 8
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Konferensbidrag (refereegranskat)abstract
- In this study, a fundamental approach to the choice of turbocharger turbine for a pulse-charged heavy-duty diesel engine is presented. A standard six-cylinder engine build with a production exhaust manifold and a Twin-scroll turbocharger is used as a baseline case. The engine exhaust configuration is redesigned and evaluated in engine simulations for a pulse-charged concept consisting of a parallel twin-turbine layout. This concept will allow for pulse separation with minimized exhaust pulse interference and low exhaust manifold volume. This turbocharger concept is uncommon, as most previous studies have considered two stage systems, various multiple entry turbine stages etc. Even more rare is the fundamental aspect regarding the choice of turbine type as most manufacturers tend to focus on radial turbines, which by far dominate the turbochargers of automotive and heavy-duty applications. By characterizing the turbine operation with regards to turbine parameters for optimum performance found in literature a better understanding of the limitations of turbine types can be achieved. A compact and low volume exhaust manifold design is constructed for the turbocharger concept and the reference radial turbine map is scaled in engine simulations to a pre-set AFR-target at a low engine RPM. By obtaining crank-angle-resolved data from engine simulations, key turbine parameters are studied with regard to the engine exhaust pulse-train. At the energetic exhaust pressure pulse peak, the reference radial turbine is seen to operate with suboptimum values of Blade-Speed-Ratio, Stage Loading and Flow Coefficient. The study concludes that in order to achieve high turbine efficiency for this pulse-charged turbocharger concept, a turbine with efficiency optimum towards low Blade-Speed Ratios, high Stage Loading and high Flow Coefficient is required. An axial turbine of low degree of reaction-design could be viable in this respect.
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| 9. |
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| 10. |
- Anton, Nicholas, et al.
(författare)
-
Twin-Scroll turbocharger turbine stage evaluation of experimental data and simulations
- 2018
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Ingår i: Institution of Mechanical Engineers - 13th International Conference on Turbochargers and. - : Institution of Mechanical Engineers. - 9781510873872 ; , s. 487-502
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Konferensbidrag (refereegranskat)abstract
- In this study a novel comparison of CFD, measured data and a ID-model is presented for a Twin-scroll turbocharger turbine stage. Both full and single admission flow divisions were taken into consideration and shown to represent "on-engine" conditions in the high and low engine rpm range respectively for a heavy-duty 6-cylinder diesel engine. With this in mind, the turbine stage was evaluated for each flow division at several rotational speeds. Both high and low pressure ratios were run. Emphasis is made on high pressure ratios as it is the most relevant case with regards to the energy levels of the exhaust flow. The purpose of the study was to gain insight into the differences and similarities between gas stand measurements, a ID-model and CFD considering performance and turbine stage parameters. The study concludes that the results from the measurements in the gas stand and ID-model, obtained best correlation with the CFD results at low turbine pressure ratios. At high pressure ratios significant deviations were observed. In order to check for discrepancies, both frozen rotor and stage interfaces were considered in the CFD-model, with an additional variant taking the rotor-volute tongue clocking into account. All interfaces resulted in the same trends, although the frozen rotor approach provided the best correlation with measured data. The clocking effect was seen not to affect the results to a great extent in this case. The main difference between the CFD and measurements in combination with the ID model-prediction primarily occur at the rotor inlet. The pressures were predicted to be substantially higher by the CFD calculations due to reduced pressure losses in the volute. Especially taking effect at high turbine pressure ratios which is most relevant for turbocharger applications and therefor the mapping process in the gas stand. This can be one of the reasons for significant deviations in efficiency, turbine parameters etc. at high pressure ratios as effectively more energy will be available to the rotor for a given turbine stage pressure ratio. In general best coherence was achieved for the full admission case. Even so, trends of main parameters such as efficiency, flow capacity and turbine parameters point in the same direction comparing CFD with calculations and measured results for both full and single admission.
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| 11. |
- Csontos, Botond, et al.
(författare)
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A Measurement of Fuel Filters' Ability to Remove Soft Particles, with a Custom-Built Fuel Filter Rig
- 2020
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; :2020
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Tidskriftsartikel (refereegranskat)abstract
- Biofuel can enable a sustainable transport solution and lower greenhouse gas emissions compared to standard fuels. This study focuses on biodiesel, implemented in the easiest way as drop in fuel. When mixing biodiesel into diesel one can run into problems with solubility causing contaminants precipitating out as insolubilities. These insolubilities, also called soft particles, can cause problems such as internal injector deposits and nozzle fouling. One way to overcome the problem of soft particles is by filtration. It is thus of great interest to be able to quantify fuel filters' ability to intercept soft particles. The aim of this study is to test different fuel filters for heavy-duty engines and their ability to filter out synthetic soft particles. A custom-built fuel filter rig is presented, together with some of its general design requirements. For evaluation of the efficiency of the filters, fuel samples were taken before and after the filters. The fuel samples were analyzed with gas chromatography-mass spectrometry (GC-MS) and x-ray fluorescence spectroscopy (XRF) to estimate the soft particle removal efficiency of each fuel filter. Furthermore, the pressure drop across the filters was measured, to provide an indication about their plugging potential. Results are presented about the concentration dependency of synthetic soft particles, both regarding pressure drop and efficiency of removal. Finally, different fuel filter materials were compared regarding their efficiency to remove soft particles. The results of this paper show the basic concepts of how soft particles can be examined in a laboratory scale fuel filter rig, and show a first estimate about the capabilities of soft particle removal by currently available fuel filters.
