Authors: K. B. Brady, C. J. Sung, and J. S. T’ien
Direct link to the paper: http://dx.doi.org/10.1016/j.ijhydene.2010.07.105
An experimental investigation into the ignition characteristics of lean pre-mixed hydrogen/airmixtures is conducted using astagnation-point flow configuration against aplatinumsurface, with a special emphasis on the determination of potential fire safety hazards associated with hydrogen release in the presence of a catalyst. Two distinct regimes are observed for this system – catalytic surface reactions and gas-phase ignition. It is demonstrated that depending on mixture equivalence ratio, catalytic surface reactions can be initiated with or without surface heating. When significant surface heat is released via catalytic reactions, gas-phase ignition can be induced, greatly increasing the apparent danger of hydrogen leaks in the presence of aplatinumsurface. The critical surface temperatures leading to catalytic ignition for hydrogen/airmixtures over aplatinumsurface are further investigated over a range of equivalence ratios and stretch rates. It is shown that ultra-lean hydrogen/airmixtures can be catalytically ignited even in the absence of external heat addition, suggesting that hydrogen leakage in the presence of aplatinumsurface may pose a fire safety risk even at room temperature. Furthermore, even without a transition to gas-phase ignition, the surface temperature that can be sustained with surface reactions alone may contribute to component degradation or itself pose a safety hazard.
Citation: K. B. Brady, C. J. Sung, and J. S. T’ien, “Ignition Propensity of Hydrogen/Air Mixtures Impinging on a Platinum Stagnation Surface,” International Journal of Hydrogen Energy 35 (20), 11412-11423 (2010).