补油距离和燃油配比对两级脉冲爆震发动机预燃裂解的影响

Effects of Fuel-Addition Distance and Fuel Ratio on Precombustion and Thermal Cracking in 2-Stage PDE

两级脉冲爆震发动机中,预燃室内煤油预燃裂解的效果对共振腔内起爆效果和可靠性有重要影响。基于稳态扩散火焰面模型,对预燃室中煤油预燃裂解的效果进行了数值仿真,讨论了补油距离d和燃油配比R对预燃裂解效果的影响,以期为进一步的预燃室设计和实验研究提供参考。计算结果表明:补油距离d主要通过影响反应物的驻留时间来影响反应产物的生成,d越大,第二级喷油位置距离预燃室出口越近,驻留时间越短,各主要活性组分产量越低;燃油配比R则同时影响预燃室内的温度和反应物的驻留时间,R越大,各主要活性组分含量越低;温度过高时不利于较稳定的活性组分产生。由此建议补油喷嘴应尽量远离预燃室出口,最佳燃油配比为3~5。

Precombustion and thermal cracking of kerosene in the precombustor of 2-Stage PDE have significant impacts on the effects and reliability of detonation in the resonant cavity. Based on the Steady Diffusion Flamelet Model,the effects of precombustion and cracking in precombustor were simulated. The influences of two factors were discussed—the fuel-addition distance（d） and fuel ratio（R）,expecting to provide references for precombustor design and further experiments. It is concluded that d affects the production of active species mainly through affecting the residence time of mixture in the precombustor,and the production of active species decreases with increasing d because of the reduction of distance to the outlet and the residence time. R affects the production of active species through affecting both the residence time and the temperature in the precombustor.Overall,the production of active species decreases with increasing R. Excessively high temperature has adverse effect on the generation of combustible active species. It is suggested that the fuel-addition nozzle should be as far from the outlet of the precombustor as possible. And the optimal fuel ratio is between 3~5.