The traditional Kagome trusses have circular cross-section ligaments. In this study, a Kagome truss with elliptical cross-sectional ligaments instead of circular cross-sectional ligaments is proposed. Additionally, a scheme for transforming the circular cross-sectional ligament into an elliptical ligament, which maintains the same cross-sectional area as the circular cross-sectional ligament, is proposed. Four Kagome truss structures with different cross-sectional ligaments are designed. Model-4 is a Kagome truss with traditional circular cross-sectional ligaments, whereas model-1, model-2, and model-3 are Kagome trusses of elliptical cross-sectional ligaments, with the major-to-minor axes ratio gradually decreasing from model-1 to model-3. Furthermore, the pressure drop and heat transfer performance of different models at different flow velocities are analyzed. A dimensionless number eta; characterizing the overall heat transfer performance is introduced to evaluate the overall performance. The results reveal that model-1, with a major-to-minor axes ratio of 4, achieved the most minor pressure drop at all velocities, and model-2 has the best heat transfer performance at high velocities. The average overall heat transfer performances of model-1, model-2, and model-3 are 5.9%, 16.3%, and 13.3% higher than that of model-4, respectively, thereby demonstrating the significance of elliptical optimization. The best overall heat transfer performance is exhibited when the major-to-minor axes ratio of the ellipse is 2.04.
Transpiration cooling is a highly efficient active thermal protection technology, which has a great application prospect in the thermal protection of hypersonic vehicles. Nevertheless, the problem of large injection pressure caused by porous structure in transpiration cooling system has been ignored in previous studies. In this work, the transpiration cooling performance of double-layer sintered metal particle plates with different particle diameter combinations and plate thickness were simulated. The results showed that the cooling effectiveness of double-layer plates was improved when the particle diameter of the porous plate in direct contact with the main stream decreased. The inner plate particle diameter and plate thickness had little effect on cooling performance. By increasing inner plate particle diameter, the coolant injection pressure can be lowered by 41% while the structural thickness was maintained. Further reducing the thickness of the outer plate to 1/4 of the total thickness can reduce the injection pressure to 38% of the single plate, which provided an optimization direction for reducing engine power consumption caused by heat dissipation.
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