Experimental research on influence of geometrical configuration on high pressure hydrogen outflow ignition process

Hydrogen is regarded as a potential future fuel for various kinds of vehicles: fuel cell cars, trucks, buses etc. Storing and transportation issues are the crucial safety problems concerned with utilization ofhydrogen. Because of its very łów density hydrogen needs to be stored under very high pressure, in range of 35 division sign 70 MPa, and this create hazard of sudden discharge of hydrogen leading to ignition and severe accident. The aim of the presented research is an experimental investigation of hydrogen ignition as a result of a compression and heating of air by shock wave generated by the discharge of the hydrogen. Mixing of the air heated up by the shock wave and expanding hydrogen can produce combustible mixture of sufficiently high temperature and can lead to ignition. The critical conditions for ignition depend mainly on hydrogen discharge pressure, geometrical configuration, parameters of the ambient air, obstacles, etc. Experimental research -was conducted on a facility specially constructed in Combustion Laboratory, the Institute of Heat Engineering, Warsaw University of Technology. The facility consists from the pressure tank and high pressure hydrogen installation. To allow visualization the observation section is equipped with high quality optical windows. Schlieren visualization system and high speed digital camera was used to register high pressure hydrogen outflow and potential ignition. The high speed digital camera was used to take Schlieren or direct pictures of the process. Additionally, the experiment is registered with use of conventional digital camera. Experiments were conducted for different discharge pressure of hydrogen and outflow to "open space " as well to specially prepared obstacles. Critical condition for which ignition occurs were evaluated for both cases. The high speed Schlieren and direct pictures taken during the experiments are presented in the paper. The influence of presence of obstacles on the feasibility of hydrogen ignition during outflow from high pressure installation is discussed and analyzed.