One Dimensional Design of Single, Two and Three-Stage Ejector of a Hypersonic Wind Tunnel

One of the most common facilities utilized in supersonic wind tunnels is multi-stage ejector system. In this system high speed air blowing with specified Mach numbers into the wind tunnel at predetermined points, helps to obtain the desired Mach number in the test section. In this study, according to characteristics of test section including Mach number, static temperature and stagnation pressure, relevant prominent features of the single-stage, two-stage and three-stage ejectors such as mass flow, velocity and stagnation pressure are computed. Two different aspects are implemented in solving governing equations of ejectors; first one is to assume the same Mach number for all ejectors and second one is based on assumption of the same stagnation pressure for the ejectors. It will be revealed that the later one is more optimal in comparison with the former criteria. Validation of the developed computational code results is performed via comparison with the experimental data of a wind tunnel operating at Mach number 2, which resulted in a difference of 5 to 7 percent.
At the earlier section, design parameters of single ejector versus different mach numbers of the test section are presented and then effect of outlet static pressure reduction as a means of vacuum generation at the exhaust of the wind tunnel is discussed. Furthermore design of two-stage ejector according to both methods of equal Mach number and the same stagnation pressure is completed and in the last section three-stage ejector is studied base on the same stagnation pressure for comprising ejectors.