A three-dimensional coupled heat transfer model is applied for numerical studies of turbulent flow and heat transfer of methane in variable cross-section cooling channels of LOX/methane rocket engines at a supercritical pressure. The results indicate that when the coolant flows through an abruptly expanding structure, the fluid flow velocity suddenly drops, and the average temperature of the fluid reaches a peak. This effect will increase with increase of the sudden contraction/expansion area ratio. After the coolant flows through the expansion structure, the vortices counteract the effect of the secondary flow generated by the centrifugal force in the convergent section of the thrust chamber. This will reduce the coolant helicity here, finally resulting in low convection heat transfer. Generally speaking, the contraction structure has a certain improvement of the heat transfer of coolant in the cooling channels. Through sensitivity analysis, the variable cross-section cooling channels whose contraction/expansion area ratio varies between 1.25 and 1.5 have the most engineering application under the cases discussed in this paper.

中文翻译：

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熏氧/甲烷火箭发动机变截面冷却通道的耦合数值分析

将三维耦合传热模型应用于数值模拟研究超临界压力下LOX /甲烷火箭发动机可变截面冷却通道中甲烷的湍流和传热。结果表明，当冷却剂流过急剧膨胀的结构时，流体的流速突然下降，并且流体的平均温度达到峰值。随着突然收缩/膨胀面积比的增加，该效果将增加。在冷却剂流过膨胀结构之后，涡旋抵消了在推力腔的会聚部分中由离心力产生的二次流的影响。这将降低冷却液的螺旋度，最终导致低对流传热。一般来说，收缩结构对冷却剂在冷却通道中的传热有一定的改善。通过敏感性分析，在本文讨论的情况下，其收缩/膨胀面积比在1.25和1.5之间变化的可变截面冷却通道具有最大的工程应用价值。