超声速燃烧冲压发动机进气道起动性能研究

采用等激波强度设计方法,并考虑变比热、激波与附面层干扰等因素的影响,对唇口平直和唇口带有斜楔的超燃冲压发动机二维混压式前体/进气道进行了初步设计,比较分析了几种方案进气道的设计点和非设计点性能,研究表明,在低飞行马赫数(Ma)下,唇口带有斜楔的前体/进气道起动性能和总压恢复优于唇口平直的,在高飞行Ma下,唇口平直的前体/进气道冲压比高、外罩阻力小,而唇口带有斜楔的前体/进气道总压恢复系数高,外罩阻力相对较大。针对超声速燃烧冲压发动机燃烧室和进气道间非定常干扰的问题,计算研究了飞行Ma=4,6下,燃烧室压力升高对进气道/隔离段流场和起动性能的影响,结果表明,在低飞行Ma条件下,燃烧引起的压力扰动容易往上游传播,甚至引起进气道不起动;随着飞行Ma的增大,隔离段的抗扰动能力是增强的;当进气道进入不起动后,进气道的捕获流量和总压恢复系数急剧下降,高飞行Ma时的捕获流量的下降幅度比低飞行Ma时大。

Investigation on Start Performance of Scramjet Inlet

A two-dimensional scramjet forebody/inlet of mixed external and internal(compression) with plane lip and wedged lip were designed by using constant shock intensity method.The effect of temperature and shock/boundary-layer interaction was considered in the design.The design and off-design performance and flow field of several types of designed forebody/inlet were calculated and compared.The comparison results indicate at lower flight speed,the starting(performance) and total pressure recovery coefficient of forebody/inlet with wedge lip is better than that with plane lip.At high flight speed,the forebody/inlet with plane lip is of high pressure ratio and lower cowl drag,the forebody/inlet with wedge lip is of high total pressure recovery coefficient and high cowl drag.Due to the problem of unsteady interaction between combustor and inlet,the effect of back pressure raise in combustor on inlet/isolator flow field and start performance was(simulated).The research results present at lower flight Mach number,it is easy for combustion-(induced) pressure waves to propagate upstream and even to result in inlet unstart.The pressure(disturbance) results from chemical energy release in the combustor.Isolator can prevent the(pressure) disturbance from influencing inlet in a certain extent and is helpful to combustion mode transition.The ability for preventing pressure disturbance to propagate upstream improves when flight Mach number is increased.For an unstarted inlet,the captured mass flow will decrease quickly.The decrease extent to the captured airflow at high flight Mach number is larger than that at low flight Mach number.