热裂解对超临界RP-3流动和耦合传热影响的数值模拟研究

Numerical Investigation of Pyrolysis Effects on Flow and Conjugate Heat Transfer of RP-3 under Supercritical Pressure

关键词:  超临界  热裂解  流阻  耦合传热

Key words:  Supercritical  Pyrolysis  Flow resistance  Conjugate heat transfer

摘要:

为深入理解再生冷却过程中裂解反应对碳氢燃料流动换热产生的影响，采用包含18组分和24步分子反应的RP-3裂解模型，对超临界压力下RP-3在底面加热的方通道内的流动换热和裂解过程开展了三维数值模拟研究。压力范围4～6MPa，加热面热流密度2.4～3.6MW/m2条件下的计算结果表明:在高温区域内剧烈进行的裂解反应会造成流体的进一步加速，导致沿程压降急剧增加，并且这一现象在4MPa时更为明显。在各流固交界面处，热流密度呈现不同的沿程变化规律。裂解反应使下壁面处的对流换热得到更大程度的强化，从而使下流固交界面的热流密度增加约0.5 MW/m2。同时，在裂解吸热和传热强化的共同作用下，裂解反应使各流固交界面的壁温最多降低150K。

Abstract:

Pyrolysis has significant influence on the flow and heat transfer of hydrocarbon fuel during the regenerative cooling process. In this article， a three-dimensional (3D) model was developed for numerically studying the flow and heat transfer of pyrolytically reacted RP-3 in the square channel under supercritical pressure. The 24-step pyrolytic reaction mechanism consisting of 18 species was incorporated into the numerical model to simulate the pyrolysis process of RP-3. Numerical investigations of the characteristics of flow resistance and heat transfer have been conducted， with various heat fluxes on the bottom-heated-surface from 2.4～3.6MW/m2 and the pressures ranging from 4 to 6MPa. Results reveal that the pressure gradient along the channel abruptly increases due to the further fluid acceleration caused by pyrolysis， which could be more evidently observed under 4MPa. It is found that the heat fluxes at the bottom， side and top wall vary in different ways. Pyrolysis could bring about greater heat transfer enhancement near the bottom wall， and accordingly， the heat flux increase at the bottom interface is about 0.5MW/m2. The dual effects of heat absorption and enhanced heat transfer caused by pyrolysis lower the wall temperature with the decrease up to 150K.