Development of a turbulent burning velocity model based on flame stretch concept for SI engines |
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Affiliation: | 1. Center for Combustion Energy, School of Vehicle and Mobility, State Key Laboratory for Automotive Safety and Energy, Tsinghua University, Beijing, China;2. CNRS-INSIS, I.C.A.R.E., 1C, Avenue de la recherche scientifique, 45071 Orléans cedex 2, France;3. SKLTCS, CAPT, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China |
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Abstract: | According to the US Energy Information Administration, fossil fuels will remain the main source of energy for transportation over the next decades and thus the combustion of these fuels remains an important concern.This research studied the flame propagation under engine in-cylinder conditions and developed a correlation for turbulent burning velocity based on the global flame stretch concept. To study the impact of engine operation on flame stretch, two speeds, two loads, and three fuel-air mixtures were investigated. The flame front was determined by processing images of the flame natural luminosity.A turbulent burning velocity model was developed using dimensional analysis. The model showed that the turbulent burning velocity decreased due to flame stretching. Higher engine speeds increased the turbulent burning velocity by increasing the turbulent intensity, yet a tradeoff between the flame stretch and the turbulent burning velocity due to higher engine speed was observed. In cases where the flame distortion was very high, the flame stretch may cancel out any benefits of a large enflamed area.Incorporating the flame stretch into the burning velocity model and coupling the developed model with GT-Power simulation software revealed that the stretch may result in a 35% reduction in turbulent burning velocity. |
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Keywords: | Burning velocity model Flame stretch Markstein number Spark-ignition engine |
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