Study On Noise Prediction And Control Methods Of Typical Ventilation Pipes Of The Cruise Ship

The cruise ship has an extremely complicated pipe system,which brings about the problem of noise that cannot be ignored while working normally.Most of the pipes are centrally arranged in the power areas such as the engine room,while the ventilation pipes of air-conditioning are directly connected to the living quarters far away from power areas.The size of pipes cannot be too large under the strict limitations of weight and size,and the flow velocity is relatively high in order to complete the function of ventilation and adjusting temperature.The noise generated by the ventilation pipes of air-conditioning has become the main factor affecting the acoustic comfort of the living quarters.In addition,our country is developing cruise economy energetically,and improving the acoustic comfort of cruise ship can not only improve the living environment of passengers and crews,but also promote the development of our economy.In this paper,the numerical prediction and control methods of noise generated by ventilation pipes are researched by combining the finite element software(MSC.Patran/Nastran),computational fluid dynamics software(FLUENT)and acoustic calculation software(Virtual.Lab)on the basis of acoustic boundary element method.The main work is as follows:(1)The theory about the numerical prediction method of noise generated by the ventilation pipes is introduced.According to the theoretical analysis,the numerical solution technique is settled.The geometric models of typical syphon and T-shaped pipe are established,and the mesh is generated,then the steady calculation is performed.When parameters meet the convergence index,and the last step of the steady calculation is set as the initial value of the unsteady calculation,then the results of time domain pulsation can be got,and set it as the sound source.The acoustic field of pipe orifice and monitoring point are calculated on the basis of acoustic boundary element method.The results show that the frequency characteristics of noise generated by ventilation pipes are broadband,and the SPL of low frequency is relatively high.The simulation results are compared with the experimental data,and the reliability of numerical computation method is verified.(2)The noise variation laws of pipe orifice are respectively discussed under series of inflow velocity,bending angle,cross-sectional shape and cross-sectional dimensions.The results show that the frequency characteristics of SPL are similar under different inflow velocities,and the peak frequencies of SPL are almost the same for different inflow velocities.But the inflow velocity has a great influence on the noise level of pipe orifice,and the SPL of monitoring point of pipe orifice is almost increased linearly as inflow velocity increases in the calculation of this paper.The noise level is gradually decreased as the bending angle increases,especially the reduction of SPL in lower frequency is obvious.The noise level of circular section pipe is lower than square and rectangular section pipe.When the ventilation quantity is certain,the noise level is gradually decreased as cross-sectional dimensions increase,especially the reduction of SPL in higher frequency is obvious.(3)The noise reduction effect of ventilation pipe is calculated and analyzed by taking expanded pipe and installing guide vane.The effects of the expansion angle of expanded pipe and the position of guide vane on noise reduction are discussed.The results show that the method of taking expanded pipe can reduce the noise of ventilation pipes,and the effect of noise reduction is better in higher frequency.The effect of noise reduction is better when the expansion angle of expanded pipe is equal to 90°,and it is easier to be processed.The method of installing guide vane can reduce the noise of ventilation pipes obviously,and the SPL decreases in the whole calculation frequency range.In addition,the noise reduction effect of the guide vane in the front part of elbow is better than in the second half of elbow.In this paper,the noise characteristics and the control methods of typical ventilation pipes are researched.This provides guidance for controlling the noise of ventilation pipes of cruise ship,and this has great significance to improve the acoustic comfort of cabin.