Burning velocities of methane-air mixtures using hot-wire anemometers in closed-vessel explosions

A new technique is described for the measurement of burning velocity in closed-vessel explosions. It entails the use of a hot-wire anemometer to measure the gas velocity ahead of the flame front. The calibration of the hot wire is described. The flame propagation is recorded using a laser source, a reflection-plate interferometer, and a high-speed camera. The technique has been used to measure CH4-air burning velocities at different equivalence ratios and over a range of pressures. The measured burning velocities are higher than most previous values, and the reasons for this are discussed. It is found that Su ∝ P−0.5. Chemical rate expressions have been used in attempts to evaluate Su on the basis of Spalding's expression for Su. The results suggest that the significant rate-determining reactions are associated with the breakdown of the hydrocarbon molecule and not with the oxidation of CO.