As a typical gas supercharging and conveying machine, roots blower has a wide range of application characteristics in its specific pressure area. The flow is usually 0.5-80 /min, and the single-stage working pressure is 53.3 -- 98kPa. The positive pressure of the blower can reach 196kPa and the negative pressure of the vacuum pump can reach 80kPa. When using countercurrent cooling, the single-stage positive pressure can reach 156.8kpa and the negative pressure can reach 78.4kpa.

In terms of application, roots blower is mostly used as air blower, which is widely used in many fields such as building materials, electricity, smelting, chemical and petrochemical industry, mining, port, textile, post and telecommunications, food, paper making, aquaculture and sewage treatment. The roots blower is usually used as a source machine for various low pressure pneumatic conveying systems. 

The basic structure of roots blower

Main parts of the blower include shell, wall board, rotor, synchronous gear, bearing and seal.

1. The chassis

The casing is an oval section cylinder body, which is generally made of high strength cast iron. The cylinder body is provided with inlet and exhaust orifices, and the external cast reinforcing bars and mounting feet are mostly integral structures. There are also some large - sized machine case with horizontal split structure, the upper and lower shell between pin positioning.

2. The wall panel

There is a wall board between the housing and the main and auxiliary fuel tanks. The first function is to act as the end cover and seal both ends of the housing. The other is to support both ends of the rotor. The one near the end of the shaft is called the front wall, and the one at the other end is called the back wall. Some wall panels are equipped with side plates, and the side plates are embedded into the shell ports during assembly, which can meet the requirements of radial positioning of rotor. Even if there is wear and tear at work, only the side board needs to be replaced, and the whole wall board will not be scrapped. Wall panels are generally made of high strength cast iron. When transporting corrosive gases, it is usually made of stainless steel, just like the case.

3. The rotor

The rotor is usually formed by the impeller and the shaft through the hot sleeve or the cold pressure. The shaft is made of high quality carbon steel or high strength alloy steel, and the driven shaft is relatively short. The impeller is usually made of high strength cast iron and stainless steel if necessary. The small rotor can also be made into a whole impeller and shaft, using high strength ductile iron casting. To reduce weight, the impeller head is often made into a hollow structure.

The rotor has two leaves and three leaves according to the number of impeller, and straight leaves and twisted blades according to the shape of impeller. Both rotor blades are straight, and the three-blade rotor has straight blade and twisted blade. In terms of acoustic performance, three leaves are better than two, and twisted leaves are better than straight ones. However, due to the limitation of processing conditions, the rotor of straight blade is more used in practice.

The profile of the impeller is called profile, and the profile is called profile. A curve is a combination of a particular set of curves. Taking the two-blade rotor as an example, the profile characteristics of circular arc profile, involute profile and cycloid profile are commonly used.

4. Synchronous gear

The function of synchronous gear is to transfer power and to determine the gap between two impeller to ensure the synchronous operation of two rotors. The main and driven gears have the same meshing parameters and are a pair of cylindrical gears whose transmission ratio is equal to 1:1. In order to facilitate circumferential adjustment, driven gear is mostly composed of gear ring and hub. When adjusting, the rotation shall be carried out according to the specified rotation direction. When rotating in the reverse direction, the gear side gap will be empty to the other side of the tooth groove, and the gap between the main and driven impeller will change accordingly.

The gear has straight teeth, oblique teeth and herringbone teeth, etc., the material is usually high quality carbon steel or high strength alloy steel. Cylindrical or taper fit between gear and shaft, gear ring and wheel bearing. When a cylinder is used for matching, a flat bond is arranged between the mating surfaces.

5. Bearing

As far as load bearing is concerned, it is mainly radial load. When the synchronous gear is straight teeth or herringbone teeth, there is no axial force. When the helical gear is used, certain axial force will be generated, but the load is small. Common bearings include deep groove ball bearings, centering roller bearings, angular contact ball bearings and cylindrical roller bearings. Cylindrical roller bearings are mostly used as bearing bearings, other bearings can not only load, but also axial positioning of the rotor.

6. Sealing

The main purpose of sealing is to prevent gas and oil leakage. Seal quality, to a certain extent, can reflect the level of product design and manufacture and performance of the pros and cons. Especially when conveying inflammable, explosive or poisonous gas, sealing is the key factor of safe operation of the blower.

Seals fall into two categories. One type is the seal of fixed position, such as the seal between the wall board and the housing, between the wall board and the oil tank, and between the bearing gland and the bearing seat. The other type is the seal of the moving part, such as the seal of the end of the shaft, the tail of the bearing seat and the extension of the shaft, which is called the dynamic seal (or shaft seal). Static seal structure is simple, generally rubber asbestos board, o-ring, and so on. Shaft seal structure is more complex, commonly used labyrinth seal, skeleton oil seal group, ring seal, packing seal and mechanical seal.