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| 12. |
- Csontos, Botond, et al.
(författare)
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Characterization of Deposits Collected from Plugged Fuel Filters
- 2019
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2019:September
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Tidskriftsartikel (refereegranskat)abstract
- Fuel filters serve as a safety belt for modern compression ignition engines. To meet the requirements from environmental regulations these engines use the common rail injection system, which is highly susceptible to contamination from the fuel. Furthermore, the public awareness towards global warming is raising the need for renewable fuels such as biodiesel. An increased fuel variety brings a higher requirement for fuel filters as well. To better understand the process of filtration, awareness of the different possible contaminants from the field is needed. This study used several chemical characterization techniques to examine the deposits from plugged fuel filters collected from the field. The vehicle was run with a biodiesel blend available on the market. The characterization techniques included X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR) joined with attenuated total reflectance (ATR) sampling, gas chromatography-mass spectrometry (GC-MS), and lastly thermal gravimetric analyzer combined with FTIR and a GC-MS (TGA/FTIR/GC-MS). In addition the remaining ash from TGA was measured in energy-dispersive X-ray spectroscopy (EDX). Deposits were scraped from the used filter, and prepared for the different analytic methods. After cleaning the deposits with different solvents, GC-MS identified the traces of glycerol and sterols in the filter. After a transesterification reaction GC-MS could identify carboxylates corresponding to degraded biodiesel. The TGA/FTIR/GC-MS revealed the presence of polymeric compounds in the deposit. XRF did not require any previous cleaning, and was used to identify different metals present in the deposits. The mentioned deposits are characterized as soft particles, and could originate from the impurities of biodiesel, presence of engine oils, or degradation of the fuel. The presented results help to better understand the current concerns with the on-board filtration of fuels, and can help to create more robust fuel systems in the future.
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| 13. |
- Csontos, Botond, et al.
(författare)
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Factors Influencing the Formation of Soft Particles in Biodiesel
- 2020
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; :2020
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Tidskriftsartikel (refereegranskat)abstract
- In order to mitigate the effect of fossil fuels on global warming, biodiesel is used as drop in fuel. However, in the mixture of biodiesel and diesel, soft particles may form. These soft particles are organic compounds, which can originate from the production and degradation of biodiesel. Further when fuel is mixed with unwanted contaminants such as engine oil the amount soft particles can increase. The presence of these particles can cause malfunction in the fuel system of the engine, such as nozzle fouling, internal diesel injector deposits (IDID) or fuel filter plugging. Soft particles and the mechanism of their formation is curtail to understand in order to study and prevent their effects on the fuel system. This paper focuses on one type of soft particles, which are metal soaps. More precisely on the role of the short chain fatty acids (SCFA) during their formation. In order to do so, aged and unaged B10 was studied. The fuel matrixes were mixed with a calcium source such as calcium oxide (CaO), calcium carbonate (CaCO3) and engine oil. The importance of SCFA was studied by influencing the presence of the acids, by degrading the fuel, by the addition of formic acid and by inert gas bubbling. The created deposits and fuels mixtures were examined with the use of pH measurements, Fourier-transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS) and ion chromatography (IC). Opposed to the expectations, the results indicate that SFCA in not the most important factor for the formation of soft particles. It is shown that the calcium sources influenced the consistency and amount of the created soft particles. From the tested contaminants, CaO showed the highest yield towards precipitates. While degradation of the fuels showed to be the most important factor to form soap type soft particles.
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| 14. |
- Giramondi, Nicola, 1991-, et al.
(författare)
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Evaluation of the Ethanol-Diesel Spray Interaction during Ignition in a Dual-Fuel DICI Engine Using an Experimentally Validated CFD Model
- 2021
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Ingår i: SAE Technical Paper 2021-01-0521. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- The ignition dynamics of an ethanol-diesel direct injection compression ignition engine is investigated based on 3D RANS simulations. Experimental results of a previous test campaign on a single-cylinder research engine equipped with two direct injectors are used to validate the CFD model. Four reference engine conditions are considered, including split and overlapped injections of ethanol and diesel at low and high load. Combustion driven by the separate direct injection of pure ethanol and diesel as pilot fuel is simulated with AVL Fire and AVL Tabkin adopting the flamelet generated manifold combustion model. The in-cylinder pressure and apparent rate of heat release traces computed in the simulations are found to be consistent with the corresponding experimental results. The influence of several simulation input parameters on ethanol combustion characteristics is evaluated, highlighting a high sensitivity to the initial in-cylinder temperature and a limited impact of the swirl number. The spatial and temporal interaction between ethanol and diesel sprays during ignition is investigated based on simulation results of in-cylinder flow features. Under the engine conditions considered in this study, ethanol ignition is found to originate within the spray plumes adjacent to the burning diesel sprays and to subsequently propagate towards the other ethanol sprays. The peak sequence identified in the ARoHR traces of experiments and simulations corresponds to the ignition sequence of the ethanol sprays. The coupling between experimental and simulation results allowed to achieve a detailed understanding of the ignition dynamics of an ethanol-diesel DICI engine. The validated simulation model will enable the performance evaluation of alternative hardware configurations of the dual-injector system.
