Experimental Investigation Of Light-Round Mechanism In Annular Combustors

Annular combustor is widely adopted in aero-engines due to its compact configuration and light weight.A detailed understanding of the light-round mechanism in annular combustors plays an important role in design stage.However,experiments in flull-scale,industrial combustor may bring challenges in measurement and cost,so the mechanism study in laboratory-scale annular combustor models becomes an effective method.A series of combustor models have been developed in this paper.First,in a single swirling burner,the velocity field under cold conditions and flame characteristics have been studied.Then the light-round mechanism study,based on TurboCombo experimental platform in Zhejiang University,is focusing on flame propagation characteristics under two different ignition modes called SFFL(Spark First Fuel Later)and FFSL(Fuel First Spark Later),together with light-round time and its regulation with equivalence ratio and bulk velocity.In SFFL mode,due to the turbulent mixing,ignition process features larger randomness,longer light-round time and light-round time is mainly controlled by flow conditions and would decrease with increasing bulk velocity.While in FFSL mode,the ignition process is faster,more stable and light-round time decreases with increasing equivalence ratio.Furthermore,the influence of turbine guide vanes at combustor outlet to ignition process is considered.Although the ignition process and flame propagation mode are similar,the light-round time features shorter value,which may be attributed to the variation of unsteady flow field in the annular combustor during the light-round sequence because of contractive flow passage and turbine guide vanes.Finally,the ignition process is studied in the oblique-injecting gyratory flow annular combustor.The introduced circumferential velocity component significantly changes the light-round sequence.In SFFL mode,flame only propagates in one direction along the velocity component,leading to a quite longer light-round time.While the whole ignition process including the circumferential flame propagation speed is mainly determined by flow conditions.In FFSL mode,although the flame remains propagating in two directions,while the process is obviously asymmetric and when the circumferential velocity component reaches a certain value,it would effectively accelerate flame propagation and reduce the light-round time.A series of characteristics and quantitative regulations are drawn in this paper through experimental investigation of ignition sequence in annular combustor models.And it may be valuable for combustor design and whole engine test,meanwhile it can afford data to validation of numerical simulation.