An experimental investigation has been carried to study the flow characters and structure of transient jet diffusion flame. The fuels used were propane and butane. The observation was made at Re=179, 1084, 1519 in case of propane, and at Re=172, 1084, 1517 in case of butane. Flow visualization technique(high speed schlieren and direct still photography) and thermocouple with compensation were used to observe the convective characteristics of flame front and the repeated position of formation of soot ring.
The convection of flame is faster as Re increase and propane more than butane. The temperature of flame is higher outside than inside to radial direction because of increasing of mixing rate due to vortex motion and downstream than upstream to axial direction because of decreasing of stretch rate.
Experimental study shows that this flow field is similar to 1D unsteady stagnant counterflow and that the change of temperature is closely related with the stretch rate in the centerline axial direction.
It is confirmed that this flow field supplies to the time dependent information for studying the time-varying strained field.
