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Particulate Emissions in a GDI with an Upstream Fuel Source

Chalmers University of Technology-Sreelekha Etikyala, Lucien Koopmans, Petter Dahlander
Published 2019-04-02 by SAE International in United States
Public health risk and resulting stringent emission regulations for internal combustion engines pose a need for solutions to reduce particle emissions (PN). Current PN control approaches include increasing fuel injection pressure, optimizing spray targeting, multiple injection strategies, and the use of tumble flaps together with gasoline particulate filters (GPF).Experiments were performed using a single-cylinder spark-ignited GDI engine equipped with a custom inlet manifold and a port fuel injector located 500 mm upstream. Particulate emissions were measured during stationary medium/high load operation to evaluate the effect of varying the mass split between the direct and upstream injectors. Mixing quality is improved substantially by upstream injection and can thus be controlled by altering the mass split between the injectors. Additional particulate measurements were performed using a thermodenuder and a catalyst to remove major part of the volatile organic compounds (VOCs) from raw emissions. This made it possible to determine particle numbers (PN) both raw emissions and solid particulates, and the size distribution of the solid particulate emissions.Upstream fuel source was found to reduce PN emissions by almost…
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48V Mild-Hybrid Architecture Types, Fuels and Power Levels Needed to Achieve 75g CO2/km

Chalmers University of Technology-Mindaugas Melaika, Sarp Mamikoglu, Petter Dahlander
Published 2019-04-02 by SAE International in United States
48V mild hybrid powertrains are promising technologies for cost-effective compliance with future CO2 emissions standards. Current 48V powertrains with integrated belt starter generators (P0) with downsized engines achieve CO2 emissions of 95 g/km in the NEDC. However, to reach 75 g/km, it may be necessary to combine new 48V powertrain architectures with alternative fuels. Therefore, this paper compares CO2 emissions from different 48V powertrain architectures (P0, P1, P2, P3) with different electric power levels under various driving cycles (NEDC, WLTC, and RTS95). A numerical model of a compact class passenger car with a 48V powertrain was created and experimental fuel consumption maps for engines running on different fuels (gasoline, Diesel, E85, CNG) were used to simulate its CO2 emissions. The simulation results were analysed to determine why specific powertrain combinations were more efficient under certain driving conditions. As expected, the greatest influence on emissions was from powertrain architectures. Increased electric power levels (from 8 kW to 20 kW) allowed more brake energy to be recovered, reducing CO2 emissions by 2 - 16% depending on the…
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Spray Characterization of Gasoline Direct Injection Sprays Under Fuel Injection Pressures up to 150 MPa with Different Nozzle Geometries

Chalmers University of Technology-Lucien Koopmans, Petter Dahlander
Denso Corp.-Akichika Yamaguchi
Published 2019-01-15 by SAE International in United States
Maximum fuel injection pressures for GDI engines is expected to increase due to positive effects on emissions and engine-efficiency. Current GDI injectors have maximum operating pressures of 35 MPa, but higher injection pressures have yielded promising reductions in particle number (PN) and improved combustion stability. However, the mechanisms responsible for these effects are poorly understood, and there have been few studies on fuel sprays formed at high injection pressures.This paper summarizes experimental studies on the properties of sprays formed at high injection pressures. The results of these experiments can be used as inputs for CFD simulations and studies on combustion behavior, emissions formation, and combustion system design. The experiments were conducted using an injection rate meter and optical methods in a constant volume spray chamber. Injection rate measurements were performed to determine the injectors’ flow characteristics. Spray imaging was performed using a high-speed video camera. Several spray properties such as the liquid spray penetration, spray plume angle, and the spray breakup point were determined as functions of the fuel injection pressure and injected fuel mass…
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Water Injection Benefits in a 3-Cylinder Downsized SI-Engine

