An experimental study on predicting the mass flow rate of self-pressurizing oxidizers through injectors

Abstract

Self-pressurizing propellants are recently gaining attention, specifically in hybrid rocket propulsion systems. Use of self-pressurizing propellants reduces system complexity and overall weight due to their high vapor pressure. N2O has been used widely as an oxidizer since it has a vapor pressure of approximately 5 MPa (730 psi) at room temperature. However, because they operate near or at saturation line, their flow exhibits two-phase behaviour. Therefore, it is difficult to model the feed system and injector flows. A method to predict the two-phase critical mass flow rate has been proposed. In addition, an experimental setup has been designed for validation of the proposed model. Multiple cold flow tests using nitrous oxide has been performed, and data obtained have been compared to that predicted by the two-phase critical flow model. Results have been showed that the proposed model estimates the actual mass flow rate within an error range of 6 to 17%.