摘要:
在直连式脉冲燃烧设备上,开展了模拟Ma4,总温935K 来流参数下的超燃发动机乙烯点火试验。试验利用了火炬点火器和引导氢气的辅助点火方式,实现了乙烯的点火和稳定燃烧。结合壁面压力测量、高速摄影和数值模拟方法,分析点火及火焰传播过程发现:(1)在现有的注油方式下,回流区有利于点火,剪切层和凹槽后部是稳焰的主要区域;(2)点火成功后,影响凹槽稳焰的主要因素为燃料与氧化剂的浓度,剪切层内和凹槽后部持续卷吸氧化剂,因而能够维持稳定的燃烧;(3)凹槽下游注入的燃料发生燃烧造成流道一定程度壅塞,是提升燃烧室压力水平的重要原因,但该处的燃烧不能够稳定,引起燃烧室内压力的振荡,而导致该处不稳定燃烧的2个主要因素为变化的氧含量和较高的流速。
Abstract:
Gaseous ethylene ignition experiments were carried out on directly-connected pulse combustion facility.The stagnation temperature and the Mach number at the isolator entrance were 935K and 2 respectively,which simulated the flight with Mach number 4.Ethylene was ig-nited successfully and stable combustion was maintained by employing torch igniter and pilot hy-drogen.Wall pressure measurement,high speed imaging and numerical simulation were em-ployed to analyze the ignition and flame propagation processes.The results indicate that:(1)the recirculation zone in the cavity avails ignition,while the shear layer and the rear of the cavity are the main regions for stable combustion;(2)after ignition,the density of the fuel and oxidizer is the key factor to stable combustion,and oxidizer that continually entering the shear layer and rear of cavity supports the stable combustion;(3 )combustion downstream of the cavity pro-motes the pressure level in the combustor,and the unstable combustion there causes pressure os-cillation.The high velocity and variation of oxygen content are the two main factors including un-stable combustion downstream of the cavity.
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