Research On Application Of Turbulent Combustion Models For Combustion Flows Of Aero-engine Combustors

In order to study the effects of complex interactions between turbulence and combustion on reacting flow fields and pollutant formation within aero-engine combustors, the three-dimensional two-phase turbulent reacting integrated flow fields and pollutant emission of three different aero-engine combustors with the dual-stage swirlers:dual-stage axial swirler rectangular model combustor, dual-stage axial swirler annular combustor and swirler cup annular combustor,have been numerically investigated, respectively. An in-house computer code AGTCNS(Aero-Gas Turbine Combustor Numerical Simulation) has been developed and the influences of different turbulent combustion models, inlet boundary conditions and combustor header structure parameters on non-reacting and reacting flow fields for dual-stage swirler combustors are investigated by this computer code. A special program has been written to create flamelet data libraries for different inlet conditions and chemical reaction mechanisms. A subroutine is compiled to couple the flamelet data libraries and AGTCNS code. Therefore the in-house code AGTCNS could be run in both single-step and multi-step chemical reaction mechanism modes. Multi-dimensional empirical analysis method and flamelet model with multi-step reaction mechanism are also used by the AGTCNS code to predict pollutant emission levels from combustors.In order to improve the compatibility of the in-house structured grid generation code AGTCGG(Aero-Gas Turbine Combustor Grid Generation), this in-house grid generation code has been developed. A special program for generating the structured grids of dual-stage axial swirler and swirler cup are written and inserted into the AGTCGG with the visualization function. For complex geometric configurations of combustors,the differential equations with sub-regional and multi-block methods are used by this code. The integrated grids of different dual-stage swirler aero-engine combustors, including a dump diffuser, cowl, swirler, flame tube as well as outer and inner annuluses in arbitrary curvilinear coordinates, are generated by this code.For verification of numerical methods and mathematical models, non-reacting and reacting flow fields of dual-stage swirler combustors are measured by the Particle Imaging Velocimetry(PIV). The Infrared thermal imager is used to measure wall temperature profiles of the flame tube within the combustor with the dual-stage axial swirler. In addition, verification experiments of outlet gas temperature and pollutant emissions of the dual-stage swirler combustors are conducted. The effects of different inlet temperature and fuel/air ratio as well as combustor header structure parameters on spray combustion fields and pollutant emission are studied experimentally. The measured results obtained are used to verify the calculated values.In order to evaluate prediction capability of different turbulent combustion models for simulating turbulent combustion in aero-engine combustors, the influences of E-A model?EDC model?S-E model and FLM model on combustion flow fields and pollutant emissions within these three combustors are numerically investigated under different inlet conditions. Calculated results obtained by these combustion models are in reasonable agreement with corresponding experimental data. It shows that these turbulent combustion models may be used to predict turbulent two phase combustion flows and pollutant emission levels of dual swirl combustors. But the influences of different turbulent combustion models on turbulent spray combustion flow fields are obvious. Calculation accuracies of these combustion models also are some different. The shapes of recirculation zone, profiles of velocity and temperature as well as profiles of outlet gas temperature and pollutant distributions obtained by different turbulent combustion models also are distinct. By comparison with experiments, Simulation capabilities of the S-E and FLM-B models are also higher than those of other combustion models. Then it is clear that the calculation accuracy and reliability may be raised by adopting reasonable turbulent combustion model.The in-house AGTCNS code is applied to predicting the influences of combustion models and inlet conditions on cold and spray combustion flow fields as well as pollutant emissions of three different dual-stage swirler combustors. Calculated results are in reasonable agreement with corresponding experimental data. It shows that the numerical methods and mathematical models are reasonable, and the computer code is useable for simulating turbulent flows, combustions and pollutant characteristics of aero-engine combustors and for providing a technical support in the optimum combustor design.