Experimental and numerical study of transient laminar counterflow diffusion flames

In the present article, we analyze the nonsteady behavior of counterflow diffusion flames subjected to a time-dependent injection velocity in the case of hydrogen–air flames. The numerical study, using a finite-difference implicit linear multistep method and employing complex kinetics, is done for sinusoidal injection velocity variations, for moderate values and also for values near the extinction limit. The frequency response is obtained in these different cases. The experimental setup comprises two axisymmetric nozzles. In order to change the inlet velocities periodically, we use a vibrating mechanism in each burner. The amplitude and the frequency of injection velocities of the opposed nozzles are synchronously modified. The OH radical emission intensity is used to measure the flame response to velocity fluctuations. The experimental results are compared to numerical calculations. Good agreement is obtained in this comparison.