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| 15. |
- Hong, Beichuan, Ph.D. student, 1989-, et al.
(författare)
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Quantification of Losses and Irreversibilities in a Marine Engine for Gas and Diesel Fuelled Operation Using an Exergy Analysis Approach
- 2020
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Konferensbidrag (refereegranskat)abstract
- Large bore marine engines are a major source of fossil fuel consumption in the transport sector. The development of more efficient and cleaner marine engine systems are always required. Exergy analysis is a second-law based approach to indicate the maximum amount of work obtainable from a given system.In this study, an exergy analysis is used to identify losses and improvement potential of a large bore Wärtsilä 31DF four-stroke marine engine system with two-stage turbocharging. An exergy-based framework is implemented on a calibrated 1D engine model to view the evolution of exergy flow over each engine sub-system while operating on different load points fuelled with natural gas and diesel separately.The overall distributions of engine energy and exergy are initially compared at a systematic level regarding the impact of fuel mode and operating load. Furthermore, the engine irreversibilities are characterized as three types: combustion, heat dissipation, and gas exchange losses. The first type, combustion irreversibility, is the largest source of engine exergy losses amounting to at least 25% of fuel exergy. A crank resolved analysis showed that premixed gas combustion produces lower exergy losses compared to diesel diffusion combustion. The second type, thermal exergy transferred and destroyed by heat losses, are summarized for the entire engine system. From the exergy view, the charge coolers present an opportunity to recover about 9% of the brake power at full load. The last type, gas exchange losses, are categorized by accounting the flow losses caused by the valve throttling, fluid friction in pipes and the irreversibility of the two-stage turbocharging system. Most of exergy destruction in gas paths occurs at turbocharging system, where the high pressure turbocharger contributes to around 40% of the total flow exergy destruction.
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| 16. |
- Karuppasamy, Arun Prasath, et al.
(författare)
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Agglomeration and Nucleation of Non-VolatileParticles in a Particle Grouping Exhaust Pipe of a Euro VI Heavy-Duty Diesel Engine
- 2019
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Ingår i: SAE Technical Paper Series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- The possibility of non-volatile particle agglomeration in engine exhaust was experimentally examined in a Euro VI heavy duty engine using a variable cross section agglomeration pipe, insulated and double walled for minimal thermophoresis. The agglomeration pipe was located between the turbocharger and the exhaust treatment devices. Sampling was made across the pipe and along the centre-line of the agglomeration pipe. The performance of the agglomeration pipe was compared with an equivalent insulated straight pipe. The non-volatile total particle number and size distribution were investigated. Particle number measurements were conducted according to the guidelines from the Particle Measurement Programme. The Engine was fuelled with commercially available low sulphur S10 diesel. Experiments conducted in heavy duty engine relevant operating points were done to sweep the effect of (i) Mass flow rate in the exhaust (ii) Temperature in the exhaust and (iii) Engine speed and thus exhaust pressure pulsation frequencies in the exhaust. The test matrix included eleven operating points at steady-state. The results show that, using the agglomeration pipe, neither significant non-volatile particle reduction nor noticeable change in particle size distribution could be proven. In the current study, nucleation of non-volatile particles could not be observed along the straight pipe. Furthermore, it was found that the variable cross-section agglomeration pipe and straight pipe showed similar results in the total particle number and particle size distribution with respect to non-volatile particles.
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| 17. |
- Karuppasamy, Arun Prasath, et al.
(författare)
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Comparison of Two Dilution and Conditioning Systems for Particle Number Measurements along the Exhaust After-Treatment System of an HD Diesel Engine
- 2021
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Ingår i: SAE Technical Paper 2021-01-0619, 2021.. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- In heavy-duty engines, Euro VI legislation regulates the total particle number (PN) in the exhaust based on the particle measurement program (PMP) guidelines. By PMP directives, the exhaust sample is diluted and conditioned to contain non-volatile particles before measuring the PN. The fraction of non-volatile and volatile particles changes along the exhaust after-treatment system and could affect the total PN measured. Therefore, it is of interest to compare the performance of the dilution systems at different positions along the after-treatment system. For this purpose, a standard PMP compliant two-stage dilution system (DS1) with evaporation tube (ET) was compared with a close coupled two-stage ejector dilution system (DS2). In DS2, the non-volatile PN was measured with a dilution temperature of 350°C (same as the DS1 ET temperature) while the volatile PN was measured with a dilution temperature of 150°C. Experiments were carried out on a heavy-duty Euro VI engine equipped with an after-treatment system consisting of diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and selective catalytic reduction (SCR) unit (with AdBlue injection) followed by ammonia slip catalyst. Sampling was made at four locations along the exhaust after-treatment system while varying the exhaust conditions namely temperature, flow rate and fuel injection pressure to vary the total PN concentration and the fraction of nucleation and accumulation mode particles from the engine. The total PN was measured using a condensation particle counter (CPC) and the particle number distribution using an Engine Exhaust Particle Sizer spectrometer (EEPS). An overall comparison shows that at higher fractions of nucleation mode particles, before the DPF, DS1 exhibited losses in nucleation mode particle in comparison with DS2. Whereas after the DPF, the loss was minimal. After the SCR, the nucleation of salt particles during excess AdBlue injection events was captured only by DS1. During motoring operation, emitting high volatile particle concentration, DS2's capacity does not seem to suffice to fully evaporate the volatile material as DS2 relies on the heat capacity of hot dilution air whereas DS1 uses an externally powered heater.
