Assessment of Gasoline Direct Injection Engine Cold Start Particulate Emission Sources

Oh, Changhoon; Cheng, Wai K.

doi:10.4271/2017-01-0795

Cited by 14 publications

(6 citation statements)

References 19 publications

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“…58 Both of these effects explain the observed increase in the baseline PSD with load. Oh and Cheng 59 showed an increase in particles from non-fuel sources due to load using a method similar to that used here. However, this increase was not noted until loads above 5 bar net IMEP.…”

Section: Resultsmentioning

confidence: 86%

Impacts of combustion phasing, load, and speed on soot formation in spark-ignition engines

Hageman

Rothamer

2019

International Journal of Engine Research

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The premixed prevaporized engine operation method was used to study the effects of main combustion thermodynamic properties and residence time on soot formation in a spark-ignition engine. Select cases were repeated under early-injection, nearly homogeneous, spark-ignition direct-injection operation to determine if the impact of the investigated parameters was the same or if the impact of in-cylinder liquid fuel injection and the resulting heterogeneous fuel-air mixture alters the trends. The original premixed prevaporized study hypothesized that soot is more likely to form after main combustion than during the main combustion event under completely homogeneous conditions. This hypothesis was tested in this study by performing premixed prevaporized combustion phasing sweeps at equivalence ratios (Φs) of 1.35 and 1.40. Both sweeps showed low sensitivity of the particle size distribution to significant changes in peak temperature and pressure during combustion, providing supporting evidence for the original hypothesis. This information was then used to design experiments to isolate the impacts of pressure (engine load) and residence time (engine speed). A premixed prevaporized load sweep showed that particulate emissions increase as a function of load/pressure. A spark-ignition direct-injection load variation showed similar pressure dependence for cases with in-homogeneous in-cylinder fuel-air distributions. A premixed prevaporized residence time variation (performed by changing engine speed) demonstrated an increase in soot formation with increased residence time. The results for identical spark-ignition direct-injection residence-time variations suggest a trade-off in soot formation between the effects of increased mixing time and increased residence time for spark-ignition direct-injection operation. The premixed prevaporized load and speed points were each investigated using Φ sweeps to determine the critical enrichment threshold for soot formation (ΦC) and the dependence of soot formation for Φ > ΦC. The spark-ignition direct-injection investigations were performed at Φ = 0.98, such that any soot formation above the non-fuel-related baseline particle size distribution could be attributed either to mixture heterogeneity or in-cylinder fuel films.

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Section: Resultsmentioning

confidence: 86%

Impacts of combustion phasing, load, and speed on soot formation in spark-ignition engines

Hageman

Rothamer

2019

International Journal of Engine Research

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“…Since a major source of the PN emission is the residual fuel film created by the injection process, derating the injection pressure would significantly change the PN emission. The PN emission levels with the derated next-generation injector, however, were on par with those of the previous-generation LTG engine injector which operated under a lower pressure [12]. Therefore, the amount of the residual fuel film should be similar, and should be representative of those in GDI engines with substantial fuel film.…”

Section: Engine Instrumentation Fuel and Operating Conditionsmentioning

confidence: 91%

“…Since there are comparatively few particles above 1000 nm, and that the number of nucleation mode particles above 23 nm is relatively small (compared to the total number of accumulation mode particles), the accumulation mode PN is a good measure of the total number density of the 23-2500 nm particles called out in PMP. Further details of the engine setup and instrumentation can be found in [12].…”

Section: Engine Instrumentation Fuel and Operating Conditionsmentioning

confidence: 99%

“…These particles are mostly in the accumulation mode of the size spectrum [6]. A large body of study has been done on the particulate emissions from engines [6][7][8][9][10], and on identifying the emission sources [11,12]. The fuel effects on the PN emissions have been addressed through a particulate matter index (PMI), which assesses the particle emission potential of the fuel through the reactivity and volatility of its components [13,14].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Ethanol Evaporative Cooling on Particulate Number Emissions in GDI Engines

Chen¹,

Zhang²,

Cheng³

2018

SAE Technical Paper Series

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The spark ignition engine particulate number (PN) emissions have been correlated to a particulate matter index (PMI) in the literature. The PMI value addresses the fuel effect on PN emission through the individual fuel species reactivity and vapor pressure. The latter quantity is used to account for the propensity of the non-volatile fuel components to survive to the later part of the combustion event as wall liquid films, which serve as sources for particulate emission. The PMI, however, does not encompass the suppression of vaporization by the evaporative cooling of fuel components, such as ethanol, that have high latent heat of vaporization. This paper assesses this evaporative cooling effect on PN emissions by measurements in a GDI engine operating with a base gasoline which does not contain oxygenate, with a blend of the gasoline and ethanol, and with a blend of the gasoline, ethanol, and a hydrocarbon additive so that the blend has the same PMI as the original gasoline. As such, the dilution and the evaporative cooling effects of the ethanol could be separated. Measurements have also been done with methanol and MTBE. The results show that evaporative cooling effect can significantly change the PN emission. The extent of the change, however, depends on the details of the operating condition such as injection timing, engine coolant temperature, and load.

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“…Early work under late injection, lean stratified charge operating conditions 6,7 identified pool fires as diffusion flames supported by fuel films on the piston and found that these were an important source of engine-out soot. More recently, however, the results of Ketter and Cheng 23 and Oh and Cheng 24 allowed them to propose that for near-stoichiometric DISI engine operation, there is insufficient oxygen in the burned gases to support diffusion flames. Under these circumstances, as in the research described in this article, the flames associated with pool fires cannot be described as diffusion flames even though their radiation aspect is similar: the visible radiation comes, in fact, from the hot soot particles formed during pyrolysis in the residual fuel-rich region, which coincides with the impingement region, where a fuel film is formed.…”

Section: Introductionmentioning

confidence: 99%

Impact of gasoline direct injection fuel films on exhaust soot production in a model experiment

Roque

Foucher

Lamiel

et al. 2019

International Journal of Engine Research

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The fuel films that can be generated during the injection process in gasoline direct injection engines are the most important factor in carbon particle mass and number. They also have an influence on combustion chamber and injector tip deposits. A model experiment was set up to study a liquid film, its evaporation, and combustion with soot generation on a metal plate in realistic engine conditions. The experiment was conducted in a dedicated constant volume vessel. A liquid fuel injection system (with injection pressures up to 100 bar) directs the spray onto a plate with a controlled temperature in the range of 80 °C–200 °C. The resulting liquid film and vaporization process were studied when subjected to interaction with a laminar spherical flame. A blend of four components was used as a gasoline surrogate. The liquid film spreading, thickness, and evaporation rates were initially measured in ambient conditions. Mie scattering and schlieren measurements in the chamber conditions returned a qualitative correlation of the vaporized area with the surface temperature. Fluorescence of the light and heavy fuel components was used to quantify the influence of the vaporization process on soot production. Simultaneous measurements of natural luminosity and KL factor were analyzed to understand the process of soot production. The results showed a critical wall temperature of 120 °C at which the maximum quantity of soot is generated, which can be due to the quantity and composition of fuel film in interaction with the entrainment flows generated during combustion.

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Assessment of Gasoline Direct Injection Engine Cold Start Particulate Emission Sources

Cited by 14 publications

References 19 publications

Impacts of combustion phasing, load, and speed on soot formation in spark-ignition engines

Impacts of combustion phasing, load, and speed on soot formation in spark-ignition engines

Effects of Ethanol Evaporative Cooling on Particulate Number Emissions in GDI Engines

Impact of gasoline direct injection fuel films on exhaust soot production in a model experiment

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