Research On The Influence Of Orifice Geometry Characteristics On The Noise Reduction Performance Of Pressure Regulating Branch In Natural Gas Field Stations

Natural gas pipelines are often in large flow and large pressure drop conditions,and the pressure regulating branch pipelines will produce noise.Noise will not only cause the vibration of pipelines and components to endanger the internal structure of pipelines,but also pollute the environment and endanger the health of staff in the workplace.Therefore,it is of great research value and engineering significance to design the noise control scheme of the pressure regulating branch pipeline.In this paper,the noise problem of the pressure regulating branch of a natural gas station is taken as the research background.Combined with the actual operating conditions of a pressure regulating branch of the station,based on the geometric characteristics of the pipeline and its internal components,the initial model of the pipeline and the comparison group model with different orifice plates are established.Large eddy simulation and FW-H acoustic models are used to simulate and analyze the aerodynamic noise of the subsonic porous jet from the outlet of the flow valve to the diffusion section of the pipeline.The initial model of the pipeline is numerically calculated.The flow area of the orifice plate is determined by the mainstream area at the outlet of the flow valve,and the initial orifice plate of the aperture comparison group is designed.Through the single factor control variable method,the geometric dimensions of the aperture,thickness and hole spacing of the orifice plate are designed and optimized,and the influence of the geometric characteristics of the orifice plate on the sound field of the flow field is analyzed.The main conclusions are as follows:(1)The decrease of the aperture of the orifice plate will increase the flow rate of the natural gas flowing through the orifice plate.The large flow rate will easily cause the vibration of the orifice plate position and increase the acoustic power level of the dipole on the wall surface of the orifice plate.At the same time,due to the decrease of the aperture,the gas in the tube is compressed after flowing through the orifice plate,resulting in an increase in the inlet pressure.When the number of orifices is greater than 1,the ’Coanda Effect’ is easy to occur due to the small initial hole spacing.In the case of a certain flow area,the decrease of the aperture means that the energy of the single ’small jet’ flowing through the orifice is small and the flow velocity is large,which accelerates the confluence of multiple ’small jets’.The energy of the converged ’large jet’ boundary is reduced,and the sound pressure level on the downstream monitoring surface is significantly suppressed.The sound pressure level of the orifice plate with 9mm aperture is reduced by 4.84 dB on the downstream far-field monitoring surface.(2)For the comparison group of 9mm aperture orifice plate,the increase of orifice plate thickness is beneficial to make the flow field tend to be stable;for the 14.4mm aperture orifice plate comparison group,when the thickness of the orifice plate increases to 20mm,it can have a significant noise suppression effect.For the comparison group with 20 mm aperture,the change of the thickness of the orifice plate cannot play an ideal role in noise control.For the perforated plate comparison group with smaller aperture,the increase of the thickness of the perforated plate is beneficial to reduce the noise intensity in the middle and low frequency bands,and also to stabilize the noise change in the high frequency band.When the aperture is 9mm and the thickness is 20mm,the sound pressure level on the downstream far-field noise detection surface is reduced by 2.55 dB.The change of the thickness of the orifice plate is beneficial to the noise control of the position near the installation orifice plate,but it is not conducive to the original noise control.In general,the change of the thickness of the orifice plate under the working condition of this paper has little effect on the noise of natural gas in the pipe.(3)The change of hole spacing will play an important role in the control of pipeline noise.Under the condition of ensuring the same flow area,the calculation results of the hole spacing comparison group of the three aperture thickness combinations show that with the increase of the hole spacing,the natural gas flows through the orifice plate.Multiple ’ small jets ’ converge farther downstream of the pipeline,and the flow rate of the single ’ large jet ’ is lower after the confluence.This process consumes turbulent energy,reduces the disturbance between gases,reduces the noise intensity in the middle and low frequency bands,but has no obvious effect on the noise in the high frequency band and the expansion of the hole distance.Due to the delayed convergence of multiple jets,the flow field downstream of the orifice plate is adjusted,and the sound power level of the dipole source near the center of the orifice plate is lower than that of the outer holes.When the aperture is 9mm and the thickness is 20mm,the sound pressure level on the downstream far-field noise detection surface is reduced by 12.28dB.In general,the increase of hole spacing has the best suppression effect on pipeline noise.