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| 18. |
- Karuppasamy, Arun Prasath, et al.
(författare)
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On the Effects of Turbocharger on Particle Number and Size Distribution in a Heavy - Duty Diesel Engine
- 2021
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Ingår i: SAE International Journal of Advances and Current Practices in Mobility. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 2641-9637 .- 2641-9645. ; 3:2, s. 882-893
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Tidskriftsartikel (refereegranskat)abstract
- Particles emitted from internal combustion engines have adverse health effects and the severity varies based on the particle size. A diesel particulate filter (DPF) in the after-treatment systems is employed to control the particle emissions from combustion engines. The design of a DPF depends on the nature of particle size distribution at the upstream and is important to evaluate. In heavy-duty diesel engines, the turbocharger turbine is an important component affecting the flow and particles. The turbine wheel and housing influence particle number and size. This could potentially be used to reduce particle number or change the distribution to become more favourable for filtration. This work evaluates the effect of a heavy-duty diesel engine's turbine on particle number and size distribution. The particle number (PN) emissions is measured with regard to varying turbine inlet conditions namely: turbine inlet temperature, exhaust mass flow rate and particle concentration at the turbine inlet (by varying fuel injection pressures). It was found that at turbine inlet temperatures of 200°C, PN remains almost constant as the particles were assumed to be held together by the volatile material. However, at 300°C there was an increase in PN across the turbine, and the increase was higher at higher mass flow rates across the turbine. Furthermore, lower injection pressures exhibited a higher rise in PN across the turbine. Interestingly, at 400°C, a reduction in PN across the turbine was observed due to oxidation. This reduction in PN was lesser while there was an increase in mass flow rate. Additionally, with higher injection pressures, a higher reduction in PN was noticed. This result is promising as catalyst coated turbine wheels could potentially enhance the effect thereby reducing PN before the after-treatment system.
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| 19. |
- Karuppasamy, Arun Prasath, et al.
(författare)
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On the Effects of Urea and Water Injection on Particles across the SCR Catalyst in a Heavy -Duty Euro VI Diesel Engine
- 2020
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Ingår i: SAE Technical Paper. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- Particle emissions from heavy-duty engines are regulated both by mass and number by Euro VI regulation. Understanding the evolution of particle size and number from the exhaust valve to the tail pipe is of vital importance to expand the possibilities of particle reduction. In this study, experiments were carried out on a heavy-duty Euro VI engine after-treatment system consisting of diesel oxidation catalyst, diesel particulate filter and selective catalytic reduction (SCR) unit with AdBlue injection followed by ammonia slip catalyst. The present work focusses on the SCR unit with regard to total particle number with and without nucleation particles both. Experiments were conducted by varying the AdBlue injection quantity, SCR inlet temperature [to vary the reaction temperature], exhaust mass flow rate [to vary the residence time in SCR], and fuel injection pressures [to vary inlet particle number and inlet NOx]. Sampling for particle measurements was performed at the inlet, upstream of the urea injector and the outlet of the SCR. Particle measurements were made using two different two-stage dilution systems, for measuring non-volatile and volatile particles, respectively. The total particle number (PN) was measured using two different condensation particle counters (CPC), one with the cut-off size at 23nm and another with a cut-off size at 7 nm to capture nuclei mode particles. An increase in the total number of particles was observed at 400°C and 1200 bar of fuel injection pressure with the higher AdBlue injection quantities compared to the dry-run SCR. At 400°C, a surge in nucleation occurs irrespective of the fuel injection pressures. An experiment was also made to isolate the water droplets effect on PN from nitrate formation. The SCR was injected with de-ionized water and a PN reduction was observed across the SCR and the reduction was higher with higher inlet PN to the SCR.
