Numerical Study On The Noise Characteristics And Noise Control Methods Of A V-ball Control Valve

Valves are typical flow control components of nuclear power plant circuit,which can adjust the circulation area to change the circulation capacity.When the fluid flows over the valve,fluid flow become complex with large press dropping and sharp velocity increasing.Strong noise is subsequently produced under the effect of multiple mechanism couplin.The noise produced by valves can spread far away via piping system while strong noise is harmful to humans and pipeline structures,thus,it makes the noise reduction research of valve pipeline systems significant.In practical projects,the specific valve pipeline system has unique noise features due to its structure and material characteristics.In order to effectively control the noise of valve pipeline systems,measures need to be taken for characteristic noise,and thus the noise characteristics need to be measured and analyzed.The present research performs a numerical analysis of the noise features of a V-type stream regulation valve employing multi-step hybrid simulation method.The inner flow field features were analysied,the frequenfy and spatial distribution of free-field noise were discused,and the effectiveness of conventional single/composite sound insulation struectures were tested.Based on the results,the main findings are summarized below:(1)With small valve opening,inlet jet of the valve can reach sound velocity locally;under other opening conditions,fluid flow inside the valve can also reach over 0.4Ma with strong aerodynamic noise.(2)The free-field noise outside the pipeline maintains broadband characteristics and uniform spatial distribution in radial direction.While,in axial direction,the noise level of down stream is higher than that of upper stream.(3)Single layer sound insulation structures can reduce the valve noise,and its effect increases with the increase of the surface density of the sound insulation material.The noise reduction effect is apparent for high frequency noise,while it is poor when the noise frequency is below 1000 Hz.(4)The noise reduction performance of composite sound insulation structure at all frequencies is very prominent.The overall sound pressure level(overall sound pressure level,OSPL)outside the pipeline reduces greatly with the increasing of the surface density of sound insulation foam.When the thickness of foam is 10 cm,the overall sound pressure level of noise near the valve,upstream and downstream of the pipeline is reduced to less than 50 d B(A),and the noise is effectively suppressed.