| With the strategy of becoming a maritime power and the policy of economic transformation and development,if China wants to overtake the ship in the curve,it must speed up the design transformation and improve the market competitiveness in the field of high-added value ship design.With the development of economy and society,people have higher and higher requirements for the cabin environment,and high-end ships also put forward extremely high requirements for the cabin noise control.The noise generated by the air distributor at the end of the air conditioning system will directly affect the comfort of people’s environment and become an important noise source of the ship cabin.Therefore,this thesis takes the marine air distributor of an air-conditioning company as the research object,aiming at the shortcomings of the air distributor,such as its static pressure speaker is generally small due to the limitation of cabin space,and optimizes the design of the air distributor to reduce aerodynamic noise.The main work of this study is as follows:(1)Based on the theory of fluid mechanics and aerodynamic noise,the characteristics of flow field and sound field of air distributor are obtained through numerical modeling and simulation analysis,and the distribution of static pressure,velocity vector and vorticity on the surface of air distributor is studied.The flow calculation results are imported into the professional acoustic software of Virtual.lab to explore the influence of flow on noise.According to the simulation results of sound field,the main position,frequency band,noise source type and broadband noise characteristics of air distributor are determined,which provides guidance for the optimal design of air distributor.(2)In that study of aerodynamic noise of air distributor.Firstly,through the arc design of the flow passage of the air distributor,the pressure pulsation and vorticity intensity of the air distributor are reduced,and the sound pressure level of the monitoring point is reduced,so that the transmission loss of the air distributor is increased by 2d B after the flow passage is improved,but the noise reduction level of the improved air distributor is reduced with the increase of the inlet flow rate.Then,the theoretical model of sound absorption structure(MPA)of micro-perforated plate is established.The influences of different parameters and seriesparallel connection modes on the sound absorption performance of MPA are explored.In order to apply MPA in the air distributor for broadband sound absorption with high sound absorption coefficient,two kinds of complex MPA absorbers(MPA-A and MPA-B)with finite thickness are designed and their parameters are preliminarily set.(3)In order to design an ideal MPA absorber in the frequency band(20-3000Hz)where aerodynamic noise is mainly generated,the parameters of MPA-A and MPA-B are optimized by grey wolf optimization algorithm,and the samples are processed according to the optimization results.Through experiments and simulation analysis,it is found that the average sound absorption coefficients of optimized MPA-A and MPA-B reach 0.86 and 0.83 respectively after 400 Hz.The bandwidth ratio of effective sound absorption coefficient above0.5 reaches 86% and 88% respectively,and the bandwidth ratio of high sound absorption coefficient above 0.8 reaches 68% and 63% respectively.The optimized MPA combination was embedded in the baffle of the air distributor,and the sound absorption effect of MPA-AB combination was the best.The average transmission loss after embedding the air distributor was 28.6d B,which was 10.7d B and 8.7d B higher than that of the prototype and the improved air distributor respectively.The average sound pressure level of the air outlet is 6d BA and2.5d BA lower than that of the prototype and the improved air distributor respectively,and the noise reduction effect is obvious,which provides a new idea for reducing the aerodynamic noise of the air distributor. |
PDF Full Text Request