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Viewing 1 to 30 of 83
2004-03-08
Technical Paper
2004-01-0564
Lucien Koopmans, Johan Wallesten, Roy Ogink, Ingemar Denbratt
To elucidate the processes controlling the auto-ignition timing and overall combustion duration in homogeneous charge compression ignition (HCCI) engines, the distribution of the auto-ignition sites, in both space and time, was studied. The auto-ignition locations were investigated using optical diagnosis of HCCI combustion, based on laser induced fluorescence (LIF) measurements of formaldehyde in an optical engine with fully variable valve actuation. This engine was operated in two different modes of HCCI. In the first, auto-ignition temperatures were reached by heating the inlet air, while in the second, residual mass from the previous combustion cycle was trapped using a negative valve overlap. The fuel was introduced directly into the combustion chamber in both approaches. To complement these experiments, 3-D numerical modeling of the gas exchange and compression stroke events was done for both HCCI-generating approaches.
2004-06-08
Technical Paper
2004-01-1967
Lucien Koopmans, Elna Strömberg, Ingemar Denbratt
A single-cylinder engine was operated in HCCI combustion mode with different kinds of commercial fuels. The HCCI combustion was generated by creating a negative valve overlap (early exhaust valve closing combined with late intake valve opening) thus trapping a large amount of residuals (∼ 55%). Fifteen different fuels with high octane numbers were tested six of which were primary reference fuels (PRF's) and nine were commercial fuels or reference fuels. The engine was operated at constant operational parameters (speed/load, valve timing and equivalence ratio, intake air temperature, compression ratio, etc.) changing only the fuel type while the engine was running. Changing the fuel affected the auto-ignition timing, represented by the 50% mass fraction burned location (CA50). However these changes were not consistent with the classical RON and MON numbers, which are measures of the knock resistance of the fuel. Indeed, no correlation was found between CA50 and the RON or MON numbers.
2004-06-08
Technical Paper
2004-01-1951
Ronny Lindagren, Ingemar Denbratt
Interest in spray-wall interactions has grown because of the development of direct-injection stratified-charge (DISC) spark ignition (SI) engines. In this type of engine, impingement of the spray on the piston wall often leads to high emissions of unburned hydrocarbons and soot. These emissions have proven to be one of the major drawbacks of the DISC SI engine, so it is important to obtain detailed knowledge about the different processes involved in spray impingement and their effects. In this study, the size and velocity of droplets reflected from a wall were characterized by Phase Doppler Anemometry (PDA). The impinging spray was also visualized using an AVL VisioScope. The experiments were carried out on a real gasoline spray impinging on a wall under simulated engine conditions in a spray chamber. A sensitivity analysis was carried out to investigate the influence of different wall properties and wall temperature, on the impingement and secondary atomization processes.
2004-06-08
Technical Paper
2004-01-1871
Jakob Fredriksson, Ingemar Denbratt
The free piston internal combustion engine used in conjunction with a linear alternator offers an interesting choice for use in hybrid vehicles. The linear motion of the pistons is directly converted to electricity by the alternator, and the result is a compact and efficient energy converter that has only one moving part. The movement of the pistons is not prescribed by a crank mechanism, but is the result of the equilibrium of forces acting on the pistons, and the engine will act like a mass-spring system. This feature is one of the most prominent advantages of the FPE (Free Piston Engine), as the lack of mechanical linkage gives means of varying the compression ratio in simple manners, without changing the hardware of the engine. By varying the compression ratio, it is also it possible to run on a multitude of different fuels and to use HCCI (Homogeneous Charge Compression Ignition) combustion.
2004-03-08
Technical Paper
2004-01-0935
Arjan Helmantel, Ingemar Denbratt
The possibilities of operating a direct injection Diesel engine in HCCI combustion mode with early injection of conventional Diesel fuel were investigated. In order to properly phase the combustion process in the cycle and to prevent knock, the geometric compression ratio was reduced from 17.0:1 to 13.4:1 or 11.5:1. Further control of the phasing and combustion rate was achieved with high rates of cooled EGR. The engine used for the experiments was a single cylinder version of a modern passenger car type common rail engine with a displacement of 480 cc. An injector with a small included angle was used to prevent interaction of the spray and the cylinder liner. In order to create a homogeneous mixture, the fuel was injected by multiple short injections during the compression stroke. The low knock resistance of the Diesel fuel limited the operating conditions to low loads. Compared to conventional Diesel combustion, the NOx emissions were dramatically reduced.
