Performance prediction method of multi-stage steam ejector system in high-altitude simulation test

Abstract

The Multi-Stage Steam Ejector System (MSSES) is essential for High-Altitude Simulation Tests (HASTs) of liquid rocket engines using active ejection. Rapid performance prediction is crucial due to the system’s high energy consumption. In this study, the one-dimensional gas dynamics theory was used to analyze MSSES performance under non-design operational conditions. The analysis is based on the assumption of constant-pressure mixing, considering that the steam and engine exhaust gas start mixing at a certain position in the cylindrical section of the second-throat ejector diffuser. An active ejecting scheme combining a rocket engine, a supersonic engine diffuser, and a four-stage MSSES was employed. Two air flow tests using an orifice plate simulated the mass flow and pressure conditions of rocket engines, providing preliminary MSSES validation before real engine tests. The nominal air mass flow rates of 0.60 and 0.34 kg/s simulated combustion products from NTO/MMH-fueled engines. Through a computational analysis of the results of the first test, we derived four key coefficients essential for characterizing the MSSES behavior under the critical operation modes. These coefficients were then applied to forecast the MSSES performance in the second testing scenario, demonstrating their utility in performance prediction. A comparison with experimental data highlights minor discrepancies, including errors of up to 15.78% in the secondary flow rate predictions and errors of up to 5.25% in the MSSES outlet pressure estimates. This knowledge, applied to an existing HAST facility, may significantly enhance the efficiency and accuracy of pre-test planning for HASTs.