| 1. |
- Aghaali, Habib, 1981-, et al.
(författare)
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Evaluation of different heat transfer conditions on an automotive turbocharger
- 2014
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Ingår i: International Journal of Engine Research. - : Sage Publications. - 1468-0874 .- 2041-3149. ; 16:2, s. 137-151
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a combination of theoretical and experimental investigations for determining the main heat fluxes within a turbocharger. These investigations consider several engine speeds and loads as well as different methods of conduction, convection, and radiation heat transfer on the turbocharger. A one-dimensional heat transfer model of the turbocharger has been developed in combination with simulation of a turbocharged engine that includes the heat transfer of the turbocharger. Both the heat transfer model and the simulation were validated against experimental measurements. Various methods were compared for calculating heat transfer from the external surfaces of the turbocharger, and one new method was suggested.The effects of different heat transfer conditions were studied on the heat fluxes of the turbocharger using experimental techniques. The different heat transfer conditions on the turbocharger created dissimilar temperature gradients across the turbocharger. The results show that changing the convection heat transfer condition around the turbocharger affects the heat fluxes more noticeably than changing the radiation and conduction heat transfer conditions. Moreover, the internal heat transfers from the turbine to the bearing housing and from the bearing housing to the compressor are significant, but there is an order of magnitude difference between these heat transfer rates.
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| 2. |
- Alemahdi, Nika, et al.
(författare)
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Understanding the effect of Intake temperature on the ϕ-sensitivity of toluene-ethanol reference fuels and neat ethanol
- 2023
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 24:7, s. 2908-2920
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Tidskriftsartikel (refereegranskat)abstract
- The low-temperature combustion (LTC) is an attractive concept that enables the modem combustion engines to move toward sustainability mainly by increasing the efficiency and decreasing the emissions. The modern combustion engines which are working based on the LTC concept have specific fuel requirements. Fuel ϕ-sensitivity is a key factor to be considered for tailoring fuels for these engines. Fuel with a high ϕ-sensitivity are more responsive to thermal or fuel stratifications; the auto-ignition properties of different air-fuel mixtures of these fuels, with different equivalence ratio (ϕ), are more diverse. This diversity provide a smoother heat release rate in stratified condition. In this study 11 different toluene–ethanol reference fuels (TERFs) in three research octane number (RON) groups of 63, 84, and 105 together with neat ethanol are evaluated. The Lund ϕ-sensitivity method is used to evaluate these fuels in a cooperative fuel research (CFR) engine. The effect of variation of intake temperature on pressure sensitivity of fuel at a constant combustion phasing is evaluated. This evaluation is performed at two intake temperature of 373 and 423 K, and the results are compared with the outcome of the Lund ϕ-sensitivity number with the intake temperature of 323 K. This study shows that the CR sensitivity response of different blends to the intake charge temperature variation depends on the fuel composition. Accumulated low temperature heat release and latent heat of vaporization. It proves that the fuel ϕ-sensitivity will vary under different thermodynamic conditions. There was a clear link between the accumulated heat released during the early reaction and CR sensitivity of the blends at different intake temperature of 373 and 423 K but the link with the latent heat of vaporization (HoV) found to be inexplicit.
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| 3. |
- Babayev, Rafig, 1995, et al.
(författare)
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Computational optimization of a hydrogen direct-injection compression-ignition engine for jet mixing dominated nonpremixed combustion
- 2022
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 23:5, s. 754-768
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen (H2) nonpremixed combustion has been showcased as a potentially viable and preferable strategy for direct-injection compression-ignition (DICI) engines for its ability to deliver high heat release rates and low heat transfer losses, in addition to potentially zero CO2 emissions. However, this concept requires a different optimization strategy compared to conventional diesel engines, prioritizing a combustion mode dominated by free turbulent jet mixing. In the present work, this optimization strategy is realized and studied computationally using the CONVERGE CFD solver. It involves adopting wide piston bowl designs with shapes adapted to the H2 jets, altered injector umbrella angle, and an increased number of nozzle orifices with either smaller orifice diameter or reduced injection pressure to maintain constant injector flow rate capacity. This work shows that these modifications are effective at maximizing free-jet mixing, thus enabling more favorable heat release profiles, reducing wall heat transfer by 35%, and improving indicated efficiency by 2.2 percentage points. However, they also caused elevated incomplete combustion losses at low excess air ratios, which may be eliminated by implementing a moderate swirl, small post-injections, and further optimized jet momentum and piston design. Noise emissions with the optimized DICI H2 combustion are shown to be comparable to those from conventional diesel engines. Finally, it is demonstrated that modern engine concepts, such as the double compression-expansion engine, may achieve around 56% brake thermal efficiency with the DICI H2 combustion, which is 1.1 percentage point higher than with diesel fuel. Thus, this work contributes to the knowledge base required for future improvements in H2 engine efficiency.
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| 4. |
- Behave, A, et al.
(författare)
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Analysis of a natural gas fuelled homogeneous charge compression ignition engine with exhaust gas recirculation using a stochastic reactor model
- 2004
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 5, s. 93-104
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Tidskriftsartikel (refereegranskat)abstract
- Combustion and emissions formation in a Volvo TD 100 series diesel engine running in a homogeneous charge compression ignition (HCCI) mode and fuelled with natural gas is simulated and compared with measurements for both with and without external exhaust gas recirculation (EGR). A new stochastic approach is introduced to model the convective heat transfer, which accounts for fluctuations and fluid-wall interaction effects. This model is included in a partially stirred plug flow reactor (PaSPFR) approach, a stochastic reactor model (SRM), and is applied to study the effect of EGR on pressure, autoignition timing and emissions of CO and unburned hydrocarbons (HCs). The model accounts for temperature inhomogeneities and includes a detailed chemical mechanism to simulate the chemical reactions within the combustion chamber. Turbulent mixing is described by the interaction by exchange with the mean (IEM) model. A Monte Carlo method with a second-order time-splitting technique is employed to obtain the numerical solution. The model is validated by comparing the simulated in-cylinder pressure history and emissions with measurements taken from Christensen and Johansson (SAE Paper 982454). Excellent agreement is obtained between the peak pressure, ignition timing and CO and HC emissions predicted by the model and those obtained from the measurements for the non-EGR, 38 per cent EGR and 47 per cent EGR cases. A comparison between the pressure profiles for the cases studied reveals that the ignition timing and the peak pressure are dependent on the EGR. With EGR, the peak pressure reduces and the autoignition is delayed. The trend observed in the measured emissions with varying EGR is also predicted correctly by the model.
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| 5. |
- Dahl, Daniel, 1982, et al.
