Research On Thrust Vector Control Of Engine Nozzle

As a non-conventional flight control technology, thrust vector control technologychanges the direction of the jet of engine nozzle to generate lateral force by mechanicaldevice. The lateral force is unrelated to the heights and speeds of aircraft. The lateralforce can adjust aircraft’s attitude quickly, so it greatly improved the aircraft’smaneuverability and agility. Missile’s movement is easy affected by submarine’svelocity and waves and others factors. In this uncontrolled condition, missile cannotmeet the requirements of water-exit posture, thus affect its operational performance.However, the thrust vector control technology can effectively control the missile’sposture under the interference of ocean currents and waves and other external factors.So missile can be launched in the conditions of great changes of water depth andsubmarine in variable speed. Therefore, the study of the thrust vector control technologyto realize missile’s underwater moving posture adjustment was very important.In this paper, a spoiler-type thrust vector control device was discussed. First of all,the numerical simulation scheme was verified. Then, five different spaces betweenspoiler and nozzle exit were numerical simulated so as to estimate the impact of spaceson the thrust vector. The results show that thrust vector control device has maximumpower and minimum loss of thrust when the install space was0mm. On this basis, thecharacteristics of flow field and lateral force were studied when the water depth and theblockage ratio were different, respectively, in cases of single-phase and two-phase.The results show that: as spoiler is installed on the nozzle, the fluid’s static pressureof upstream of the spoiler rise. There is adverse pressure gradient along the nozzle wallwhich leads to the separation of the boundary layer. The nozzle expansion section elseappear an oblique shock that emanated from the separation point. Flow filed pressure ofthe zone behind oblique shock wave and boundary layer separation region are higherthan before. The pressure distribution of nozzle expansion section is uneven, whichresult in lateral force. The total lateral force of the engine nozzle is rose with theincrease of blockage ratio, but the engine nozzle is accompanied by congestionphenomenon and decline of the total lateral force as the blockage ratio increase to acertain degree. This indicates that spoiler-type thrust vector control device can producelateral force but the lateral force is limited. The changes of the total lateral force are mainly caused by the variations of the normal force of nozzle expansion section. Asoperating water depth increase, thrust and lateral force are declined. Under waterenvironment, oblique shock wave has changed and enters the nozzle expansion sectionwhen the water depth ascends to a certain degree, this is what eventually induces thereduction of normal force of nozzle expansion section. However, as operating waterdepth changes, normal force of nozzle expansion section remains unchanged whennozzle works in air environment. The results show that the diminution of the total lateralforce is mainly caused by the rise of normal force of spoiler when the fluid medium isair. Nevertheless, the descent of the normal force of spoiler’s profiles and nozzleexpansion section lead to reduction of the total lateral force when the fluid medium istwo-phase.