| When the natural gas gathering station is diverted,the flow state of the medium in the pipe is prone to abrupt change,and then aerodynamic noise is formed.When the field station is in normal operation,the noise exceeds the standard mainly from the air pipe,elbow,tees,valves and other resistance components.To solve this problem,using FW-H sound analogy theory and large eddy simulation as the theoretical basis,using pro/E modeling software to create three-dimensional models of continuous elbows,manifolds,and tees,using ANSYS Fluent finite element analysis software Numerical Simulation.Combined with the results of numerical simulation,an expansion chamber muffler was designed and reasonable and effective noise prevention and control measures were proposed.First of all,the static simulation of the flow field in the station’s resistance components(continuous elbow,manifold,and tee)was performed.Based on the simulation results,the flow field structure was obtained,and the noise core area and the main noise area of each component were determined.The monitoring points are set at the core of the noise and the LES model is used for non-stationary simulation.The sound pressure level of continuous elbow flow noise in the station increases with the angle of the elbow,reaching a maximum of 93.6 dB when the angle is 90°,exceeding the corresponding standard upper limit value of 85 dB in China;airflow noise along the elbow When the radius of curvature decreases,when R>2D,the noise in the continuous elbow pipe section is lower than the national standard;the air flow noise increases with the increase of the pipe speed,and the growth rate increases with the inlet flow rate first and then decreases.For every 2m/s increase in speed,the sound pressure level at the elbow pipe wall is increased by 1～3dB.Therefore,reasonable adjustment of the elbow angle,bending radius,and flow velocity is an important factor to control the noise in the pipe section.By changing the number of outlet pipes of the manifold and the different positions of the intake pipe,the three-dimensional simulation analysis of the flow field in the manifold shows that:With the increase in the number of outlet pipe outlets,the noise within the outlet pipe is reduced.One inlet,one outlet,one inlet and two outlet manifolds,inlet and outlet piping are staggered,and the sound pressure level in the piping is greater than that of the opposite connection.When the inlet and outlet manifolds of one inlet and three outlets are connected correspondingly to the middle outlet piping,the sound pressure level is minimum.By changing the pipe diameter and connection method of the three links,the three-dimensional simulation analysis is performed on the flow field in the three-way pipe,in which the U-type three-way pipe segment has the highest sound pressure level,and the full arc three-way pipe segment has the lowest sound pressure level and its sound pressure level.The maximum value is less than 8%of U-type three-way,so it can be considered widely used.Selecting the header section with excessive noise,compare and select the taper muffler to calculate and determine the basic size of the taper muffler:the total length of the muffler is 1000mm,the inlet and outlet diameter is 200mm,the expansion cavity diameter is 600mm,and the expansion cavity length is long.600mm.A muffler was installed at the inlet pipe of the manifold and the noise reduction effect was analyzed.The simulation results showed that the muffler had good noise attenuation effect in the middle and low frequency bands.The noise reduction amount at each monitoring point was between 0 and 40 dB,and the highest was 37.5.dB,average noise reduction 15.2dB. |
