Effects of swirl and air-fuel ratio on premixed combustion in a closed vessel

Experiments were performed to reveal the effects of the equivalence ratio and the turbulence characteristics on the combustion of a propane-air homogeneous mixture. A turbulent flame propagating nearly axisymmetrically in the swirling flow was produced in a disc-type combustion chamber. The burning velocity S_T, the burning zone thickness δ_T of turbulent flames and the laminar burning velocity S_L were measured under various conditions. The main results obtained are as follows: (1) both S_T and S_L depend on the equivalence ratio and achieve maximum values under the condition of slightly rich mixture; (2) the value of δ_T increases with the increase of S_T/S_L and there is a correlation between δ_T and S_T/S_L; (3) the ratio of the main stage of burn duration to the total burn duration decreases and the ratio of the early stage increases with the increase of turbulence intensity, and these are almost independent of the equivalence ratio.