2013-09-08
Technical Paper
2013-24-0087
Carlo Beatrice, Natale Rispoli, Gabriele Di Blasio, Giorgos Patrianakos, Margaritis Kostoglou, Athanasios Konstandopoulos, Abdurrahman Imren, Ingemar Denbratt, Roberto Palacin
The EU emission standards for new rail Diesel engines are becoming even more stringent. EGR and SCR technologies can both be used to reduce NOx emissions; however, the use of EGR is usually accompanied by an increase in PM emissions and may require a DPF. On the other hand, the use of SCR requires on-board storage of urea. Thus, it is necessary to study these trade-offs in order to understand how these technologies can best be used in rail applications to meet new emission standards. The present study assesses the application of these technologies in Diesel railcars on a quantitative basis using one and three dimensional numerical simulation tools. In particular, the study considers a 560 kW railcar engine with the use of either EGR or SCR based solutions for NOx reduction. The NOx and PM emissions performances are evaluated over the C1 homologation cycle.
2011-08-30
Technical Paper
2011-01-1889
Mats Andersson, Jonas Warnberg, Stina Hemdal, Petter Dahlander, Ingemar Denbratt
The evaporation of different fuels and fuel components in hollow-cone sprays at conditions similar to those at stratified cold start has been investigated using a combination of planar laser-induced fluorescence (LIF) and Mie scattering. Ketones of different volatility were used as fluorescent tracers for different fuel components in gasoline-like model fuels and ethanol-based fuels. LIF and Mie images were compared to evaluate to what extent various fuel components had evaporated and obtained a spatial distribution different from that of the liquid drops, as a function of fuel temperature and time after start of injection. A selective and sequential evaporation of fuel components of different volatility was found.
2005-04-11
Technical Paper
2005-01-0177
Arjan Helmantel, Jonas Gustavsson, Ingemar Denbratt
An experimental investigation was carried out in which an HSDI Common Rail Diesel engine was operated in both HCCI and conventional Diesel combustion modes, using conventional Diesel fuel in both cases. The engine used in the experiments was a single cylinder version of a modern passenger car engine with a displacement of 480 cc. In HCCI mode, the fuel was injected in multiple stages during the compression stroke, using a nozzle with a 60° included angle. To control the phasing and rate of combustion, the effective compression ratio was reduced by retarded intake valve closing. In addition, increased amounts of EGR were used. HCCI operation reduced soot and NOx emissions significantly. The use of a narrow included angle for conventional Diesel operation increased emissions significantly. The effect of a wider included angle and modifications to the piston were investigated experimentally and numerically.
2005-04-11
Technical Paper
2005-01-0097
M. Skogsberg, P. Dahlander, R. Lindgren, Ingemar Denbratt
This paper focuses on ways of improving the spray formation from spray-guided multi-hole gasoline direct injection injectors. Work has been done both experimentally using laser diagnostic tools and numerically using Computational Fluid Dynamics. Laser Induced Exciplex Fluorescence (LIEF) measurements in a constant pressure spray chamber and optical engine measurements have shown that injectors with 6-hole nozzles and 50-degree umbrella angles are unsuitable for stratified combustion because they produce steep air-fuel ratio gradients and create a spray with overly-deep liquid fuel penetration as well as presence of liquid fuel around the spark plug. In order to study injector performance, numerical calculations using the AVL FIRE™ CFD code were performed. The numerical results indicate that by increasing the injector umbrella angle, the extent of piston wall wetting can be decreased.