SAE International Journal of Advances and Current Practices in Mobility

Chalmers University of Technology-Jayesh Khatri, Ingemar Denbratt, Petter Dahlander, Lucien Koopmans
  • Journal Article
  • 2019-01-0034
Published 2019-01-15 by SAE International in United States
With progressing electrification of automotive powertrains and demands to meet increasingly stringent emission regulations, a combination of an electric motor and downsized turbocharged spark-ignited engine has been recognized as a viable solution. The SI engine must be optimized, and preferentially downsized, to reduce tailpipe CO2 and other emissions. However, drives to increase BMEP (Brake Mean Effective Pressure) and compression ratio/thermal efficiency increase propensities of knocking (auto-ignition of residual unburnt charge before the propagating flame reaches it) in downsized engines.Currently, knock is mitigated by retarding the ignition timing, but this has several limitations. Another option identified in the last decade (following trials of similar technology in aircraft combustion engines) is water injection, which suppresses knocking largely by reducing local in-cylinder mixture temperatures due to its latent heat of vaporization. Addition of adequate water can lead to stoichiometric air/fuel ratio engine operation, and hence both reduction in fuel consumption and full utilization of a three-way catalytic converter (TWC).Further information about effects of various water injection parameters is required. Thus, in this study, a 4-stroke, 1.5 liter, 3-cylinder…
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Modelling of Hybrid Electric Vehicle Powertrains - Factors That Impact Accuracy of CO₂ Emissions

Chalmers University of Technology-Sarp Mamikoglu, Petter Dahlander
Published 2019-01-15 by SAE International in United States
Modelling is widely used for the development of hybrid electric vehicle (HEV) powertrain technologies, since it can provide accurate prediction of fuel consumption and CO₂ emissions, for a fraction of the resources required in experiments. For comparison of different technologies or powertrain parameters, the results should be accurate relative to each other, since powertrains are simulated under identical model details and simulation parameters. However, when CO₂ emissions of a vehicle model are simulated under a driving cycle, significant deviances may occur between actual tests and simulation results, compromising the integrity of simulations. Therefore, this paper investigates the effects of certain modelling and simulation parameters on CO₂ emission results, for a parallel HEV under three driving cycles (NEDC, WLTC and RTS95 to simulate real driving emissions (RDE)). A sensitivity analysis on battery state of charge levels (SOC), control systems, component data resolutions, warm-up phase, time-step, driver controller behavior and 0D vs 1D simulation parameters is carried out and their effect on CO₂ emission results are investigated. While any change in one of the parameters may result…
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Methane Direct Injection in an Optical SI Engine - Comparison between Different Combustion Modes

Chalmers University of Technology-Mindaugas Melaika, Mats Andersson, Petter Dahlander
Published 2019-01-15 by SAE International in United States
Natural gas, biogas, and biomethane are attractive fuels for compressed natural gas (CNG) engines because of their beneficial physical and chemical characteristics. This paper examines three combustion modes - homogeneous stoichiometric, homogeneous lean burn, and stratified combustion - in an optical single cylinder engine with a gas direct injection system operating with an injection pressure of 18 bar. The combustion process in each mode was characterized by indicated parameters, recording combustion images, and analysing combustion chemiluminescence emission spectra. Pure methane, which is the main component of CNG (up to 98%) or biomethane (> 98 %), was used as the fuel. Chemiluminescence emission spectrum analysis showed that OH* and CN* peaks appeared at their characteristic wavelengths in all three combustion modes. The peak of OH* and broadband CO2* intensities were strongly dependent on the air/fuel ratio conditions in the cylinder. Lower OH* and CO2* intensities were observed with lean air/fuel mixtures because under these conditions, more air was present, the combustion reactions were slower, and the cylinder pressure was higher. CN* was formed by the spark…
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Impact of Conventional and Electrified Powertrains on Fuel Economy in Various Driving Cycles

Chalmers University of Technology-Sarp Mamikoglu, Jelena Andric, Petter Dahlander
Published 2017-03-28 by SAE International in United States
Many technological developments in automobile powertrains have been implemented in order to increase efficiency and comply with emission regulations. Although most of these technologies show promising results in official fuel economy tests, their benefits in real driving conditions and real driving emissions can vary significantly, since driving profiles of many drivers are different than the official driving cycles. Therefore, it is important to assess these technologies under different driving conditions and this paper aims to offer an overall perspective, with a numerical study in simulations. The simulations are carried out on a compact passenger car model with eight powertrain configurations including: a naturally aspirated spark ignition engine, a start-stop system, a downsized engine with a turbocharger, a Miller cycle engine, cylinder deactivation, turbocharged downsized Miller engine, a parallel hybrid electric vehicle powertrain and an electric vehicle powertrain. These are tested in seven driving cycles including the NYCC, FTP75, NEDC, WLTC, US06, HWFET and CADC. The impacts of different technologies on fuel economy and CO2 emissions are analyzed, with respect to different operating conditions. Results reveal…
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Reduction of Soot Formation in an Optical Single-Cylinder Gasoline Direct-Injected Engine Operated in Stratified Mode Using 350 Bar Fuel Injection Pressure, Dual-Coil and High-Frequency Ignition Systems

