Investigation of Throttling Response Characteristics of Axial-Injection End-Burning Hybrid Rockets

Abstract

In this study, the authors conducted four experiments to investigate the response time of axial-injection end-burning hybrid rockets under throttling operations. Oxidizer mass flow rate and chamber pressure were throttled by two methods, by actuating valves in a fluid circuit consisting of two oxidizer supply lines and by motor control. Chamber pressure and oxidizer mass flow rate were measured during each firing. The results show that a chamber pressure response time was observed when oxidizer mass flow rate was increased (turn-up operation). The chamber pressure response time increases as the rate of change of oxidizer mass flow rate increases. In addition, the chamber pressure response time also increases as the difference in the oxidizer port velocity before and after throttling increases. Therefore, it is considered that the chamber pressure response time is the time that it takes for the diffusion flame to achieve a steady-state stand-off distance in response to a change in oxidizer port velocity.