Quasi-steady characteristics of flowing propane/air mixture ignited by a heated surface

Abstract

Quasi-steady behavior of a flowing propane/air mixture ignited by a surface heated at a constant power was investigated as a first step in assessing the physical risk of alternative clean energy. A series of experiments was carried out in which flowing propane was exposed to a heated surface at various supplied voltages and flow velocities. From the experimental results, the following findings were obtained: (1) ignition initiated from the bottom of the heated surface, and a flame first propagated on the downstream side of the heated surface; (2) the existence of the critical heat flux to ignite the flowing mixture was found, which was a major difference between ignition by a constant-temperature, hot surface and that by a constant-heat-flux, heated surface; (3) the limit of ignition temperature was expressed as a function of flow velocity, and the size of heated surface, yielding a curve which converges to a critical value of ignition temperature. The experimentally-measured dependence of the critical heat flux and ignition temperature on the flow velocity was consistent with the prediction of theoretical analysis conducted in this study.