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Viewing 1 to 30 of 1474
2014-04-01
Journal Article
2014-01-1255
Jacqueline O'Connor, Mark Musculus
Post injections have been shown to reduce engine-out soot emissions in a variety of engine architectures and at a range of operating points. In this study, measurements of the engine-out soot from a heavy-duty optical diesel engine have conclusively shown that interaction between the post-injection jet and soot from the main injection must be, at least in part, responsible for the reduction in engine-out soot. Extensive measurements of the spatial and temporal evolution of soot using high-speed imaging of soot natural luminosity (soot-NL) and planar-laser induced incandescence of soot (soot-PLII) at four vertical elevations in the piston bowl at a range of crank angle timings provide definitive optical evidence of these interactions. The soot-PLII images provide some of the most conclusive evidence to date that the addition of a post injection dramatically changes the topology and quantity of in-cylinder soot.
2014-04-01
Journal Article
2014-01-1256
Randy Hessel, Rolf D. Reitz, Mark Musculus, Jacqueline O'Connor, Daniel Flowers
One in-cylinder strategy for reducing soot emissions from diesel engines while maintaining fuel efficiency is the use of close-coupled post injections, which are small fuel injections that follow the main fuel injection after a short delay. While the in-cylinder mechanisms of diesel combustion with single injections have been studied extensively and are relatively well understood, the in-cylinder mechanisms affecting the performance and efficacy of post injections have not been clearly established. Here, experiments from a single-cylinder heavy-duty optical research engine incorporating close- coupled post injections are modeled with three dimensional (3D) computational fluid dynamics (CFD) simulations. The overall goal is to complement experimental findings with CFD results to gain more insight into the relationship between post-injections and soot. This paper documents the first stage of CFD results for simulating and analyzing the experimental conditions.
2014-04-01
Technical Paper
2014-01-1253
Benedikt Heuser, Thomas Laible, Markus Jakob, Florian Kremer, Stefan Pischinger
Abstract Within this paper, the two possible alternative and biomass-based fuel candidates Di-n-butyl ether (DNBE) and 1-octanol are investigated with regard to their utilization in a diesel-type engine. In order to asses the fuels emission-reduction potential, both have been tested in a single cylinder engine (SCE) and a high pressure chamber (HPC) in comparison to conventional EN590 diesel at various load points. Due to its reduced reactivity 1-octanol features a longer ignition delay and thus higher degrees of homogenization at start of combustion, whereas DNBE ignites rather rapidly in both the HPC and the engine leading to a predominantly mixing controlled combustion. Thus, both fuels feature completely different combustion characteristics. However, compared to diesel, both fuels contribute to a significant reduction in Filter Smoke Number (FSN) up to a factor of 15.
2014-04-01
Technical Paper
2014-01-1254
Kar Mun Pang, Mehdi Jangi, Xue-Song Bai, Jesper Schramm
Abstract In this reported work, 2-dimsensional computational fluid dynamics studies of n-heptane combustion and soot formation processes in the Sandia constant-volume vessel are carried out. The key interest here is to elucidate how the chemical kinetics affects the combustion and soot formation events. Numerical computation is performed using OpenFOAM and chemistry coordinate mapping (CCM) approach is used to expedite the calculation. Three n-heptane kinetic mechanisms with different chemistry sizes and comprehensiveness in oxidation pathways and soot precursor formation are adopted. The three examined chemical models use acetylene (C2H2), benzene ring (A1) and pyrene (A4) as soot precursor. They are henceforth addressed as nhepC2H2, nhepA1 and nhepA4, respectively for brevity. Here, a multistep soot model is coupled with the spray combustion solver to simulate the soot formation/oxidation processes.
2014-04-01
Journal Article
2014-01-1270
Thorsten Brands, Peter Hottenbach, Hans-Jürgen Koss, Gerd Grunefeld, Adrien Brassat, Philipp Adomeit, Stefan Pischinger
Abstract Fuel consumption and NOx emissions of gasoline engines at part load can be significantly reduced by Controlled Auto-Ignition combustion concepts. However, the range of Gasoline Controlled Auto-Ignition (GCAI) operation is still limited by lacking combustion stability at low load and by high pressure-rise rates toward higher loads. Previous investigations indicate that the auto-ignition process is particularly determined by the thermodynamic state of the charge and by stratification effects of residual gas, temperature, and air-fuel ratio. However, little experimental data exist on the direct influence of mixture stratification on local ignition and heat-release rate (HRR) in direct-injection (DI) GCAI engines, because it is challenging to measure all the relevant charge and combustion parameters quasi-simultaneously with sufficient spatial/temporal resolution and precision.