(författare)
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HCCI/SCCI load limits and stoichiometric operation in a multicylinder naturally aspirated spark ignition engine operated on gasoline and E85
- 2011
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Ingår i: International Journal of Engine Research. - 1468-0874 .- 2041-3149. ; 12:1, s. 58-68
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Tidskriftsartikel (refereegranskat)abstract
- To meet demands for improvements in the CO 2 emissions and fuel economy of gasoline passenger car engines advanced combustion strategies, to replace (or combine with) conventional spark ignition, must be developed and implemented. One possible strategy is homogeneous charge compression ignition (HCCI) achieved using negative valve overlap (NVO). However, several issues need to be addressed before this combustion strategy can be fully implemented in a production vehicle, one being to increase the upper load limit. One constraint at high loads is that the combustion becomes too rapid, leading to excessive pressure-rise rates and large pressure fluctuations (ringing), causing noise. A potential solution to this is to use charge stratification, but charge stratification normally gives rise to increased NO x emissions. Tests with a multicylinder engine reported here confirmed that there is significant potential to increase the upper load limit using charge stratification. In addition, the possibility of operating the engine in stoichiometric conditions, using a combination of NVO and external exhaust gas recirculation (EGR) (thus allowing the increased NO x emissions to be countered using a three-way catalyst) was investigated. Stoichiometric operation was found to be possible for both homogeneous and stratified modes, across a wide operating range, with small compromises in maximum load and fuel consumption. Nevertheless, delaying the need for a mode shift, and operating in stoichiometric conditions when entering a mode shift, should be beneficial in a drive cycle.
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| 6. |
- Dahl, Daniel, 1982, et al.
(författare)
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The role of charge stratification for reducing ringing in gasoline engine homogeneous charge compression ignition combustion investigated by optical imaging
- 2013
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 14:5, s. 525-536
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Tidskriftsartikel (refereegranskat)abstract
- Homogeneous charge compression ignition offers the possibility to reduce the fuel consumption of gasoline passenger car engines. However, the combustion strategy is limited to low loads due to pressure oscillations at higher loads. A strategy for extending the homogeneous charge compression ignition load range is charge stratification, using, for example, late direct injection to prolong the combustion duration and reduce the rate of pressure rises and pressure oscillations. In this study, local temperatures and fuel concentrations near top dead centre in a gasoline engine operating in homogeneous charge compression ignition mode were measured using two-wavelength planar laser-induced fluorescence, and the following combustion was analysed using high-speed video to investigate the effects of fuel and temperature stratification on combustion in order to explain the ringing inhibiting effect of charge stratification for fuels displaying single-stage ignition. The extent of spatial distribution of combustion timing correlated well with the extent of fuel and temperature stratification. Furthermore, the gas was leaner and hotter in early igniting regions, while it was richer and colder in late igniting regions. The dampening effects of charge stratification on the combustion speed and pressure oscillations are probably due to rich conditions in the latest burning regions (where combustion is usually most intense) slowing down combustion, which explains why the strategy only works when the global air-to-fuel ratio is not excessively lean.
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| 7. |
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| 8. |
- Etikyala, Sreelekha, 1991, et al.
(författare)
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Visualization of soot formation in load transients during GDI engine warm-up
- 2023
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 24:7, s. 3073-3084
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Tidskriftsartikel (refereegranskat)abstract
- Reducing the emissions of pollutants, and particularly soot particles, from internal combustion engines is one of the greatest challenges faced by car manufacturers. Although modern gasoline direct injection (GDI) engines produce relatively low particulate emissions during steady state operation under near-stoichiometric conditions, they can produce much higher particulate emissions during transients that cause abrupt changes in load, fuel consumption, and the air-to-fuel ratio. Emissions during transients are particularly high when the engine coolant temperature is low, as occurs during engine start-up. Consequently, there is a need to find ways of reducing particulate emissions during load transients. This paper therefore investigates particulate formation during load transients in a single-cylinder GDI engine equipped with an endoscope in the cylinder head. A transient sequence was designed in which the engine load was increased from 4 bar NMEP to a maximum of 12 bar NMEP in 2 s at an engine speed of 2000 rpm. During the transients, the engine’s particulate emissions were measured in terms of particulate number (PN) and images of the combustion process inside the cylinder were captured via the endoscope using a high-speed camera to identify locations where soot formation occurred. Experiments were conducted at a range of coolant temperatures and using different injection strategies to determine how these parameters affect PN emissions. The coolant temperature was found to be the dominant factor governing PN emissions during transients. Luminescence data obtained by analyzing the flame images agreed well with the measured PN emissions during transients. Under all varied parameters in the transients except delayed injection, soot was mainly formed from wall films. For transients with delayed fuel injection, much of the piston film could be avoided but soot formation instead became mixing-dominated. Variation of the air-fuel ratio had little effect on PN emissions during transients. At all coolant temperatures, PN emissions were lowest when using a split injection strategy but delaying the injection timing increased PN emissions even though the endoscope images suggested a lower frequency of diffusion flame formation. No conditions were found under which the PN emissions during transients with low coolant temperatures could be reduced to levels comparable to those seen with warm coolant.
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| 9. |
- Franken, Tim, et al.
(författare)
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Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry
- 2020
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 21:10, s. 1857-1877
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the assessment of direct water injection in spark-ignition engines using single cylinder experiments and tabulated chemistry-based simulations. In addition, direct water injection is compared with cooled low-pressure exhaust gas recirculation at full load operation. The analysis of the two knock suppressing and exhaust gas cooling methods is performed using the quasi-dimensional stochastic reactor model with a novel dual fuel tabulated chemistry model. To evaluate the characteristics of the autoignition in the end gas, the detonation diagram developed by Bradley and co-workers is applied. The single cylinder experiments with direct water injection outline the decreasing carbon monoxide emissions with increasing water content, while the nitrogen oxide emissions indicate only a minor decrease. The simulation results show that the engine can be operated at lambda = 1 at full load using water-fuel ratios of up to 60% or cooled low-pressure exhaust gas recirculation rates of up to 30%. Both technologies enable the reduction of the knock probability and the decrease in the catalyst inlet temperature to protect the aftertreatment system components. The strongest exhaust temperature reduction is found with cooled low-pressure exhaust gas recirculation. With stoichiometric air-fuel ratio and water injection, the indicated efficiency is improved to 40% and the carbon monoxide emissions are reduced. The nitrogen oxide concentrations are increased compared to the fuel-rich base operating conditions and the nitrogen oxide emissions decrease with higher water content. With stoichiometric air-fuel ratio and exhaust gas recirculation, the indicated efficiency is improved to 43% and the carbon monoxide emissions are decreased. Increasing the exhaust gas recirculation rate to 30% drops the nitrogen oxide emissions below the concentrations of the fuel-rich base operating conditions.
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| 10. |
- Franken, T., et al.
(författare)
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Multi-objective optimization of water injection in spark-ignition engines using the stochastic reactor model with tabulated chemistry
- 2019
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 20:10, s. 1089-1100
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Tidskriftsartikel (refereegranskat)abstract
- Water injection is investigated for turbocharged spark-ignition engines to reduce knock probability and enable higher engine efficiency. The novel approach of this work is the development of a simulation-based optimization process combining the advantages of detailed chemistry, the stochastic reactor model and genetic optimization to assess water injection. The fast running quasi-dimensional stochastic reactor model with tabulated chemistry accounts for water effects on laminar flame speed and combustion chemistry. The stochastic reactor model is coupled with the Non-dominated Sorting Genetic Algorithm to find an optimum set of operating conditions for high engine efficiency. Subsequently, the feasibility of the simulation-based optimization process is tested for a three-dimensional computational fluid dynamic numerical test case. The newly proposed optimization method predicts a trade-off between fuel efficiency and low knock probability, which highlights the present target conflict for spark-ignition engine development. Overall, the optimization shows that water injection is beneficial to decrease fuel consumption and knock probability at the same time. The application of the fast running quasi-dimensional stochastic reactor model allows to run large optimization problems with low computational costs. The incorporation with the Non-dominated Sorting Genetic Algorithm shows a well-performing multi-objective optimization and an optimized set of engine operating parameters with water injection and high compression ratio is found.