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| 20. |
- Karuppasamy, Arun Prasath, 1988-
(författare)
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Particle Characterization in the Exhaust Devices of Direct Injection Engines
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Minimizing pollutants are of utmost importance to ensure sustainability in transportation. Particle emissions from internal combustion engines are especially harmful to human health, while also contributing to global warming. In an effort to counteract climate change and enhance air quality, various technological solutions are currently being scrutinized with the objective to abate transport emissions. Increasing focus has been directed towards electric powertrain solutions, prompting the development of battery technology, charging systems and power grid infrastructure. However, given the present uncertainty around the time and resources required for the electrification of heavy-duty transport, it would be worth investigating advanced solutions for reducing tailpipe emissions from internal combustion engine vehicles. This current research work investigates the evolution of exhaust particles along the exhaust and after-treatment system of a heavy-duty engine. The findings presented in this thesis can be used for devising effective particle emission mitigation techniques. The impact on particle number (PN) and distribution was evaluated for individual exhaust system devices, namely: a periodic particle grouping pipe, a turbocharger turbine, and a selective reduction catalyst (SCR). A specially designed periodic particle grouping pipe, intended to increase particle grouping did not prompt particulate grouping and the reduction of non-volatile particle number in the exhaust system. Particles smaller than 50 nm were observed to be predominant in the exhaust stream and showed no relevant response to induced periodic grouping. Exhaust conditions such as temperature, flow-rate and initial particle concentration influence the number and distribution of particles entering the turbine of the turbocharger. At low loads, the turbine caused particle fragmentation due to impingement, increasing the PN in size range 30 to 200 nm. On the other hand, temperatures above 400°C at the turbine inlet promoted soot oxidation, enabling the reduction of the PN at high loads.When operating the engine at high loads with increased NOx emissions and high exhaust temperatures, excess urea injection upstream of the SCR catalyst triggered the formation of ammonium salts in the exhaust stream. Subsequently, a surge in particles less than 23 nm was observed across the SCR catalyst, leading to a NOx-PN trade off.As the nature of particle emissions changes along the after-treatment system, sample conditioning may affect PN readings. To this purpose, the impact of sample conditioning procedure and of the adopted diluter type on PN measurements was also investigated. PN measurements were carried out using two different dilutions systems: a two-stage rotating disk diluter with an evaporation tube and a two-stage ejector diluter with hot air dilution. Motoring tests outlined that volatile particle removal is enhanced using the rotating disk diluter.In conclusion, it is not only the DPF which impacts tailpipe emissions, but also the turbocharger turbine and the SCR under certain conditions. A comprehensive method has been devised and presented to select a suitable dilution and conditioning system while evaluating PN measurements in the exhaust devices.
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| 21. |
- Larsson, Tara, 1993-, et al.
(författare)
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A Batch Blending System for Continuous Production of Multi-Component Fuel Blends for Engine Laboratory Tests
- 2020
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Ingår i: SAE International Journal of Advances and Current Practices in Mobility. - SAE : SAE International. - 2641-9645.
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Konferensbidrag (refereegranskat)abstract
- The increased rates of research on complex fuel blends in engine applications poses a need for more efficient and accurate fuel blending processes in engine laboratories. Making the fuel blending process automatic, effective, accurate and flexible saves time, storage space and cost without compromising the tests of future fuel alternatives. To meet these requirements, an automatic fuel blending system, following a sequential batch process, was designed and tested for engine laboratory application.The fuel blending system was evaluated in terms of functionality, safety, accuracy and repeatability. The functionality and safety was evaluated through a risk analysis. Whereas, the accuracy and repeatability of the system was investigated through blend preparation tests. The results show that the minimum fuel mass limitation of the system is 0.5 kg. This allows for blends with fuel ratios as low as 7 vol-% to be prepared by the system. The mean relative errors for all tested fuels are below 5% by mass, enabling a wide range of fuels to be used in the system. The absolute error in fuel ratio is 0.5 vol-% or less. In addition, the relative error in fuel ratio of the prepared blends is below 4% for all but one of the tested blends. Moreover, the system can prepare all of the tested fuel blends in 5 minutes.
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| 22. |
- Larsson, Tara, 1993-, et al.
(författare)
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Future Fuels for DISI Engines: A Review on Oxygenated, Liquid Biofuels
- 2019
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Ingår i: SI Combustion. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- Global warming and climate change have led to a greater interest in the implementation of biofuels in internal combustion engines. In spark ignited engines, biofuels have been shown to improve efficiency and knock resistance while decreasing emissions of unburned hydrocarbons, carbon monoxide and particles.This study investigates the effect of biofuels on SI engine combustion through a graphical compilation of previously reported results. Experimental data from 88 articles were used to evaluate the trends of the addition of different biofuels in gasoline. Graphs illustrating engine performance, combustion phasing and emissions are presented in conjunction with data on the physiochemical properties of each biofuel component to understand the observed trends.Internal combustion engines have the ability to handle a wide variety of fuels resulting in a broad range of biofuel candidates. Three groups of oxygenated liquid biofuels were investigated in this review: alcohols, ethers and furans. While the investigated alcohols showcase properties associated with increased engine efficiencies (such as higher chemical knock resistance, greater charge cooling and faster laminar flame speeds). They also pose the challenge of greater fuel consumption due to lower energy densities than gasoline. Ethers and furans, on the other hand are favored by current engine designs as they exhibit properties (such as the energy density) closer to gasoline alongside increased chemical knock resistance.The compiled data summarizes the possibilities to improve efficiency and fuel economy for biofuel and binary blends in SI engines. However, the results also, show that some of the trends are more complex than anticipated. The effect of biofuels on combustion speed, regulated emissions and exhaust temperatures are not proven to be as self-evident as reported in previous studies. Results on multiple blends with focus on the effect of blending on properties would help improve the picture of the effect of future fuels on SI combustion.
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| 23. |
- Larsson, Tara, 1993-, et al.
