The investigation of hydrogen released on the mixed jets with an axisymmetric jet and an asymmetric jet

Hydrogen released from complex multi-pipeline leakage sources can increase the difficulty of predicting the risk region of hydrogen and the probability of explosion accident. To investigate the collision and mixing features of subsonic hydrogen jets released from multi-pipeline leakage sources, an experimental platform for gas visualization and quantitative measurement is constructed. The differences in flow field structure and concentration distribution of vertical axisymmetric hydrogen jet, vertical asymmetric hydrogen jet and mixed hydrogen jets are compared and analyzed. Furthermore, the effects of multiple factors on the jet centerline, concentration decay, hazardous volume and diffusion height of the mixed region are predicted. The numerical simulation results are verified by the experimental data. Results indicate that the asymmetric hydrogen jet causes the mixed region centerline of hydrogen to deviate from the vertical axis under the combined effect of momentum-dominant and buoyancy. With the increase of the volumetric flow rate, the slope of the mixed region centerline initially decreases and then increases, with the smallest slope occurring at a volumetric flow rate of 159 NL/min. Either the increase of the leakage orifice diameter or the decrease of the distance between two leakage orifices can cause the slope of the mixed region centerline to decrease. Among three factors, the leakage orifice diameter has the most obvious effect on the concentration decay. The hydrogen diffusion height gets the highest when the ratio of leakage orifice diameter to pipeline inner diameter is 0.4 among five leakage orifice diameters. The distance between two leakage orifice has no significant influence on the hazardous volume. The investigation provides valuable data to support the prediction of the dangerous range of hydrogen leakage in complex multi-pipeline leakage sources.