System design and experimental verification of an internal insulation panel system for large-scale cryogenic wind tunnel

Abstract With the rapid development of aerodynamics for high speed aircraft, the flight experiments need to be carried out under ultra-high Reynolds number condition to simulate actual high-speed flight conditions, which puts forward higher requirements for the wind tunnel. Large-scale cryogenic wind tunnel is one of the best testing facilities to reach ultra-high Reynolds number, which increases rapidly as the decrease of the flow temperature because the viscosity of the working gas decreases and the density increases. As a result, a pressurized tunnel at very low temperatures can provide real-flight Reynolds numbers. The thermal insulation system is crucial for the design and operation of the cryogenic wind tunnel. In this paper, the features of an internal insulation system for the cryogenic wind tunnel are firstly highlighted in comparison with traditional insulation systems. The internal thermal insulation system for the cryogenic wind tunnel is discussed. In order to evaluate the thermal insulation performance, the heat transfer calculation for a typical wind tunnel region with the diameter of two meters is carried out using finite element method based on the analyses of the heat transfer conditions. The averaged heat load from the environment is obtained to optimize the liquid nitrogen consumption during the wind tunnel operation. The thickness of the panel should be 150 mm to reach the design target of averaged heat flux 60 W/m2. Meanwhile, the typical region is constructed according to the new internal insulation system. Cryogenic test is conducted and it is proven that the new internal insulation system could efficiently prevent the environment heat flow and ensure the normal operation of the cryogenic wind tunnel.