2005-04-11
Technical Paper
2005-01-0380
Tobias Husberg, Ingemar Denbratt, Monica Ringvik, Johan Engström
Experiments were conducted with a single cylinder heavy duty research engine, based on the geometry of a Volvo Powertrain D12C production engine. For these tests the engine was configured with a low compression ratio, low swirl, common rail fuel injection system and an eight-orifice nozzle. The combustion process was visualized by video via an inserted endoscope. From the resulting images temperatures were evaluated with the two-color method. In addition, the combustion and emission formation were simulated using the multiple flamelet concept implemented in the commercial CFD code STAR-CD. The models used in this paper are considered state-of-the-art. The purpose of this paper is to demonstrate the possibilities offered by combining several methods in the evaluation of novel engine concepts. Therefore, results from the optical measurements, the CFD simulations and global emission experimental data were compared.
2004-10-25
Technical Paper
2004-01-3003
Ronny Lindgren, Ingemar Denbratt
The effects of a gasoline spray impinging on a heated surface were investigated under simulated engine conditions in an earlier study. The data from the experimental investigation have now been compared to results obtained from Computational Fluid Dynamic (CFD) simulations generated using several different numerical models for spray-wall impingement found in the literature. It was found that the models based on single-drop experiments do not predict the outcome of spray impingement well in some respects. Their major drawback was that the predicted diameter distributions of the reflected drops in the secondary spray were shifted downwards from the measured drop size distributions. The tested models predicted the normal velocity component relative to the wall well. However, they were less good at capturing the tangential velocity component relative to the wall.
2005-04-11
Technical Paper
2005-01-1646
Tobias Husberg, Savo Gjirja, Ingemar Denbratt, Alaa Omrane, Marcus Aldén, Johan Engström
Piston temperature experiments were conducted in a single-cylinder heavy-duty Diesel research engine, based on the Volvo Powertrain D12C engine both by use of optical temperature sensitive phosphor and of thermocouples mounted on the piston surface. In the former case, a thin coating of a suitable thermographic phosphor was applied to the areas on the piston surface to be investigated. The optical measurements of piston temperatures made involved use of an optical window and of an endoscope. The possibility of using optical fibres into guide light in and out of the engine was also investigated. Results of the optical and of the thermocouple measurements were compared and were also related to more global data with the aim of exploring the use of thermographic phosphors for piston- temperature measurements in Diesel engines. Thermographic phosphors thermometry was found to represent an alternative to the thermocouple method since it easily can be applied to various piston geometries.
2015-09-06
Technical Paper
2015-24-2504
Gerben Doornbos, Emma Adams, Per-Anders Carlsson, Daniel Dahl, Mats Laurell, Håkan Schyllander, Par Gabrielsson, Milica Folic, Ingemar Denbratt, Magnus Skoglundh
Commercial three way catalysts have limited capacity towards reducing NOx in the presence of excessive oxygen. This prevents lean-burn combustion concepts from meeting legislative emission standards. A solution towards decreasing NOx emissions in the presence of excess air is the use of a passive-SCR system. Under rich conditions ammonia is formed over an ammonia formation catalyst, the ammonia is stored in the SCR and in its turn reacts with the NOx under lean engine conditions. Here up-scaled Pt/Al2O3 and Pd/Al2O3 catalysts as well as a commercially Pd-Rh based three-way catalyst (TWC) are evaluated using both engine and further lab-scale tests. The purpose of these tests is to compare the ammonia production for the various catalysts under various lambda values and temperatures by means of engine and lab scale tests. The Pd/Al2O3 showed little sensitivity to temperature both under engine and lab scale experiments.
2015-09-06
Journal Article
2015-24-2491
Tankai Zhang, Karin Munch, Ingemar Denbratt
Global warming driven by “greenhouse gas” emissions is an increasingly serious concern of both the public and legislators. A potentially potent way to reduce these emissions and conserve fossil fuel resources is to use n-butanol, iso-butanol or octanol (2-ethylhexanol) from renewable sources as alternative fuels in diesel engines. The effects of adding these substances to diesel fuel were therefore tested in a single-cylinder heavy duty diesel engine operated using factory settings. These alcohols have better calorific values, flash points, lubricity, cetane numbers and solubility in diesel than shorter-chain alcohols. However, they have lower cetane numbers than diesel, so either hydrotreated vegetable oil (HVO) or Di-tertiary-butyl peroxide (DTBP) was added to the diesel-alcohol mixtures to generate blends with the same Cetane Number (CN) as diesel.
