Performance Control Of Turbojet Engine Based On Equlibrium Manifold

Aero engines are very complex systems with high degree of nonlinear character. It is necessary to establish a high reliability and reasonable model in the process of engine research and control system design. Using mathematical model to instead of the engine as the research object can save a lot of expensive funds, also avoid lost control accidents in real engine testing.In this paper, use some experimental data on the basis of the establishment of the engine component characteristic model. On this basis, use simulation data by components characteristic model to replace the real engine test data for the modeling of performance parameters based on equilibrium manifold construction,and using these models for the engine performance optimization.The research work of this paper mainly includes the following aspects:First, establishde the nonlinear model of double shaft turbofan engine by it's complex thermodynamic process. Improvement the existed thermodynamic model of the engine: One side, the component characteristic surfaces of the engine are guaranteed with NURBS.This method effectively inhibit the problem of divergent prone in numerical calculation, and improve the calculation accuracy. another side, laryngeal area of inside nozzle has been added to the model, established a two-input of the turbine engine component characteristics model, , and did a series of simulation calculation using this new model ,validate the correctness of the model from the side of physics. Analyze engine characteristic, research its control law, and design the controller system are on the basis of the nonlinear components model. The components model also the basis to establish real-time model and expansion the research of performance parameters.Second, using equilibrium manifold principle, established the commonly structure of characteristic sections parameters model, these parameters can denote the performance of the engine. Especially, take some important parameters as objects, such as high-pressure turbine inlet temperature, low-pressure turbine outlet temperature and surge margin compressor surge margin. Established the turbine inlet and outlet temperature, and analyzed the relation between the two temperatures, through modify the low-pressure turbine outlet temperature which can be measured, estimated the high-pressure turbine inlet temperature which is difficult to measure, achieving the high-pressure turbine inlet temperature by soft measurement. This method not only constructed redundancy measure of the temperature of engine, but also make a foundation for the direct control of the high-pressure turbine inlet temperature, improved the capability of temperature protect loop control system. Established the surge margin model of compressor, this model has simple structure and can be used for real-time computation.Finally, a two-variable equilibrium manifold of turbofan engine has been established, and accomplished preliminary study about the performance optimize using this model.