(författare)
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The Effect of Pure Oxygenated Biofuels on Efficiency and Emissions in a Gasoline Optimised DISI Engine
- 2021
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:13, s. 3908-
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Tidskriftsartikel (refereegranskat)abstract
- The negative impact of transport on climate has led to incentives to increase the amount of renewable fuels used in internal combustion engines (ICEs). Oxygenated, liquid biofuels are promising alternatives, as they exhibit similar combustion behaviour to gasoline. In this article, the effect of the different biofuels on engine efficiency, combustion propagation and emissions of a gasoline-optimised direct injected spark ignited (DISI) engine were evaluated through engine experiments. The experiments were performed without any engine hardware modifications. The investigated fuels are gasoline, four alcohols (methanol, ethanol, n-butanol and iso-butanol) and one ether (MTBE). All fuels were tested at two speed sweeps at low and mid load conditions, and a spark timing sweep at low load conditions. The oxygenated biofuels exhibit increased efficiencies, even at non-knock-limited conditions. At lower loads, the oxygenated fuels decrease CO, HC and NOx emissions. However, at mid load conditions, decreased volatility of the alcohols leads to increased emissions due to fuel impingement effects. Methanol exhibited the highest efficiencies and significantly increased burn rates compared to the other fuels. Gasoline exhibited the lowest level of PN and PM emissions. N-butanol and iso-butanol show significantly increased levels of particle emissions compared to the other fuels
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| 24. |
- Larsson, Tara, 1993-, et al.
(författare)
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Undiluted Measurement of sub 10 nm Non-Volatile and Volatile Particle Emissions from a DISI Engine Fueled with Gasoline and Ethanol
- 2021
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Ingår i: Undiluted Measurement of sub 10 nm Non-Volatile and Volatile Particle Emissions from a DISI Engine Fueled with Gasoline and Ethanol. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- In this paper, a High-Temperature Electrical Low-Pressure Impactor (HT-ELPI+) was used to measure particles from a light-duty direct injected spark ignited (DISI) engine fueled with gasoline and ethanol. The HT-ELPI+ measured volatile and non-volatile particle emissions down to 6 nm without the need for dilution. Particle emissions were measured at four operating points while sweeping the end of injection, and at idle operation. The total particle number (PN) and particle size distribution (number and mass) for both non-volatile and volatile emissions were measured with the HT-ELPI+ and compared to the measured PN using two 71.4 times diluted Condensation Particle Counters (CPCs) with two different cut-off sizes, with 23 nm and 7 nm cut-off, respectively. The results show an increase in particle emissions in terms of particle mass and total particle number for ethanol compared to gasoline. The difference in soot mass emissions is small between the fuels. However, PN shows a significant increase for ethanol, especially at low engine speed due to a deterioration in the evaporation, mixture formation and air entrainment of ethanol. A majority of the emitted particles exhibit particle sizes below 23 nm, wherein the highest numbers occurred below 10 nm. At steady-state operation, no clear difference was observed between the diluted and undiluted measurements. On the contrary, a significant difference is detected between the undiluted and diluted measurements of ethanol at idle. These observations could indicate a greater significance of dilution at lower exhaust gas temperatures and mass flow rates or when a large number of nucleation mode particles are emitted from the engine.
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| 25. |
- Larsson, Tara, 1993-, et al.
(författare)
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Undiluted Measurement of the Particle Size Distribution of Different Oxygenated Biofuels in a Gasoline-Optimised DISI Engine
- 2021
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- The utilisation of internal combustion engines is one of the main causes of particle emissions in urban areas. As the interest for the utilisation of biofuels increases, it is important to understand their effect on particle number emissions. In this paper, the particle size distribution and the particle number emissions from a gasoline-optimised direct-injected spark-ignited (DISI) engine are investigated. The effects of five different biofuel alternatives on these emissions were evaluated and compared to gasoline. The utilisation of the high-resolution, high-temperature ELPI+ enabled undiluted measurements of the particle size distribution down to 6 nm, without extensive cooling of the engine exhaust. Contrary to other studies, the results show that the particle number emissions for the three measured cut-off sizes (23, 10 and 7 nm) increased with the utilisation of oxygenated biofuels. The results indicate that the decreased volatility and energy density of the alcohols has a more significant impact on the particle formation in a DISI engine than the increased oxygen content of these fuels.
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| 26. |
- Mahendar, Senthil, et al.
(författare)
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Alcohol lean burn in heavy duty engines: Achieving 25 bar IMEP with high efficiency in spark ignited operation
- 2021
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 22:11, s. 3313-3324
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Tidskriftsartikel (refereegranskat)abstract
- Knock is the most crucial limitation in attaining the peak load required at high efficiency in heavy duty (HD) spark ignition (SI) engines. Renewable fuels such as ethanol and methanol have high resistance to autoignition and can help overcome this limitation. To reduce knock and improve efficiency further, dilution can be used to add specific heat capacity and reduce combustion temperature. This work studied diluted combustion and knock characteristics of gasoline, ethanol, and methanol on a HD SI single cylinder engine for a wide load range. Ethanol and methanol displayed excellent knock resistance which allowed a peak gross IMEP of 25.1 and 26.8 bar respectively, compared to gasoline which only reached 8.3 bar at [Formula: see text]1.4 with a compression ratio of 13. Over 18% increase in gross IMEP was possible for gasoline and ethanol when increasing air excess ratio from 1 to 1.4. Methanol achieved the target gross IMEP at [Formula: see text]1 and required no spark retard at [Formula: see text]1.6. A peak indicated efficiency above 48% was recorded for ethanol and methanol at [Formula: see text]1.6 and gross IMEP of approximately 21 bar. At part loads, stable operation was possible until [Formula: see text]1.8 for all fuels. Increase in intake temperature showed a marginal improvement in stability but no increase in lean limit. The concept shows promise as diluted combustion of ethanol and methanol reduced knock and achieved diesel baseline load. With optimization, there is potential to improve efficiency further and possible cost savings compared to commercial diesel engines.