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| 11. |
- Franken, T., et al.
(författare)
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Prediction of thermal stratification in an engine-like geometry using a zero-dimensional stochastic reactor model
- 2020
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 21:9, s. 1750-1763
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Tidskriftsartikel (refereegranskat)abstract
- The prediction of local heat transfer and thermal stratification in the zero-dimensional stochastic reactor model is compared to direct numerical simulation published by Schmitt et al. in 2015. Direct numerical simulation solves the Navier–Stokes equations without incorporating model assumptions for turbulence and wall heat transfer. Therefore, it can be considered as numerical experiment and is suitable to validate approximations in low-dimensional models. The stochastic reactor model incorporates a modified version of the Euclidean Minimum Spanning Tree mixing model proposed by Subramaniam et al. in 1998. To capture the thermal stratification of the direct numerical simulation, the total enthalpy (H) is used as the only mixing limiting scalar within the newly proposed H-Euclidean-Minimum-Spanning-Tree. Furthermore, a stochastic heat transfer model is incorporated to mimic turbulence effects on local heat transfer distribution to the walls. By adjusting the Cϕ mixing time and Ch stochastic heat transfer parameter, the stochastic reactor model predicts accurately the thermal stratification of the direct numerical simulation. Comparing the Woschni, Hohenberg and Heinle heat transfer model shows that the modified Heinle model matches accurately the direct numerical simulation results. Thereby, the Heinle model accounts for the influence of turbulent kinetic energy on the characteristic velocity in the heat transfer coefficient calculation. This highlights the importance of incorporating turbulence effects in low-dimensional heat transfer models. Overall, the zero-dimensional stochastic reactor model with the H-Euclidean-Minimum-Spanning-Tree mixing model, the stochastic heat transfer model and the modified Heinle correlation have proven successfully the prediction of mean quantities like temperature and heat transfer and thermal stratification of the direct numerical simulation.
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| 12. |
- Giramondi, Nicola, et al.
(författare)
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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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| 13. |
- Grahn, Markus, 1978, et al.
(författare)
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Data-driven emission model structures for diesel engine management system development
- 2014
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 15:8, s. 906-917
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Tidskriftsartikel (refereegranskat)abstract
- This article discusses some specific data-driven model structures suitable for prediction of NOx and soot emissions from a diesel engine. The model structures can be described as local linear regression models where the regression parameters are defined by two-dimensional lookup tables. It is highlighted that this structure can be interpreted as a B-spline function. Using the model structure, models are derived from measured engine data. The smoothness of the derived models is controlled by using an additional regularization term, and the globally optimal model parameters can be found by solving a linear least squares problem. Experimental data from a five-cylinder Volvo passenger car diesel engine is used to derive NOx and soot models, using a leave-one-out cross-validation strategy to determine the optimal degree of regularization. The model for NOx emissions predicts the NOx mass flow with an average relative error of 5.1% and the model for soot emissions predicts the soot mass flow with an average relative error of 29% for the mea- surement data used in this study. The behavior of the models for different engine management system settings regarding boost pressure, amount of exhaust gas recirculation, and injection timing has been studied. The models react to the dif- ferent engine management system settings in an expected way, making them suitable for optimization of engine manage- ment system settings. Finally, the model performance dependence on the selected model complexity and on the number of measurement data points used to derive the models has been studied.
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| 14. |
- Grandin, Börje, et al.
(författare)
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A study of the influence of exhaust gas recirculation and stoichiometry on the heat release in the end-gas prior to knock using rotational coherent anti-Stokes-Raman spectroscopy thermometry
- 2002
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 3:4, s. 209-221
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Tidskriftsartikel (refereegranskat)abstract
- Heat release in the end-gas prior to autoignition was investigated using different experimental methods including transducers for heat flux and pressure as well as rotational coherent anti-Stokes-Raman spectroscopy, which is a laser-based method for non-intrusive instantaneous thermometry of the gas. The time history was examined in the cases of mixtures of various stoichio-metries, where some were diluted with exhaust gas recir-culation (EGR). The measured temperature history was compared with the isentropic temperature calculated from the cylinder pressure trace. This comparison revealed a difference in heat release from low-temperature reactions in the end-gas for the various mixtures tested at a constant indicated mean effective pressure and a fixed position of 50 per cent burnt charge. It is shown that lean mixtures tend to exhibit the highest knock intensity, mainly due to a decrease in specific heat, as compared to the richer mixtures, which result in an earlier knock onset and as a consequence higher knock intensity. Furthermore, the comparison of temperatures indicates that the rich mixtures have a high heat release from low-temperature chemistry, which to some extent negates the higher specific heat of the charge. As a consequence, a slight enrichment of the charge can lead to higher knock intensity in comparison with a stoichiometric mixture. In spite of the lower specific heat of the charge when a stoichiometric charge was diluted with cooled EGR, these mixtures showed a very low tendency to knock.
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| 15. |
- Hemdal, Stina, 1974, et al.
(författare)
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In-cylinder soot imaging and emissions of stratified combustion in a spark-ignited spray-guided direct-injection gasoline engine
- 2011
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 12:6, s. 549-563
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Tidskriftsartikel (refereegranskat)abstract
- The combustion in a spark-ignited spray-guided gasoline direct-injection engine operating in a stratified mode has been studied by in-cylinder imaging of the fuel, OH*, and soot distributions. Information on the fuel distribution was obtained by laser-induced fluorescence imaging of the aromatic molecules in the gasoline. The OH* and soot distributions were simultaneously visualized by detection of the natural emissions at 306nm (OH*) and around 530nm (soot) using two intensified charge-coupled device cameras. In addition to the in-cylinder observations, engine-out soot emissions, NO(x), and HC were measured. The engine was operated at a speed of 2000 r/min and an indicated mean effective pressure of 2.5 bar, with a fully open throttle, resulting in a globally lean combustion with a fuel-air equivalence ratio of about 0.25. The gasoline was injected in single or double injections by an outward-opening piezo-actuated injector. The combustion was ignited efficiently at locally fuel-rich conditions. The soot formation and oxidation were investigated for the two injection strategies, each with three injection timings and two fixed ignition timings. The results showed that soot was efficiently formed and oxidized. From the in-cylinder measurements, it could be seen that the soot luminescence intensity quickly rose and then declined, while the combustion temperature was still increasing. Furthermore, the OH* intensity was still increasing as the soot luminescence was declining. The soot incandescence peak intensity occurred at a crank angle degree close to 50 per cent mass burned, and the OH* intensity peak arose later, shortly before the maximum soot temperature around top dead centre (TDC). When the injection timing was retarded, with constant ignition timing with respect to injection, it was found that the total soot luminosity increased. In addition, less OH* chemiluminescence was observed during the decrease of the soot incandescence, implying conditions less favourable for efficient soot oxidation in the later part of the combustion for retarded injections. This was confirmed by the engine-out soot emission measurements, which showed increased soot levels as the injection was retarded. It was also found that fuel impinged on the spark plug during the injections, resulting in a persistent jet flame close to the spark plug in the centre of the cylinder, which is believed to contribute to engine-out soot emissions.
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| 16. |
- Hlaing, Ponnya, et al.
