IGNITION DYNAMICS IN AN ANNULAR COMBUSTOR WITH GYRATORY FLOW MOTION

In concepts of integrated design of combustor and turbine, an annular combustor model is developed and featured with multiple oblique-injecting swirling injectors to introduce gyratory flow motion in the combustion chamber. The ignition process is experimentally investigated to study the effects of introducing circumferential velocity component U-c, to the light-round sequence. Experiments are carried out with premixed propane/air mixture in ambient conditions. The light round sequence is recorded by a high-speed camera, which provides detailed flame azimuthal positions during the sequence and gives access to the light-round time tau and the circumferential flame propagation speed S-c. The results have also been compared with that obtained from a straight-injecting annular combustor. The effects of bulk velocity U-b, thermal power P and equivalence ratio Phi are also explored. Due to the gyratory flow motion induced by oblique injection, the flame fronts only propagate along the direction of circumferential flow. Both of the circumferential flame propagation speed increase with increasing bulk velocity in two injection types. It seems mainly to depend on bulk velocity, regardless of Phi, in oblique-injecting combustor when compared with the straight one. It indicates that the circumferential velocity component would play a dominant role in light-round sequence when it is sufficient higher than the displacement flame speed.