Numerical Investigation of Nozzle Aspect Ratio Effects on Hydrogen Jet Release Characteristics

As one of the carbon-free energies, hydrogen is considered as an important energy carrier in the 21st century. The minimum ignition energy of hydrogen is the lowest among flammable gases, hence, hydrogen leaking from pinholes, narrow gaps, or broken pipes can be ignited by ignition sources such as static electricity. Understanding of the characteristics of the hydrogen jet release is crucial for the better design and the applications. In this paper, the hydrogen under-expanded jet and flammable envelope were studied by simulation method. The effects of the nozzle shape and release pressure on the under-expanded jet, the downstream shock structure and flammable envelope were investigated. The simulation results showed that the nozzle geometry had great influence hydrogen under-expanded jet. And the maximum flammable length increased with the increasing of aspect ratio. For the split nozzle, with the increasing of pressure the hydrogen diffusion region of minor axes in the near-to-nozzle field increased but decreased of major axes.