(författare)
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Estimates of the air-fuel ratio at the time of ignition in a pre-chamber using a narrow throat geometry
- 2023
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 24:2, s. 622-638
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Tidskriftsartikel (refereegranskat)abstract
- The benefits of pre-chamber combustion (PCC), such as improved engine efficiency and reduced NOx emissions, are primarily observed when operating at lean conditions with an active pre-chamber, where auxiliary fuel is supplied directly to the pre-chamber. Estimating the pre-chamber excess air ratio (λ) is important in the active pre-chamber concept to gain insights into the pre-chamber combustion phenomenon. Experimental investigations were performed using a narrow-throat pre-chamber at global-λ 1.6, 1.8, and 2.0. The fraction of fuel energy injected in the pre-chamber over the total fuel energy was fixed at 3%, 7%, and 13% for each global-λ. The mixture formation process inside the pre-chamber is first simulated using the 1-D simulation software GT-Power to analyze the pre-chamber λ at the ignition timing. However, the 1-D results were unable to reproduce the experimental observations on the pre-chamber pressure buildup accurately. Upon simulating the same conditions using the 3-D CFD software CONVERGE, the pre-chamber λ estimated from the CFD model is well-correlated to the experimental data. The CFD results indicate that the amount of fuel trapped in the pre-chamber at the inlet valve closing timing is over-predicted by the 1-D simulations. A correlation between the injected and the trapped fuel in the pre-chamber is proposed by theoretical scavenging models and applied to the 1-D simulation results to improve pre-chamber λ prediction accuracy.
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| 17. |
- Hull, Angelica, et al.
(författare)
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Alternative fuel for a standard diesel engine
- 2006
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Ingår i: International Journal of Engine Research. - 1468-0874 .- 2041-3149. ; 7:1, s. 51-63
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Tidskriftsartikel (refereegranskat)abstract
- Alternative fuels have been developed for the commercial diesel products Mkl and EN590. Appropriate additives were selected from a broad range of oxygenates including alcohols, acetals, ethers, esters, and nitrates by a process of systematic elimination. The resulting fuels called Biodiesel 15 meet all existing standards in force for diesel fuel, are stable, and have similar performance characteristics to standard diesel. Significantly Biodiesel 15 is much cleaner than standard diesel with around 30 per cent or more reductions in particulate matter in the exhaust emissions. Carbon dioxide (CO2) emissions are much lower with Biodiesel 15 than with standard diesel products. Other regulated emissions are on a par with Mkl. The fuel consumption of Biodiesel 15 is 2 per cent lower than that of conventional Mkl.
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| 18. |
- Hull, A, et al.
(författare)
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An alternative fuel for spark ignition engines
- 2006
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Ingår i: International Journal of Engine Research. - 1468-0874 .- 2041-3149. ; 7, s. 203-214
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Tidskriftsartikel (refereegranskat)abstract
- Alternative fuels have been developed for standard spark ignition engines. The fuels, which contain generic bio components, maintain all the advantages of ethanol, that is the ability to increase considerably the octane number of gasoline and reduce the amount of harmful pollutants in the exhaust emissions of engines operating on such blends. In contrast to ethanol the new fuel components do not increase the vapour pressure of gasoline-ethanol blends, have a better tolerance to water and do not increase the fuel consumption. The bio component based fuels also compare favourably with mineral sourced octane boosters such as MTBE. Additionally reformulation of the base gasoline becomes unnecessary.
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| 19. |
- Hult, Johan, et al.
(författare)
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Spatiotemporal flame mapping in a large-bore marine diesel engine using multiple high-speed cameras
- 2020
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 21:4, s. 622-631
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Tidskriftsartikel (refereegranskat)abstract
- A calibrated multiple high-speed camera arrangement recording the flame emission from three different directions has been demonstrated on an engine. From the multiple views, the flame position inside the engine cylinder can be spatially mapped, allowing quantitative studies of the dynamics of ignition, flame development and propagation. Through space carving, the three-dimensional flame contour can be estimated. From this contour, properties like flame length, flame height, ignition locations and flame directions can be extracted. The technique is demonstrated by measurements on diesel flames inside a marine two-stroke engine with a bore diameter of 500 mm. It is found to be a valuable tool for spatiotemporal flame mapping in this asymmetric industrial combustion system.
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| 20. |
- Johansson, Peter, et al.
(författare)
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Variations in piston second land pressure as a function of ring gap position
- 2010
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Ingår i: International Journal of Engine Research. - 1468-0874 .- 2041-3149. ; 11:2, s. 153-161
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Tidskriftsartikel (refereegranskat)abstract
- The inter-ring pressure and the potential reverse blow-by flow that can drive oil towards the combustion chamber can strongly influence the in-cylinder oil consumption in diesel engines. This paper reports on an experimental investigation of the effect of both cycle-to-cycle variations and variations over a longer period on inter-ring pressure. The inter-ring pressure and piston ring movement were also simulated as a function of ring gap position. The experimental part of the project showed small cycle-to-cycle variations in the second land pressure as well as large variations over time. Simulations of the second land pressure with different ring gap positions showed a similar range of variation in second land pressure as the experimental variation.
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| 21. |
- Kalghatgi, G. T., et al.
(författare)
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Surrogate fuels for premixed combustion in compression ignition engines
- 2011
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 12:5, s. 452-465
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Tidskriftsartikel (refereegranskat)abstract
- Simple surrogate fuels are needed to model practical fuels, which are complex mixtures of hydrocarbons. The surrogate fuel should match the combustion and emissions behaviour of the target fuel as much as possible. This paper presents experimental results using a wide range of fuels in both the gasoline and diesel auto-ignition range, but of different volatilities and compositions, in a single cylinder diesel engine. Premixed combustion in a compression ignition engine is defined, in this paper, to occur when the injection event is clearly separated from the combustion and the engine-out smoke is very low - below 0.05 FSN (filter smoke number). Under such circumstances, if the combustion phasing is matched for two fuels at a given operating condition and injection timing, the emissions are also comparable regardless of the differences in composition and volatility. For the experimental conditions considered, combustion phasing at a given operating condition and injection timing depends only on the octane index (OI), OI = (1-K)RON + KMON, where RON and MON are research and motor octane numbers and K is an empirical constant that depends on operating conditions. A mixture of iso-octane, n-heptane and toluene can be found to match the RON and MON of any practical gasoline and will be a very good surrogate for the gasoline since it will have the same OI. If the compression ratio is greater than 14, practical diesel fuels, with DCN (derived cetane number) between 40 and 60, will have comparable ignition delays to n-heptane, which is an adequate surrogate for such fuels. However, premixed combustion can be attained only at much lower loads at a given speed with diesel fuels compared to gasolines.
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| 22. |
- Khatri, Jayesh, 1993, et al.
(författare)
-
Effect of relative humidity on water injection technique in downsized spark ignition engines
- 2021
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 22:7, s. 2119-2130
-
Tidskriftsartikel (refereegranskat)abstract
- Combustion knock is a major barrier to achieving high thermal efficiency in spark ignition engines. Water injection was recently identified as a potential way of overcoming this barrier. To evaluate its general applicability, experiments were performed on a downsized three-cylinder spark ignition engine, varying the humidity of the intake air, the water injection timing, and the engine speed. The minimum quantity of injected water required to maintain a given load (and thus level of engine performance) was determined under each set of tested conditions. The knock-suppressing effects of water injection were found to be related to changes in the fuel–air mixture’s specific heat ratio (kappa) rather than evaporative cooling, and to therefore depend on the total quantity of water in the cylinder rather than the relative humidity per se. The total quantity of water in the cylinder was also shown to be a key determinant of advancement in combustion phasing and particulate emissions under various conditions.