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| 27. |
- Mahendar, Senthil, et al.
(författare)
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Challenges for Spark Ignition Engines in Heavy Duty Application: A Review
- 2018
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- Spark Ignition (SI) engines operating on stoichiometric mixtures can employ a simple three-way catalyst as after-treatment to achieve low tailpipe emissions unlike diesel engines. This makes heavy duty (HD) SI engines an attractive proposition for low capital cost and potentially low noise engines, if the power density and efficiency requirement could be met. Specific torque at low speeds is limited in SI engines due to knock. In HD engines, the higher flame travel distances associated with higher bore diameters exacerbates knock due to increased residence time of the end gas. This report reviews the challenges in developing HD SI engines to meet current diesel power density. It also focuses on methods to mitigate them in order to achieve high thermal efficiency while running on stoichiometric condition. High octane renewable fuels are seen as a key enabler to achieve the performance level required in such applications. Apart from higher octane rating, the effect of higher latent heat of vaporization in liquid alcohol fuels was found to be beneficial in all operating conditions as it tended to reduce in-cylinder temperature and associated heat loss of the engine. Exhaust gas recirculation (EGR) was seen to be beneficial both at full load in limiting knock and part load conditions to decrease pumping losses. Increased in-cylinder turbulence was also seen to be beneficial in limiting knock as it reduces residence time of the end gas. Results and trends of combinations of these factors are discussed with respect to increasing engine specific torque and efficiency. The effect on emissions and part load conditions is included where results are available and gaps in knowledge are presented.
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| 28. |
- Mahendar, Senthil Krishnan, 1988-
(författare)
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Mitigating Knock in Heavy Duty Spark Ignition Engines : Experiments and simulations of diluted ethanol and methanol combustion
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To effectively reduce fossil fuel dependence in the transport sector, an unprecedented increase in renewable fuel production is required. Short chain alcohols, such as ethanol and methanol, are well placed as they can be produced in a variety of renewable pathways from most carbon sources. Due to its high autoignition resistance, ethanol and methanol cannot be used as drop-in fuels in compression ignition engines that are prevalent in the heavy duty (HD) transport sector but can be an immense advantage when used in HD spark ignition (SI) engines.One crucial disadvantage experienced by HD SI engines is the end gas autoignition or knock which limits engine load, compression ratio and efficiency. It was not established if ethanol and methanol can in fact achieve the required load range in HD SI engines and if so, how efficient they would be. Diluting the air-fuel mixture with excess air or exhaust gas recirculation can add knock resistance by lowering in-cylinder temperature. Though dilution increases load and efficiency, it also increases instability and ultimately causes misfires. In this thesis, diluted combustion, knock limit and performance of ethanol and methanol was studied using a single cylinder heavy duty research engine. The required load was achieved with relatively good efficiency at lean operation and potential for improving efficiency further was investigated using 1D simulations. The modifications needed to utilize a semi-predictive combustion model in diluted operation were presented. Using simulations, the impact of turbulence on the performance of Miller valve timing and the effect of squish area on piston shapes to improve turbulence was discussed. With Miller timing and fast combustion using high squish pistons, lean burn ethanol and methanol can offer high efficiency, on par with compression ignition engines. If ethanol or methanol production can be scaled up, HD SI engines can provide good performance, low capital and operating cost for future transport.
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| 29. |
- Mahendar, Senthil Krishnan, et al.
(författare)
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Numerical Investigation of Increasing Turbulence through Piston Geometries on Knock Reduction in Heavy Duty Spark Ignition Engines
- 2019
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- Knock in heavy duty (HD) spark ignition (SI) engines is exacerbated by a large bore diameter and a higher flame travel distance. An increase in turbulence close to TDC can improve combustion speed and reduce knock through low residence time for end gas auto-ignition. Since HD SI engines are usually derived from diesel engines, it is common to have a swirl motion that does not dissipate into turbulence. To increase flame speed and limit knock, squish can be used to produce turbulence close to TDC. In this study, two different piston bowl geometries are examined: The re-entrant and quartette. The influence of squish area on turbulence production by these piston geometries were investigated using motored simulations in AVL FIRE. The effect of increased turbulence on knock reduction was analyzed using a calibrated 1D GT-Power model of a HD SI engine and the performance improvement was estimated. The effect of clearance height and input swirl level on turbulence was studied for both piston geometries to determine their sensitivity. A lower squish area quartette piston provided the same knock advantage corresponding to a higher squish area re-entrant piston due to additional turbulence production by swirl breakdown. With zero swirl, there was no difference in the turbulence produced by re-entrant and quartette pistons, however, a considerable increase in TKE was observed compared to the baseline swirl level re-entrant case as piston driven flow imparted more turbulence early in the compression stroke.
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| 30. |
- Mahendar, Senthil Krishnan, 1988-, et al.
