煤油燃料超燃冲压发动机燃烧特性实验研究

Experimental Investigation on Combustion Characteristics in Kerosene-Fueled Scramjet Engine

关键词:  燃烧特性  超燃冲压发动机  火焰吹熄  火焰稳定  超声速流动

Key words:  Combustion characteristics  Scramjet  Flame blowout  Stable flame  Supersonic flow

摘要:

为研究空气节流时序对超燃冲压发动机点火和火焰稳定的影响，通过实验方法研究了13个状态的煤油燃料超燃冲压发动机的燃烧特性。通过先锋氢气和节流空气增强煤油燃烧的稳定性，利用两个固定位置的压力传感器监测火焰稳定状态，采用纹影和OH-PLIF相结合的测量手段，获得了流场结构和火焰发展信息。发动机入口来流条件为马赫数2.0，总温950K，总压0.82MPa。在空气节流的作用下，煤油被先锋火焰引燃，在先锋氢撤除后，煤油仍然可以稳定燃烧。在扩张段中，空气节流和燃烧共同作用产生的激波串移动速度约为52m/s，但在凹槽内其速度仅为3.7m/s。观测监测点压力变化情况可以区分所研究状态的火焰稳定与否，通过对13个研究状态的考察，获得了火焰稳定临界曲线。当所研究状态点在临界曲线右上方区域时，火焰状态稳定；当所研究状态点在临界曲线左下方区域时，火焰将被吹熄；当所研究状态点在临界曲线上时，火焰不稳定，在空气节流撤除之前将被吹熄。

Abstract:

In order to investigate the time sequence of air throttling on ignition and flame stabilization in the Scramjet combustor， thirteen experimental cases on the combustion characteristics of a kerosene-fueled Scramjet engine were investigated， which are enhanced by pilot hydrogen and air throttling. Two pressure monitors are used to monitor the flame state， wall pressure measurements， Schlieren images， and OH-PLIF are applied simultaneously to obtain information on the flow field and flame development. The results are obtained under inflow conditions of Mach number of 2.0， a stagnation temperature of 950K， and a stagnation pressure of 0.82MPa. With the aid of air throttling， the kerosene is ignited by the pilot flame， and the kerosene flame remains stable even after the pilot hydrogen is switched off. The speed of the shock train generated by the throttling air and combustion is about 52m/s in the expansion section， but only about 3.7m/s in the cavity region. Whether or not flame is stable can be distinguished by the monitor pressure， and the critical curve of flame stability is obtained by investigating the thirteen cases. When the case point locates in the right-up region of the critical curve， the flame is stable. When the case point locates in the left-down region of the critical curve， the flame will be blown off. There is a special case lying on this curve for which the flame is unstable and will be blown out before the throttling air is switched off.