How to understand the silencer of Roots blower correctly and what is the mechanism of noise generation of Roots blower? Roots blower without muffler, there is a certain risk, adding muffler is a necessary measure, and if the blower inlet is directly connected to the pipeline, then there is no need to install an imported muffler. We call it “Roots blower silencer”.
The support of the muffler shell of Roots blower and the connecting parts with the shell shall have enough rigidity and strength, the structural design shall be reasonable, and it shall be able to bear various additional forces such as exhaust reaction force, thermal expansion thrust, torque and vibration force caused by high-speed steam flow with impurities. The body shall be able to withstand various impacts caused by temperature and pressure alternation. The integrity of the whole pipe should be maintained after several times of quick opening.
The noise reduction index, safety performance and service life of Roots blower silencer are much better than those of similar products on the market through optimization design according to the principle of noise reduction by small hole depressurization injection. It can better meet the requirements of various boilers and pressures of low pressure, medium pressure, sub high pressure, high pressure, ultra-high pressure, subcritical and other parameters in electric power, metallurgy, petroleum, chemical industry, textile, papermaking, food and other industries It is necessary to reduce the noise of exhaust steam (gas) in pressure vessel pipeline and exhaust steam (gas) of safety valve and release valve.
The main material of Roots blower silencer is made of ultra-fine sound-absorbing glass wool with good sound absorption frequency performance and high temperature resistance, as well as the combination of foreign special treated silencing filter material and other materials.
The noise can be reduced by more than 30 dB by muffler, which can achieve the same effect as imported products. With bypass safety valve, the opening pressure is 2.0 ~ 2.2kgfm2. When the bypass safety valve is opened, the material of the silencing filter must be replaced before it can be used again. This series of products are suitable for 1.0Mpa working pressure dryer.
Noise source of Roots blower:
Roots blower contains a variety of noise sources, and the main parts of noise radiation are:
1) Aerodynamic noise radiated by inlet and outlet;
2) Mechanical noise radiated by casing, motor, bearing, etc;
3) The solid sound radiated by the vibration of the root. Among these local noises, the aerodynamic noise radiated from the inlet and outlet is the strongest, and other noises such as mechanical noise and electromagnetic noise are unnecessary under the premise of normal operation of the blower. According to the spectrum analysis of Roots blower noise, it is characterized by low frequency and wide band. The aerodynamic noise of blower is mainly composed of two parts: torsional noise and eddy noise.
Torsional noise is caused by the fact that the evenly distributed blades on the mission wheel attack the surrounding gas medium, causing the gas pressure fluctuation around. When the air flows through the blade, a boundary layer is formed on the surface of the blade, especially the boundary layer on the suction side is easily thickened, resulting in many vortices. At the trailing edge of the blade, the boundary layer sinks of suction side and pressure side form the so-called wake area. In the wake region, the pressure and velocity of the flow are much lower than those in the main flow region. Therefore, when the task wheel turns the elbow, the air flow in the blade exit region has a great non-uniformity. This kind of uneven air flow periodically affects the surrounding medium, causing pressure fluctuation and forming noise. The more uneven the air flow is, the greater the noise is.
Eddy current noise
Vortex noise is also known as vortex noise or turbulence noise. It is mainly due to the turbulent boundary layer and the separation of vortices and vortices when the air flows through the blades. And caused the pressure fluctuation on the blade. There are four reasons for its occurrence
The first is that after the turbulent boundary layer is formed by the airflow on the surface of the object, the disordered pressure pulse of the airflow in the boundary layer is used for the blade, the inner and outer surface of the volute and some external surfaces, which causes noise;
The second is that when the air flows through the object, the vortex will fall when the boundary layer develops to a certain level, and the larger pulsation will be formed when the boundary layer leaves the vortex;
The third reason is that the turbulence degree of the incoming flow causes the pulsation of the effective force of the blade to form noise;
The fourth is the noise caused by the secondary eddy current.
There are two main reasons for installing silencer in Roots blower
1. Noise problem. The noise of Roots blower is relatively large, especially the large-scale roots blower. Sometimes the muffler can only play a part of the noise reduction effect. For some smaller roots blowers, muffler is a necessary accessory, and the surrounding noise should be controlled.
2. Impurity problem. In the working environment of Roots blower, it is inevitable that some solid substances are inhaled. Therefore, the muffler also has a major role in protecting the blower from damage.
Roots blower without muffler, there is a certain risk, adding muffler is a necessary measure, and if the blower inlet is directly connected to the pipeline, then it is not necessary to install an imported muffler, but the necessary filtration measures should be taken before the gas is imported.