| In order to study the unsteady combustion and flow field of a complex integrated afterburner of aero-engine,an In-house code based on Large Eddy Simulation method was developed and valuated in this paper,which lay the foundation for the thermoacoustic analyse.First,the geometry of the integrated afterburner was complicated with hollow vanes,cone and almost a hundred cooling holes on the cooling shield and vanes,the mesh generation of such a structure was quite a challenge without simplification.Therefore,a Solid-Shielded method with structured mesh was adopted and implemented in the code to simplify the mesh generation of the integrated afterburner.And a classic surface-mounted fence flow with experimental data was selected and simulated to validate the method.The results showed that the Solid-Shielded method could effectively improve the calculating efficiency and shorten the time of grid generation;and compared with Halo-Cell method and experimental data,the prediction of both method showed the same flow field structure of the fence flow and agreed quite well with the experimental measurements.Second,in order to improve the accuracy of the numerical simulation of the integrated afterburner flow field,sub-grid-scale(SGS)k equation and dynamic turbulence models were developed and implemented in the In-house code,and a Sydney bluff-body burner with both non-reacting and reacting flow field experimental data was selected to study the influence of different sub grid scale turbulence model.And the implementation of SGS turbulence combustion model was also carried out in this paper,to achieve the ability of the code to predict turbulent combustion.Simulation with different combustion models(EBU,single-step and multistep flamelet combustion models)were carried out to study the influence of the combustion models on turbulent diffusion flames.The results showed that the dynamic model provided better prediction for bluff-body flows than the SGS turbulent kinetic energy model and the Smagorinsky model;and that the results simulated by three combustion model showed good satisfaction with the experiment data in lean combustion region,but not good in oil-rich region,but the multi-step flamelet model gave a better overall performance.Finally,the Solid-Shield method together with dynamic SGS turbulence model were adopted to simulate the non-reacting turbulent flow in the integrated afterburner,the results showed that some periodic executive vortexes can be seen in the predicted flow field;and there are stable recirculation zones behind the hollow blade,which can hold and propagate flames.On the other hand,a large structure vortex can be found behind the center cone,which could lead to overmuch pressure drop.It can be concluded from the discussion that the design of the integrated afterburner need to be optimized,and the developed in-house CFD code was approved to be a sufficient tool to simulate the complex flow field,such as the integrated afterburner of aero-engine. |
