Effect of swirl on the regression rate in hybrid rocket motors

In this work, the effect of swirl on regression rate ( r b ) in a hybrid rocket motor is investigated numerically. The r b increased monotonically with inlet swirl number and was also found to depend on the inlet swirl profile. The swirl velocity profiles with the peak closer to the axis yielded higher r b . Parametric study on fuel grains of various lengths and diameters ( L / D ⩽ 25 ) shows that swirl is more effective in improving the average r b for short grains ( L / D < 5 ) and large diameter grains.