| Aircraft engine jet noise is one of the main source of aircraft noise,and reducing aircraft jet noise is conducive to improving the acoustic stealth performance and survivability of aircraft,and improving the overall performance index of aircraft.In this paper,the aerodynamic properties,flow field characteristics and jet noise characteristics of chevron-microjet nozzle,shock vector nozzle and double S bent nozzle are studied,and the change law of jet noise is obtained,and the corresponding suppression technology is adopted to reduce the jet noise,so as to achieve the purpose of noise reduction,which provides a reference for the future study of aircraft jet noise,and mainly obtains the following conclusions:(1)The large eddy simulation(LES)method and the Ffowcs Williams-Hawkings(FW-H)method were used to study the change law of jet noise of the tail nozzle,and the micro-nozzle was added on the basis of the chevron nozzle,in the investigation of mitigating jet noise by chevron-microjet nozzle integrating active and passive control technology,the jet state of high subsonic and supersonic flow regimes were examined,and the total sound pressure level of the chevron-microjet nozzle in the high subsonic jet was reduced by an average of 5d B compared with the sawtooth nozzle.The supersonic jet is reduced by an average of 3d B.In the study of jet noise of chevron nozzle by microjet with different mass flow ratios,the total sound pressure level of chevron-microjet nozzle in all directions is reduced by an average of 5d B,and the noise reduction effect of chevron-microjet nozzle on jet noise is better with a mass flow ratio of 0.098%,and the microjet effectively suppresses the jet noise of chevron nozzle.(2)Based on the mixed sound analogy method,in the investigation of the variation law of jet noise of shock vector nozzle and the influence of different changing factors on jet noise.In different mainstream drop pressure ratios,the thrust vector angle decreases with the increase of the main drop pressure ratio,the thrust coefficient increases with the increase of the mainstream drop pressure ratio,the total sound pressure level of the shock vector nozzle in the overexpansion state is small,and the total sound pressure level of the fully expanded and underexpanded states is similar.At the single and double gap secondary flow nozzle position,the total sound pressure level of the double gap is on average about 6d B higher than that of the single gap secondary flow,while the total sound pressure level of the single gap secondary flow near the nozzle outlet position is smaller.In different free-flow Ma,the total sound pressure level of 0.05 is about twice that of free-flow Ma of 1.00 and 1.50,while the total sound pressure level of free-flow Ma of 1.00 and 1.50 is similar.(3)Two cross-sectional design methods were used to model the double S bent nozzle,the total sound pressure level of the rectangular section and the super elliptical section double S bent nozzle in the upper vertical plane was larger than that of the lower vertical plane and water level,and the total sound pressure level of the rectangular section double S bent nozzle in the direction of 30°～120° was smaller.The particle swarm algorithm is used to optimize the BP neural network to optimize the structure of the double S bent nozzle,the optimized double S bend nozzle has good aerodynamic performance parameters,in the vertical plane,the optimized double S bend nozzle is about 2d B higher than the experimental double S bend nozzle in the-30°～50° direction,but the average reduction in other directions is about 13 d B,the optimized double S bend nozzle has a good suppression effect on the jet noise,which plays an important role in improving the maneuverability and acoustic stealth performance of the double S bent nozzle. |
