Numerical simulation of n-dodecane spray combustion based on OpenFOAM

基于OpenFOAM的正十二烷喷雾燃烧数值模拟

School of Power and Energy, Northwestern Polytechnical University, Xi’an 710072, China

Received: 18 August 2020

Abstract

For the purpose of providing the scientific insights to combustion characteristics of spray jet, numerical calculations of reacting and non-reacting spray cases are performed for ECN (engine combustion network) Spray A (n-dodecane spray combustion) which coupled finite chemistry combustion model PaSR and detailed chemical reaction kinetics based on OpenFOAM. The applicability and accuracy of the spray model is verified in the non-reacting spray case, and it is found that the predicted spray characteristics such as the penetration length of liquid and vapor and the mixture fraction are in good agreement with the test results. The two processes of low-temperature reaction and high-temperature ignition experienced by n-dodecane spray ignition are analyzed in reacting spray case, and it is found that the low-temperature reaction continues to exothermic before high-temperature ignition, and continues to proceed stably after high-temperature ignition, which promotes high-temperature ignition and flame stability. Finally, the effects of different fuel injection pressures on ignition delay time and flame lift-off length are studied.

摘要

为了深入理解喷雾射流的燃烧特性，基于OpenFOAM平台，采用有限速率PaSR燃烧模型和详细化学反应动力学相结合的方法，对ECN（engine combustion network）Spray A（正十二烷喷雾燃烧）无反应和有反应2种情况进行数值计算。无反应情况下验证了该喷雾模型的适用性和精确性，发现预测的液体和蒸气穿透长度、混合分数等喷雾特性参数与试验结果吻合很好；反应情况下分析了正十二烷喷雾点火经历的低温反应和高温点火2个过程，发现低温反应在未发生高温点火前持续放热，在高温点火后仍持续稳定进行，起到促进高温点火和稳定火焰作用；研究了不同燃油注入压力对点火延迟时间和火焰浮升高度的影响。