Soot Formation in Direct Injection Spark Ignition Engines Under Cold-idle Operating Conditions PDF Download

Author: Justin Edward Ketterer
Publisher:
ISBN:
Category :
Languages : en
Pages : 182

View

Book Description
Direct injection spark ignition engines are growing rapidly in popularity, largely due to the fuel efficiency improvements in the turbo-downsized engine configuration that are enabled by direct injection technology. Unfortunately, direct injection spark ignition engines also emit higher concentrations of particulate matter than conventional port fuel injected engines. In light of evidence linking particulate matter to adverse human health impacts, particulate emissions standards have been strengthened in both the United States and in Europe. A great deal of research seeking particulate emissions reductions is ongoing. This study contributes to this body of research by offering a refined explanation of the soot formation process in direct injection engines under cold-idle operating conditions. A number of engine and rapid compression machine experiments were conducted in order to understand the impacts of engine operating conditions and fuel composition on particulate matter emissions. Using these data, a conceptual model describing the formation of soot in direct injection engines is outlined. This model suggests that soot forms after the main combustion event in fuel vapour plumes surrounding liquid fuel films on cylinder surfaces through pyrolytic reactions enabled by heat transfer from burned gases from the primary combustion event.

Author: F. Zhao
Publisher: Elsevier
ISBN: 008055279X
Category : Technology & Engineering
Languages : en
Pages : 129

View

Book Description
The process of fuel injection, spray atomization and vaporization, charge cooling, mixture preparation and the control of in-cylinder air motion are all being actively researched and this work is reviewed in detail and analyzed. The new technologies such as high-pressure, common-rail, gasoline injection systems and swirl-atomizing gasoline fuel injections are discussed in detail, as these technologies, along with computer control capabilities, have enabled the current new examination of an old objective; the direct-injection, stratified-charge (DISC), gasoline engine. The prior work on DISC engines that is relevant to current GDI engine development is also reviewed and discussed. The fuel economy and emission data for actual engine configurations have been obtained and assembled for all of the available GDI literature, and are reviewed and discussed in detail. The types of GDI engines are arranged in four classifications of decreasing complexity, and the advantages and disadvantages of each class are noted and explained. Emphasis is placed upon consensus trends and conclusions that are evident when taken as a whole; thus the GDI researcher is informed regarding the degree to which engine volumetric efficiency and compression ratio can be increased under optimized conditions, and as to the extent to which unburned hydrocarbon (UBHC), NOx and particulate emissions can be minimized for specific combustion strategies. The critical area of GDI fuel injector deposits and the associated effect on spray geometry and engine performance degradation are reviewed, and important system guidelines for minimizing deposition rates and deposit effects are presented. The capabilities and limitations of emission control techniques and after treatment hardware are reviewed in depth, and a compilation and discussion of areas of consensus on attaining European, Japanese and North American emission standards presented. All known research, prototype and production GDI engines worldwide are reviewed as to performance, emissions and fuel economy advantages, and for areas requiring further development. The engine schematics, control diagrams and specifications are compiled, and the emission control strategies are illustrated and discussed. The influence of lean-NOx catalysts on the development of late-injection, stratified-charge GDI engines is reviewed, and the relative merits of lean-burn, homogeneous, direct-injection engines as an option requiring less control complexity are analyzed.

