Research On Modeling And Control Of Short/Vertical Take-off And Landing Propulsion System

S/VTOL is an important function that fixed-wing fighter craves at present.Its core is the propulsion system with thrust vector function.It is a multi-disciplinary cross-integration field,and it is difficult to model.This paper focuses on this field,and carries out modeling research on three objects: engine with lift fan,engine fan with variable bypass ratio and axisymmetric vector nozzle.Based on the universality of components among different models of F135,the F-35 B propulsion system is reproduced by GASTURB,and the strong coupling between components is verified.Aiming at the core technology of counter-rotating lift fan,a comparative modeling study was carried out with conventional non-counter-rotating fan.Firstly,the conventional lift fan model is established by the elementary cumulative method;then the reverse stage is designed based on the rotor and replaces the stator to form the intermediate counter-rotating fan;based on the principle of shaft power similarity,the aerodynamic parameters of the intermediate fan are kept unchanged,and the new fan has the same shaft power with the original conventional fan by modifying the flow,geometric size and rotational speed of the intermediate fan.Thus,they can be driven by the same main engine.The dynamic and steady state simulation shows that the thrust of lift fan components tends to be the same by adjusting the lowpressure spool rotational speed itself under the same fuel input.S/VTOL propulsion system varies greatly in different modes,and the effect of bypass ratio on fan flow field can not be ignored.Based on the theory of axial elementary stage cumulative and radial balance equation,this paper reveals the mechanism by establishing a quasi-two-dimensional fan model.In the model solution,a dual-level iteration algorithm for conventional state and a three-level iteration algorithm for variable bypass ratio state are constructed respectively.The accuracy of the model is verified by the simulation of conventional design point,and the influence of bypass ratio on the fan characteristic line is shown by the simulation of variable bypass ratio,the fan shows best performance on nominal bypass ratio.A nine-dimensional equilibrium equation describing the complex spatial motion of axisymmetric vectored nozzle was established by transformation of space coordinate system and constraints analysis.A two-dimensional interpolation model describing the mapping relationship between vector angle and displacement of actuator was established by solving the equation.Based on the simulation conclusion that the geometric center distance between the throat section and the exit section is constant,the simplified relationship between the vector angle and the central coordinate is established and the dynamic deflection law of the vector angle is designed.The simulation results show that the deflection law and displacement interpolation model can ensure the dynamic distribution of vector trajectory to meet the expected settings.