Effects of the physical properties and chemical reactions of hydrocarbon fuel on the interaction between discrete film jets and the mainstream

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL International Journal of Thermal Sciences Pub Date : 2024-11-12 DOI:10.1016/j.ijthermalsci.2024.109528

Dingyuan Wei, Silong Zhang, Jingying Zuo, Jianfei Wei, Xin Li, Wen Bao

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Abstract

The use of gaseous hydrocarbon fuel in discrete film cooling has been shown to be an efficient approach for meeting the internal thermal protection needs of scramjet engines. The film cooling process using large molecular hydrocarbon fuels differs from conventional inert cooling gases, as their physical properties and chemical reactions significantly influence the interaction between the film outflow and the main flow, thereby affecting overall film cooling effectiveness. The study aims to conduct numerical investigations to explore the influence of coolant physical parameters, chemical characteristics, and the structural configuration of discrete holes on the cooling efficiency of cylindrical discrete film cooling systems. The results show that the cooling efficiency of the inert hydrocarbon fuel discrete film surpasses that of the air discrete film under identical blowing ratio conditions, and the chemical reactions of the hydrocarbon fuel can further increase the spreading cooling range of the discrete film. The trend of secondary flow intensity within the discrete hole is correlated with the hole length-to-diameter ratio, and the air medium and hydrocarbon fuel have different sensitivities to changes in this ratio, which are affected by viscous dissipation effects. Furthermore, the chemical reactions of the hydrocarbon fuel enhance the lateral cooling range of the discrete film. The chemical reactions weaken the intensity of kidney-shaped vortex pairs within the jet, which is reflected in the spreading direction moving toward the outside of the mixing layer, promoting the expansion of the coverage range of the discrete film. Moreover, increasing the L/D ratio from L/D = 2 to L/D = 5 results in a 10 % expansion of the lateral cooling range of the hydrocarbon fuel discrete film. The length-to-diameter ratio of the discrete film hole influences the external flow characteristics of film cooling by altering the internal turbulence, thereby impacting the overall cooling performance of the discrete film.

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碳氢化合物燃料的物理特性和化学反应对离散薄膜射流与主流之间相互作用的影响

在离散薄膜冷却中使用气态碳氢化合物燃料已被证明是满足扰流喷气发动机内部热保护需求的有效方法。使用大分子碳氢化合物燃料的薄膜冷却过程不同于传统的惰性冷却气体，因为它们的物理特性和化学反应会显著影响薄膜外流与主气流之间的相互作用，从而影响整体薄膜冷却效果。本研究旨在进行数值研究，探讨冷却剂物理参数、化学特性和离散孔结构配置对圆柱形离散薄膜冷却系统冷却效率的影响。结果表明，惰性碳氢化合物燃料离散膜的冷却效率超过了相同吹气比条件下的空气离散膜，而且碳氢化合物燃料的化学反应可以进一步增大离散膜的扩散冷却范围。离散孔内二次流强度的变化趋势与孔的长径比相关，空气介质和碳氢化合物燃料对长径比的变化具有不同的敏感性，这受到粘性耗散效应的影响。此外，碳氢化合物燃料的化学反应增强了离散薄膜的横向冷却范围。化学反应削弱了射流内肾形涡旋对的强度，这反映在向混合层外侧移动的扩散方向上，促进了离散膜覆盖范围的扩大。此外，将长径比从 L/D = 2 提高到 L/D = 5 会使碳氢化合物燃料离散膜的横向冷却范围扩大 10%。离散薄膜孔的长径比通过改变内部湍流来影响薄膜冷却的外部流动特性，从而影响离散薄膜的整体冷却性能。

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来源期刊

International Journal of Thermal Sciences 工程技术-工程：机械

CiteScore

8.10

自引率

11.10%

发文量

531

审稿时长

55 days

期刊介绍： The International Journal of Thermal Sciences is a journal devoted to the publication of fundamental studies on the physics of transfer processes in general, with an emphasis on thermal aspects and also applied research on various processes, energy systems and the environment. Articles are published in English and French, and are subject to peer review. The fundamental subjects considered within the scope of the journal are: * Heat and relevant mass transfer at all scales (nano, micro and macro) and in all types of material (heterogeneous, composites, biological,...) and fluid flow * Forced, natural or mixed convection in reactive or non-reactive media * Single or multi–phase fluid flow with or without phase change * Near–and far–field radiative heat transfer * Combined modes of heat transfer in complex systems (for example, plasmas, biological, geological,...) * Multiscale modelling The applied research topics include: * Heat exchangers, heat pipes, cooling processes * Transport phenomena taking place in industrial processes (chemical, food and agricultural, metallurgical, space and aeronautical, automobile industries) * Nano–and micro–technology for energy, space, biosystems and devices * Heat transport analysis in advanced systems * Impact of energy–related processes on environment, and emerging energy systems The study of thermophysical properties of materials and fluids, thermal measurement techniques, inverse methods, and the developments of experimental methods are within the scope of the International Journal of Thermal Sciences which also covers the modelling, and numerical methods applied to thermal transfer.