Oxyhydrogen-air explosion characteristics in water jetting propulsion

Abstract

Hydrogen has attracted many researchers in the field of explosion jetting propulsion owing to its appealing advantages of zero carbon emissions, wide flammability range, and ease of preparation. However, the research gap in hydrogen explosion characteristics in water jetting scene has slowed down the advancement of the impulsive jetting propulsion field. In this work, static tests under three typical explosion jetting scenes (vertical submerged jetting, oblique submerged jetting, and aerial jetting) are conducted to reveal their explosion and thrust characteristics. The static tests results demonstrate that although the peak pressures of the aerial and vertical submerged explosion jettings are comparable, the peak thrust of the former is dramatically reduced by 40.6 %. We also find that the maximum pressure rise rate and peak pressure of the oblique submerged jetting are 22.9 % and 11.4 % lower than those of the vertical submerged jetting, respectively. Meanwhile, the peak thrust of the inclined jetting is also reduced by 14.1 % compared to the vertical jetting. High-speed photography applied to capture the evolution details of the oxyhydrogen-air explosion reveals that the preceding differences are attributed to the asymmetrical water repulsion phenomenon. Specific impulse is used to characterize the propulsion performance of the oxyhydrogen-air–water explosion jetting at varied volume fractions, and the results show that the maximum specific impulse is obtained for a given 0.45 kg thruster at 40 % water volume and 4:6 ratio of air to oxyhydrogen. The correctness of the explosion characterization metrics and thrust results are finally corroborated via the outdoor aquatic-aerial jetting propulsion tests.