2015-09-06
Technical Paper
2015-24-2538
Lars Christian Riis Johansen, Ingemar Denbratt, Stina Hemdal
Abstract The emissions from a parallel hybrid combustion engine and electric powertrain operated on a modified New European Drive Cycle (NEDC) was investigated in order to determine the relation between emissions and the road and engine load profile. The effect of simulated electric motor assistance during accelerations on emissions was investigated as a means to reduce particulate and gaseous emissions. The time resolved particulate number and size distribution was measured in addition to gaseous emissions. The combustion engine was a downsized, three cylinder spark ignited direct injection (SIDI) turbocharged engine fuelled with gasoline. Electric motor assistance during accelerations was simulated by reduction of the vehicle mass. This reduced engine load during accelerations. Fuel rich engine transients occurred during accelerations. NOx emissions were reduced with electric assistance due to a reduction in engine load.
2013-04-08
Technical Paper
2013-01-0254
Jonas Warnberg, Marius Boehmer, Ingemar Denbratt
A regular flex-fuel engine can operate on any blend of fuel between pure gasoline and E85. Flex-fuel engines have relatively low efficiency on E85 because the hardware is optimized for gasoline. If instead the engine is optimized for neat ethanol, the efficiency may be much higher, as demonstrated in this paper. The studied two-liter engine was modified with a much higher compression ratio than suitable for gasoline, two-stage turbocharging and direct injection with piezo-actuated outwards-opening injectors, a stratified combustion system and custom in-house control system. The research engine exhibited a wide-open throttle performance similar to that of a naturally aspirated v8, while offering a part-load efficiency comparable to a state-of-the-art two-liter naturally aspirated engine. NOx will be handled by a lean NOx trap. Combustion characteristics were compared between gasoline and neat ethanol.
2007-09-16
Technical Paper
2007-24-0012
Andreas W. Berntsson, Ingemar Denbratt
The effects of using an SI stratified charge in combination with HCCI combustion on combustion phasing, rate of heat release and emissions were investigated in engine experiments to identify ways to extend the operational range of HCCI combustion to lower loads. In the experiments an optical single-cylinder engine equipped with a piezo electric outward-opening injector and operated with negative valve overlap (NVO) and low lift, short duration, camshaft profiles, was used to initiate HCCI combustion by increasing the exhaust gas recirculation (EGR) and thus retaining sufficient thermal energy to reach auto-ignition temperatures. Two series of experiments with full factorial designs were performed, to investigate how the tested parameters (amounts of fuel injected in pilot injections and main injections, stratification injection timing and spark-assistance) influenced the combustion.
2007-10-30
Technical Paper
2007-01-4167
Henrik Salsing, Ingemar Denbratt
Combustion characteristics of dimethyl ether, DME, have been investigated experimentally, in a heavy duty single cylinder engine equipped with an adapted common rail fuel injection system, and the effects of varying injection timing, rail pressure and exhaust gas recirculation on the combustion and emission parameters. The results show that DME combustion does not produce soot and with the use of exhaust gas recirculation NOX emissions can also be reduced to very low levels. However, high injection pressure and/or a DME adopted combustion system is required to improve the mixing process and thus reduce the combustion duration and carbon monoxide emissions.
2008-04-14
Journal Article
2008-01-0426
Daniel Dahl, Ingemar Denbratt, Lucien Koopmans
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.
2007-10-29
Technical Paper
2007-01-4009
Monica Larsson, Ingemar Denbratt
This investigation includes a comparison of two Fischer Tropsch (FT) fuels derived from natural gas and a Rapeseed Methyl Ester (RME) fuel with Swedish low sulfur Diesel in terms of emissions levels, fuel consumption and combustion parameters. The engine used in the study was an AVL single cylinder heavy-duty engine, equipped with a cylinder head of a Volvo D12 engine. Two loads (25% and 100%) were investigated at a constant engine speed of 1200 rpm. The engine was calibrated to operate in different levels of EGR and with variable injections timings. A design of experiments was constructed to investigate the effects of these variables, and to identify optimal settings. The results showed that the soot emissions yielded by FT and RME fuels are up to 40 and 80 percent lower than those yielded by the Swedish Diesel. In addition the FT fuel gave slightly lower, and the RME significant higher NOx emissions than the Swedish Diesel.
