碳氢燃料超燃冲压发动机进气道与燃烧室匹配性能试验研究

Experimental Study on the Interaction between Inlet and Combustor of Hydrocarbon Fueled Scramjet

在模拟飞行马赫数Ma=6,高度25km条件的液体碳氢燃料超燃冲压发动机自由射流试验中,对比研究了4种不同进气道,不同燃烧室入口条件下模型发动机的点火与燃烧性能。试验结果表明几何内收缩比3的侧压式进气道的出口压强低而无法实现模型发动机的点火;进气道增加部分前体压缩,模型发动机则能够维持稳定燃烧,得到正推力;采用较高收缩比5 35的三维进气道的出口流场畸变程度较高,降低了隔离段抗反压的能力,会对燃烧性能产生很大影响,燃烧效率、发动机推力显著下降,甚至可能导致发动机熄火。不同长度的隔离段对比研究表明隔离段加长能够提高抗反压能力,有助于实现煤油分级燃烧,提高燃烧效率。

Experimental investigations on the combustion process of a liquid hydrocarbon fueled scramjet, igni ted by hydrogen pilot flame, and with four different inlets, were conducted in free-jet tests, which simulated the fly conditions of Ma= 6 and H=25km. Ignition failed with inlet of geometry internal contraction ratio Re=3, which was comprised of two sweep side compression walls with a contraction of 6° and without horizontal compression surface, due to low static pressure at inlet exit. Stable combustion was sustained in scramjet and positive thrust was measured with inlet of Re 3, comprising an additional part of horizontal external compression surface. Adapting inlet of higher Re=5.35, comprising a whole horizontal compression surface, would result in severely distorted airflows at inlet exit, which deteriorated the behavior of isolator, decreased combustion performance, at some cases, even leaded to extinction. Two isolators with different length to-hydraulic diameter ratios （2.5 and 5） were contrasted, and it was shown that longer isolator increase the ability of isolating the interaction between inlet and combustor and part fuels can be injected about downstream of isolator to improve combustion efficiency.