凝结相变对低温风洞雷诺数试验的影响

为了研究凝结相变对低温风洞雷诺数试验能力的影响,基于Fluent软件建立了气-液两相凝结流动模型,相变模型采用考虑非等温效应修正的经典成核理论和Gyarmathy液滴生长理论;针对不同来流压力和不同试验雷诺数工况条件,对氮气绕流NACA 0012翼型进行了数值模拟。模拟结果表明:随着来流温度的降低,翼型附近区域气体膨胀越过气态饱和线并达到过冷状态,进一步降低来流温度则会在宏观层面上观测到凝结相变对当地流场的改变,与无凝结相变的流场相比,释放的潜热加热气流导致马赫数降低及压力系数的改变;在确保不破坏翼型气动性能试验的前提下,充分利用气体过冷区域来降低来流压力以此减少驱动功率和液氮喷入量是可行的,或者保持来流压力不变提升低温风洞的试验雷诺数。

Effect of condensation phase transient on Reynold number test for cryogenic wind tunnel

In order to investigate the condensation effect on Reynold number test for the cryogenic wind tunnel, a two-phase condensing flow model was established based on the Fluent software. The classic nucleation theory considering the non-isothermal effect and Gyarmathy droplet growth theory were employed for the prediction of spontaneous condensation. Under varying inflow pressures and testing Reynold numbers, the numerical simulations of nitrogen flowing around the NACA 0012 airfoil were carried out. The simulation results showed that the decrease of incoming flow temperature resulted in rapid expansion and the gas supercooled state at region near the airfoil surface. With further reduction of the incoming flow temperature, significant change of local flow fields affected by condensation was observed at a macroscopic level. The release of latent heat heated up the nitrogen flow and thus resulted in a deceleration of Mach number and a deviation of pressure coefficient in comparison with the case without condensation. Without destroying the airfoil aerodynamic performance test, it was feasible to make full use of gas supercooling for reducing the incoming flow pressure, which also meant few cost of driving power and liquid nitrogen injection. Alternatively, keeping the incoming flow pressure constant increased the testing Reynold number of the cryogenic wind tunnel.