Simulation Of The Geometric Effects On The Performance Of Counterflow Thrust Vectoring Nozzle

With the rapid development of high technology and its application in radar,avionics and other combat system, which make the environment of modern air combatmuch complicated, new aircraft must have super maneuverability, agility and lowerradar signature to take dominant position in over-the-horizon and close air-to-aircombat. The thrust vectoring technology must be developed instead of theconventional aerodynamic rudder for which is unable to meet the control force andmoment during high angle of attack and other complex flight condition. Counterflowthrust vectoring technology is a promising technology for which has the ultra compact,higher survival ability, lower weight, lower observable and higher efficiency in thrustvectoring control.The geometric effects on the performance of counterflow thrust vectoring nozzlewere studied by the Fluent software. The studies were as follows:(1)The numerical simulation and comparative analysis of suction pressure effectson aerodynamic characteristics of a2D counterflow vectoring nozzle were conductedunder no outflow disturbance conditions. By simulating the shrinkable experimentalmodel which was studied in NASA Lanly research center, the simulation results wereconcluded during the inceasing suction pressure difference: the thrust vectoring angleincreases, and the resultant thrust ratio decreases; the secondary suction flow directionshifts from counterflow to coflow; the secondary suction flow ratio has littledifference in conterflow condition, and the secondary suction flow ratio widelyincreases in coflow condition. By comparative analysis between calculating andexperimental results, the method of changing the suction pressure difference toobtained thrust vectoring angle is feasible, and the numerical method is rational.At thesame time, this paper explains the relationship between the thrust vectoring angle, thethrust resultant ratio and the suction pressure difference using the internal flowstructure and shear layer’s characteristics in collars, which accounts for the importanteffects ofreverse shear layer’s characteristics on the the performance of nozzle.(2)The geometric effects on aerodynamic characteristics of a2D counterflowvectoring nozzle were conducted under subsonic outflow disturbance conditions. Bycreating a2D geometric model, the effects of the slot width, terminal angle, suctionangle, horizontal height, vertical section height, collar length were studied on the thrust vectoring angle, the resultant thrust ratio, wall pressures, secondary mass flowratio. Under subsonic outflow disturbance, the thrust vector angle and resultant thrustratio significantly reduces compared with no outflow disturbance; the secondary massflow ratio increases; as the jet attatchment problem is not serious caused by too largethrust vectoring angle, so configuration settings should pay more attention to improvethe thrust vectoring performance.(3)The effects of lateral length on aerodynamic characteristics of a3Dcounterflow vectoring nozzle were conducted under subsonic outflow disturbanceconditions. The conclusion was as follows during the increasing lateral length: thecoflow and counterflow secondary flow ratio increase; the thurst vectoring angleincreases, but the increasing rate decreases; the thrust resultant ratio decreasesbecause of increasig thrust loss.