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Valve noise generated by the factors
Noise generated by valves, shredders and weaving machines is due to mechanical noise generated by mechanical vibration or frictional impact of solid parts. The following analysis of the valve noise generated by the factors. In the heating system can not do without pumps, pipes and valves, but these are again the source of noise generating facilities. Generally speaking, the noise source is mainly pipe noise, valve noise and liquid flow state, in other words, pressure and flow rate. The following specific noise source generation: First of all, to talk about more easily understood pipe. When the liquid flows through the pipeline, noise will be generated due to turbulence and pressure disturbance caused by friction excitation. Especially when the Reynolds number is greater than 2400, the turbulent flow with a large number of irregular tiny vortices can be said to be " Noisy "state. In particular, turbulent flow interacts with the passage of these impeding fluids when flowing through throttling or depressurisation valves, abrupt pipe sections or sharp bends. The sound power level (dB) as a function of flow rate can be expressed as As: â–³ Lw = 60lg, if the pipeline design can also produce cavitation noise. Let's talk about the relatively complex point of the valve. Valves with throttling or pressure limiting effects are the most influential sources of noise in liquid delivery pipelines. When the fluid flow velocity in the pipeline is sufficient, if the valve is partially closed, a large area choke will be formed at the inlet of the valve and the liquid flow rate will increase while the internal static pressure will decrease in the choke area. When the flow velocity is greater than or equal to the medium critical velocity, Below or equal to the evaporation pressure of the medium, bubbles are formed in the fluid. Bubbles with the liquid flow in the valve downstream of the choke area, the flow rate gradually decreased, the static pressure increases, the bubble has been crushed, causing fluid pressure fluctuations in the irregular, this special turbulence known as cavitation, resulting The noise is called cavitation noise. In the flow of large, high pressure pipeline, almost all of the throttle valve can produce cavitation noise, this cavitation noise down the pipe can be spread far, this random noise can stimulate the valve or pipe The inherent vibrations of the movable components in these components act on other adjacent components and are transmitted to the surface of the pipe, producing a tonal sound similar to the metal collision. Cavitation noise power and the flow rate of the seventh power or the eighth power proportional to the valve so to reduce the noise can be multi-stage cascade valve, the purpose is to gradually reduce the flow rate. As we often use the cut-off valve, the use of low into the high flow direction, so when the fluid flow through the valve chamber, it will be under the control valve flap (ie, choke area) to create low-pressure high-speed zone, resulting in bubbles. After the valve and then through the formation of high-pressure low-speed area, the bubble has been squeezed broken cavitation noise.