Author: Iason Dimou
Publisher:
ISBN:
Category :
Languages : en
Pages : 9

View

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

View

Book Description
A semi-detailed soot model was successfully implemented in the KIVA3v2-ERC code, which features a discrete multi-component (DMC) fuel vaporization model. A spark ignition model and the G-equation turbulent flame propagation model were also implemented for modeling direct-injection spark-ignition (DISI) engines. Chemistry parallelization for the soot model was also successfully realized in this work. Chemistry parallelization and a newly developed chemistry solver (SpeedCHEM) further reduced the computational time and enabled the successful application of the final code (KIVA-DMC-detsoot-G-SC) to DISI engines with the consideration of multi-component surrogates for real gasoline fuels and 3-D full cylinder engine grids. The semi-detailed soot model considered: soot inception from a four-ring aromatic (A4), soot surface growth through acetylene (C2H2) and aromatics from single-ring to four-ring species (A1, A2, A3, A4), soot coagulation, and soot oxidation through O2 and OH. A reduced polycyclic aromatic hydrocarbon (PAH) chemistry mechanism was coupled with n-heptane, iso-octane and toluene chemistry mechanisms. The combination of the chemistry mechanisms and the soot model was then validated based on experiments in terms of ignition delay, fundamental premixed flames, SANDIA constant volume chamber spray combustion. The pyrolysis process is also a significant process for soot formation at the conditions of DISI engines. Important species for soot formation from toluene pyrolysis processes were also validated based on experiments, and then coupled with the current n-heptane/iso-octane/toluene/PAH chemistry mechanisms for application to DISI engines. The vaporization of wall films plays a significant role in soot formation and a grid-independent wall film vaporization model was formulated for predicting soot emissions near wall films Predicted in-cylinder pressure and particle size distributions (PSDs) were compared to available premixed engine experimental studies. Quantitative agreements of in-cylinder particle distributions are also obtained. The improved models were then applied to studies of soot emissions from early- and late-injection strategies in a four-valve single-cylinder gasoline DISI engine, and the trends were consistent with literature or experimental data.

Author: Kevin David Cedrone
Publisher:
ISBN:
Category :
Languages : en
Pages : 191

View

Book Description
Gasoline consumption and pollutant emissions from transportation are costly and have serious, demonstrated environmental and health impacts. Downsized, turbocharged direct-injection spark ignition (DISI) gasoline engines consume less fuel and achieve superior performance compared with conventional port fuel injected spark ignition (PFI-SI) engines. Although more efficient, turbocharged DISI engines have new emissions challenges during cold start. DISI fuel injection delivers more liquid fuel into the combustion chamber, increasing the emissions of unburned hydrocarbons. The turbocharger slows down activation (warm-up) of the catalytic exhaust after-treatment system. The objective of this research is to find a control strategy that: 1. Accelerates warm-up of the catalyst, and 2. Maintains low emissions of unburned hydrocarbons (UBHCs) during the catalyst warm-up process. This research includes a broad experimental survey of engine behaviour and emission response for a modern turbocharged DISI engine. The study focuses on the idle period during cold-start for which DISI engine emissions are worst. Engine experiments and simulations show that late and slow combustion lead to high exhaust gas temperatures and mass flow rate for fast warm-up. However, late and slow combustion increase the risk of partial-burn misfire. At the misfire limit for each parameter, the following conclusions are drawn: 1. Late ignition timing is the most effective way to increase exhaust enthalpy flow rate for fast catalyst warm-up. 2. By creating a favourable spatial fuel-air mixture stratification, split fuel injection can simultaneously retard and stabilize combustion to improve emissions and prevent partial-burn misfire. 3. Excessive trapped residuals from long valve overlap limit the potential for valve timing to reduce cold-start emissions. 4. Despite their more challenging evaporation characteristics, fuel blends with high ethanol content showed reasonable emissions behaviour and greater tolerance to late combustion than neat gasoline. 5. Higher exhaust back-pressure leads to high exhaust temperature during the exhaust stroke, leading to significantly more post-flame oxidation. 6. Post-flame oxidation in the combustion chamber and exhaust system play a critical role in decreasing the quantity of catalyst-in emissions due to hydrocarbons that escape primary (flame) combustion. A cold start strategy combining late ignition, 15% excess air, and high exhaust backpressure yielded the lowest cumulative hydrocarbon emissions during cold start.

Author: Hua Zhao
Publisher: SAE International
ISBN: 0768040345
Category : Technology & Engineering
Languages : en
Pages : 854

View

Book Description
This book provides a complete description of instrumentation and in-cylinder measurement techniques for internal combustion engines. Written primarily for researchers and engineers involved in advanced research and development of internal combustion engines, the book provides an introduction to the instrumentation and experimental techniques, with particular emphasis on diagnostic techniques for in-cylinder measurements.

