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Investigation of homogeneous lean SI combustion in high load operating conditions

Chalmers University of Technology-Kristoffer H. Clasen, Lucien Koopmans
  • Technical Paper
  • 2020-01-0959
To be published on 2020-04-14 by SAE International in United States
Homogeneous lean combustion (HLC) can be utilized to substantially improve SI ICE efficiency which is vital in the process of enabling clean, efficient and affordable propulsion for the next generation light duty vehicles. More research is however necessary to ensure robustness, fuel efficiency/ NOx trade-off and utilization of HLC. Utilization can be improved by expanding the HLC operating window to higher engine torque domains which increases impact on real driving. The authors have earlier assessed dedicated HLC boosting in a downsized 2lt engine but it was found that HLC operation could not be achieved above 15 bar IMEP due to instability and knock. The observation led to the conclusion that there exists a lean load limit. Therefore, further experiments have been conducted in a single cylinder research SI GDI engine to increase understanding of high load lean operation. HLC is known to suppress end-gas autoignition (knock) by decreasing reactivity and temperatures, but during the experiments knock was observed to be prominent and increasing in severity when engine load was increased despite operating ultra-lean close to…
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Water Injection System Application in a Mild Hybrid Powertrain

Chalmers University of Technology-Jayesh Khatri, Lucien Koopmans
  • Technical Paper
  • 2020-01-0798
To be published on 2020-04-14 by SAE International in United States
The potential of 48V Mild Hybrid is promising in meeting the present and future CO2 legislations. There are various system layouts for 48V hybrid system including P0, P1, P2. In this paper, P2 architecture is used to investigate the effects of water injection benefits in a mild hybrid system. Electrification of the conventional powertrain uses the benefits of an electric drive in the low load-low speed region where the conventional SI engine is least efficient and as the load demand increases the IC Engine is used in its more efficient operating region.Engine downsizing and forced induction trend is popular in the hybrid system architecture. However, the engine efficiency is limited by combustion knocking at higher loads thus ignition retard is used to avoid knocking and fuel enrichment becomes must to operate the engine at MBT (Maximum Brake Torque) timing; in turn neutralizing the benefits of fuel savings by electrification. Water injection suppresses engine knocking and enables operating at stoichiometric air-fuel ratio. In addition to that, the injection of water reduces flame temperature, giving room to…
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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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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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Homogeneous Lean Combustion in a 2lt Gasoline Direct Injected Engine with an Enhanced Turbo Charging System

Chalmers University of Technology-Kristoffer Clasen, Lucien Koopmans
Volvo Car Corp.-Daniel Dahl
Published 2018-09-10 by SAE International in United States
In the quest for a highly efficient, low emission and affordable source of passenger car propulsion system, meeting future demands for sustainable mobility, the concept of homogeneous lean combustion (HLC) in a spark ignited (SI) multi-cylinder engine has been investigated. An attempt has been made to utilize the concept of HLC in a downsized multi-cylinder production engine producing up to 22 bar BMEP in load. The focus was to cover as much as possible of the real driving operational region, to improve fuel consumption and tailpipe emissions. A standard Volvo two litre four-cylinder gasoline direct injected engine operating on commercial 95 RON gasoline fuel was equipped with an advanced two stage turbo charger system, consisting of a variable nozzle turbine turbo high-pressure stage and a wastegate turbo low-pressure stage. The turbo system was specifically designed to meet the high demands on air mass flow when running lean on higher load and speeds. Also, a dual coil ignition system was used for enhanced ignition ability and a lean NOx emissions exhaust after-treatment system (EATS) dummy was…
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Reducing Pressure Fluctuations at High Loads by Means of Charge Stratification in HCCI Combustion with Negative Valve Overlap