2008-04-14
Technical Paper
2008-01-0037
Andreas W. Berntsson, Mats Andersson, Daniel Dahl, Ingemar Denbratt
Future requirements for emission reduction from combustion engines in ground vehicles might be met by using the HCCI combustion concept. In this study, negative valve overlap (NVO) and low lift, short duration, camshaft profiles, were used to initiate HCCI combustion by increasing the internal exhaust gas recirculation (EGR) and thus retaining sufficient thermal energy for chemical reactions to occur when a pilot injection was introduced prior to TDC, during the NVO. One of the crucial parameters to control in HCCI combustion is the combustion phasing and one way of doing this is to vary the relative ratio of fuel injected in pilot and main injections. The combustion phasing is also influenced by the total amount of fuel supplied to the engine, the combustion phasing is thus affected when the load is changed. This study focuses on the reactions that occur in the highly diluted environment during the NVO when load and pilot to main ratio are changed.
2009-11-02
Journal Article
2009-01-2815
Malin Ehleskog, Savo Gjirja, Ingemar Denbratt
When increasing EGR from low levels to a level that corresponds to low temperature combustion, soot emissions initially increase due to lower soot oxidation before decreasing to almost zero due to very low soot formation. At the EGR level where soot emissions start to increase, the NOx emissions are low, but not sufficiently low to comply with future emission standards and at the EGR level where low temperature combustion occurs CO and HC emissions are too high. The purpose of this study was to investigate the possibilities for shifting the so-called soot bump (where soot levels are increased) to higher EGR levels, or to reduce the magnitude of the soot bump using very high injection pressures (up to 240 MPa) while reducing the NOx emissions using EGR. The possibility of reducing the CO and HC emissions at high EGR levels due to the increased mixing caused by higher injection pressure was also investigated and the flame was visualized using an endoscope at chosen EGR values.
2009-11-02
Technical Paper
2009-01-2813
Jan Eismark, Michael Balthasar, Anders Karlsson, Timothy Benham, Magnus Christensen, Ingemar Denbratt
Soot formation and oxidation are complex and competing processes during diesel combustion. The balance between the two processes and their history determines engine-out soot values. Besides the efforts to lower soot formation with measures to influence the flame lift-off distance for example or to use HCCI-combustion, enhancement of late soot oxidation is of equal importance for low-λ diffusion-controlled low emissions combustion with EGR. The purpose of this study is to investigate soot oxidation in a heavy duty diesel engine by statistical analysis of engine data and in-cylinder endoscopic high speed photography together with CFD simulations with a main focus on large scale in-cylinder gas motion. Results from CFD simulations using a detailed soot model were used to reveal details about the soot oxidation.
2009-11-02
Technical Paper
2009-01-2695
Xiaoqi Cui, Arjan Helmantel, Valeri Golovichev, Ingemar Denbratt
The purpose of the investigation presented here was to compare the effects of fuel composition on combustion parameters, emissions and fuel consumption in engine tests and simulations with five fuels: a Diesel-water emulsion, a Diesel-ethanol blend, a Diesel-ethanol blend with EHN (cetane number improver), a Fischer-Tropsch Diesel and an ultra-low sulfur content Diesel. The engine used in the experiments was a light duty, single cylinder, direct injection, common rail Diesel engine equipped with a cylinder head and piston from a Volvo NED5 engine. In tests with each fuel the engine was operated at two load points (3 bar IMEP and 10 bar IMEP), and a pilot-main fuel injection strategy was applied under both load conditions. Data were also obtained from 3-D CFD simulations, using the KIVA code, to compare to the experimental results and to further analyze the effects of water and ethanol on combustion.