2014-04-01
Technical Paper
2014-01-1222
Simon F. Dingle, Alasdair Cairns, Hua Zhao, John Williams, Oliver Williams, Rana Ali
Abstract This work was concerned with study of lubricant introduced directly into the combustion chamber and its effect on pre-ignition and combustion in an optically accessed single-cylinder spark ignition engine. The research engine had been designed to incorporate full bore overhead optical access capable of withstanding peak in-cylinder pressures of up to 150bar. An experiment was designed where a fully formulated synthetic lubricant was deliberately introduced through a specially modified direct fuel injector to target the exhaust area of the bore. Optical imaging was performed via natural light emission, with the events recorded at 6000 frames per second. Two port injected fuels were evaluated including a baseline commercial grade gasoline and low octane gasoline/n-heptane blend. The images revealed the location of deflagration sites consistently initiating from the lubricant itself.
2014-04-01
Technical Paper
2014-01-1223
Claudio Forte, Enrico Corti, Gian Marco Bianchi, Stefania Falfari, Stefano Fantoni
Abstract Knocking combustions heavily limits the efficiency of Spark Ignition engines. The compression ratio is limited in the design stage of the engine development, letting to Spark Advance control the task of reducing the odds of abnormal combustions. A detailed analysis of knocking events can help improving engine performance and diagnosis strategies. An effective way is to use advanced 3D CFD (Computational Fluid Dynamics) simulation for the analysis and prediction of combustion performance. Standard 3D CFD approach is based on RANS (Reynolds Averaged Navier Stokes) equations and allows the analysis of the mean engine cycle. However knocking phenomenon is not deterministic and it is heavily affected by the cycle to cycle variation of engine combustions. A methodology for the evaluation of the effects of CCV (Cycle by Cycle Variability) on knocking combustions is here presented, based on both the use of Computation Fluid Dynamics (CFD) tools and experimental information.
2014-04-01
Technical Paper
2014-01-1221
Jiankun Shao, Christopher Rutland
Knock in a Rotax-914 engine was modeled and investigated using an improved version of the KIVA-3V code with a G-equation combustion model, together with a reduced chemical kinetics model. The ERC-PRF mechanism with 47 species and 132 reactions [1] was adopted to model the end gas auto-ignition in front of the flame front. The model was validated by a Caterpillar SI engine and a Rotax-914 engine in different operating conditions. The simulation results agree well with available experimental results. A new engineering quantified knock criterion based on chemical mechanism was then proposed. Hydroperoxyl radical (HO2) shows obvious accumulation before auto-ignition and a sudden decrease after auto-ignition. These properties are considered to be a good capability for HO2 to investigate engine knock problems.
2014-04-01
Journal Article
2014-01-1220
Yu Chen, Robert Raine
In this work, the effects of engine operational parameters, λ, spark timing, and compression ratio, on knock tendency and intensity as well as H2 supplementation are studied. We postulated, verified and eventually used the duration from ignition to 70% mass fraction burnt (MFB0-70%) as an explanatory variable to describe the knock tendency and intensity. In this manner, the physical factors and fuel factors that are introduced by the differences in test conditions can be differentiated. Practically, in terms of percentage of knocking cycles or the spark timing at audible knock, knock tendency decreases as λ increases and increases with H2 supplementation. However, when MFB duration is taken into account, then for the same MFB duration, knock tendency increases as λ increases and decreases with H2 supplementation.
2014-04-01
Journal Article
2014-01-1219
Orian Welling, James Moss, John Williams, Nick Collings
One of the limits on the maximum fuel efficiency benefit to be gained from turbocharged, downsized gasoline engines is the occurrence of low speed pre-ignition (LSPI). LSPI may lead to high pressures and extreme knock (megaknock or superknock) which can cause severe engine damage. Though the mechanism leading to megaknock is not completely resolved, LSPI is thought to arise from local auto-ignition of areas in the cylinder which are rich in low ignition delay “contaminants” such as engine oil and/or heavy ends of gasoline. These contaminants are introduced to the combustion chamber at various points in the engine cycle (e.g. entering from the top land crevice during blow-down or washed from the cylinder walls during DI wall impingement). This paper describes a method for testing the propensity of different contaminants to cause a local pre-ignition in a gasoline engine. During one cycle, a small amount of contaminant is injected into one cylinder of a 4 cylinder engine.
