Compressible Turbulent Flow And Aerodynamic Noise Analysis On Multi-Stage High Pressure Reducing Valve

As the key component of such energy-saving projects as cogeneration,heating and steam supply,high pressure reducing valve is known as the "throat" of industrial systems.With the development of major national projects,complex working conditions such as high pressure,high temperature and high flow rate are constantly emerging.Internal flow of the high pressure reducing valve will become very complicated,and the quasi-structure gathers near the throttling element,resulting in unstable flow in the nearby regions.This in turn induces aerodynamic noise,which jeopardizes the health of operator and normal operation of devices.Traditional domestic high pressure reducing valve s have been difficult to meet the requirements and can only rely on imports.In the event of a ZTE "core break" incident,China's major energy system projects will face a full-blown danger,posing a major threat to national security,social stability and economic development.Therefore,in order to avoid the phenomenon of “card neck” reappearing abroad,it is urgent to carry out independent development,flow and aerodynamic noise analysis of high pressure reducing valves.This paper is supported by the Special Major Scientific Project from Science and Technology Department of Zhejiang Province through the No.2012C11018-1,the Natural Science Fund Key Project of Zhejiang Province through the No.LZ17E050002,and the Key Innovation Team of Zhejiang Province through the No.2011R50005,to conduct analysis on the compressible turbulent flow and aerodynamic noise of multi-stage high pressure reducing valve(MSHPRV)through theoretical,numerical and experimental methods.The main research contents and results are as follows:To begin with,the structure design of MSHPRV suitable for complex working conditions was carried out,and the multi-stage pressure reducing and throttling principle was analyzed.Numerical simulation was conducted on the compressible turbulent flow of MSHPRV,and characteristics of compressible flow field were analyzed.The compressible flow experiment was carried out to analyze the flow characteristics and verify the accuracy of numerical method.The study of compressible flow parameterization was carried out to investigate the influence of different structural parameters on the compressible turbulent flow field.Results show that the designed structure can better control the steam energy and the expansion process of steam,and realize multi-stage pressure reducing process.Steam pressure,velocity,temperature and energy consumption are all abrupt in the throttling components of multi-stage sleeves,porous valve core and perforated plate.The flow characteristics of MSHPRV are linear flow characteristics.The experiment proves that the numerical simulation method is adopted.The structural parameters have a great influence on the subsonic coverage area,noise control performance,turbulent dissipation performance and enthalpy loss distribution.Secondly,the aerodynamic noise characteristics of quadrupole source and dipole source inside the MSHPRV were separately analyzed by the sound source independent method,and the contribution of two sources was compared and analyzed to determin the dominant one.The effect of valve openings on aerodynamic noise inside MSHPRV was analyzed.The results show that with the increase of frequency,the maximum sound pressure,sound pressure of each monitoring point,sound intensity,sound power level and noise distribution range are first reduced and then increased with quadrupole source.However,the acoustic parameters of the dipole source are gradually reduced.Aerodynamic noise inside MSHPRV exhibits continuous broadband characteristics dominated by intermedia te frequency and high frequency.At the same frequency point,the maximum sound pressure of the quadrupole source is larger than the dipole source,and the quadrupole source is the dominant noise source inside MSHPRV.With the increase of valve opening,the maximum sound pressure,the sound pressure at the monitoring point,the maximum sound intensity,and the noise distribution area of both quadrupole source and dipole source are gradually increased.However,the increase in sound pressure caused by the dipole source is higher than that of the quadrupole source.Thirdly,the large eddy simulation method was used to study the instantaneous turbulence characteristics of MSHPRV.Visualize the vorticity distribution inside MSHPRV,and using Q criterion to effectively capture the internal vortex structure and its evolution law in MSHPRV.The relationship between vortex motion and sound pressure was analyzed to explore the mechanism of vortex induced noise.The results show that with the advancement of time,the pressure reducing gradient and velocity increasing gradient of the multi-stage sleeves,porous valve core and perforated plate are gradually increased,and the maximum sub-grid turbulent dissipation rate of the symmetry plane is gradually increased.At the initial moment,the vortex exhibits a radial periodic oscillation.As time progresses,it exhibits strong three-dimensional characteristics.As the flow progresses,the axial,circumferential and radial vapor vortices collide and dissipate.The quasi-order structure in MSHPRV is mainly concentrated in the vicinity of the throttling elements such as the multi-stage sleeves,porous valve core and the perforated plate,resulting in unstable flow in the nearby watershed.As time progresses,the quasi-order structure gradually expands from the throttling element to the entire flow field,and the in-flow vortex ring grows in the axial direction.Here,a distinct vortex zone is visible at the throttling element,wherein the vortex ring is connected by a rib vortex.The maximum sound pressure of aerodynamic noise inside MSHPRV exhibits a linear correlation with the maximum instantaneous total vorticity.Finally,the active noise reduction technology controlled by sound source was carried out.Here,the structural parameters of perforated plate were optimized to optimize the vortex distribution.Numerical models of perforated plate with different stages,thickness,aperture and arc chamfer was established,and the effecs of structural parameters on the aerodynamic noise inside MSHPRV were analyzed.A mathematical model of the structural parameters of perforated plate and maximum sound pressure was established.The results show that with the increase of the perforated plate stages and circular chamfer,the maximum sound pressure,maximum sound intensity,aerodynamic noise affected area and noise radiat ion range are gradually reduced.However,the increase in the thickness and aperture of the perforated plate results in more intense noise radiation.Moreover,within the range of ±10% error of the fitting curve between the maximum sound pressure and frequency points,the data points basically fall within this interval.The mathematical relationship between the structural parameters of perforated plate and the maximum sound pressure inside MSHPRV can provide a theoretical reference for the actual aerodynamic noise research.