Chalmers University of Technology-Daniel Dahl, Mats Andersson, Andreas Berntsson, Ingemar Denbratt
Volvo Car Corporation-Lucien Koopmans
Published 2009-06-15 by SAE International in United States
Future demands for improvements in the fuel economy of gasoline passenger car engines will require the development and implementation of advanced combustion strategies, to replace, or combine with the conventional spark ignition strategy. 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 the combustion becoming too rapid, leading to excessive pressure-rise rates and large pressure fluctuations (ringing), causing noise.In this work, efforts were made to reduce these pressure fluctuations by using a late injection during the later part of the compression. A more appropriate acronym than HCCI for such combustion is SCCI (Stratified Charge Compression Ignition). The approach was evaluated in tests with a single-cylinder metal research engine and a single-cylinder optical engine. The latter was used to characterize the combustion in laser-based analyses including laser-induced florescence (LIF) determinations of fuel tracer, OH and CH2O (formaldehyde)…
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An Evaluation of Different Combustion Strategies for SI Engines in a Multi-Mode Combustion Engine

SAE International Journal of Engines

Chalmers University of Technology-Daniel Dahl, Ingemar Denbratt
Volvo Car Corporation-Lucien Koopmans
  • Journal Article
  • 2008-01-0426
Published 2008-04-14 by SAE International in United States
Future pressures to reduce the fuel consumption of passenger cars may require the exploitation of alternative combustion strategies for gasoline engines to replace, or use in combination with the conventional stoichiometric spark ignition (SSI) strategy. Possible options include homogeneous lean charge spark ignition (HLCSI), stratified charge spark ignition (SCSI) and homogeneous charge compression ignition (HCCI), all of which are intended to reduce pumping and thermal losses.In the work presented here four different combustion strategies were evaluated using the same engine: SSI, HLCSI, SCSI and HCCI. HLCSI was achieved by early injection and operating the engine lean, close to its stability limits. SCSI was achieved using the spray-guided technique with a centrally placed multi-hole injector and spark-plug. HCCI was achieved using a negative valve overlap to trap hot residuals and thus generate auto-ignition temperatures at the end of the compression stroke.The experiments were performed using a 6 cylinder, 3.2 liter Volvo engine equipped with cam profile switching (CPS), variable cam timing (VCT) for both intake and exhaust valves, and a spray guided direct injection (SGDI) system.…
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Ion Current Sensing in an Optical HCCI Engine with Negative Valve Overlap

Chalmers University of Technology-Martin Larsson, Ingemar Denbratt
Volvo Car Corporation-Lucien Koopmans
Published 2007-01-23 by SAE International in United States
Ion current sensors have high potential utility for obtaining feedback signals directly from the combustion chamber in internal combustion engines. This paper describes experiments performed in a single-cylinder optical engine operated in HCCI mode with negative valve overlap to explore this potential. A high-speed CCD camera was used to visualize the combustion progress in the cylinder, and the photographs obtained were compared with the ion current signals. The optical data indicate that the ions responsible for the chemiluminescence from the HCCI combustion have to be in contact with the sensing electrode for an ion current to start flowing through the measurement circuit. This also means that there will be an offset between the time at which 50% of the fuel mass has burned and 50% of the ion current peak value is reached, which is readily explained by the results presented in the paper. In addition the results show that the ion current sensor generates good combustion phasing signals for HCCI combustion with negative valve overlap at low engine speeds and low engine loads, provided…
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Comparative Study of In-Cylinder Pressure Sensors for Combustion Engine Feedback Control

Chalmers University of Technology-Martin Larsson, Ingemar Denbratt
Volvo Car Corporation-Lucien Koopmans
  • Technical Paper
  • 2006-08-0187
Published 2006-05-01 by Society of Automotive Engineers of Japan in Japan
Developing more sensitive controls for internal combustion engines to meet increasingly strict emission limits is becoming an urgent task, especially for automotive engines. Pressure-sensing systems could be important components of such controls, especially since recent advances have reduced their costs, and increased both their durability and the available options. For these reasons three different types of pressure sensor (one piezo-resistive, one fiber optic and one gasket-type) were installed and evaluated in a single-cylinder SI engine, using a water-cooled piezoelectric pressure sensor as a reference system. In addition, heat release analysis and pressure ratio management strategies were explored to compare the potential utility of different combustion-phasing measures. This paper describes the key findings and discusses their implications.