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.

Highlights

  • non⁃reacting spray cases are performed for ECN

  • detailed chemical re⁃ action kinetics based on OpenFOAM

  • The applicability and accuracy of the spray model is verified in the non⁃reac⁃ ting spray case

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Summary

Introduction

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。 Spray A 有大量可用的试验数据,包括环境温 度、环境密度、燃油注入压力等参数变化相对应的试 验数据,ECN 团队利用高速摄像技术得到了正十二 烷喷雾的瞬态过程,利用 Mie 散射和 Rayleigh 散射 技术对 无反应情况下气体的混合情况进行定量 测量[6] 。

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Conclusion

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