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| 23. |
- Lackmann, Tim, 1983, et al.
(författare)
-
Investigation of turbulence–chemistry interactions in a heavy-duty diesel engine with a representative interactive linear eddy model
- 2020
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 21:8, s. 1469-1479
-
Tidskriftsartikel (refereegranskat)abstract
- Simulations of a heavy-duty diesel engine operated at high-load and low-load conditions were compared to each other, and experimental data in order to evaluate the influence of turbulence–chemistry interactions on heat release, pressure development, flame structure, and temperature development are quantified. A recently developed new combustion model for turbulent diffusion flames called representative interactive linear eddy model which features turbulence–chemistry interaction was compared to a well-stirred reactor model which neglects the influence of turbulent fluctuations on the mean reaction rate. All other aspects regarding the spray combustion simulation like spray break-up, chemical mechanism, and boundary conditions within the combustion chamber were kept the same in both simulations. In this article, representative interactive linear eddy model is extended with a progress variable, which enables the model to account for a flame lift-off and split injection, when it is used for diffusion combustion. In addition, the extended version of representative interactive linear eddy model offers the potential to treat partially premixed and premixed combustion as well. The well-stirred reactor model was tuned to match the experimental results, thus computed pressure and apparent heat release are in close agreement with the experimental data. Representative interactive linear eddy model was not tuned specifically for the case and thus the computed results for pressure and heat release are in reasonable agreement with experimental data. The computational results show that the interaction of the turbulent flow field and the chemistry reduce the peak temperatures and broaden up the turbulent flame structure. Since this is the first study of a real combustion engine (metal engine) with the newly developed model, representative interactive linear eddy model appears as a promising candidate for predictions of spray combustion in engines, especially in combustion regimes where turbulence–chemistry interaction plays an even more important role like, example given, in low-temperature combustion or combustion with local extinction and re-ignition.
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| 24. |
- Leufvén, Oskar, et al.
(författare)
-
Investigation of compressor correction quantities for automotive applications
- 2012
-
Ingår i: International Journal of Engine Research. - : SAGE Publications (UK and US) / Professional Engineering Publishing (Institution of Mechanical Engineers). - 1468-0874 .- 2041-3149. ; 13:6, s. 588-606
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Turbo performance is represented using maps, measured for one set of inlet conditions. Corrections are then applied to scale the performance to other inlet conditions. A turbo compressor for automotive applications experiences large variations in inlet conditions, and the use of two stage charging increases these variations. The variations are the motivation for analyzing the correction quantities and their validity. The corrections reveals a novel surge avoidance strategy, where the result is that a reduction in inlet pressure increases the surge margin for eight maps studied. The method to investigate the applicability of the strategy is general.An experimental analysis of the applicability of the commonly used correction factors, used when estimating compressor performance for varying inlet conditions, is presented. The experimental campaign uses measurements from an engine test cell and from a gas stand, and shows a small, but clearly measurable trend, with decreasing compressor pressure ratio for decreasing compressor inlet pressure. A method is developed, enabling measurements to be analyzed with modified corrections.An adjusted shaft speed correction quantity is proposed, incorporating also the inlet pressure in the shaft speed correction. The resulting decrease in high altitude engine performance, due to compressor limitations, are quantified and shows a reduction in altitude of 200 – 600 m, for when engine torque has to be reduced to due limited compressor operation.
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| 25. |
- Leufvén, Oskar, et al.
(författare)
-
Measurement, analysis and modeling of compressor flow for low pressure ratios
- 2016
-
Ingår i: International journal of engine research. - : Sage Publications. - 1468-0874 .- 2041-3149. ; 17:2, s. 153-168
-
Tidskriftsartikel (refereegranskat)abstract
- Increasingly stringent emissions legislation combined with consumer performance demands, have driven the development of downsized engines with complex turbocharger arrangements. To handle the complexity model-based methods have become a standard tool, and these methods need models that are capable of describing all operating modes of the systems. The models should also be easily parametrized and enable extrapolation. Both single and multiple stage turbo systems can operate with a pressure drop over their compressors, both stationary and transient. The focus here is to develop models that can describe centrifugal compressors that operate both in normal region and restriction region from standstill to maximum speed. The modeling results rely on an analysis of 305 automotive compressor maps, whereof five contain measured restriction operation, and two contain measured standstill characteristic. A standstill compressor is shown to choke at a pressure ratio of approximately 0.5, and the corresponding choking corrected mass flow being approximately 50% of the compressor maximum flow capacity. Both choking pressure ratio and flow are then shown to increase with corrected speed, and the choking pressure ratio is shown to occur at pressure ratios larger than unity for higher speeds. Simple empirical models are proposed and shown to be able to describe high flow and pressure ratios down to choking conditions well. A novel compressor flow model is proposed and validated to capture the high flow asymptote well, for speeds from standstill up to maximum.
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| 26. |
- Lipatnikov, Andrei, 1961
(författare)
-
A priori test of perfectly stirred reactor approach to evaluating mean fuel consumption and heat release rates in highly turbulent premixed f lames
- 2023
-
Ingår i: International Journal of Engine Research. - 1468-0874 .- 2041-3149. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Unsteady three-dimensional Direct Numerical Simulation (DNS) data obtained earlier by Dave et al. (J Fluid Mech 2020; 884: A46) from a statistically planar and one-dimensional, highly turbulent, moderately lean hydrogen-air flame propagating in a box are processed to perform a priori test of perfectly stirred reactor model. The test aims in particularly at estimating mesh resolution (or filter width within large eddy simulation framework) required to neglect variations in the temperature and mixture composition within a computational cell when evaluating mean (or filtered) fuel consumption and heat release rates. For this purpose, fuel consumption and heat release rates sampled directly from the DNS data and averaged over a cube of width ∆ are compared with fuel consumption and heat release rates calculated using the temperature and species concentrations averaged over the same cube. Moreover, turbulent burning velocities computed by integrating the former and latter rates are compared with one another. A ratio of ∆ to a laminar flame thickness δL is varied from 0.44 to 1.8. The obtained results indicate that the tested simple approach performs reasonably well (poor) if ∆< 0.5δL (∆> δL , respectively). This result is further supported by directly filtering fuel consumption rate in a laminar premixed flame. The values of the thickness δL , calculated using detail chemical mechanisms for different fuels under elevated temperatures and pressures associated with combustion in piston engines, indicate that it is difficult to satisfy the constraint of ∆< 0.5δL in contemporary unsteady multidimensional numerical simulations of turbulent burning in such engines.
