Impact of nozzles on a valveless pulse detonation rocket engine without the purge process

To investigate the impact of exit nozzles on the operation and the propulsive performance of a valveless pulse detonation rocket engine (PDRE) without the purge process, experiments have been carried out under wide operating frequencies. Gasoline and oxygen-enriched air were used as fuel and oxidizer. Two detonation tubes and twenty-one nozzles with different shapes were employed in this study. It was observed that both the contraction ratio and the expansion ratio have an influence on the performance of the PDRE. Nozzles with converging sections decrease the highest operating frequency of the valveless PDRE, even if it cannot operate normally with nozzles whose contraction ratios are larger than four. The expansion ratio almost has no impact on the operation of the valveless PDRE, but the thrust decreases when the expansion ratios of diverging nozzles are larger than five. Most converging nozzles increase the thrust of the valveless PDRE, especially when the fill fractions were greater than one, while most diverging nozzles increase the thrust when the fill fractions were smaller than one. A maximum thrust increase of 25% has been obtained when nozzles were utilized.