2014-04-01
Journal Article
2014-01-1218
Yoshihiro Okada, Shigeki Miyashita, Yoshihiro Izumi, Yutaka Hayakawa
Abstract This paper analyzes low-speed pre-ignition (LSPI), a sudden pre-ignition phenomenon that occurs in downsized boosted gasoline engines in low engine speed high-load operation regions. This research visualized the in-cylinder state before the start of LSPI combustion and observed the behavior of particles, which are thought to be the ignition source. The research also analyzed pre-ignition by injecting deposit flakes and other combustible particulate substances into the combustion chamber. The analysis found that these particles require at least two combustion cycles to reach a glowing state that forms an ignition source. As a result, deposits peeling from combustion chamber walls were identified as a new mechanism causing pre-ignition. Additionally, results also suggested that the well-known phenomenon in which the LSPI frequency rises in accordance with greater oil dilution may also be explained by an increase in deposit generation.
2014-04-01
Technical Paper
2014-01-1217
Kengo Kumano, Shiro Yamaoka
Abstract The cooled EGR system has been focused on as a method for knocking suppression in gasoline engines. In this paper, the effect of cooled EGR on knocking suppression that leads to lower fuel consumption is investigated in a turbo-charged gasoline engine. First, the cooled EGR effect is estimated by combustion simulation with a knock prediction model. It shows that the ignition timing at the knocking limit can be advanced by about 1 [deg. CA] per 1% of EGR ratio, combustion phasing (50% heat release timing) at the knocking limit can be advanced by about 0.5 [deg. CA] per 1% of EGR ratio, and the fuel consumption amount can be decreased by about 0.4% per 1% of EGR ratio. Second, the effect of cooled EGR is verified in an experimental approach. By adding inert gas (N2/CO2) as simulated EGR gas upstream of the intake pipe, the effect of EGR is investigated when EGR gas and fresh air are mixed homogeneously.
2014-04-01
Technical Paper
2014-01-1216
Caroline Nicola Orlebar, Arndt Joedicke, William Studzinski
Abstract This study investigates the effects of octane quality on the performance, i.e., acceleration and power, and fuel economy (FE) of one late model US vehicle, which is powered by a small displacement, turbocharged, gasoline direct injection (GDI) engine. The relative importance of the gasoline parameters Research and Motor Octane Number (RON and MON) in meeting the octane requirement of this engine to run at an optimum spark timing for the given demand was considered by evaluating the octane index (OI), where OI = (1-K) RON + K MON and K is a constant depending on engine design and operating conditions. Over wide open throttle (WOT) accelerations, the average K of this Pontiac Solstice was determined as −0.75, whereby a lower MON would give a higher OI, a higher knock resistance and better performance.
2014-04-01
Technical Paper
2014-01-1233
Raphael Gukelberger, Terrence Alger, Jess Gingrich, Barrett Mangold
Abstract The use of cooled EGR in gasoline engines improves the fuel efficiency of the engine through a variety of mechanisms, including improving the charge properties (e.g. the ratio of specific heats), reducing knock and enabling higher compression ratio operation and, at part loads conditions in particular, reducing pumping work. One of the limiting factors on the level of improvement from cooled EGR is the ability of the ignition system to ignite a dilute mixture and maintain engine stability. Previous work from SwRI has shown that, by increasing the ignition duration and using a continuous discharge ignition system, an improved ignition system can substantially increase the EGR tolerance of an engine [1, 2]. This improvement comes at a cost, however, of increased ignition system energy requirements and a potential decrease in spark plug durability. This work examines the impact of engine operating parameters on the ignition energy requirements under high dilution operation.
2014-04-01
Technical Paper
2014-01-1232
Juwon Kim, JongShin Lee, SeungHyun Rew, Donghyeon Lee, Cha-Lee Myung, Simsoo Park
Abstract To evaluate the potential of a dedicated LPG direct injection (LPDI) vehicle, we investigated several engine control parameters that are closely related to the characteristics of mixture preparation and nano-particle emissions. Many researches have pointed out that any amount of particle emissions from GDI vehicles were made during the cold start and cold transient phase. Therefore, in the study, four types of engine control strategies for the LPDI vehicle were applied to evaluate particle number (PN) concentration and regulated emissions in the cold start phase and the hot start phase under the FTP-75 cycle. The reduction rate of the PN concentration with LPG application reached approximately over 99% less than that of the GDI vehicle.
