Ignition Characteristics of Steady and Dynamic Release of Pure Silane into Air

Abstract

Dynamic and steady release tests have been performed to uncover the precise condition for pure silane ignition upon its release into air. Two regimes (dynamic and steady) are studied. In dynamic tests, silane is released from a vessel with a known pressure. It is found that prompt ignition is not observed even with the source pressure down to 0.15 MPa. In steady flow tests, a reproducible critical exit velocity is found above which silane can be released indefinitely into air without any ignition. With the aid of the laminar boundary layer theory, it is found that ignition always occurs in a well-defined mixture fraction called the most reactive mixture fraction. The critical exit velocity and the most reactive mixture fraction suggest that silane release without prompt ignition is most likely caused by flow strains or by scalar dissipations, which prevent chemical reactions of silane oxidation.

Calculation of flammability limits of silane–oxygen and silane–air mixtures

“…It was numerically demonstrated [2] that the presence of water vapor in the mixture in an amount greater than a certain limiting value initiates the ignition of the silane-oxygen mixture. It was later demonstrated in the experiments [9] on silane injection into air that addition of a water drop with a volume of 10 μl leads to rapid ignition of the silane-air mixture. Thus, as the silane concentration in the mixture exceeds the stoichiometric level, the flammability limits behave nonmonotonically (Fig.…”