| With the development of underwater military equipment,pump-jet propulsion technology has gradually entered the research field of scholars at home and abroad,and has become a hot research topic of underwater propulsion technology in recent years.In order to adapt to the complex and changeable underwater environment and better meet the requirements of modern submarine propulsion performance and concealment,higher requirements are put forward for high-efficiency and low-noise of pump-jet propelsor.This paper takes the pump-jet propelled submarine under cruise condition of the whole watershed as the object,combines the methods of computational fluid dynamics and computational fluid acoustics to analyze the influence of main structural parameters of pump injection on its flow and acoustics characteristics.Firstly,a threedimensional model of the axial-flow pump jet propeller and submarine is established,and the flow field is calculated by the RNG k-ω and DES turbulence model.On this basis,rotating components,stationary components,flow around submarine and jet noise are calculated by the acoustic finite element method,and numerical results are compared with test data to verify the reliability of simulation results.The main work of this research is as follows:(1)Design of axial flow rear stator pump-jet propulsor.The streamline method is used to design the pump-jet propeller.Three-dimensional numerical modeling and three-dimensional solid print modeling of the pump jet propeller are carried out.The reliability of flow field calculation and acoustic calculation is verified by comparing the thrust data of the test and simulation and the noise data of the pump jet.(2)Research on the influence of cruise state on flow and acoustic characteristics of pump-jet propelled submarines.Analysis of flow and acoustic characteristics of pump-jet propelled submarine due to change of speed.The results shows that during the cruise,there is obvious blockage of the flow path in the local area of the pump jet,and the higher the cruise speed,the more serious the blockage is.The higher the speed,the larger the jet core area and the more stable the flow field.The impeller-induced noise is the main hydrodynamic noise source of the pump-jet propulsion submarine during its voyage.The spectrum characteristics of impeller noise are similar to those of pressure fluctuation in the flow field,and the blade frequency is the periodic fluctuation characteristic.The sound pressure level of noise caused by pressure fluctuation on the overflow wall presents obvious dipole symmetrical distribution in the meridian,while the noise of the quadrupole jet has certain uniformity in the sagittal arc,and there is a maximum value along the direction of jet flow in meridian.When the speed changes,the level of flow-induced noise increases with the increase of navigation speed on the whole,but the directional distribution characteristics are the same.(3)Effect of structural parameters on flow and acoustic characteristics of pumpjet propulsion submarines.The influence laws of impeller blade number,guide vane number,and nozzle inlet and outlet area ratio on flow and acoustic characteristics of pump jet propeller were analyzed.The results show that a smaller number of impeller blades,guide vanes,and a smaller ratio of nozzle inlet and outlet area are beneficial to improve the internal flow condition of pump injection.The total thrust of pump injection decreases with the increase of vanes of an impeller or guide vanes,increases with the increase of area ratio of nozzle inlet and outlet,and the open water efficiency decreases with the increase of three structural parameters.The increase in the vane number of impellers leads to an overall upward trend of all kinds of flow noises,while the increase in the vane number of guide vanes and the ratio of nozzle inlet and outlet area has different effects on different noises.The directivity distribution of all kinds of flow noise is the same when the structure parameters change. |
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