THE TRANSITION TO TURBULENCE OF MICROGRAVITY GAS-JET DIFFUSION FLAMES

This paper discusses results obtained in a study of the transition to turbulence of gas jet diffusion flames in microgravity. The experiment s were conducted at the 2.2-second Drop Tower of the NASA Lewis Resear ch Center, Propane flames burning in quiescent air at atmospheric pres sure were investigated. Significant differences have been observed bet ween the transition processes of gas jet diffusion flames in micrograv ity and normal gravity These include the appearance of large scale str uctures in microgravity which are manifested at the flame base and are convected downstream. These structures appear intermittently at first , and, then, as Reynolds number is increased, a continuous train of st ructures is observed along the flame front. The experimental observati ons are explained in terms of flow transition and instability of the s hear layer associated with the injection of the jet how into quiescent surroundings.