Understanding partial fuel stratification for low temperature gasoline combustion using large eddy simulations

Priyadarshini, Priya; Sofianopoulos, Aimilios; Mamalis, Sotirios; Lawler, Benjamin; Pintor, Dario Lopez; Dec, John E.

doi:10.1177/1468087420921042

Cited by 14 publications

(19 citation statements)

References 56 publications

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“…The current paper extends the work of Priyadarshini et al 56 by evaluating two additional mechanisms and by extending the test matrix to include highly stratified conditions. Details on the validation of the CFD model can be found in Priyadarshini et al 56 The top row of Figure 4 shows the results for low stratification (SOI 2 = 2160 CAD aTDC). It can be observed that for all the combustion metrics, the model is in very good agreement with the experiments when SKM1 is used.…”

Section: Compositional Stratification Analysismentioning

confidence: 69%

“…Finally, it should be noted that the CFD model used in this investigation has been already validated by Priyadarshini et al 56 for low and moderate levels of stratification and using SKM1. The current paper extends the work of Priyadarshini et al 56 by evaluating two additional mechanisms and by extending the test matrix to include highly stratified conditions. Details on the validation of the CFD model can be found in Priyadarshini et al 56 The top row of Figure 4 shows the results for low stratification (SOI 2 = 2160 CAD aTDC).…”

Section: Compositional Stratification Analysismentioning

confidence: 97%

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A comparative study of gasoline skeletal mechanisms under partial fuel stratification conditions using large eddy simulations

Guleria

Pintor

Dec

et al. 2021

International Journal of Engine Research

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Partial fuel stratification (PFS) is a low temperature combustion strategy that can alleviate high heat release rates of traditional low temperature combustion strategies by introducing compositional stratification in the combustion chamber using a split fuel injection strategy. In this study, a three-dimensional computational fluid dynamics (CFD) model with large eddy simulations and reduced detailed chemistry was used to model partial fuel stratification at three different stratified conditions. The double direct injection strategy injects 80% of the total fuel mass at −300 CAD aTDC and the remaining 20% of the fuel mass is injected at three different timings of −160, −50, −35 CAD to create low, medium, and high levels of compositional stratification, respectively. The PFS simulations were validated using experiments performed at Sandia National Laboratories on a single-cylinder research engine that operates on RD5-87, a research-grade E10 gasoline. The objective of this study is to compare the performance of three different reduced chemical kinetic mechanisms, namely SKM1, SKM2, and SKM3, at the three compositional stratification levels and identify the most suitable mechanism to reproduce the experimental data. Zero-dimensional chemical kinetic simulations were also performed to further understand differences in performance of the three reduced chemical kinetic mechanisms to explain variations in CFD derived heat release profiles. The modeling results indicate that SKM3 is the most suitable mechanism for partial fuel stratification modeling of research-grade gasoline. The results also show that the autoignition event progresses from the richer to the leaner compositional regions in the combustion chamber. Notably, the leaner regions that have less mass per unit volume, can contribute disproportionately more toward heat release as there are more cells at leaner equivalence ratio ranges. Overall, this study illuminates the underlying compositional stratification phenomena that control the heat release process in PFS combustion.

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Section: Compositional Stratification Analysismentioning

confidence: 69%

Section: Compositional Stratification Analysismentioning

confidence: 97%

A comparative study of gasoline skeletal mechanisms under partial fuel stratification conditions using large eddy simulations

Guleria

Pintor

Dec

et al. 2021

International Journal of Engine Research

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“…Then, a second injection supplies the remaining 20% of the fuel at a variable timing, SOI2, during the compression stroke. Experimental results 11,12 and computational fluid dynamics simulations 42,44 have shown that SOI2 = 200 CAD results in the most wellmixed charge (even more well mixed than earlier SOI2s). Variable levels of stratification were created by retarding SOI2 from 200 CAD to later crank angles.…”

Section: Results Under Partially Stratifiedmentioning

confidence: 99%

“…Custom fuels are compared to a surrogate fuel for a regular-grade, E10, AKI 88.4 (RON 92), research gasoline, known as RD5-87, the formulation of which is shown in Table . This surrogate was previously developed by the authors based on the actual fuel composition, and it was validated against experimental results under LTGC conditions. − …”

Section: Numerical Methods and Fuel Specificationsmentioning

confidence: 99%

Experimental Evaluation of a Gasoline-like Fuel Blend with High Renewable Content to Simultaneously Increase φ-Sensitivity, RON, and Octane Sensitivity

