Abstract By utilizing airborne hydrocarbon fuels working as coolant, active regenerative cooling method is a significant method for maintaining the reliability of the scramjet engine components. At high temperatures, the pyrolysis of hydrocarbon fuels occurs and provides extra heat absorption capacity. Investigation on coupled heat transfer and pyrolysis of fuels is essential for the design of cooling channels. This paper aims to study the pyrolysis effects on convective heat transfer of supercritical aviation kerosene RP-3 in vertical upwards. Firstly, a simple molecular kinetic model was proposed for RP-3 pyrolysis. Then the performance of two Reynolds-averaged Navier-Stokes turbulence models with three constant turbulent Prandtl numbers in predicting the fluid-thermal behaviors of reacting flow were evaluated. At last, the mechanisms of pyrolysis effect on heat transfer in the heat transfer deterioration region and the cracked region were investigated. The results showed that the pyrolysis affected heat transfer from two aspects: providing heat absorb or release capacity through the endothermic (exothermic) pyrolysis reactions, changing the fuel properties by the variations in composition. In the heat transfer deterioration region, the effect of heat absorption dominants over the effect of additional decreased in density and specific heat capacity by pyrolysis on the heat transfer, thus a lower wall temperature and larger heat transfer coefficients were observed when considering pyrolysis. In the cracked region, under the present condition, the competitive outcome of the above two led to an improved heat transfer by pyrolysis, and the improved effect first increased and then decreased as the fuel conversion increasing. This work provides a fundamental understanding of the behaviors of hydrocarbon fuel inside the cooling channels, which is valuable for the cooling structure design.

中文翻译：

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热解对超临界航空煤油对流传热特性的影响研究

摘要 利用空气中的碳氢燃料作为冷却剂，主动蓄热冷却方法是维持超燃冲压发动机部件可靠性的重要方法。在高温下，碳氢燃料会发生热解并提供额外的吸热能力。研究燃料的传热和热解耦合对于冷却通道的设计至关重要。本文旨在研究热解对超临界航空煤油RP-3垂直向上对流传热的影响。首先，提出了一个简单的分子动力学模型用于 RP-3 热解。然后评估了具有三个恒定湍流 Prandtl 数的两个雷诺平均 Navier-Stokes 湍流模型在预测反应流的流体-热行为方面的性能。最后，研究了传热劣化区和裂纹区热解对传热的影响机理。结果表明，热解从两个方面影响传热：通过吸热（放热）热解反应提供热量吸收或释放能力，通过成分变化改变燃料特性。在传热劣化区，吸热的影响大于热解引起的密度和比热容的额外降低对传热的影响，因此在考虑热解时观察到较低的壁温和较大的传热系数。在裂纹区域，在目前的条件下，上述两者的竞争结果导致热解传热得到改善，随着燃料转化率的增加，改善效果先增大后减小。这项工作提供了对冷却通道内碳氢燃料行为的基本理解，这对于冷却结构设计很有价值。