The Effect of Diffuser Geometry on the Starting Pressure Ratio of a Supersonic Wind Tunnel

To reduce the starting and stopping loads at intermittent blow-down supersonic wind tunnels, diffuser performance is important to keep the starting pressure ratio as low as possible. A parametric study on diffuser performance for the JAXA 1m x 1m supersonic wind tunnel (JSWT) was conducted by numerical simulation. It was found that it is difficult to estimate performance by using only quasi-1D non-viscous theory because of shock waveboundary layer interactions. To improve the diffuser performance, a modified diffuser configuration was designed with a viewpoint of shock train phenomena. The modified JSWT diffuser is more slender than the original and its higher performance was confirmed by numerical simulation. This design concept was also validated experimentally with a 10% scale model tunnel at a Mach number of 3.0.