Pintor

Dec

2021

Energy Fuels

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High-performance renewable fuels (HPFs) are an alternative to conventional petroleum fuels that could greatly reduce the carbon footprint of internal combustion engines. The combination of high-HPF-content fuels with advanced engine technologies [such as advanced compression ignition (ACI)] that have been demonstrated to provide efficiencies well above those of diesel engines is a promising pathway for substantial reductions in CO2 with low criteria emissions. One of the key fuel properties for the operation of ACI engines is φ-sensitivity. However, regular gasoline is not very φ-sensitive under naturally aspirated conditions, meaning that intake boosting is required to take advantage of this property. Thus, there is strong motivation to design HPF fuel blends that improve φ-sensitivity at lower pressures and simultaneously increase the research octane number (RON) and octane sensitivity (S) to make them improved fuels suitable for both ACI and spark-ignition engines. In this study, a holistic methodology was used to design a five-component gasoline-like blend (termed CB#2) that contains 40%vol of a mixture of 2-methyl furan and 2,5-dimethyl furan (which is representative of products of a viable pathway to make furans from bio-feedstock). Simulations show promising results when CB#2 is compared to regular E10 gasoline (RD5-87). Measurements show that CB#2 has RON = 97.4 and S = 13.6, improving the RON and S of RD5-87 by 5.4 and 6.3 units, respectively, and suggesting that CB#2 is suitable for spark-ignition engines. Fuel blend CB#2 has been experimentally evaluated in the low-temperature gasoline combustion engine at Sandia National Laboratories, and the results are compared with those of RD5-87. Fuel blend CB#2 requires less intake heat than RD5-87 to autoignite under premixed, naturally aspirated conditions, indicating that CB#2 operates under the ACI mode easier than regular gasoline. Both CB#2 and RD5-87 allow virtually the same maximum engine load under premixed, high-boost conditions. Finally, CB#2 shows significantly higher φ-sensitivity than RD5-87.

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“…It raises the local mean equivalence ratio even further, resulting in slower and more fluctuated initial flame propagation. 14 Priyadarshini et al, 15 observed that when injecting too late, past 50°CA bTDC at 1200 rpm, the fuel is injected into a smaller cylinder volume. The benefits of the bulk flow motion are thus difficult to achieve.…”

Section: Introductionmentioning

confidence: 99%

Investigations of split injection properties on the spray characteristics using a solenoid high-pressure injector

Dhanji

Zhao

2021

International Journal of Engine Research

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An on-going challenge with Gasoline direct injection (GDI) engines is achieving rapid activation of the exhaust catalyst during cold starts, in order to reduce the Nitrogen Oxide (NOx) emissions. Injecting late in the compression stroke, in the efforts to form a stratified mixture, provides the fuel insufficient time to be entrained with the surrounding charge. This results in locally fuel rich diffusion combustion and the formation of high levels of particulate matter. Employing a split injection strategy can help tackle these issues. The current study examines the effects of a split injection strategy on the spray characteristics. Varying pulse width (PW) combinations, split ratios and dwell times are investigated using a Solenoid actuated high pressure injector. The injected quantity and the droplet characteristics of a target plume are investigated. The experiments were performed in a constant volume spray chamber. The droplet velocities and sizes were measured using Phase Doppler Particle Anemometry (PDA). Short and large PWs, in the range of 0.3–0.8 ms, were investigated. The results revealed that the highest injected quantity of fuel was measured with the shortest dwell time of 2 ms, owing to increased interactions between the injection events, which led to larger Sauter mean diameters (SMDs) measured. The SMDs for the shorter PW of 0.4 ms were generally larger than 0.8 ms PW. The droplets in this case were affected by the closely spaced opening and closing events of the Solenoid valve.

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Understanding partial fuel stratification for low temperature gasoline combustion using large eddy simulations

Cited by 14 publications

References 56 publications

A comparative study of gasoline skeletal mechanisms under partial fuel stratification conditions using large eddy simulations

A comparative study of gasoline skeletal mechanisms under partial fuel stratification conditions using large eddy simulations

Experimental Evaluation of a Gasoline-like Fuel Blend with High Renewable Content to Simultaneously Increase φ-Sensitivity, RON, and Octane Sensitivity

Investigations of split injection properties on the spray characteristics using a solenoid high-pressure injector

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