Validation of heat transfer models and optimization of heat shielding performance of high-temperature multilayer insulations for hypersonic vehicles

Abstract

Multilayer insulation (MLI) is widely used in hypersonic vehicles because of its low density and excellent thermal insulation performance. However, the insulation mechanism of MLI remains poorly understood, leading to conflicting views on how to enhance its thermal insulation capabilities. In this study, two different numerical models were built and validated with experiment data to investigate key factors influencing MLI performance. The analysis focused on the effects of reflective screen positioning, the surface emissivity of reflective screens and the radiation properties parameters of fibrous materials on the thermal insulation performance of the MLI. The results show that the thermal insulation performance is better when the reflective screens are placed close to the thermal boundary. Moreover, insulation materials with lower absorption coefficients enhance the effectiveness of the reflective screens, further improving the thermal insulation performance of MLI. In addition, the study reveals that the thermal insulation mechanisms differ between the upper and lower surfaces of the reflective screens. Lower emissivity on the upper surface combined with higher emissivity on the lower surface optimizes the thermal insulation performance of MLI. These findings offer valuable insights for advancing MLI designs and improving its application in future high-speed vehicles.