| Valves can be used to regulate fluid flow and pressure,and strong noise is prone to occur in the throttling process.Strong noise not only damages human health,but also causes abnormal vibration of structural components in pipeline system.Therefore,it is of great research value and engineering significance to analyze the relationship between valve structure and flow field inside and outside the tube.In this paper,the main geometric characteristics of the branch flow control valve are extracted based on the noise problem of the pressure regulating branch of a natural gas station.The geometric model of the porous injection and the geometric model of the porous hedge injection valve body are established.The large eddy simulation and FW-H acoustic model are used to simulate and analyze the aerodynamic noise in the characteristic fluid domain of the transonic porous injection.The influence of the hole type,hole diameter and hole center spacing on the internal flow field and the internal and external acoustic field characteristics is analyzed.The measures to suppress the aerodynamic noise by adding diversion components and reducing the hole diameter in the outlet pipeline are proposed.The main conclusions are as follows :2(1)The internal flow field and internal and external sound field of porous jet injection flow in open fluid environment are simulated and analyzed.The results show that there is a more obvious Coanda effect between the jets with small center spacing,which makes the jet structure more stable after confluence,and the length of the core section of the confluence jet is positively correlated with the aperture.The distribution of strong turbulent kinetic energy is consistent with the distribution of strong quadrupole sound source,and the strong turbulent state in the turbulent boundary layer of hole wall and the boundary region of jet flow of hole group is the main physical source of quadrupole sound source.Reducing the aperture and increasing the center spacing are conducive to reducing the volume of the strong turbulent region at the jet boundary after the convergence.(2)Compared with the circular hole,the thickness of turbulent boundary layer in the square hole is not uniformly distributed in the circumferential direction,and the high turbulent kinetic energy region of the jet boundary after confluence is reduced.The power of quadrupole sound source is reduced,and the total sound pressure level at the far-field noise monitoring point is reduced.When the center spacing is small,the total sound pressure level at the far-field noise monitoring point can be reduced by more than 12 d B,but when the center spacing is greater than twice the aperture,the far-field noise suppression effect is not obvious.(3)In the three-dimensional valve body with high-speed porous jet impinging injection as the main feature,the flow field characteristics and sound field characteristics of the three-dimensional valve body model with four different apertures and outlet pipes are compared and analyzed.The results show that multiple large-scale turbulent vortexes generated by the jet impinging jet of each hole group in the outflow pipeline are the main source of noise.The vortex scale is positively correlated with the length of the jet core section related to the same aperture.The interaction position of each vortex boundary is the main strong-power quadrupole sound source area.The evolution process of the central vortex structure time-space unsteady,and the evolution period is at the millisecond level.(4)Reducing the hole diameter and adding a guide component at the outlet of the hole group can suppress the generation of large-scale vortex in the outlet pipeline and achieve the effect of noise suppression.Reducing the aperture can reduce the length of the jet core section,weaken the jet injection hedge intensity between symmetrical hole groups,reduce the turbulent vortex scale and turbulence intensity in the outlet pipeline,and have an obvious inhibitory effect on the axial noise and circumferential noise.A-weighted sound pressure level at the monitoring point of the external sound field can be reduced by 6 d B(A)to 14 d B(A).The addition of guide components can reduce the tangential velocity of gas,reduce the turbulent vortex scale in the outlet area of the hole group,and guide the flow along the axial direction.The results of sound field monitoring show that the addition of deflector can transfer the strong air flow noise to the high-frequency direction and suppress the noise in the downstream area of the valve body.A-weighted sound pressure level at the downstream monitoring point can be reduced by 6 dB(A). |
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