超高压燃油雾化及诱导激波引燃机理的基础研究

Study on the mechanisms of atomization and ignition induced by shock waves of fuel spray under ultra-high injection pressure will be performed by using theoretical analysis, numerical simulation and experimental measurement. Firstly, formation and evolution characteristics of induced shock waves will be analyzed using experimental method and two-phase flow large eddy simulation (LES) methodology. The interaction between induced shock waves and spray will be discussed. The effects of compressibility and aerodynamic heating on Kelvin-Helmholtz and Rayleigh-Taylor instability will be analyzed based on a instability theory of a liquid jet. Then, the dispersion relations for surface waves on a fuel jet under ultra-high injection pressure will be derived. The effects of shock waves on the Richtmyer-Meshkov instability in the fuel/air mixing layer will be investigated using LES method. High speed camera techniques will be employed to analyze the feasibility and technique of the ignition induced by shock waves. Finally, the mathematical models for atomization and ignition for fuel jet in ultra-high injection pressure will be established and validated based on numerical simulation and experimental results. The study of mechanisms of atomization and ignition induced by shock waves of ultra-high injection pressure will be help to improve our understanding of atomization of liquid fuel and enriched relative basic theory. Therefore, the study has theoretical guiding significance.

应用实验、数值模拟和理论分析相结合的方法，对超高压燃油雾化及诱导激波引燃机理进行深入的研究。采用实验和气液两相流大涡模拟方法分析超高压燃油喷雾诱导激波的形成与演变规律，探讨超高压燃油雾化诱导激波与喷雾之间的耦合作用关系。采用射流稳定性理论研究可压缩性和气动热效应对超高压燃油射流KH和RT不稳定特性的影响。建立并求解超高压燃油射流表面波色散方程。基于大涡模拟方法研究激波对喷雾混合区Richtmyer-Meshkov不稳定的作用机制。采用高速摄影技术研究超高压燃油喷雾诱导激波引燃的可行性和技术途径。最后通过实验与数值模拟相结合的方法，建立并验证超高压燃油雾化与激波引燃模型。深入超高压柴油射流雾化及诱导激波引燃机理的研究，有助于加深人们对超高压燃油射流雾化机理的理解和认识，丰富和发展燃油雾化的相关基础理论，具有重要的理论意义。

本项目采用理论、数值仿真和试验相结合的方法研究了超高压燃油（300MPa~400MPa）雾化和诱导激波的引燃机理。结果表明，随着喷射压力的提高，喷雾贯穿距离增大，但增长幅度逐渐降低。超高压下的液体射流马赫数Ma普遍大于1，射流前端会产生前缘激波并受到激波的作用。超声速喷雾会诱导出一系列准周期性的激波并冲刷喷雾本体，随着环境压力的增加，激波的冲刷频率增加。当喷油压力为300MPa，孔径为0.2mm，室温条件下环境背压从0.5MPa增加到2.0MPa时，激波冲刷频率从474kHz增加到712kHz。本次研究还考虑气动可压缩性和热效应建立了SS-KH-RT破碎模型可以比KH-RT模型更好的预测超高压燃油喷雾条件下的喷雾贯穿距和液滴粒径值。基于新模型的仿真研究表明，随着喷油压力的提高，喷雾场内亚声速和超声速液滴的数量均增加，喷雾场内液滴总数持续增加，喷雾区域气体质量逐渐增加。在低于柴油燃点的高温环境下，超高压燃油喷雾会首先引燃喷雾两侧的柴油蒸汽。随着喷油压力的提高，着火区域面积也会逐渐增加。