Theoretical Investigation of the Shock-Tube Diaphragm Influence on Pressurized-Hydrogen Jet Release Ignition Limits

A new method is used in the present work in order to theoretically investigate the effects of diaphragm material, diaphragm thickness, and driver gas on the temperature and chemical kinetics in the gas region downstream of the shock wave in a round cross-sectional area shock tube with a diameter of 0.10 m for cases with a partial diaphragm opening. The initial pressure ratio across the diaphragm is 400. The driven gas is air at atmospheric conditions. Pure H₂ and H₂/N₂ dilutions are accounted for as driver gases, respectively. Two different diaphragm materials are respectively accounted for, such as 302 stainless steel and 410 stainless steel. Because the initial pressure difference between the driver gas and the driven gas is kept constant for all cases, an increase in the diaphragm thickness leads to an increase in the opening diameter of the diaphragm, which leads to an increase in the temperature of the gas in the region downstream of the shock wave. The dilution of 0.80 of H₂ with 0.20 of N₂, in mole fractions, leads to a temperature reduction by up to 46% when compared to the case of pure H₂ as a driver gas. In regard to the diaphragm material, the same diaphragm thickness leads to a higher opening diameter for 302 stainless steel than for 410 stainless steel. Moreover, the rate constants of chemical reaction H₂ + O₂ → HO₂ + H are significantly affected by the driver-gas dilutions.