2009-11-02
Technical Paper
2009-01-2787
Monica AC Johansson, Malin Ehleskog, Savo Gjirja, Ingemar Denbratt
It has been previously shown that engine-out soot emissions can be reduced by using Fischer-Tropsch (FT) fuels, due to their lack of aromatics, compared to conventional Diesel fuels. In this investigation the engine-out emissions and fuel consumption parameters of an FT fuel derived from natural gas were compared to those of Swedish low sulfur diesel (MK1) when used in Low Temperature Combustion mode in a single cylinder heavy-duty diesel engine. The effects of varying Needle Opening Pressure (NOP), Charge Air Pressure (CAP) and Exhaust Gas Recirculation (EGR) according to an experimental design on the measured variables were also assessed. CAP and EGR were found to be the most significant factors for the combustion and emission parameters of both fuels. Increases in CAP resulted in lower soot emissions due to enhanced charge mixing, however NOx emissions rose as CAP increased.
2009-04-20
Technical Paper
2009-01-0841
Henrik Salsing, Raúl Ochoterena, Ingemar Denbratt
DME was tested in a heavy duty diesel engine and in an optically accessible high-temperature and pressure spray chamber in order to investigate and understand the effect of nozzle parameters on emissions, combustion and fuel spray concentration. The engine study clearly showed that smaller nozzle orifices were advantageous from combustion, efficiency and emissions considerations. Heat release analysis and fuel concentration images indicate that smaller orifices result in higher mixing rate between fuel and air due to reductions in the turbulence length scale, which reduce both the magnitude of fuel-rich regions and the steepness of fuel gradients in the spray, which enable more fuel to burn and thereby shorten the combustion duration.
2009-04-20
Journal Article
2009-01-1496
Stina Hemdal, Ingemar Denbratt, Petter Dahlander, Jonas Warnberg
Gasoline and gasoline-ethanol sprays from an outward-opening piezo-injector were studied in a constant volume/pressure chamber using high-speed imaging and phase doppler anemometry (PDA) under stratified cold start conditions corresponding to a vehicle ambient temperature of 243 K (−30°C/−22°F); in-cylinder air pressure of 5 bar, air temperature of 350 K (−30°C/−22°F) and fuel temperature of 243 K. The effects of varying in-cylinder pressure and temperature, fuel injection pressure and fuel temperature on the formation of gasoline, E75 and pure ethanol sprays were investigated. The results indicate that fuel composition affects spray behaviour, but less than expected. Furthermore, varying the temperature of the fuel or the air surrounding the spray also had minor effects. As expected, the fuel injection pressure was found to have the strongest influence on spray formation under stratified conditions.
2009-06-15
Technical Paper
2009-01-1785
Daniel Dahl, Mats Andersson, Andreas Berntsson, Ingemar Denbratt, Lucien Koopmans
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).
2007-01-23
Technical Paper
2007-01-0030
Monica Larsson, Ingemar Denbratt
Experiments were performed using a Light-Duty, single-cylinder, research engine in which the emissions, fuel consumption and combustion characteristics of two Fischer-Tropsch (F-T) Diesel fuels derived from natural gas and two conventional Diesel fuels (Swedish low sulfur Diesel and European EN 590 Diesel) were compared. Due to their low aromatic contents combustion with the F-T Diesel fuels resulted in lower soot emissions than combustion with the conventional Diesel fuels. The hydrocarbon emissions were also significantly lower with F-T fuel combustion. Moreover the F-T fuels tended to yield lower CO emissions than the conventional Diesel fuels. The low emissions from the F-T Diesel fuels, and the potential for producing such fuels from biomass, are powerful reason for future interest and research in this field.
2007-04-16
Technical Paper
2007-01-0210
Andreas W. Berntsson, Ingemar Denbratt
This work evaluates the effect of charge stratification on combustion phasing, rate of heat release and emissions for HCCI combustion. Engine experiments in both optical and traditional single cylinder engines were carried out with PRF50 as fuel. The amount of stratification as well as injection timing of the stratified charge was varied. It was found that a stratified charge can influence combustion phasing, increasing the stratification amount or late injection timing of the stratified charge leads to an advanced CA50 timing. The NOx emissions follows the CA50 advancement, advanced CA50 timing leads to higher NOx emissions. Correlation between CA50 can also be seen for HC and CO emissions when the injection timing was varied, late injection and thereby advanced CA50 timing leads to both lower HC and CO emissions.
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