N_2O/C_3H_8发动机气液同轴离心式喷嘴喷雾性能数值模拟研究

Numerical simulation of spray performance of coaxial swirling injector for N_2O/C_3H_8 engine

采用数值计算方法对氧化亚氮/丙烷（N2O/C3H8）发动机样机气液同轴离心式喷嘴的喷雾性能进行了研究,得到了环缝外喷嘴气相喷注压降和内喷嘴缩进深度对离心式喷嘴喷雾流场的影响.分析结果表明,较低的气相喷注压降（＜0.3 MPa）会显著的影响液滴在流场中的蒸发速率以及流场流强、混合比、索太尔平均直径（SMD）和n值的分布;气相喷注压降从0.3 MPa增加至0.6 MPa,稳定喷雾流场液滴SMD和n值分别在2.41～1.68,2.03～0.98范围内变化并逐渐减小.内喷嘴缩进深度从0 mm增加至6 mm,稳定喷雾流场液滴的SMD和n值受其影响较小,均分别在1.70～0.94,2.36～0.99范围内波动.喷嘴的最佳燃烧区主要分布在下游轴向位置0.015～0.035m范围内并随着气相喷注压降的升高和内喷嘴缩进深度的增大逐渐靠近喷嘴出口.该设计喷嘴在发动机热试实验中表现出很好的性能.

Numerical computation method is conducted to investigate the spray performance of nitrous oxide/propane engine centrifugal injector. As a result, the impacts of gas injecting pressure drop and recessing distance on spray flow field of centrifugal injector were obtained. The result indicates that the lower gaseous phase injecting pressure drop （〈0.3 MPa） affects the evaporation rates of propane droplet, gas flow flux, mixture ratio, and distribution of SMD and n significantly. As the gas injecting pressure increases from 0.3 MPa to 0.6 MPa, the values of SMD and n will change in the range of 2.41-1.68 and 2.03-0.98 respectively, and decrease gradually. As the recess depth of inner injector increases from 0 mm to 6 mm, the SMD and n values of droplet in the stable spray flow field will vary slightly, which fluctuate within 1,70~0.94 and 2.36-0.99 respectively. The best combustion zone of the injector distributes mostly in the downstream position of 0.015-0.035 m, and approaches to the injector outlet gradually along with the increase of gas pressure drop and recess depth. The injector has obtained a good effect in C3H8/N2O engine hot test.