| Short/vertical takeoff and landing(S/VTOL)aircraft has both advantages of the helicopter and traditional fighter,the aircraft realized short takeoff and vertical landing by the lift produced by the propulsion system,so the lift technology has been the focus of the aviation powers country.This paper revolves around the propulsion system for short/vertical takeoff and landing aircraft,to carry out the research of the overall performance calculation method and the configuration scheme of the propulsion system and lift parameters matching,the research of aerodynamic characteristics law and the deflection implementation method of the three bearing deflection nozzle,and the vectored nozzle and,and the research of the interference effect between the jets of the propulsion system and ground.The performance calculation model of the lift fan and the tip turbine-driven lift fan were built based on conventional turbofan engine modeling method and the performance calculation model of four kinds of compound propulsion system based on lift fan were obtained,the performance parameters of four kinds of propulsion system were compared and analyzed.The study shows that the shaft-driven lift fan propulsion system is the preferred solution for S/VTOL aircraft power plant.The performance calculation model of the shaft-driven lift fan propulsion system which is similar to F135 was built,and the working mechanism of the shaft-driven lift fan’s propulsion system was analyzed.The approximate model of the shaft-driven lift fan propulsion system’s performance was built using approximate modeling method and the maximum lift under certain limitation conditions and also the corresponding design parameters of the lift components were obtained.The mode conversion dynamic performance calculation model of the propulsion system was built,and the mode conversion control laws at both low altitude flight and ground takeoff state were obtained by regulating multiple variables coordinately,the study shows that the mode conversion control laws at the two states are similar,which both adjust the area of the bypass ejection outlet and the low pressure turbine guide vane throat quickly in the initial phase of the mode conversion to ensure the equitable distribution of the airflow between the bypass and core duct of the engine,high pressure rotor speed does not exceed,the temperature before the high pressure turbine is not affected to increase greatly by the bypass bleed.The wall static pressure distribution of the three bearing deflection nozzle was measured,and the adaptability of various turbulence models in the calculation of flow field characteristics of the three bearing deflection nozzle was verified.The aerodynamic profiling design research of the nozzle at non vector state and 90°state was carried out using numerical simulation method and approximate modeling principle,the profile which keeps the nozzle’s aerodynamic performance optimum at 90° state was obtained.The flow’s characteristics and energy loss mechanism of the nozzle at small and larger vector angle state were analyzed,and the aerodynamic characteristic of the three bearing deflection nozzle at steady state was obtained.Based on dynamic mesh technology,the aerodynamic characteristic of the three bearing deflection nozzle at unsteady state was obtained,and the aerodynamic performance and the flow field characteristic of the nozzle at steady and unsteady state were compared and analyzed.The effect of the distance between the nozzle’s outlet and the ground on the nozzle’s aerodynamic performance was analyzed.The research of the deflection implementation method of the three bearing deflection nozzle has been carried out using the geometric modeling method based on the aerodynamic characteristics analysis of the three bearing deflection nozzle.The nozzle’s deflection control law model was built,the control law of each nozzle segment’s rotation angle which ensures the axis of each nozzle segment in the same pitch surface during nozzle deflection process was obtained,and the suitable control law for the nozzle was preferred by comparing various kinds of nozzle deflection control law.The motion law model for each nozzle segment was built,and the movement law of the each nozzle segment at absolute coordinate was obtained.The driving torque calculation model of each nozzle segment was built,and the variation regulation with the nozzle deflection angle of the required torque of each nozzle segment was obtained,the effect of the geometric parameters on each nozzle segment’s driving torque was analyzed.The influence mechanism of aerodynamic and geometric parameters on the interference effect between the single jet and the ground was analyzed,and the lift loss coefficient variation with each factor was obtained.The numerical model of the interference effects between the twin jets and ground were built,and the influence of aerodynamic and geometric parameters on the interference effect between the twin jets and the ground was analyzed.The study shows that the fountain flow generates lift force on the flat,at the same time,the interference occurs between the fountain stream closed to the lower surface of the plate and the jet,the fountain stream forms low pressure zone around the jet by the induced effect of the jet,and further reduces the pressure under the plate,and increases the lift loss.The twin jets lift loss characteristics approximate model was built based on approximate modeling technology,the interaction effect of each factor on the twin jets lift loss characteristics was studied,the study shows that jets spacing has less impact on the lift loss characteristics and can be ignored,the height of the plate is the main factor affecting the lift loss characteristics,when the plate at low altitude,the impact of each factor on the ground interference effect gets strong,when the plate at higher altitude,the impact of each factor on the ground interference effect gets weaken. |
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