Numerical Investigation On The Aerodynamic And Infrared Radiation Characteristics Of Spherical Convergent Flap Nozzles

Future fighter aircraft requirements vary widely , and include conventional takeoff and landing ,supersonic cruise capability , super maneuverability ,low signature ,and even short takeoff and vertical landing. To meet these anticipated requirements, advanced exhaust nozzle will require multifunction capabilities, including independent area control ,multi-axis vectoring ,reversing or blocking , and low signature . An investigation has been conducted on the Spherical Convergent Flap Nozzle .The effects of several geometric parameters on the aerodynamics and infrared characteristics of SCFN were investigated at nozzle pressure ratios up to approximately 7.012.In the aerodynamics characteristics section, firstly, nozzle throat aspect ratio ( wt ht) was varied between1.265 and 4.4. For the range of throat aspect ratios investigated , there is the double-peak phenomenon in the mach number contours . The length of temperature core region has decreased and vorticity has increased with increased nozzle throat aspect ratio. In the other hand , the decreases of the internal performance are observed, thrust ratio 0.6% and discharge coefficient 2.8%. Secondly, in the pitch and yaw vectoring situation , mach contours fields and static-pressure distributions are changed which are used to explain the thrust ratio and discharge coefficient. When the pitch angle is 20o, the thrust loss and discharge loss is 0.147% and 0.4%. When the yaw angle is 15o, the thrust loss and discharge loss is 0.1% and 0.15%.In the no vectoring situation , the infrared radiation from the ZOX symmetry has decreased with increased nozzle throat aspect ratio, the largest infrared radiation suppression is 34.9%. But, compared with the axisymmetric nozzle, the infrared radiation of the non-axisymmetric nozzle enhanced from 20o to 80o in the ZOY symmetry, the largest infrared radiation suppression is 42.1%. The pitch-vectoring caused infrared radiation suppression from the ZOY symmetry. The yaw-vectoring caused infrared radiation suppression from the ZOY and ZOX symmetry.