2014-04-01
Journal Article
2014-01-1231
Derek Splitter, James Szybist
The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in mid-level alcohol-gasoline blends with 24% vol./vol. iso-butanol-gasoline (IB24) and 30% vol./vol. ethanol-gasoline (E30). A single-cylinder research engine is used with a low and high compression ratio of 9.2:1 and 11.85:1 respectively. The engine is equipped with hydraulically actuated valves, laboratory intake air, and is capable of external exhaust gas recirculation (EGR). All fuels are operated to full-load conditions with λ=1, using both 0% and 15% external cooled EGR. The results demonstrate that higher octane number bio-fuels better utilize higher compression ratios with high stoichiometric torque capability. Specifically, the unique properties of ethanol enabled a doubling of the stoichiometric torque capability with the 11.85:1 compression ratio using E30 as compared to 87 AKI, up to 20 bar IMEPg at λ=1 (with 15% EGR, 18.5 bar with 0% EGR).
2014-04-01
Journal Article
2014-01-1228
Thomas G. Leone, Edward D. Olin, James E. Anderson, Hosuk H. Jung, Michael H. Shelby, Robert A. Stein
Engine dynamometer testing was performed comparing fuels having different octane ratings and ethanol content in a Ford 3.5L direct injection turbocharged (EcoBoost) engine at three compression ratios (CRs). The fuels included midlevel ethanol “splash blend” and “octane-matched blend” fuels, E10-98RON (U.S. premium), and E85-108RON. For the splash blends, denatured ethanol was added to E10-91RON, which resulted in E20-96RON and E30-101 RON. For the octane-matched blends, gasoline blendstocks were formulated to maintain constant RON and MON for E10, E20, and E30. The match blend E20-91RON and E30-91RON showed no knock benefit compared to the baseline E10-91RON fuel. However, the splash blend E20-96RON and E10-98RON enabled 11.9:1 CR with similar knock performance to E10-91RON at 10:1 CR. The splash blend E30-101RON enabled 13:1 CR with better knock performance than E10-91RON at 10:1 CR. As expected, E85-108RON exhibited dramatically better knock performance than E30-101RON.
2014-04-01
Technical Paper
2014-01-1230
Thomas Wallner, Andrew Ickes, Jeff Wasil, James Sevik, Scott Miers
Abstract This study evaluates iso-butanol as a pathway to introduce higher levels of alternative fuels for recreational marine engine applications compared to ethanol. Butanol, a 4-carbon alcohol, has an energy density closer to gasoline than ethanol. Isobutanol at 16 vol% blend level in gasoline (iB16) exhibits energy content as well as oxygen content identical to E10. Tests with these two blends, as well as indolene as a reference fuel, were conducted on a Mercury 90 HP, 4-stroke outboard engine featuring computer controlled sequential multi-port Electronic Fuel Injection (EFI). The test matrix included full load curves as well as the 5-mode steady-state marine engine test cycle. Analysis of the full load tests suggests that equal full load performance is achieved across the engine speed band regardless of fuel at a 15-20°C increase in exhaust gas temperatures for the alcohol blends compared to indolene.
2014-04-01
Technical Paper
2014-01-1227
Hiromitsu Ando, Yasuyuki Sakai, Kazunari Kuwahara
Abstract The relationships between the octane number and the carbon atom number and the molecular structure of alkanes were comprehensively analyzed by using the detailed kinetic model generated by there automatic reaction scheme generation tool, KUCRS [1, 2]. The octane number is an index showing the ignition delay in the engine temperature regime, that is, the engine ignition temperature range. The high octane number is observed in the following two cases; 1 The ignition delay of the low temperature region is large.2 The ignition delay of the low temperature region is the same, but the transition temperature for NTC (Negative Temperature Coefficient) region is low.
2014-04-01
Journal Article
2014-01-1226
Elana Chapman, Richard S. Davis, William Studzinski, Pat Geng
Classic, hot-spot induced pre-ignition is a phenomenon that has been observed in gasoline spark ignited engines over the past 60-70 years. With the development of turbocharged, direct-injected (DI) gasoline engines, a new pre-ignition phenomenon occurring at low engine speeds and high loads has been encountered. Termed Stochastic Pre-ignition (SPI), it has become a significant issue to address in allowing for the full potential of gasoline turbo DI technology to improve powertrain efficiency. Many researchers are studying all aspects of the causes of Stochastic Pre-ignition, including causes by oil, fuel and engine hardware systems. The focus of this specific research was to study the relationship of fuel octane and volatility to Stochastic Pre-ignition behavior utilizing a GM 2.0L Gasoline Turbocharged DI engine (LHU).