Author: Kevin R. Lang
Publisher:
ISBN:
Category :
Languages : en
Pages : 172

View

Book Description
(Cont.) By timing split injection such that the second injection event hits the overlap back flow, a small mixture preparation and emissions benefit was achieved. Earlier IVO results in a longer back flow period, however the impact on mixture preparation is small. The observed reduction in HC emissions resulted from a higher residual gas fraction due to early IVO, which yielded later combustion phasing, which in turn yielded increased post-flame oxidation. Under steady-state cold coolant conditions, operation of a 4-cylinder engine with three cylinders running rich and the fourth used to pump air into the exhaust manifold resulted in near total oxidation of CO and HC at sufficiently retarded spark timing. Exhaust gas temperatures and enthalpy flow rates were significantly higher than for the conventional engine configuration at fast idle. Using this strategy to perform real cold starts proved challenging without the additional hardware needed for sufficient control over air flow to the engine.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 303

View

Book Description
Particulate formation studies have been conducted using both spark-ignition premixed pre-vaporized (PMPV) operation and spark-ignition direct-injection (SIDI) operation. The effects of fuel chemistry, mixture enrichment, pressure, temperature, and residence time have been characterized for premixed flames using PMPV operation. The influence of fuel physical properties, in-cylinder liquid films, pressure, and residence time were studied using SIDI operation. The PMPV studies demonstrated a non-fuel baseline (NFB) particulate size distribution (PSD) that was insensitive to fuel composition and enrichment below a critical enrichment level. The critical enrichment level needed to generate significant soot above the NFB as a function of fuel type and operating condition was then determined. A toluene reference fuel (TRF30: 50% isooctane, 20% n-heptane, and 30% toluene by volume) was demonstrated to match the in-cylinder chemical sooting tendencies of a tier II certification grade gasoline due to matching of the gasoline's aromatic fraction and carbon to hydrogen ratio (C/H). Sensitivity of the sooting tendency to aromatic fraction was validated by testing fuels with varying toluene volume fraction. A PMPV combustion phasing sweep established that extreme changes in the main combustion temperature and pressure result in minor changes in particulate formation. Equivalence ratio sweeps at several loads and two speeds revealed that both increased pressure and in-cylinder residence time reduce the critical enrichment threshold under premixed conditions. Injection timing sweeps during SIDI operation using EEE and TRF30 proved that the high boiling point components in EEE result in higher particulate emission when compared with TRF30 which vaporizes more easily. Under SIDI operation, lower speed reduced total particle number but produced similar particulate mass due to a tradeoff between increased mixing time and increased residence time. Increased load under stoichiometric SIDI operation was shown to increase particulate with a dependence similar to that seen for PMPV operation at the richest mixtures. Comparisons between the PMPV and SIDI cases provide a method for interpreting the relative importance of chemical and physical parameters in an SI engine at different operating conditions by providing a separation of the effects of fuel chemical sooting tendency from fuel physical property impacts on in-cylinder mixture formation.

Author: David Jonathan Kayes
Publisher:
ISBN:
Category :
Languages : en
Pages : 388

View

Book Description

Author: Mark P. Musculus
Publisher:
ISBN:
Category :
Languages : en
Pages : 19

View

Book Description
Based on a phenomenological model of diesel combustion and pollutant-formation processes, a number of fuel additives that could potentially reduce in-cylinder soot formation by altering combustion chemistry have been identified. These fuel additives, or ''combustion modifiers'', included ethanol and ethylene glycol dimethyl ether, polyethylene glycol dinitrate (a cetane improver), succinimide (a dispersant), as well as nitromethane and another nitro-compound mixture. To better understand the chemical and physical mechanisms by which these combustion modifiers may affect soot formation in diesel engines, in-cylinder soot and diffusion flame lift-off were measured, using an optically-accessible, heavy-duty, direct-injection diesel engine. A line-of-sight laser extinction diagnostic was employed to measure the relative soot concentration within the diesel jets (''jetsoot'') as well as the rates of deposition of soot on the piston bowl-rim (''wall-soot''). An OH chemiluminescence imaging technique was utilized to measure the lift-off lengths of the diesel diffusion flames so that fresh oxygen entrainment rates could be compared among the fuels. Measurements were obtained at two operating conditions, using blends of a base commercial diesel fuel with various combinations of the fuel additives. The ethanol additive, at 10% by mass, reduced jet-soot by up to 15%, and reduced wall-soot by 30-40%. The other fuel additives also affected in-cylinder soot, but unlike the ethanol blends, changes in in-cylinder soot could be attributed solely to differences in the ignition delay. No statistically-significant differences in the diesel flame lift-off lengths were observed among any of the fuel additive formulations at the operating conditions examined in this study. Accordingly, the observed differences in in-cylinder soot among the fuel formulations cannot be attributed to differences in fresh oxygen entrainment upstream of the soot-formation zones after ignition.