Somasekharan Nithin, Srikrishnan A R, Kumar Harihara Sudhan, Ganesh Krishna Prasad, Mohammad Akram, Velamati Ratna Kishore
Department of Aerospace Engineering, Amrita School of Engineering Coimbatore, Amrita Vishwa Vidyapeetham, Tamil Nadu 641112, India.
Department of Aerospace Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
Entropy (Basel). 2023 Mar 10;25(3):481. doi: 10.3390/e25030481.
Film cooling as applied to rocket nozzles is analyzed numerically with emphasis on the assessment of the effect of the mixing of coolant with the hot stream. Cooling performance, as characterized by cooling effectiveness, is studied for three different coolants in the three-dimensional, turbulent flow field of a supersonic convergent-divergent nozzle operating with a hot stream temperature of 2500 K over a range of blowing ratios. The coolant stream is injected tangentially into the mainstream using a diffuser-type injector. Parameters influencing the effectiveness, such as coolant injector configuration and mixing layer, are analyzed. Thermal and species mixing between the coolant and the mainstream are investigated with regard to their impact on cooling effectiveness. The results obtained provide insight into the film cooling performance of the gases and the heat transfer characteristics associated with these three gases. An injector taper angle of 30° results in the most effective cooling among the configurations considered (0°, 15°, 30° and 45°). Mixing of the coolant with the hot stream is examined based on the distributions of velocity, temperature and species. The higher values of cooling effectiveness for Helium are attributed to its thermophysical properties and the reduced rate of mixing with the hot stream. The results further indicate that through optimization of the blowing ratio and the coolant injector configuration, the film cooling effectiveness can be substantially improved.
对应用于火箭喷嘴的气膜冷却进行了数值分析，重点评估冷却剂与热气流混合的效果。在超声速收敛-发散喷嘴的三维湍流流场中，研究了三种不同冷却剂在一系列吹风比下的冷却性能，以冷却效率来表征。热气流温度为2500K。冷却剂流通过扩散器型喷射器切向注入主流。分析了影响冷却效率的参数，如冷却剂喷射器结构和混合层。研究了冷却剂与主流之间的热混合和组分混合对冷却效率的影响。所得结果有助于深入了解气体的气膜冷却性能以及与这三种气体相关的传热特性。在所考虑的结构（0°、15°、30°和45°）中，喷射器锥角为30°时冷却效果最佳。基于速度、温度和组分的分布研究了冷却剂与热气流的混合情况。氦气冷却效率较高归因于其热物理性质以及与热气流混合速率较低。结果还表明，通过优化吹风比和冷却剂喷射器结构，气膜冷却效率可大幅提高。