2014-04-01
Technical Paper
2014-01-1224
Yunliang Qi, Yaqi Xu, Zhi Wang, Jianxin Wang
Super knock which occurs in highly boosted spark ignition engines in low speed pre-ignition regime can lead to severe engine damage. However, super knock occurs occasionally, it is difficult to clearly identify the causes. The widely accepted assumption for the cause of this phenomenon is oil intrusion. Most of oils have been proved to have higher cetane number than n-heptane dose, indicating that the intruded oil is very liable to auto-ignition in a boosted engine. Although there have been reported the type of base oil and additive has significant effect on pre-ignition frequency, the oil induced super knock is still so far not supported by any direct evidence. This paper presents the effect of direct oil intrusion into cylinder on super knock. The experiment was carried out in a single cylinder engine. The diluted oil by gasoline with different ratio was directly injected into cylinder using a modified single-hole injector with 4MPa injection pressure.
2014-04-01
Technical Paper
2014-01-1206
Young Suk Jo, Raymond Lewis, Leslie Bromberg, John B. Heywood
Abstract 1 Downsizing and turbocharging a spark-ignited engine is becoming an important strategy in the engine industry for improving the efficiency of gasoline engines. Through boosting the air flow, the torque is increased, the engine can thus be downsized, engine friction is reduced in both absolute and relative terms, and engine efficiency is increased. However knock onset with a given octane rating fuel limits both compression ratio and boost levels. This paper explores the operating limits of a turbocharged engine, with various gasoline-ethanol blends, and the interaction between compression ratio, boost levels, and spark retard, to achieve significant increases in maximum engine mean effective pressure and efficiency.
2014-04-01
Journal Article
2014-01-1207
Quan Liu, Alasdair Cairns, Hua Zhao, Mohammadreza Anbari Attar, Luke Cruff, Hugh Blaxill
Abstract The work was concerned with visualisation of the charge homogeneity and cyclic variations within the planar fuel field near the spark plug in an optical spark ignition engine fitted with an outwardly opening central direct fuel injector. Specifically, the project examined the effects of fuel type and injection settings, with the overall view to understanding some of the key mechanisms previously identified as leading to particulate formation in such engines. The three fuels studied included a baseline iso-octane, which was directly compared to two gasoline fuels containing 10% and 85% volume of ethanol respectively. The engine was a bespoke single cylinder with Bowditch style optical access through a flat piston crown. Charge stratification was studied over a wide spectrum of injection timings using the Planar Laser Induced Fluorescence (PLIF) technique, with additional variation in charge temperature due to injection also estimated when viable using a two-line PLIF approach.
2014-04-01
Technical Paper
2014-01-1204
Manfred Amann, Daniel Ouwenga
Abstract As boosted, direct injected gasoline engines become more prevalent in the automotive market, the boosting system architecture and efficiency are intimately entwined with the efficiency and performance of the engine. Single-stage as well as two-stage boosting systems, comprising of either two turbochargers or a supercharger in combination with a turbocharger, are potential configurations. When combining an internal combustion engine with boosting hardware, a mechanical, fluid-dynamic and thermodynamic coupling is created and the system as a whole will need to be treated as such.
2014-04-01
Journal Article
2014-01-1205
Kang Xu, Hui Xie, Minggang Wan, Tao Chen, Hua Zhao
The goal of this research was to study and quantify the effect of exhaust valve timing and residual gas dilution on in-cylinder flow patterns, flame propagation and heat release characteristics in a spark ignition engine. Experiments were carried out in a recently developed single cylinder optical engine. Particle image velocimetry (PIV) was applied to measuring and evaluating the in-cylinder flow field. Detailed analysis of flame images combined with heat release data was presented for several engine operating conditions, giving insight into the combustion process in terms of visible flame area and flame expansion speed. Results from PIV measurement indicates that the limited alteration of the in-cylinder bulk flow could be observed with the variation of exhaust valve timing. The in-cylinder fluctuating kinetic energies and their Coefficient of Variations (COVs) decrease with the advance of the exhaust valve timing.