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| 27. |
- Lipatnikov, Andrei, 1961
(författare)
-
A priori test of perfectly stirred reactor approach to evaluating mean fuel consumption and heat release rates in highly turbulent premixed flames
- 2023
-
Ingår i: International Journal of Engine Research. - 1468-0874 .- 2041-3149. ; 24:9, s. 4034-4043
-
Tidskriftsartikel (refereegranskat)abstract
- Unsteady three-dimensional Direct Numerical Simulation (DNS) data obtained earlier by Dave et al. (J Fluid Mech 2020; 884: A46) from a statistically planar and one-dimensional, highly turbulent, moderately lean hydrogen-air flame propagating in a box are processed to perform a priori test of perfectly stirred reactor model. The test aims in particularly at estimating mesh resolution (or filter width within large eddy simulation framework) required to neglect variations in the temperature and mixture composition within a computational cell when evaluating mean (or filtered) fuel consumption and heat release rates. For this purpose, fuel consumption and heat release rates sampled directly from the DNS data and averaged over a cube of width (Formula presented.) are compared with fuel consumption and heat release rates calculated using the temperature and species concentrations averaged over the same cube. Moreover, turbulent burning velocities computed by integrating the former and latter rates are compared with one another. A ratio of (Formula presented.) to a laminar flame thickness (Formula presented.) is varied from 0.44 to 1.8. The obtained results indicate that the tested simple approach performs reasonably well (poor) if (Formula presented.) ((Formula presented.), respectively). This result is further supported by directly filtering fuel consumption rate in a laminar premixed flame. The values of the thickness (Formula presented.), calculated using detail chemical mechanisms for different fuels under elevated temperatures and pressures associated with combustion in piston engines, indicate that it is difficult to satisfy the constraint of (Formula presented.) in contemporary unsteady multidimensional numerical simulations of turbulent burning in such engines.
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| 28. |
- Mahendar, Senthil, et al.
(författare)
-
Alcohol lean burn in heavy duty engines: Achieving 25 bar IMEP with high efficiency in spark ignited operation
- 2021
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 22:11, s. 3313-3324
-
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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| 29. |
- Manente, Vittorio, et al.
(författare)
-
Gasoline partially premixed combustion, the future of internal combustion engines?
- 2011
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 12:3, s. 194-208
-
Tidskriftsartikel (refereegranskat)abstract
- Gasoline partially premixed combustion showed the potential of very high efficiency, emissions of nitrogen oxides (NOx) and soot below future emission regulations, and acceptable acoustic noise from idle up to 26 bar gross indicated mean effective pressure. For instance, gross indicated efficiencies in the range of 53 to 55 per cent were achieved in the whole load range keeping NOx below 0.30 g/kWh, soot below 0.30 filter smoke number (FSN), and relative maximum pressure rise rate below 8 bar/crank angle degree. The goal was achieved by developing an appropriate EGR-lambda (exhaust gas recirculation/relative excess of air) combination and an advanced injection strategy, and by making minor modifications to the engine layout. The current paper presents a summary of the advantages of using gasoline-type fuels (research octane number (RON) from 80 to 69) in a heavy-duty compression ignition engine. Low-octane-number gasoline fuels were chosen because they can run from idle to maximum load without any major modification to the engine layout and because low-load operations are achievable even when the engine is cold and the inlet temperature is low. Experiments were carried out in two single-cylinder engines, Scania D12 and Scania D13, using a total of three different engine setups. The influence of different types of gasoline (RON from 99 to 69) on this novel combustion concept was analysed. A comparison between gasoline and diesel fuels is presented and the viability of reaching 50 per cent brake efficiency while keeping low emissions of NOx and soot is shown.
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| 30. |
- McGurk, C., et al.
(författare)
-
A comparative analysis of moving average filter and Kalman filter for large diesel engine test cell back-pressure control
- 2023
-
Ingår i: International Journal of Engine Research. - : Sage Publications. - 1468-0874 .- 2041-3149. ; 24:7, s. 3186-3196
-
Tidskriftsartikel (refereegranskat)abstract
- Diesel engine combustion releases many harmful components, thus there are continuous efforts into improving the efficiency of these engines and reducing the harmful gasses and particulates to meet the emission authorities targets. To develop and sell new engine-related products, these engines are required to run and to be audited in diesel engine test cells. A critical measurement for benchmark testing is the exhaust back-pressure, which is the resultant exhaust flow from the engine and a product of the air and fuel consumed. The back-pressure is controlled by restricting the flow of the exhaust using a butterfly valve and this pressure must be set to the defined limits to ensure engine compliance. Setting this limit takes time and consumes large volumes of fuel, which causes additional emissions. Therefore, a feedback control solution to regulate this back-pressure is desirable. In current practice, a moving average filter is used on two commercial standard engine softwares – SGS CyFlex® and AVL Puma 2® Data Acquisition and Control Systems to provide a useful signal for feedback control. Considering the presence of erratic noise associated with the back-pressure measurement, a Kalman Filter with tunable measurement uncertainty and process noise gains is also considered. By modifying the script in SGS CyFlex® and AVL PUMA 2®, a Kalman Filter is implemented for the first time on diesel engine test cells and a comparative analysis between the performance of the two filters is provided. Both filters effectively reduce the noise of the system, with the Kalman Filter showing a closer tracking to the desired system response. This demonstrates the potential of applying the Kalman Filter to provide the feedback signal for improved back-pressure control that could reduce the fuel consumption during testing, thereby makes testing process more economical and environment friendly. The script and results presented in this work will open up the opportunities of applying Kalman filtering method’s in various engine testing functions, which will have broader impact in the current industrial practice.
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| 31. |
- Miles, Paul C., et al.
(författare)
-
A review of design considerations for light-duty diesel combustion systems
- 2016
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 17:1, s. 6-15
-
Tidskriftsartikel (refereegranskat)abstract
- Practical aspects of light-duty diesel combustion system design are reviewed, with an emphasis on design considerations reported by manufacturers and engine design consultancies. The factors driving the selection of compression ratio, stroke-to-bore ratio, and various aspects of combustion chamber geometry are examined, along with the trends observed in these parameters in recently released engines. The interactions among geometric characteristics, swirl ratio, and the fuel injection nozzle parameters are also reviewed.
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| 32. |
- Muric, Kenan, et al.
(författare)
-
Zero-dimensional modeling of NOx formation with least squares interpolation
- 2014
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 15:8, s. 944-953
-
Tidskriftsartikel (refereegranskat)abstract
- Physical models of NOx formation are becoming more and more interesting in the area of combustion feedback control. The fact that cylinder pressure sensors are made available on the market enables fast and accurate calculations of heat release, which is an essential part of every physical NOx formation model. This article describes such a zero-dimensional model for a diesel engine using crank angle-resolved cylinder pressure to determine heat release. The model also incorporates the thermal effect of exhaust gas recirculation that is proven to have a major effect on NOx formation rates. The reaction mechanisms used to describe NOx formation rates are given by the well-known Zeldovich mechanism. The model output results given in this article show an average deviation of about 12.0% from acquired measured NOx data. The least squares interpolation approach indicates a negligible difference from the original model with an average deviation of 1.2% in 25 measurement points.
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| 33. |
- Pasternak, M., et al.
