Abstract
This paper reports on an experimental investigation of the effect of flame speed on the quenching distance. In a rectangular section channel, the quenching distance of methane-air, propane-air and ethylene-air flames, arriving on the quenching element with different speeds, is investigated. The experiments are performed in a constant volume combustion chamber comprising two volumes separated by the quenching section. The quenching tests are performed at pressure close to atmospheric, with an initial temperature of the walls and flammable mixture of 293 K. Flame quenching is assessed from pressure measurements, while the apparent flame speed is determined from fast schlieren imaging. The results show a similar trend for the three fuels considered: the quenching distance for laminar propagating flames is about twice smaller than when the flow becomes turbulent, close to the entrance of the channel. In the case of laminar flames, the quenching distance is almost constant at 1.3-1.5 mm for the conditions considered, while for turbulent flames, depending on the fuel and equivalence ratio, the quenching distance is in the range 2-2.5 mm. Starting from the quenching theory, the results are analyzed and the effects of flame curvature and turbulence are discussed.