Experimental Investigation on the Pressure Drop Characteristics of a Gas Generator During Gas Injection Process

Aiming at the gas injection technique for maintaining the performance of liquid-propellant rocket engines over a wide throttling range, an experimental study was conducted using the head cavity of a certain type gas generator as the object. White oil and water were selected as the substitute working liquids, while gaseous helium (GHe) and gaseous nitrogen (GN₂) were used as injected gases. Pressures at typical positions were measured, and the phase distribution at the head cavity inlet and nozzle outlets was visually captured. The effects of flow rate, gas type and liquid type were tested and compared. The results indicate that, injecting gas could significantly increase the pressure of head cavity, and improve the nozzle atomization effect at low-thrust conditions. The nozzle pressure drop increases linearly with the gas injection rate at a given liquid flow rate. Across varying liquid flow rates, a fixed amount of gas injection results in nearly constant multiplicative increases in the nozzle pressure drop. GHe is recommended as the preferred injecting gas due to its superior pressurization capability compared to GN₂. This work could provide fundamental data for understanding gas injection mechanisms and promote its mature application in the development of deep-throttling technology.