横向脉冲喷流超声速燃烧流场数值模拟与分析

为了研究横向脉冲喷流对燃烧室流场结构及燃烧特性的影响,对带后台阶的超燃冲压发动机燃烧室横向氢气喷流超声速燃烧流场进行了数值模拟。采用有限体积法求解多组元Navier-Stokes (NS)方程,分别对定常喷流与两种脉冲喷流超声速燃烧流场进行了数值计算,对比分析了三种氢气喷注方案下的流场结构、氢气掺混燃烧特性及燃烧室总压恢复特性。研究表明:脉冲干扰仅对燃烧室内局部流场产生周期性影响,且有利于氢气的横向扩散;采用与定常喷注喷流参数相同的脉冲喷注方案时,可在脉冲干扰区内保持氢气掺混量与定常喷注基本相同,氢气燃烧量与总压恢复系数整体上与定常喷注基本一致;采用特征时间内喷出氢气质量流量与定常喷注相同的脉冲喷注方案时,在燃烧室出口处氢气掺混量和燃烧量较定常喷注分别提高了21.94%和32.24%,总压恢复系数仅减小4.17%。采用脉冲喷注方案增加了燃料与空气接触面面积,对燃料掺混及燃烧起促进作用。

Numerical Study of Supersonic Combustion Flowwith Transverse Pulse Jet

In order to study the effects of transverse pulse jet on the flow field structure and combustion characteristics of the combustion chamber, the numerical simulation of the transverse hydrogen jet supersonic combustion flow field in scramjet combustor with backward-facing step is carried out. Steady and pulse injection flow fields are calculated respectively with Reynold-averaged multi-component N-S equations solved, based on the finite volume method. The effects of the pulse injection schemes on the flow field structures, characteristics of hydrogen mixing and combustion, as well as the characteristics of total pressure recovery were analyzed. Results show that the interference of pulse injection, contributes to the transverse diffusion of hydrogen, has a periodic effect only on the local flow field in the combustion chamber. When the pulse injection scheme with the same injection parameters as steady scheme, the mixing of hydrogen in the pulse interference area, the combustion of hydrogen and the total pressure recovery coefficient on the whole are in accordance with the steady. When the pulse injection with the same mass flux hydrogen as the steady in the characteristic time, the mixing and combustion of hydrogen at the exit of the combustor increased by 21.94% and 32.24%, respectively, and the total pressure recovery coefficient is decreased only by 4.17%. Pulse injection schemes could increase the interface of fuel and air, which promotes the mixing and combustion of fuel.