(författare)
-
Diesel engine performance mapping using a parametrized mixing time model
- 2018
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 19:2, s. 202-213
-
Tidskriftsartikel (refereegranskat)abstract
- A numerical platform is presented for diesel engine performance mapping. The platform employs a zero-dimensional stochastic reactor model for the simulation of engine in-cylinder processes. n-Heptane is used as diesel surrogate for the modeling of fuel oxidation and emission formation. The overall simulation process is carried out in an automated manner using a genetic algorithm. The probability density function formulation of the stochastic reactor model enables an insight into the locality of turbulence–chemistry interactions that characterize the combustion process in diesel engines. The interactions are accounted for by the modeling of representative mixing time. The mixing time is parametrized with known engine operating parameters such as load, speed and fuel injection strategy. The detailed chemistry consideration and mixing time parametrization enable the extrapolation of engine performance parameters beyond the operating points used for model training. The results show that the model responds correctly to the changes of engine control parameters such as fuel injection timing and exhaust gas recirculation rate. It is demonstrated that the method developed can be applied to the prediction of engine load–speed maps for exhaust NO x , indicated mean effective pressure and fuel consumption. The maps can be derived from the limited experimental data available for model calibration. Significant speedup of the simulations process can be achieved using tabulated chemistry. Overall, the method presented can be considered as a bridge between the experimental works and the development of mean value engine models for engine control applications.
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| 34. |
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| 35. |
- Sharma, Nikhil, 1986, et al.
(författare)
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Morphological characterization of soot from a compression ignition engine fueled with diesel and an oxygenated fuel
- 2023
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 24:3, s. 1063-1076
-
Tidskriftsartikel (refereegranskat)abstract
- Compression ignition (CI) engines are highly efficient and are therefore often the first choice in application of heavy machinery and heavy duty vehicles. However, diesel engines are known to emit soot and oxides of nitrogen (NOx) emission. Replacing fossil diesel fuel with renewable fuel is one possibility to reduce emissions and to meet legislative requirements. In this experimental work, an oxygenated fuel blend was investigated for soot morphology and results were compared with fossil diesel fuel without oxygenates. Soot was sampled at a medium load case in a light duty single cylinder research engine and samples were analyzed with a transmission electron microscope (TEM). Furthermore, combustion characteristics and particle number (PN) emissions were compared for both fuels. The primary particle diameter (Dp), fringe length (L), fringe separation (S), and tortuosity (T) were also discussed in terms of soot nanostructure. The particle size distribution (PSD) showed a reduction in PN over for the renewable fuel blend compared to diesel. This PN reduction was from 107 to 106 (one order magnitude lower). The maximum Dp from morphological analysis of diesel fuel and renewable fuel was 69.93 and 66.36 nm respectively. Size range of fringe separation (S) was nearly identical for both fuels. Diesel fuel has marginally higher fringe separation, fringe length, and tortuosity. This investigation is valuable for fuel industries which are continuously upgrading renewable and oxygenated fuels to meet stringent emission norms.
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| 36. |
- Somhorst, Joop, 1965, et al.
(författare)
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Effects of thermal barrier coating porosity on combustion and heat losses in a light duty diesel engine
- 2024
-
Ingår i: International Journal of Engine Research. - 1468-0874 .- 2041-3149. ; 25:5, s. 940-958
-
Tidskriftsartikel (refereegranskat)abstract
- Plasma sprayed thermal barrier coatings (TBCs), applied in internal combustion engines, can have a profound impact on the apparent rate of heat release. Upon fuel jet contact with the piston wall, the heat loss seems to increase compared to an uncoated piston and combustion appears delayed. Permeable porosity of plasma sprayed TBCs is identified as one of the possible causes for this unwanted effect. In this article the impact of open porosity and sealing of the TBC surface are investigated with single cylinder engine experiments and with simulations. Based on the results, a mechanism is presented to explain the observations.
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| 37. |
- Somhorst, Joop, et al.
(författare)
-
Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine
- 2021
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 22:3, s. 890-910
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of two thermal barrier coatings and their surface roughness on heat transfer, combustion, and emissions has been investigated in a single-cylinder light-duty diesel engine. The evaluated thermal barrier coating materials were plasma-sprayed yttria-stabilized zirconia and hard anodized aluminum, which were applied on the piston top surface. The main tool for the investigation was cylinder pressure analysis of the high-pressure cycle, from which the apparent rate of heat release, indicated efficiency, and heat losses were derived. For verification of the calculated wall heat transfer, the heat flow to the piston cooling oil was measured as well. Application of thermal barrier coatings can influence engine operating conditions like charge temperature and ignition delay. Therefore, extra attention was paid to choosing stable and repeatable engine operating points. The experimental data were modeled using multiple linear regression to isolate the effects of the coatings and of the surface roughness. The results from this study show that high surface roughness leads to increased wall heat losses and a delayed combustion. However, these effects are less pronounced at lower engine loads and in the presence of soot deposits. Both thermal barrier coatings show a reduction of cycle-averaged wall heat losses, but no improvement in indicated efficiency. The surface roughness and thermal barrier coatings had a significant impact on the hydrocarbon emissions, especially for low-load engine operation, while their effect on the other exhaust emissions was relatively small.
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| 38. |
- Sowman, J., et al.
(författare)
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Nonlinear model predictive control applied to multivariable thermal and chemical control of selective catalytic reduction aftertreatment
- 2019
-
Ingår i: International Journal of Engine Research. - : SAGE Publications Ltd. - 1468-0874 .- 2041-3149. ; 20:10, s. 1017-1024
-
Tidskriftsartikel (refereegranskat)abstract
- Manufacturers of diesel engines are under increasing pressure to meet progressively stricter NO x emission limits. A key NO x abatement technology is selective catalytic reduction in which ammonia, aided by a catalyst, reacts with NO x in the exhaust stream to produce nitrogen and water. The conversion efficiency is temperature dependent: at low temperature, reaction rates are temperature limited, resulting in suboptimal NO x removal, whereas at high temperatures, they are mass transfer limited. Maintaining sufficiently high temperature to allow maximal conversion is a challenge, particularly after cold start, as well as during conditions in which exhaust heat is insufficient, such as periods of low load or idling. In this work, a nonlinear model predictive controller simultaneously manages urea injection and power to an electric catalyst heater, in the presence of constraints.
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| 39. |
- Thibblin, Anders, et al.
(författare)
-
A study of suspension plasma-sprayed insulated pistons evaluated in a heavy-duty diesel engine
- 2020
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 21:6, s. 987-997
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal barrier coatings can be used to reduce the heat losses in heavy-duty diesel engines. A relatively new coating method for thermal barrier coatings is suspension plasma-spraying. Single-cylinder engine tests have been run to evaluate how heat losses to piston, cylinder head and exhausts as well as the specific fuel consumption are influenced by coating pistons with two different suspension plasma-sprayed thermal barrier coatings and one atmospheric plasma-sprayed thermal barrier coating, and comparing the results to those from an uncoated steel piston. The two suspension plasma-sprayed thermal barrier coatings showed reduced heat losses through the piston and less heat redirected to the cylinder head compared to conventional atmospheric plasma-sprayed thermal barrier coating, while one suspension plasma-sprayed coating with yttria-stabilized zirconia as top coat material showed increased exhaust temperature. However, the indicated specific fuel consumption was higher for all tested thermal barrier coatings than for an uncoated engine. The best performing thermal barrier coating with respect to indicated specific fuel consumption was a suspension plasma-sprayed coating with gadolinium zirconate as top coat material.
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| 40. |
- Tornehed, Petter, et al.
