Issues related to the measurement of regression rate of fast-burning hybrid fuels

The measurement of the regression rate of a hybrid rocket fuel is the subject matter of this paper. This is an involved problem because both the regression rate and the oxidizer mass flux Gox vary with the port diameter, which itself varies during combustion. This paper addresses the issue of how Gox should be varied to obtain the regression rate correctly. The most commonly used weight loss method has been employed here. Three methods used here to vary the Gox are artificially changing the port diameter, changing the mass flow rate of the oxidizer, and interrupted burn test. From the experiments conducted, it was evident that the interrupted burn test was the best method. These experiments were also carried out for a larger motor and the results compared quite well with established literature. The role of the recirculation zone size near the head end and the overall heat transferred back to the fuel surface in influencing the regression rate have been explained. The role of the recirculation zone diminishes as the length of the rocket motor is increased.