Research On The Underwater Working Performance Of Scarfed Nozzle

Traditional supercavitating vehicles rely on solid rocket motors to provide the thrust required for navigation.The engine nozzle is installed in the end of the body of the vehicles,and this layout easily leads to instability of the vehicles.By using scarfed nozzle to advance engine of the vehicles,the stability and steering maneuverability of the vehicles can be greatly improved.In order to study the performance of the scarfed nozzle,and analyze the effect of different factors on the underwater performance of the scarfed nozzle.This paper used the numerical simulation method,combined with the Mixture multiphase flow model,the RNG k-εturbulence model and the Singhal et al.cavitation model.By using the above method,the numerical calculation of the underwater flow field of supercavitating torpedoes with scarfed nozzles is completed.The flow field states of the scarfed nozzle in air flow field and in underwater flow field are calculated.Besides,flow state of scarfed nozzle with different nozzle geometric parameters,flow state of using the secondary gas nozzle jet propulsions system,flow state of scarfed nozzle with different shapes of navigation bodies,and flow state of scarfed nozzle working at different depths are also calculated.By analyzing the above calculation results,the following conclusions are obtained:Compared with the flow state in air,the liquid water prevents high-temperature gas from continuing to expand when scarfed nozzle working underwater.This phenomenon causes the compression wave to move forward and strengthen,and effective thrust F_eff drops.When scarfed nozzle working underwater,the increase of bevel angle?and expansion half angleαwill result in a reduction in the effective thrust of the nozzle.Increase in the throat radius _tR will cause the effective thrust to increase first and then decrease.Increase in the inlet pressure _cP increases the effective thrust.The addition of the gas secondary injection causes the appearance of lateral forces.When two nozzles useing the gas secondary jet system,lateral force is further increased by23.7%.Appropriate optimization of the vehicle shape and reduction of the depth can improve the thrust performance of the nozzle and reduce the resistance of the vehicle.