Roots-type blower is a positive displacement blower. It relies on the change of the volume of the working chamber formed by the rotation of two involute "8"-shaped rotors to transport gas. Its working principle is the same as that of a gear pump. That is, each rotor is equivalent to a gear with only two teeth. Roots blower, English name Roots blower, is a volumetric rotary blower, a rotary compressor that uses two blade-shaped rotors to make relative motion in the cylinder to compress and transport gas. The blower has a simple structure and is convenient to manufacture, and is suitable for gas delivery and pressurization in low-pressure occasions, and can also be used as a vacuum pump.
Roots blower is a volumetric rotary blower. This compressor maintains the meshing of the two rotors by means of a synchronous gear at the end of the rotor shaft. Each concave curved part on the rotor and the inner wall of the cylinder form a working volume. During the rotation of the rotor, the gas is taken away from the suction port. The gas is backflowed, when the pressure in the working volume suddenly rises, and the gas is then transported to the exhaust channel. The two rotors are not in contact with each other, and they are sealed by a tightly controlled gap, so Roots Rotary Lobe Blower the discharged gas is not polluted by lubricating oil.
Its biggest feature is that when the pressure is adjusted within the allowable range, the flow rate changes little, the pressure selection range is very wide, and it has the characteristics of forced gas transmission. The medium does not contain oil when conveying. Simple structure, convenient maintenance, long service life and small vibration of the whole machine.
vacuum pump. Due to the pulsation of airflow velocity and pressure caused by periodic suction, exhaust and instantaneous isovolumetric compression, large aerodynamic noise will be generated. In addition, the gaps between the rotors and between the rotors and the cylinder cause gas leakage, which reduces efficiency. The exhaust volume of the Roots blower is 0.15~150 cubic meters per minute, and the rotation speed is 150~3000 rpm. The single-stage pressure ratio is usually less than 1.7, up to 2.1, and can be used in multi-stage series
According to the shape of the rotor, the Roots blower is divided into two-blade type and three-blade type. The three-lobed rotor is sucked and exhausted three times by two rotors every time it rotates. Compared with the two-blade type, the gas pulsation is small, the vibration is also small, and the noise is low.
The difference with the centrifugal fan is relatively big:
⒈The working principle is different. The centrifugal fan uses a curved fan blade, and the gas is thrown to the casing by centrifugal force, while the Roots fan uses two 8-shaped fan blades, and the gap between them is very small. to squeeze the gas to the air outlet.
⒉ Due to different working principles, generally their working pressures are different, the outlet pressure of the Roots fan is relatively high, while the centrifugal fan is relatively small.
⒊The air volume is different. Generally, the Roots fan is used in places where the air volume requirement is not large but the pressure requirement is high, while the centrifugal fan is used in the place where the pressure requirement is low and the air volume requirement is large.
⒋The manufacturing precision is different. The Roots blower requires high precision and strict assembly requirements, while the centrifugal blower is relatively loose.
According to the theory of fluid mechanics, the flow process of gas will be accompanied by losses. For example, after the gas flows through the throttling device, the pressure of the gas flow is reduced accordingly, that is, they lose the useful work of the fan. Since all this happens in the process of conveying gas by the fan, the energy of the fan is wasted.
The operating point of the fan is the intersection of the performance curve of the fan at a certain speed and the resistance characteristic line of the pipe network. When the fan is actually running, it does not always stay at the design operating point. It will change with the needs of users or changes in external conditions, that is, the fan is actually working under variable working conditions. In order to make the wind pressure or air volume of the fan reach a certain target value, it is necessary to artificially control the fan or the pipe network, also known as adjustment. Through effective adjustment, it can not only meet the requirements of production on flow or pressure, but also maximize energy saving under the condition that the fan can work stably. In short, the purpose of regulation is to meet performance requirements, expand (stabilize) operating conditions, achieve energy savings, and prevent surges.
Fans can achieve the same purpose with different adjustment methods, but the energy-saving effects are different.
According to theoretical analysis and practical proof, the following four conclusions can be drawn.
(1) For blowers and compressors, the outlet throttling adjustment method consumes the most power. Although the relative flow Qr (the ratio of the actual flow Q to the design flow Q0) decreases, the power also decreases accordingly. For example, when Q=0.65 Q0, the corresponding power is reduced to about 80% of the original, but compared with other adjustment methods, the energy consumption still ranks first.
(2) If the relative flow does not change much (or the adjustment depth is small), the power consumption of several adjustment methods is not very different. That is, the adjustment method has little effect on the energy saving effect, and even not only does not save energy, but consumes more power due to the existence of the adjustment device (such as a hydraulic coupler).
(3) Generally speaking, the greater the adjustment depth, the more significant the energy-saving effect. Therefore, it is necessary to choose the adjustment method carefully in order to obtain the maximum benefit.
⑷ The variable speed adjustment curve is close to the ideal curve. Therefore, the variable speed adjustment method is superior, especially the energy saving scheme that adopts the variable frequency motor speed regulation is the best, but the frequency conversion device needs to be added. It is recommended to actively try out the frequency conversion speed regulation of small and medium capacity; due to the high price of the large capacity and high voltage frequency conversion speed regulation device, it should be combined with the specific situation and comprehensively compared to decide the choice. In short, it is necessary to consider not only the adjustment performance, but also the initial investment, reliability and economy of the equipment, and comprehensively evaluate the advantages and disadvantages of the adjustment method.
Mainly used in sewage treatment, aquaculture, pneumatic conveying, cement, chemical industry, foundry, flour and other national economic sectors.
