Study of regression rate characteristics in a hybrid rocket motor

We characterize the effect of punctured discs, that acts as circular protrusions at predefined axial locations of a lab-scale hybrid rocket motor. The fuel employed is paraffin, while the oxidizer is oxygen. The quantities measured are the burn duration and the exhaust plume length. It is seen that the burn duration is reduced for the same quantity of fuel and oxidizer as compared to the case with no protrusion. On the other hand, the exhaust plume length as measured from moderately time-resolved image processing reveals longer plume length. Also observed is that the exhaust plume length for the non-protrusion case reveals sudden dip and flare, which denotes more erratic operation as compared to the case with protrusion. The higher regression rate (low burn time) measured for the case with protrusion is analyzed computationally for isothermal flow. It is seen that higher levels of turbulence as compared to the case of no protrusion aids in pronounced heat and mass transfer resulting in higher regression rate.