Coupling Calculations Of Flow-Induced Noise For Control Valve Under Internal Turbulent Flow

Control valves, as important components of piping system, are the principle part of noise sources of piping system noise. The fluid dynamic noise (flow induced vibration noise) of control valve produced by internal turbulent flow is the major parts of the control valve noise. Related studies show that the noise of control valvs near the large piping system was up to 100 decibels. Such great noise is probable to have great potential hazards:on the one hand, it was harmful to the staff's physical and mental health in this work environment; On the other hand, the noise, inevitably accompanied by severe vibration, could exacerbate the vibration of its adjacent piping, taking the industrial production and personnel security at risk. In 1997, China promulgated the "law of the People's Republic of China on the Prevention and Control of Environmental Noise Pollution" to protect and improve the living environment. Therefore, the numerical calculation of the noise generated by control valve and puts forward effective noise reduction measures is a very important and meaningful topic.So this dissertation set the flow-rate control valve of thermal generator as the research object, calculated the external noise under internal turbulence from interior to exterior. The calculation of the valve's external noise take into account the dual mechanism of flow-induced vibration noise that acoustic wall pressure fluctuation (AWPF) and turbulent wall pressure fluctuation (TWPF), and analyzed their effects in different frequency. The analysis results show that the external noise is combination of two kinds of noise generating mechanism, in the low frequency 800 Hz, TWPF play a leading role and above 800 Hz, AWPF play a leading role, and the external noise is close to the larger one.Then, comparing the internal and external monitor point's SPL spectrum curve, draw a conclusion that:the large scale vortex existing in the internal turbulence is the main sources of external noise. So it is an effective way to reduce the valve external noise to break the large scale vortex. According to the project of NSFC (The research of subsonic nozzle jet noise reducing scheme based on porous structure, the scheme to set a porous structure at valve cavity to break the large scale vortex to reduce the noise was adopted. Finally, this dissertation confirmed the feasibility of the noise reduction scheme by contrasted internal flow field, the internal source, internal acoustic field and external sound field of the structure-modified valve and prototype.