| As the terminal device of variable air volume of marine air conditioner,the air distributor regulates the air supply volume by changing the internal air circulation section,and plays the role of terminal dissipation in the air conditioning pipeline.However,the main problems of marine air distributor in China are as follows: first,the structure design of the flow channel is unreasonable,the internal resistance coefficient of the box increases,the dynamic pressure loss is large,and the jet range is small,which results in uneven air supply in the cabin and large aerodynamic noise;second,the traditional VAV air conditioning system adopts the unified air supply or manual control of the air distributor,which can not be adjusted in real time with the actual temperature and air volume demand in the cabin At present,the whole modularization of the variable air volume controller of the air distributor in China,the strong coupling relationship between the parameters of the control loop system,the poor flexibility,stability and control accuracy of the system;fourthly,the existing high-end air distributor products are mainly monopolized by foreign brands,the domestic air distributor is still in the stage of introduction and imitation,and the design and manufacturing methods are not mature enough to adapt to the current situation Today,the development of network and information society.Therefore,this paper mainly uses fluent simulation software,CFD numerical simulation analysis and experimental method to study the resistance,aerodynamic noise and VAV regulation performance of the air distributor.The main research contents are as follows:(1)Optimization design and experimental verification of low energy consumption quiet channel structure.The range analysis method is used to optimize and predict the combination of structural parameters.The results of resistance performance test and error transfer analysis show that the resistance coefficient of the improved air distributor is reduced by 20.7% under rated condition.Among the three structural parameters,h has the most significant influence on the resistance coefficient,d is the second,and D has the least.(2)Experiment and Simulation of aerodynamic noise.Through the noise experiment,the acoustic performance of the air distributor is studied.The experimental results show that under the same static pressure,the noise of the air distributor increases with the increase of air volume.Under the rated working condition,the total sound pressure level of each measuring point of the original air distributor is 56.3 d B(A),and after improvement,the total sound pressure level of each measuring point is 38.6 d B(A).Under various working conditions,the sound pressure level at the outlet of the improved air distributor is lower than 55 d B(A),which meets the requirements of IMO ship noise standard.The distribution of sound power level,pressure fluctuation and noise contribution on the surface of the air distributor are analyzed by using broadband noise and FW-H model.The simulation results show that the peak frequency of the sound pressure level at the measuring point of the improved air distributor changes from the original medium high frequency to the low frequency which is insensitive to the human ear.The noise concentration point in the air distributor basically coincides with the vortex in the flow field.The internal fluctuating pressure of the improved air distributor is smaller and the flow field is more stable.After optimization,the A-weighted sound pressure level characteristics of the air distributor are obviously improved.(3)Design of predictive model of valve opening control based on neural network.In this paper,the original training data of various working conditions of the air distributor are collected through the VAV debugging experiment,and a prediction model based on BP neural network is established by using MATLAB neural network toolbox function.With the help of the self-learning ability and approximation ability of neural network,the optimal solution of VAV control system valve opening is obtained by inputting the set air volume and static pressure,without any complexity The parameters identification and integral differential correction of the valve actuator can avoid frequent action,which is simple,convenient and fast.The neural network and the least square fitting formula are used to compare the test results of the valve actuator’s forward and reverse stroke.The results show that the error between the predicted results and the expected results is less than 5%,which is in good agreement with the calculation results of the fitting formula.The numerical simulation calculation method of resistance coefficient and aerodynamic noise and the research results of VAV control system based on neural network can provide reference for the optimal design of VAV air distributor for ships,which is of great significance to further improve the performance of air distributor and improve the living comfort of cabins. |
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