Fuel Regression Characteristics of a Novel Axial-Injection End-Burning Hybrid Rocket

The regression characteristics of axial-injection end-burning hybrid rocket were experimentally investigated using a laboratory-scale motor. The axial-injection end-burning type fuel grains were made by high-accuracy three-dimensional printing. Firing tests were conducted using gaseous oxygen as the oxidizer at a chamber pressure range of 0.10 to 0.43 MPa. Results of 15 static firings tests show that fuel regression rate increases as the chamber pressure rises, and fuel regression rate decreases as the oxidizer port velocity increases. A data reduction method was developed to avoid the difficulty in calculating oxidizer-to-fuel ratio. A simplified fuel regression model based on the granular diffusion flame model is developed to investigate regression characteristics. The trend in results as calculated using the granular diffusion flame model agrees with that in experimentally observe values. However, this does not hold true in tests with varying oxidizer port velocity. A granular diffusion flame model only takes into account simple solid propellant regression. Therefore, modification of the model is needed for calculating the fuel regression rate of an end-burning hybrid rocket.