Study On Combustion Structure And Flame Stability In Micro Afterrburner

The afterburner is arranged between the engine turbine outlet and the tail nozzle.When it working,fuel mixes with the remaining oxygen from the combustion chamber and burns in the afterburner,which can greatly increase the Exhaust temperature and flow rate and engine thrust in a very short time.The afterburner can be used for aero engines and combined engines to solved the problem of thrust demand under special working conditions.At present,afterburning is mainly used in large engines,but there are few studies on afterburning at small scales.Due to the reduced size,the miniature afterburner faces problems of short fuel residence time,poor atomization and mixing effects,and flame stability.In order to solve the problem of low performance,this article conducts the following research.First of all,this paper uses a zero-dimensional model to evaluate the performance of the micro-afterburner for preliminary understanding of the thrust gain which the micro-afterburner can bring.Further,this paper studys the influence of the total pressure recovery coefficient,fuel equivalent ratio and combustion efficiency on the performance of the engine on the afterburner.According to the needs of simulation research and ground test,preliminary design of the stabilizer and fuel injection rod structure was carried out,and the basic structure design of the micro afterburner was completed to pave the way for the follow-up research.A three-dimensional simulation study was carried out on the fuel atomization and mixing characteristics under different injection schemes,including different injection flow angles,nozzle numbers and injection combinations.According to the simulation results,the fuel atomization blending effect of single-hole injection is better than that of double-hole injection,and the fuel atomization blending effect under the jet angle of 90° is the best.The combined fuel supply will increase the range of the proper oil-gas ratio area in the return zone after the stabilizer,and increase the heat release capacity of the return zone,which is beneficial to flame stability and propagation.Another three-dimensional simulation study on the key structural parameters of the flame stabilizer and the combustion performance was carried out under different incoming flow conditions.Further,comparing the effects of the stabilizer opening rate,jet angle and aerodynamic parameters on the flame stability characteristics.Through comparative analysis,it is found that the flame stability is the best when the stabilizer opening ratio is 0.08 and the fuel jet angle is 60°,and when the intake swirl angle is small,it can promote mass heat exchange,which is conducive to flame propagation and combustion.At this time,when the intake swirl is too large,it will reduce the stability of the flame on duty and the combustion efficiency of the combustion chamber.The ground ignition test was carried out on a miniature afterburner,and the flame stability and propagation characteristics of the combustor under different working conditions were comparatively studied.The test shows that with the increase of the inlet velocity and swirl intensity of the afterburner,the flame stability performance decreases,and there is a minimum fuel flow required for flame stability increases.When multiple flame stabilizers work at the same time,the flame propagation performance increases with the increase of the fuel flow of the ignition stabilizer.