Numerical investigation of nitrogen condensation flow over airfoil in cryogenic wind tunnel

Cryogenic wind tunnel is an equipment for the requirement of high Reynolds number test of the aircraft via the method of reducing the test temperature. However, the test validity is extremely possible to be destroyed by the occurrence of condensation in cryogenic environment. To understand the characteristics of condensation flow over the airfoil, a two-phase flow was developed with the help of ANSYS Fluent. For 0.137-m NACA 0012-64 airfoil, numerical simulations of 32 cases under three different Reynolds numbers (similar to 26 x 10(6), similar to 38 x 10(6) and similar to 44 x 10(6)) were implemented. The simulated results show that only when the temperature of local gas-flow crosses the saturation line and is lower than a critical point there is enough condensate to alter some flow properties noticeably, such as pressure, temperature and Mach number. The achievement of maximum local supercooled degree decreases with the increase in operating total pressure. For a given test Reynolds number, when the static pressure and temperature of the gas is on the lower temperature side of the saturation curve, a reduction of operating pressure and temperature among a reasonable range is also believed to not cause the condensation effect on the aerodynamic test. On the bright side, lower operating pressure will provide the advantages of less liquid nitrogen injection and less drive power of fan. From another point of view, under the premise of ensuring that the gas-flow local temperature is higher than that at Wilson point, the reduction in the operating temperature as much as possible can greatly increase the test Reynolds number. The built two-phase model supplies an approach for investigating the condensation effect on airfoil test in cryogenic wind tunnel, and resulting findings guide the determination of working conditions for airfoil Reynolds number test.