By changing the throttling area, the pressure reducing valve changes the flow rate and the kinetic energy of the fluid, resulting in different pressure losses, so as to achieve the purpose of reducing pressure. So why does the pressure reducing valve make noise? It is mainly summarized into three aspects:
1. aerodynamic noise.
2. Fluid dynamics noise.
3.Mechanical vibration noise of pressure reducing valve.
When a compressible fluid such as steam passes through the pressure reducing part in the pressure reducing valve, the noise generated by the conversion of the mechanical energy of the fluid into sound energy is called aerodynamic noise. This kind of noise is the most troublesome noise to deal with in the noise of the pressure reducing valve. The reasons for this noise are divided into two cases, one is caused by fluid turbulence, and the other is caused by shock waves caused by the fluid reaching a critical flow rate. Aerodynamic noise cannot be completely eliminated because the fluid turbulence caused by the pressure reducing valve is unavoidable.
fluid dynamic noise
The fluid dynamic noise is generated by the turbulent flow and eddy current after the fluid passes through the pressure reducing port of the pressure reducing valve. Or the noise generated by the interaction of the inner surface of the pipeline, its frequency and noise level are relatively low, generally does not constitute a noise problem. ② Cavitation noise, that is, during the decompression process of the pressure reducing valve, when the fluid flow rate reaches a certain value, the fluid (liquid) begins to vaporize, and when the pressure of the bubbles in the liquid reaches a certain value, it will explode. When the bubble explodes, a high pressure and shock wave are generated locally. The pressure at the moment of the impact can reach 196 MPa, but the pressure decays sharply away from the center of the explosion. This shock wave is a major contributor to pressure reducing valve cavitation and noise. The measure to reduce mechanical vibration and noise is that when designing the pressure reducing valve, the pressure reducing value of the pressure reducing valve must be controlled below the critical value, and preferably below the initial Δp, because the actual pressure reducing value of the pressure reducing valve reaches At the initial value of Δp, the liquid begins to cavitate, and the noise will increase sharply.In addition, pay attention to the flow direction of the fluid medium relative to the valve disc
Mechanical vibration noise of pressure reducing valve
Noise generated by mechanical vibration The parts of the pressure reducing valve will generate mechanical vibration when the fluid flows, and the mechanical vibration can be divided into two forms: ① Low-frequency vibration. This kind of vibration is caused by the jet and pulsation of the medium. The reasons for this are that the flow velocity at the valve outlet is too fast, the pipeline arrangement is unreasonable, and the rigidity of the valve moving parts is insufficient. ② High frequency vibration. This kind of vibration will cause resonance when the natural frequency of the valve is consistent with the excitation frequency caused by the flow of the medium. It is generated by the pressure reducing valve within a certain pressure reduction range, and once the conditions change slightly, the noise will change greatly. . This kind of mechanical vibration noise has nothing to do with the flow speed of the medium, and is mostly caused by the unreasonable design of the pressure reducing valve itself. The measures to reduce mechanical vibration and noise are to reasonably design the clearance between the pressure reducing valve bushing and the valve stem, the machining accuracy, the natural frequency of the valve and the rigidity of the moving parts, and the correct selection of materials.
The noise analysis of the above three aspects is the whole content of why the pressure reducing valve generates noise. We can draw a conclusion from the above content that the noise generated by the pressure reducing valve is generally related to its own manufacturing process.and designclosely related.