二次燃烧对多喷管运载火箭底部热环境影响研究

Effect of secondary combustion on the multi-nozzle rocket base thermal environment

火箭飞行时,尾焰中富燃燃气将继续与空气中氧气发生二次燃烧,导致尾流场温度升高。基于三维可压缩Navier-Stokes方程、混合RANS/LES湍流模型、DOM辐射模型和有限速率化学动力学模型建立多喷管火箭尾焰反应流模型,并通过与风洞试验数据对比验证了模型有效性。基于此,开展了6个不同高度下双喷管火箭和四喷管火箭反应流与冻结流流场对比分析。研究表明:二次燃烧主要发生在羽流混合层中,引起的流场峰值温度增幅随飞行高度增加而减小,最高可达10.16%,最低仅为0.86%。同一高度下,当羽流由近场向远场转变时,二次燃烧效应逐渐增强。相较于双喷管火箭,二次燃烧对四喷管火箭底部热环境影响更小。另外,多喷管火箭底部峰值热流随高度增加基本表现为先增大后减小的趋势。

During rocket launching,the secondary combustions between the fuel-rich exhaust gas and the oxygen of air were made,leading to a temperature rise.Based on three-dimensional compressible Navier-Stokes equation,hybrid RANS/LES turbulence model,DOM model,and finite-rate chemical kinetics,the reaction model of multi-nozzle rocket was established.And the validity of model was verified by comparing with the wind tunnel experimental data.Then,a comparison study between reaction and frozen flows of two-/four-nozzle rockets was developed.The results showed that the secondary combustion mainly occurred in the mixed layer.With the increase of the flight altitudes,the increase of the peak temperature caused by afterburning decreased,while the maximum was 10.16%and the minimum was 0.86%.At the same height,the afterburning effect was strengthened with increasing distance from nozzle exit.Comparing with two-nozzle rocket,the afterburning had less effect on the four-nozzle rocket base thermal environment.In addition,the peak heat flux of the rocket base increased first and then decreased with height.