Supersonic ejector-driving system under low pressure: a performance evaluation^*

We have developed a low-density wind tunnel that simulates Martian atmospheric flight on the ground. This wind tunnel employs a supersonic ejector-drive system to realize high-speed flow under low-density conditions. This study presents a general evaluation method for the ejector driver of the wind tunnel under low-pressure conditions. As an evaluation parameter for the pressure-recovery ratio, which is a representative value of the driving performance, the ejector-drive parameter (EDP) determined from the design and operating conditions is applied, verifying its effectiveness under atmospheric conditions. Accordingly, we investigate the effectiveness of the EDP at low pressures and its scalability to complex multiple supersonic nozzles. Our results suggest that the pressure-recovery ratio is correlated with the EDP even when the ambient pressure, system configuration, and operational conditions change. The EDP allows us to predict the Mach number, and can provide us with an appropriate framework for ejector design optimization.