Experimental Study on Transpiration Cooling of Nose Cones With Graded Porous Structures

Transpiration cooling is the preferred solution for achieving efficient thermal protection of the nose cone in long-endurance vehicles. However, the stagnation-point effect often causes localized overheating at the leading edge of the nose cone. In this study, a novel nose cone featuring a graded porous distribution was designed and fabricated using additive manufacturing to optimize the distribution of the coolant and improve phase change transpiration cooling performance. The transpiration cooling performance of the graded-porosity nose cone and the uniform-porosity nose cone was compared. The transpiration cooling regime diagrams based on the coolant flow rate and the heat flux for the two nose cones were summarized and analyzed. The results indicate that the non-overheated regime, locally overheated regime, and wholly overheated regime are sequentially experienced within the porous structure as the external heat flux increases or the coolant flow rate decreases. The graded-porosity nose cone exhibits superior transpiration cooling performance. Under the same water flow rate, the graded-porosity nose cone transitions into the wholly overheated regime at a higher heat flux density, demonstrating its capability to withstand greater thermal loads. Under the same heat load, the graded-porosity nose cone transitions into the non-overheated regime at a lower water flow rate, demonstrating its higher efficiency in utilizing the coolant. In terms of steady-state performance, the graded-porosity nose cone achieves the best improvement in temperature uniformity of 84%. Under fluctuating thermal load conditions, the graded-porosity nose cone exhibits superior thermal stability.