Scale effect of fuel regression rate in hybrid rocket motor

The scale effect of solid fuel regression rate in hybrid rocket motors is investigated theoretically based on pipe turbulent boundary combustion theory firstly, and a practicable scaling criterion of solid fuel regression rate has been obtained. The criterion indicates that solid fuel regression rate decreases with fuel port diameter and is proportional to d−0.2d−0.2 when convective heat transfer is dominant in hybrid rocket motor. Based on the criterion, a numerical model combined with turbulence, combustion, solid fuel pyrolysis and solid–gas coupling model was established to simulate three different size motors, and an analysis was also performed on experimental data of different motors. Both the numerical results and experimental data verified the scaling criterion of solid fuel regression rate under different fuel port sizes.