Research On Throughflow Model And Simulation Methodology For Full Gas Turbine Engines

The overall performance simulation of traditional gas turbines is mainly based on the zero-dimensional calculation method,which is limited by the simplification of the model.Its simula-tion accuracy depends on a large number of test data of the components and whole engine,and cannot reveal the flow details inside components.In terms of component design and aerody-namic performance analysis,advanced numerical simulation methods,represented by through-flow theory and full three-dimensional computational fluid dynamics methods,have made great progress,but most of them currently remain at the component level in engineering application.In order to apply the advanced theories of high-dimensional numerical simulation methods to the overall performance simulation of gas turbines,this paper conducts in-depth research on throughflow model and corresponding computational fluid dynamics methods and,by fully in-tegrates the model and methods,establishes a set of time-marching based throughflow model for the performance calculation of full gas turbine engines.The corresponding flow analysis program is developed,and the investigation of numerical simulation by throughflow model is carried out for the gas turbine components,including compressor,turbine,combustion,and the composed thermal system of the gas turbine.In this paper,the time-marching based throughflow theory is systematically studied,and the basic governing equations in a relative body-fitted coordinates system are deduced for the bladeless area and the bladed area in the gas turbine flow channel.For the combustion chamber flow,the combustion heat release is modelled by using the distributed fuel source terms,and a simplified model based on the Riemann problem is used to describe the flow through the cooling holes on the flame tube wall.Based on the above theoretical study,this paper develops a set of time-marching based throughflow solvers,which adopts a high-order upwind scheme for the calculation of convective flux and supports both the explicit and the implicit time-marching schemes.In addition,the solver embeds newly developed relaxation method for inlet and outlet boundary conditions and inviscid wall boundary conditions based on the normal momentum equation,to ensure the stability and efficiency of the throughflow solving.At the same time,in order to adapt to the grid generation demand of the complex structure in the full engine,flux transfer model among multi-subzone is established.A detailed and in-depth theoretical research is carried out on the core problem of the time-marching based throughflow model——the modeling of the body force source terms.First,a time-marching based one-dimensional governing equations model is established,and a corre-sponding solver is developed as a simplified means of theoretical analysis and numerical ver-ification for body force models.For the viscous body force model based on the entropy dis-tribution,the applicable area limitation in the relative coordinate system is analyzed in detail,and a novel viscous body force model applicable to the entire region is developed accordingly.In order to simulate the deflection effect of the blade on the airflow stably and robustly,dif-ferent blade force modeling methods are described in detail,and their applications in analysis and design problems are discussed.On this basis,an explicit blade force modeling method deduced from the normal momentum equation of the stream surface is developed and veri-fied by an ideal case.According to the discontinuity theory,the influence of the blade force source term on the shock capture properties of the throughflow model is investigated,and the criteria for the conservation of the blade force through the shock under different throughflow governing equations are given,which certificates the superiority of governing equations in the quasi-orthogonal body-fitted coordinates system form.The analytical closure theory of the throughflow governing equations for the blade force source term is further developed,and the”standard two-dimensional” throughflow governing equation is derived,and theoretical analy-sis conclusions are given on its conservation properties,and the the propagation characteristics of perturbation wave.Finally,in view of the discontinuity problems on the leading and trailing edges of blade mean surface in throughflow calculation,a hybrid processing method,coupling leading and trailing edges stream surface modification with the discontinuity solution,is devel-oped to improve the reliability and accuracy of the throughflow model under the transonic and supersonic flow conditions.The verifications of the gas turbine components throughflow models are carried out,and the corresponding solvers are developed and improved.In order to make the turbomachine throughflow solver is capable of being applied in practical engineering,a series of empirical models have been embedded to support the throughflow characteristics prediction for all types of turbomachines only except for radial-flow turbines.A number of engineering cases of axial-flow compressor,centrifugal compressor and axial-flow turbine are used to evaluate the solver and coupled empirical models.The calculation results are in good agreement with the exper-imental or three-dimensional calculation data,which verifies the validity of the turbomachine throughflow solver.With regard to the combustion throughflow model,the numerical case of the micro turbojet engine combustion chamber is used for verification.The results show that the developed combustion throughflow solver is robust and stable,which can quickly and rea-sonably simulate the flow phenomenons inside the combustion chamber,and predict the outlet temperature accurately.The construction of the throughflow solving model of the full gas turbine are carried out followed by corresponding computation verifications.With the integration of the turbomachine solver and the combustion solver,a throughflow solver for the full gas turbine engine is devel-oped.A micro turbojet engine and a dual-rotor,separate-exhaust turbofan engine are used to verify the full engine throughflow solver.The results show that the developed gas turbine engine throughflow model can be widely applied to fast throughflow simulation of gas turbines with different configurations,and can quickly and conveniently predict the overall characteristics of engine,including throttle,altitude,and speed,in which the accuracy meets the engineering requirements.