Research On Cycle Parameters Optimization And Modeling Technology Of Low Infrared Turbofan Engine

With the rapid development of infrared detection and guidance technology,the demand for infrared stealth of aircraft is becoming more and more urgent.Turbofan engine is the main power form of combat aircraft,and its exhaust system is an important infrared radiation source.However,most of the infrared stealth measures used in an engine without considering the need of infrared stealth in the overall design stage will have a negative impact on its performance.On the basis of it,the cycle parameters optimization and modeling technology of low infrared turbofan engine is studied in this paper.The main arrangements are as follows:Firstly,the design method of turbofan engine based on AEDsys is studied.Constraint analysis module,mission analysis module,parameter cycle analysis module,performance cycle analysis module,installation performance analysis module and data transfer between modules are compiled.The constraint analysis module is used to transform the mission requirements of aircraft into constrained boundaries to form the solution space of the aircraft's sea-level thrust load and wing load.The mission analysis module includes the fuel consumption calculation model of the aircraft,which can be used to calculate the fuel consumption of the aircraft,the total take-off weight and sea-level thrust of the engine.The parametric cycle analysis module establishes the relationship between the key design parameters and engine performance at the design point.The performance cycle analysis module can be used to calculate engine performance at non-design points.The installation performance analysis module is used to estimate the drag coefficients of subsonic inlet,supersonic inlet and nozzle.The simulation results verify the accuracy and effectiveness of the above modules.Secondly,the cooling structure of the central cone and the inner wall of the nozzle expansion section is added to the parameter cycle analysis module,and a prediction method of the infrared radiation intensity of the exhaust system is proposed.Based on the improved parameter cycle analysis module,FSQP algorithm is used to optimize the engine cycle parameters.The simulation results show that:after optimization of cycle parameters,the unit thrust of the engine decreases by only 1.89%,while the total backward infrared radiation intensity of the exhaust system decreases by 41.85%.The infrared characteristics of the exhaust system are effectively suppressed.Thirdly,according to the design results of turbofan engine design method,combined with the empirical formulas of each component in the design stage and the infrared prediction method of exhaust system,a turbofan engine component-level model with infrared prediction is established.The design points and several typical non-design points are selected for calculation and compared with the simplified engine model.The results show that:the error of design point is less than 2%,and that of non-design point is less than 5%.The precision of the component-level model is up to the requirement.Moreover,the simplified engine model has certain credibility,and its accuracy can meet the requirements of the initial stage of engine design.Finally,the performance optimization control of the minimum infrared feature mode is proposed.The optimization principle of the minimum infrared characteristic mode is explored.Based on the component level model of turbofan engine with infrared prediction,the film cooling structure of the inner wall of the expansion section of the central cone and tail nozzle is added.Four-variable control parameters are used to optimize two working points near the subsonic cruise of the engine.The simulation results show that the thrust of the engine is constant,the backward infrared radiation of the exhaust system decreases by more than 30%,and the infrared suppression effect is remarkable.Considering flying range,a minimum infrared characteristic mode considering fuel consumption is proposed.Compared with the previous mode,infrared radiation increases by 0.32%,and fuel consumption decreases by 0.67%.