Multi-stage pump structure principle, structure principle of multi-stage pump

The multi-stage pump is based on the change of the volume of the pump chamber to achieve suction, compression and exhaust, and the multi-stage pump is a kind of centrifugal pump. The multi-stage pump can be divided into many types according to the structure, and each structure principle is different.

First, the trochoidal type eccentrically mounted in the multi-stage pump chamber is a rotor with a trochoidal profile. It rotates along the inner wall of the pump chamber and divides the pump chamber into two variable volumes. The balance of the pump is good, so the operation is relatively stable, the vibration is also small, the rotation speed can be increased, the size can be small, the pumping speed is large, and it is suitable for the development of mechanical multi-stage pump with large pumping speed. Because the suction line is short and thick, it is beneficial to increase the pumping speed of the multi-stage pump under low pressure.

Second, the fixed-plate fixed-stage multi-stage pump is equipped with an eccentric rotor near the inner surface of the multi-stage pump in the pump casing. The pump casing is equipped with a radial vane which is always in contact with the surface of the rotor. When the rotor rotates, it slides. The slide can be divided up and down to divide the multi-stage pump chamber into two variable volumes. The fixed-stage multi-stage pump has a small pumping speed, with single-stage and double-stage pumping, and the ultimate vacuum of the pump can reach 10-1Pa. The multi-stage pump has a simple structure, a long service life and easy maintenance. However, due to its poor working performance as a rotary vane pump, it has rarely been produced and applied.

3. The rotary vane rotary vane multi-stage pump rotor is mounted in the multi-stage pump casing with a certain eccentricity and is close to the fixing surface of the inner surface of the pump casing. Two (or more than two) rotary vanes are installed in the rotor slot. When the rotor rotates, the rotary vane can reciprocate along its radial groove and is always in contact with the inner wall of the pump casing. The rotary vane rotates with the rotor, and the pump chamber can be divided into several variable volumes. Rotary vane pumps are low multi-stage pumps. It can be used alone or as a foreline pump for other high vacuum pumps or ultra-high multi-stage pumps. Multi-stage rotary vane pumps are mostly small and medium-sized pumps and the products have been serialized. Rotary vane pumps are available in both single-stage and double-stage pumps, and are generally made in two stages to achieve higher pumping. The majority of rotary vane multistage pumps are single-work chamber structures. Two radial slides are commonly used and three oblique slides are also used. Through-slide multi-stage pumps are also used.

4. Spool valve type multi-stage pump is equipped with a slide valve outside the eccentric rotor. The rotation of the rotor causes the slide valve to slide and roll along the inner wall of the pump housing. The upper slide valve rod of the slide valve can be in the swingable slide guide. Sliding and dividing the multi-stage pump chamber into two variable volumes. The pumping principle of the spool-type multi-stage pump is similar to the rotary vane pump, but the structure of the two is different. Spool valve pump is the use of slide valve mechanism to change the volume of the suction chamber, it is called a multi-stage sliding valve pump.

Fifth, multi-stage jet pump often single-stage injector consists of two or more injectors and condenser in series, known as multi-stage jet pump. The function of the condenser is to condense and remove the condensable vapor in the mixture to reduce the load of the lower injector.

The condenser is installed in front of the inlet of the first stage injector, mainly to reduce the load of the first stage pump. Only when the pumped mixture contains a large amount of condensable vapor, and its vapor partial pressure is stronger than the saturated vapor pressure corresponding to the cooling water temperature. The intermediate condenser is installed in the middle of the multi-stage pump. The specific position should be determined by the partial pressure of the steam in the mixture entering the condenser and the cooling water temperature, and its role is to reduce the load of the lower-stage pump. After the rear condenser is installed in the final ejector, it is mainly used to eliminate exhaust gas and noise of the final ejector, and is sometimes used to recover waste heat of the ejector.