(författare)
-
Modelling lubrication oil particle emissions from heavy-duty diesel engines
- 2013
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 14:2, s. 180-190
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Tidskriftsartikel (refereegranskat)abstract
- The impact of lubrication oil on particle exhaust emissions has attracted increasing attention as emissions of fuel-derived particles have been reduced. This paper presents a model for assessing the oil-related exhaust particle emissions of heavy-duty diesel engines. The model contains four sub-models describing the hydrocarbon, ash, carbon and sulphate particles. All sub-models were developed based on the results of a literature review, complemented by controlled engine tests to fill the knowledge gaps and verify assumptions where necessary. Exhaust after-treatment devices, such as diesel particulate filters, are not included in the model at this stage; in engines equipped with such devices, the modelling results could be used to assess the input of oil-related particulate matter into the exhaust after-treatment system or serve as a basis for further development. The modelling results indicate that the contribution of oil to airborne exhaust particles is substantial under low-load and motoring conditions. Reducing oil consumption is an effective way to reduce oil-related particle emissions.
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| 41. |
- Tunestål, Per, et al.
(författare)
-
Editorial: Special Issue on emission modeling
- 2014
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 15:8, s. 897-897
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 42. |
- Uczak de Goes, Wellington, 1990-, et al.
(författare)
-
Porous thermal barrier coatings for enhancing the efficiency of internal combustion engines
- 2022
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149.
-
Tidskriftsartikel (refereegranskat)abstract
- Internal combustion engines have a key role in the social and economic advancement of modern society but also a significant contribution to greenhouse gas emissions. For these engines, to preserve their role, a higher efficiency, that dramatically reduces the environmental impact, is necessary. To achieve increased engine efficiency, a technical solution is to lower the heat losses in the combustion chamber. Among them, the heat losses to the pistons are the preferential route, due to their extensive impact on fuel consumption. In this paper, porous thermal barrier coatings with large pores were applied to the pistons of diesel engines to improve engine efficiency. Atmospheric Plasma Spray (APS) process and porosity former TBC feedstock were employed to obtain high porosity coatings with large pores. Scanning Electron Microscopy (SEM) was utilized to investigate the microstructure of the coating in coupons and pistons. The optical properties of the coatings were explored with two methods: the spectral normal hemispherical reflectivity at room temperature (SNHRRT) and spectral normal emissivity at high temperature (SNEHT). The coatings’ behavior under thermal cyclic conditions was assessed by Flame Rig Test. Microstructure analysis was also performed before and after the test to identify the failure mechanisms. The engine efficiency was evaluated by measuring the Indicated Specific Fuel Consumption (ISFC) in a single-cylinder engine test. The results showed that porous coating with large pores combined with a higher emissivity can withstand the engine environment well and have the potential to provide enhancements in engine efficiency.
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| 43. |
- Winkler, Niklas
(författare)
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Effect of pressure oscillations on in-cylinder heat transfer - through large eddy simulation
- 2015
-
Ingår i: International Journal of Engine Research. - Royal Inst Technol, Div Internal Combust Engines, Dept Machine Design, S-10044 Stockholm, Sweden. : SAGE Publications. - 1468-0874 .- 2041-3149. ; 16:6, s. 705-715
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Tidskriftsartikel (refereegranskat)abstract
- As fuel consumption is a key issue for next-generation internal combustion engines, the heat release rate is increased and the duration shortened towards partially premixed combustion and in extreme cases towards homogeneous charge compression ignition to increase thermal efficiency. However, a steep rise in the heat release rate may trigger pressure oscillations in the combustion chamber, which have shown to increase the heat transfer, lowering efficiency and increasing fuel consumption. The aim of this research is to find the physical mechanisms that cause the increased in-cylinder heat transfer in the presence of pressure oscillations. According to the author's knowledge, the physical mechanisms responsible for the increased heat transfer have yet not been well understood for this application. Several of the hypotheses for this work are therefore based on the research performed for pulsating turbulent pipe flow. A numerical study has been performed using the large eddy simulation approach, where the pressure oscillations in the combustion chamber have been triggered by an artificially imposed heat source. The results show an increase in heat transfer in relation to pressure amplitude, in accordance with previous experimental studies. The mechanism found is a rapid transport of high-temperature fluid from the heat source towards the wall due to large-scale velocity fluctuations emerged from the pressure oscillations resulting in increased heat transfer.
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| 44. |
- Lehnert, Bastian, et al.
(författare)
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Quantifying extinction imaging of fuel sprays considering scattering errors
- 2023
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Ingår i: International Journal of Engine Research. - 1468-0874. ; 24:10, s. 4413-4420
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we use the measurement technique of high-speed Diffuse Back Illumination Extinction Imaging (DBI-EI) to obtain quantitative information in the form of projected liquid volume (PLV) in a highly transient GDI process. For the DBI-EI setup we use a LED-Panel as the light source, which fulfills diffuse back illumination extinction imaging criteria. Measurements were carried out in a constant volume chamber, allowing easy optical access, and enabling measurements at real world ambient engine conditions. For the experiments, we use an Engine Combustion Network (ECN) Spray G injector and measure the sprays at ECN conditions. Moreover, we mount the injector in a motorized rotational system, enabling measurements of the sprays at precisely defined angles of observation. The DBI-EI technique requires a light source radiating uniformly in a certain range of an angle. Because of the diffuse radiation, an error in the quantification of the liquid phase results from the detection of multiple and forward scattered photons. This leads to an underestimation of the optical depth ((Formula presented.)), which further results in a false calculation of the projected liquid volume. Therefore, we must assume that DBI-EI results are wrong. To enable the use of DBI-EI in all spray regions independent of the measurement setup, we present a simulation-based method, which is correcting the (Formula presented.) for scattering effects. Results show, that the measured (Formula presented.) of the experimental setup, which we used in this work, is underestimated by at least a factor of 2.2. This factor increases with increasing spray densities. We can use the corresponding corrected PLV data to reconstruct three-dimensional data of the liquid volume fraction with the tomographic method filtered back projection. Thus, we obtain time and spatial resolved quantitative spray information, with an approach to correct undesired scattering effects, while keeping the experimental effort low.
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| 45. |
- Mosbach, S., et al.
(författare)
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Dual injection homogeneous charge compression ignition engine simulation using a stochastic reactor model
- 2007
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Ingår i: International Journal of Engine Research. - 1468-0874. ; 8:1, s. 41-50
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Tidskriftsartikel (refereegranskat)abstract
- Multiple direct injection (MDI) is a promising strategy to enable fast-response ignition control as well as expansion of the homogeneous charge compression ignition (HCCI) engine operating window, thus realizing substantial reductions of soot and NOx emissions. The present paper extends a zero-dimensional-probability-density-function-based stochastic reactor model (SRM) for HCCI engines in order to incorporate MDI and an improved turbulent mixing model. For this, a simplistic spray model featuring injection, penetration, and evaporation sub-models is formulated, and mixing is described by the Euclidean minimal spanning tree (EMST) sub-model accounting for localness in composition space. The model is applied to simulate a gasoline HCCI engine, and the in-cylinder pressure predictions for single and dual injection cases show a satisfactory agreement with measurements. From the parametric studies carried out it is demonstrated that, as compared with single injection, the additional second injection contributes to prolonged heat release and consequently helps to prevent knock, thereby extending the operating range on the high load side. Tracking the phase space trajectories of individual stochastic particles provides significant insight into the influence of local charge stratification owing to direct injection on HCCI combustion.
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