Characteristic Analysis And Mathmatical Modeling Of Ma0-2 Geometric Adjustable Inlet

The performance of the inlet plays a crucial role in the comprehensive performance of the propulsion system.For the warplane with wide Mach number operation,the inlet is required to operate stably and efficiently at different working points in the flight envelope.When the incoming flow conditions change,the inlet needs to be adjusted in real time to meet the performance requirements of different incoming flow conditions.At the same time,effective integrated control of the propulsion system is needed to realize the stable operation of the fighter under different Mach Numbers.Integrated control of the propulsion system requires that the control system can always perceive the inlet outlet performance parameters,which requires the establishment of accurate and real-time mathematical model of the inlet.In order to solve the problem of inadequate inlet performance,this paper designed a two-dimensional variable geometry inlet based on Angle adjustment of inclined plate,auxiliary adjustment and section adjustment.Through the above adjustment means,the inlet performance was significantly improved.Considering that most of the existing mathematical models of inlet are modeled by physical laws,or the modeling scope is narrow,this paper establishes an inlet model operating in the Ma0-2 range,and gives the control rules of inlet based on the model.At first,this paper gives the general method of two demessional variable geometry inlet design.Using the basic aerodynamic relationship and CFD numerical calculation method,desiging of the inlet at the design point of Ma2 benchmark type surface,through the Angle of inclined plate adjustment won the off-design point geometry type surface,and designed into the inlet valve and valve makes meet the demand of different working condition.It ensures that the total pressure recovery coefficient in the subsonic range is not less than 0.94 and not less than 0.85 under the high Mach number of the supersonic range,and meets the flow demand under different inlet conditions.On this basis,the effects of different influencing factors on inlet performance parameters in subsonic range,transonic range and supersonic range were studied respectively.Secondly for inlet model by adopting the method of optimization of Latin hypercube reasonablely design the numerical calculation points.Using the response surface analysis and RBF neural network established the mathematical model for transonic range of inlet respectively.The model input parameters are flow Mach number,height to flow,the inlet valve opening,outlet pressure,and the output parameters for the inlet flow coefficient,total pressure recovery coefficient and drag coefficient.By comparing the verification found for flow coefficient and the total recovery coefficient modeling error of two methods are smaller than 5.5%.The relative error and the drag coefficient of the model is set up under the high Mach number is larger,but the absolute error is still small.The model of inlet Mass flow rate and total pressure recovery coefficient is established by the method of flow field analysis and numerical calculation fitting in the supersonic range.The model error is less than 2%.Finally,the method of acquiring the control law of the inlet under different flight tasks is given.According to the established mathematical model and the existing control block diagram of the actuator,the inlet control system model based on Mach number control is established,and the simulation verification is carried out at different task points.It is found that the control model of inlet can describe the dynamic regulation process of inlet well and has a good real-time performance.It is of certain reference value to the integrated control modeling of propulsion system.