Three bearing swivel nozzle vector deflection law study and fluid field calculation

Based on the special design requirements for the three bearing swivel nozzle (3BSN) applied to short takeoff and vertical landing fighter, the 3BSN profiling method and motion law research were developed by geometry constraint condition. The three segment rotation law of time controlled linear and nonlinear regulations for the nozzle is deduced and studied. According to the size of a small turbojet engine, a scaled 3BSN is designed by the development profiling method and the nozzle segment rotation law, the nozzle flow field characteristics is calculated and analyzed by CFD numerical simulation technology. By means of the CFD numerical simulation technology, the nozzle flow characteristic in three dimensions at the different vector angle and the aerodynamic performance at different nozzle pressure ratio are obtained. The results show that adopting the nonlinear control law for the nozzle vector angle can reduce the nonlinear control variables and overcome the nozzle design difficulty and control complexity on the premise of ensuring the nozzle's mobility. The thrust coefficient of the 3BSN designed based on a small turbojet engine is lower than the ideal nozzle at 0° state and higher than that at 90° state, the thrust coefficient of the nozzle at 0° state is higher about 1% than at 90° state when the nozzle is working at the maximum pressure ratio on the ground.