2014-04-01
Technical Paper
2014-01-1202
Xiao Yu, Zhijun Wu, Cheng Wang, Jun Deng, Zongjie Hu, Liguang Li
A novel reciprocating engine version of oxy-fuel combustion cycle combined with water direct injection (known as internal combustion rankine cycle) is presented in this paper. Water is injected near top dead center to control the reaction rate of the oxy-fuel mixture, as well as the peak in-cylinder temperature. The evaporation of the water mist will increase the mass of working gas inside the cylinder, and enhances the thermo efficiency and MEP. Moreover, the injected water is heated up through heat exchangers by both engine coolant and exhaust gas, and the waste heat is effectively recovered this way. This study investigates the combustion and emission characteristics of ICRC under different engine loads based on a single-cylinder, air-cooled SI engine fueled with propane. An extra diesel injector is employed to inject water with high injection temperature (160°C).
2014-04-01
Technical Paper
2014-01-1203
Hidemasa Kosaka, Tomoyuki Akita, Kazunari Moriya, Shigeaki Goto, Yoshihiro Hotta, Takaji Umeno, Kiyomi Nakakita
Abstract Free Piston Engine Linear Generator (FPEG) with features of thin and compact build, high efficiency and high fuel flexibility is developed. The FPEG consists of a two-stroke combustion chamber, a linear generator and a gas spring chamber. The key technologies to realize stable continuous operation are lubricating, cooling, and control logic. This paper proposes the original structure of the FPEG for enabling stable continuous operation. The main feature is a hollow circular step-shaped piston. The smaller-diameter side of the piston constitutes the combustion chamber, and the larger-diameter side constitutes the gas spring chamber. The larger cross-sectional area of the gas spring chamber leads to lower compression temperature of the gas spring chamber and consequently decreased heat loss. In addition, an oil cooling passage is built in the column stay, which ensures the enough cooling ability of the piston.
2014-04-01
Journal Article
2014-01-1200
Randall D. Partridge, Walter Weissman, Takanori Ueda, Yoshihiro Iwashita, Paul Johnson, George Kellogg
ExxonMobil, Corning and Toyota have collaborated on an Onboard Separation System (OBS) to improve gasoline engine efficiency and performance. OBS is a membrane based process that separates gasoline into higher and lower octane fractions, allowing optimal use of fuel components based on engine requirements. The novel polymer-ceramic composite monolith membrane has been demonstrated to be stable to E10 gasoline, while typically providing 20% yield of ∼100 RON product when using RUL 92 RON gasoline. The OBS system makes use of wasted exhaust energy to effect the fuel separation and provides a simple and reliable means for managing the separated fuels that has been demonstrated using several generations of dual fuel test vehicles. Potential applications include downsizing to increase fuel economy by ∼10% while maintaining performance, and with turbocharging to improve knock resistance.
2014-04-01
Journal Article
2014-01-1201
Paul Ferrey, Yves Miehe, Cyrille Constensou, Vincent Collee
Combustion simulations and single cylinder engine tests show a clear potential when coupling the Variable Compression Ratio (VCR) engine with the Variable Valve Actuation (VVA) technologies. Simulations demonstrate the thermodynamic benefit from increasing the geometric Compression Ratio (CR>18:1) in combination with VVA compared to VVT strategies, thanks to the use of Atkinson / Miller Cycles. 3D combustion simulations of high compression ratio combustion chamber geometries used with Early or Late Intake Valve Closing strategies have been carried out with IFP-C3D™. They show an indicated efficiency increase up to 12 or 13% between compression ratio 10:1 and 18-20:1 at low loads (BMEP < 8 bar).
2014-04-01
Technical Paper
2014-01-1214
Thomas Lauer, Michael Heiss, Nikola Bobicic, Werner Holly, Stefan Pritze
Abstract The combustion of highly boosted gasoline engines is limited by knocking combustion and pre-ignition. Therefore, a comprehensive modelling approach consisting of cycle-to-cycle simulation, reactor modelling with detailed chemistry and CFD-simulation was used to predict the knock initiation and to identify the source of pre-ignition. A 4-cylinder DISI test engine was set up and operated at low engine speeds and high boost pressures in order to verify the accuracy of the numerical approach. The investigations showed that there is a correlation between the knocking combustion and the very first combustion phase. The onset of knock was simulated with a stochastic reactor model and detailed chemistry. In parallel, measurements with an optical spark plug were carried out in order to identify the location of knock onset. The simulation results were in good agreement with the measurements. Deposits and oil/fuel-droplets are possible triggers of pre-ignition.
Viewing 1 to 30 of 1474

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