数值模拟气液针栓式火箭发动机喷雾燃烧对声学激励的响应

为研究气液针栓式火箭发动机的声学振荡特性并为其优化设计提供指导,加工了具有矩形燃烧室的LOX/GCH₄针栓式发动机,采用Euler-Lagrange方法仿真横向速度扰动产生的声学响应,以期在热试前了解声学激励频率对非稳态喷雾燃烧过程的影响。仿真结果表明,采用的横向速度扰动能在燃烧室内产生同频率的一阶横向声学振荡响应。喷雾燃烧对声学激励的响应强弱受扰动频率与燃烧室一阶横向振荡模态固有频率的相对大小影响较大。当扰动频率与该固有频率相等时,压力和燃烧释热随速度扰动出现同相振荡,压力振荡幅值显著增高导致燃烧室前半段的喷雾和火焰同步摆动；同时,燃烧室内存在扩散燃烧变为预混燃烧的趋势,甲烷在更短的距离内燃烧完全且燃烧室温度趋于均匀。

Numerical simulation on spray combustion responses to acoustic excitation in a gas-liquid pintle rocket engine

In order to investigate the acoustic oscillation characteristics of gas-liquid pintle rocket engine and provide a reference for later optimization designs, a LOX/GCH₄ pintle engine with rectangular combustor was manufactured. The Euler-Lagrange method was used to simulate the acoustic response produced by transverse velocity disturbance, and the effect of acoustic excitation frequency on the transient spray combustion process was studied before fire tests. Numerical results show that the adopted transverse velocity disturbance can produce the first-order transverse acoustic oscillation response with the same oscillation frequency in the combustion chamber. The response of spray combustion to acoustic excitation can be greatly affected by the relative size of the disturbance frequency and the combustor natural frequency of first-order transverse oscillation mode. When the disturbance frequency and the natural frequency are equal, the pressure and heat of reaction oscillate in phase with the velocity disturbance in the first half of combustor, and the significant increase of pressure oscillation amplitude also causes spray flame to swing synchronously. Meanwhile, there is a tendency to shift from diffusion combustion to premixed combustion in the combustor. Methane burns completely in the shorter distance and the combustor temperature tends to be uniform.