SAE International Journal of Engines

Chalmers University of Technology-Anders N. Johansson, Stina Hemdal, Petter Dahlander
  • Journal Article
  • 2017-01-9278
Published 2017-03-14 by SAE International in United States
The current trend toward more fuel efficient vehicles with lower emission levels has prompted development of new combustion techniques for use in gasoline engines. Stratified combustion has been shown to be a promising approach for increasing the fuel efficiency. However, this technique is hampered by drawbacks such as increased particulate and standard emissions.This study attempts to address the issues of increased emission levels by investigating the influence of high frequency ionizing ignition systems, 350 bar fuel injection pressure and various tumble levels on particulate emissions and combustion characteristics in an optical SGDI engine operated in stratified mode on isooctane.Tests were performed at one engine load of 2.63 bar BMEP and speed of 1200 rpm. Combustion was recorded with two high speed color cameras from bottom and side views using optical filters for OH and soot luminescence.The results indicated that increasing the fuel injection pressure led to faster burn as well as a reduction in soot luminescence. The ionizing ignition system generated faster initial combustion. Increasing the tumble level reduced the soot luminescence at all injection…
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Experimental Investigation of the Influence of Boost on Combustion and Particulate Emissions in Optical and Metal SGDI-Engines Operated in Stratified Mode

SAE International Journal of Engines

Chalmers Univ. of Technology-Anders N. Johansson, Petter Dahlander
  • Journal Article
  • 2016-01-0714
Published 2016-04-05 by SAE International in United States
Boosting and stratified operation can be used to increase the fuel efficiency of modern gasoline direct-injected (GDI) engines. In modern downsized GDI engines, boosting is standard to achieve a high power output. However, boosted GDI-engines have mostly been operated in homogenous mode and little is known about the effects of operating a boosted GDI-engine in stratified mode.This study employed optical and metal engines to examine how boosting influences combustion and particulate emission formation in a spray-guided GDI (SGDI), single cylinder research engine. The setup of the optical and metal engines was identical except the optical engine allowed optical access through the piston and cylinder liner.The engines were operated in steady state mode at five different engine operating points representing various loads and speeds. The engines were boosted with compressed air and operated at three levels of boost, as well as atmospheric pressure for comparison. The fuel used was market gasoline (95 RON) blended with 10% ethanol. The spark plug and injector were mounted in parallel with the intake valves. The gas motion induced by the…
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Experimental Investigation of Methane Direct Injection with Stratified Charge Combustion in Optical SI Single Cylinder Engine

Chalmers University of Technology-Petter Dahlander
Vilnius Gediminas Technical University-Mindaugas Melaika
Published 2016-04-05 by SAE International in United States
This paper assesses methane low pressure direct injection with stratified charge in a SI engine to highlight its potential and downsides. Experiments were carried out in a spark ignited single cylinder optical engine with stratified, homogeneous lean and stoichiometric operational mode, with focus on stratified mode. A dual coil ignition system was used in stratified mode in order to achieve sufficient combustion stability. The fuel injection pressure for the methane was 18 bar. Results show that stratified combustion with methane spark ignited direct injection is possible at 18 bar fuel pressure and that the indicated specific fuel consumption in stratified mode was 28% lower compared to the stoichiometric mode. Combustion and emission spectrums during the combustion process were captured with two high-speed video cameras. Combustion images, cylinder pressure data and heat release analysis showed that there are fairly high cycle-to-cycle variations in the combustion. Both blue pre-mixed flame and soot luminescence occurred in the combustion. The occurrence of soot luminescence was also supported by the emission spectrum. Soot formation sources were found to be localized…
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