The liquid rocket propellant burns inadequately in the combustion chamber; therefore, the exhaust gas reacts with oxygen and the heat that was generated, which in turn affects the thermal environment. By using finite-rate chemical kinetics and discrete ordinates method, the calculation model for the four-engine rocket exhaust flowfield is established, and numerically investigates the afterburning effect on the thermal environment of the engine exhaust plume under different altitudes. The results show that the afterburning reactions have little influence on the Mach number exhaust flow, and the difference between the peak temperatures of reacting and non-reacting flows is less than 5%. However, a significant increase in temperature of the mixing layer can be found, and the afterburning effect on the thermal environment reduces with increases in the flight altitude. At the same altitude, the temperature increment of the reacting flow in the far-field region is higher than that of the near-field region. Moreover, as the flight altitude increases from 15 to 35 km, the increase of the rocket base heat flux caused by the afterburning can vary from 9.4% to 2.7%. The results provide a theoretical basis for the designing of the thermal protection systems of multi-engine rockets.

液体火箭推进剂在燃烧室内燃烧不充分；因此，废气与氧气和产生的热量发生反应，进而影响热环境。利用有限速率化学动力学和离散纵坐标法，建立了四发火箭排气流场的计算模型，数值研究了不同高度下发动机排气羽流对热环境的加力影响。结果表明，后燃反应对排气马赫数的影响不大，反应气流和非反应气流峰值温度相差小于5%。然而，可以发现混合层的温度显着升高，随着飞行高度的增加，对热环境的加力效应减弱。在相同高度下，远场区域反应流的温度增量高于近场区域。而且，随着飞行高度从 15 公里增加到 35 公里，加力燃烧引起的火箭基座热通量的增加可以从 9.4% 到 2.7% 不等。研究结果为多发火箭热防护系统的设计提供了理论依据。