EXPERIMENTAL AND NUMERICAL STUDY OF TRANSIENT LAMINAR COUNTERFLOW DIFFUSION FLAMES

In the present article, we analyze the nonsteady behavior of counterfl ow diffusion flames subjected to a time-dependent injection velocity i n the case of hydrogen - air flames. The numerical study, using a fini te-difference implicit linear multistep method and employing complex k inetics, is done for sinusoidal injection velocity variations, for mod erate values and also for values near the extinction limit. The freque ncy response is obtained in these different cases. The experimental se tup comprises two axisymmetric nozzles. In order to change the inlet v elocities periodically, we use a vibrating mechanism in each burner. T he 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 ex perimental results are compared to numerical calculations. Good agreem ent is obtained in this comparison.