Experimental Study on Flame Propagation in Monodispersed and Mono-sized Fuel Spray by Using Microgravity Conditions

Abstract

A fundamental study on spray combustion was carried out by using microgravity conditions produced by a 100 m drop shaft. A monodispersed and mono-sized droplet cloud was used for experiments as a simple model of a spray. Such a droplet cloud was generated by using the principle of the Wilson's cloud chamber. Methanol droplet clouds were employed in the present work. Pressure was set 0.2 MPa for all experiments. The mean droplet diameter and the ratio of the liquid fuel mass to the total fuel mass were varied in the rage of 7-45 µm and 0-60%, respectively. Almost monodispersed and mono-sized droplet clouds were generated and ignited successfully under microgravity conditions. It was found that the flame speed of fuel droplet clouds exceeds that of premixed gases of the same total equivalence ratio in two regions of the total equivalence ratio. One region exists in the lean side and the other exists in the rich side. For the mixtures of 0.8 in the total equivalence ratio, the flame speed takes the maximum value when the mean droplet diameter is about 11 µm and the liquid equivalence ratio is about 0.2.