Numerical Analysis of Ejector Flow Performance for High-Altitude Simulation

Abstract

In this study we perform a computational numerical analysis to examine the flow characteristics of a system composed of a rocket engine, supersonic diffuser, and ejector system. When the nozzle expansion ratio of a rocket engine increases, it is necessary to maintain high-vacuum conditions during ground hot testing, which requires a supersonic diffuser and ejector system. The integrated model, consisting of multiple systems and a single-ejector system model, exhibits a difference in the initial volume to be evacuated. Although some differences are observed during the initial vacuum transition process, both models maintain the same final vacuum pressure (4 kPa). During the initial vacuum process, if the injection pressure of the ejector decreases below the design pressure, vacuum degradation occurs because of momentum deficiency, followed by pressure perturbations as the vacuum process resumes. Once the rocket engine ignites and flow is supplied to the suction region, two flow regions exist around the ejector nozzle exit. As these flows mix and move downstream, flow separation occurs in the expansion region. When the injection pressure of the ejector falls below the design pressure, the flow separation region moves forward, and this shift helps maintain the designed vacuum suction conditions.

Keywords

• rocket engine nozzle
• supersonic diffuser
• ejector system
• vacuum
• pressure oscillation
• flow separation