Gas Bubble Shape and Shock Wave Propagation Process of Underwater Detonation

An underwater detonation gas experiment system was established to explore the problem of detonation gas jet formed in the underwater working process of pulse detonation engine (PDE). The development and changing process of gas bubble in the first detonation cycle of PDE was experimentally investigated. An underwater jet model of PDE based on the gas-liquid two-phase two-fluid model was established and the space-time conservation element and solution element (CE/SE) method was employed to numerically simulate the propagation and attenuation process of shock wave formed by the interaction of detonation wave and water. The results show that the gas bubble expands into the shape of 'pea' with different development laws between the axial and radial dimensions as it is blocked by the external water environment when the gas jet hits the water surface. The gas bubble has always maintained high pressure due to the gas-water impact and the restricted gas diffusion meanwhile. The leading shock wave propagates much faster than the gas bubble development, and pressure of leading shock wave quickly decays to the ambient pressure after separating from the gas bubble. Pressure of the leading shock wave attenuates most severely in the axial direction, which results in a change in its intensity directivity. The reflected shock wave formed by reflection of the leading shock wave at the gas-liquid interface colliding with the intercepting shock wave formed by the subsequent airflow results in the return stroke, which causes a high pressure peak near the nozzle. © 2021, Editorial Department of Journal of Propulsion Technology. All right reserved.