(författare)
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Semi-Predictive Modeling of Diluted Ethanol and Methanol Combustion in Conventional Spark Ignition Operation
- 2021
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- Alcohols offer high resistance to autoignition which is necessary to attain the required load in heavy duty (HD) spark ignition (SI) engines. Dilution increases thermal efficiency and reduces propensity to autoignition making it an important combustion strategy. Reliable and robust prediction at increased dilution is necessary to support development of high efficiency spark ignition engines and the transition to renewable fuels. A previous experimental study demonstrated 25 bar gross IMEPg for ethanol and methanol at λ=1.4 excess air ratio and over 48% indicated efficiency at λ=1.6 on a single cylinder engine. Based on this dataset, a semi-predictive model (SITurb) was fitted for a range of excess air ratios and engine loads. With the default model, poor accuracy was observed above λ=1.4. Ignition delay was incorrectly predicted at λ=1.6 and λ=1.8. To improve the prediction at high dilution, an improved laminar flame speed correlation was included which reduced the ignition delay error to within ±3 CAD over the range of tested excess air ratios. To improve prediction of burn duration at high dilution, the turbulent flame speed calibration constant was made dependent on dilution level similar to previous research. With both improvements, under ±5% error in IMEPg and under ±3 CAD error in burn duration was achieved at all dilution levels. Finally, the Douaud and Eyzat knock model was evaluated with respect to full load operation of ethanol and methanol and its agreement to knock limited phasing discussed. Semi-predictive models are simple to implement and will be instrumental in gas exchange modeling and optimization of HD SI engines using future alcohol fuels. This study provides the accuracy of standard models and improvements needed to predict performance at diluted conditions.
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| 31. |
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| 32. |
- Mahendar, Senthil, et al.
(författare)
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The Impact of Miller Valve Timing on Combustion and Charging Performance of an Ethanol- and Methanol-Fueled Heavy-Duty Spark Ignition Engine
- 2021
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 14:5, s. 733-748
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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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| 33. |
- Thantla, Sandhya, et al.
(författare)
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Characterization of an organic Rankine cycle system for waste heat recovery from heavy-duty engine coolant and exhaust
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To meet the strict legislations imposed on carbon-dioxide emissions, organic Rankine cycle (ORC) waste heat recovery (WHR) technology is being extensively studied and applied in long haulage heavyduty (HD) truck engines. The focus of this paper isto characterize an ORC system of a HD long-haulage commercial truck engine that uses single and dual heat sources for WHR. The main objective of this work is to estimate the improvement in the system’s performance when the number of heat sources is increased. Two different WHR configurations: (i) integrated with the engine exhaust and (ii) integrated with both the engine coolant and the exhaust, are studied using the 1D simulation tool GT-Suite. Two types of scroll expanders, adopted from literature, are used in the ORC system configurations to analyze and compare their effect on the overall performance of the engine. Performance of the scroll expanders are generated from their semi-empirical models and R1233zD is used as the working fluid. With engine exhaust as the only heat source, both the expanders exhibit similar performance potentials at their optimum speeds. With two heat sources, fuel-saving is considerably improved, provided the coolant temperature is increased to 120°C and above. For the chosen conditions, expander A, at its optimum coolant temperature of 150oC, leads to around 5.7% fuel-saving; whereas, expander B, at its optimum coolant temperature of 130oC, leads to 5.5% fuel-saving. Further, this paper discusses the effect of expander speeds, expander volumes and superheating on the overall system efficiency.
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| 34. |
- Thantla, Sandhya, et al.
(författare)
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Performance Analysis of Volumetric Expanders in Heavy-Duty Truck Waste Heat Recovery
- 2019
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Ingår i: SAE Technical Paper Series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- With increasing demands to reduce fuel consumption and CO2 emissions, it is necessary to recover waste heat from modern Heavy Duty (HD) truck engines. Organic Rankine Cycle (ORC) has been acknowledged as one of the most effective systems for Waste Heat Recovery (WHR) due to its simplicity, reliability and improved overall efficiency. The expander and working fluid used in ORC WHR greatly impact the overall performance of an integrated engine and WHR system. This paper presents the effects of volumetric expanders on the ORC WHR system of a long haulage HD truck engine at a steady-state engine operating point chosen from a real-time road data. Performance of a long haulage HD truck engine is analyzed, based on the choice of three volumetric expanders for its WHR system, using their actual performance values. The expanders are: An oil-free open-drive scroll, a hermetic scroll and an axial piston expander with working fluids R123, R245fa and ethanol, respectively. Performance of the engine that accommodates the WHR system, with each expander and working fluid combination, is assessed based on the overall system efficiency that can be achieved through heat recovery from the engine exhaust. This simulation study is carried out using validated 0D models of the scroll expanders and performance data of the piston expander, adopted from literature, and a 1D system model of a long haulage HD truck engine encompassing a WHR system. Under the given conditions, the open-drive scroll expander (R123) leads to a higher system efficiency of 6.3% at an optimum expander speed of 3400 rpm with an estimated fuel saving of 3.6% in the vehicle under study. The hermetic scroll expander (R245fa) exhibits potential performance at higher rotational speeds; it leads to 5.4% system efficiency at 5000 rpm and 3% fuel-saving. The axial piston expander (ethanol) results in a consistent performance over a wide range of expander speeds. The effect of sizing a volumetric expander in improving the overall system efficiency is also investigated. This study provides insights on the suitability of volumetric expanders in HD truck WHR.
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