| With the increasingly fierce competition for marine resources, Waterjet propulsion iswidely used to underwater vehicles because of its huge development potential, its noise leveldetermines the concealment of the vehicles. Jet noise is the main factor of the waterjetpropellers noise. The research of waterjet and waterjet propulsion is widely carried out, butflew involved in the field of waterjet noise. It is accomplished in this thesis that studying onthe characteristics of waterjet noise with an axial piston valve type pump source.By theoretical analysis on two main sources of waterjet noise, the turbulence radiatednoise and the cavitation noise, it is made out how the velocity, working pressure, pressurepulsation and nozzle geometry affect on the waterjet noise. A conclusion is obtained thatreducing the pressure pulsation and improving the nozzle geometry structure will decrease thenoise of water jet.Considering the pressure fluctuation characteristics of piston pump, as wall as thevariability of the waterjet system working condition, this thesis designs a model ofaccumulator group to reduce pressure pulsation. In accumulator group, the designing ofaccumulators charge pressure is accomplished.According to the characteristics of waterjet noise, simulation models of different nozzlesare built, which are used to investigate the flow field and turbulence kinetic energy of thedifferent nozzles. By the comparison analysis of the cavitation ratio in different nozzles, aconclusion is obtained that the streamlined structure can effectively prevent the occurrence ofcavitation, thus reduce the cavitation noise.Finally, experiment on the noise of the cylindrical nozzle and the conical nozzle underdifferent conditions has been accomplished. The testing results show that the noise of conicalnozzle is significantly lower than the cylindrical nozzle in the same inlet condition. And usingthe accumulator to absorb the pressure pulsation can significantly reduce the noise. |
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