EFFECT OF SWIRL ON THE COMBUSTION OF A HOMOGENEOUS MIXTURE IN A CLOSED VESSEL.

In order to reveal the effect of turbulence on combustion, the swirling flow of a propane-air homogeneous mixture was produced in a cylindrical combustion chamber. The mixture was ignited by an electric spark at the center of the vessel, and the flow and flame propagation were measured with a two-dimensional LDA system, high-speed laser schlieren photography and an ion probe. From these measurements, the burning velocity, S//T, and the burning zone thickness, delta //T, of turbulent flames were successfully determined under various conditions of turbulence intensity. Further, the turbulence characteristics of swirl and its decay process were investigated. The main results of this study are as follows: (1) S//T increases with increasing the turbulence intensity and delta //T increases with S//T, (2) the turbulence intensity increases in the burning zone of the turbulent flame, (3) the turbulence energy in the burned gas decays rapidly as compared with that in the unburned gas, and (4) after the completion of combustion, the fraction of higher-frequency components of turbulence decreases rapidly.