What Is a Rotary Vane Pump and How Does It Work?

What Is a Rotary Vane Pump ?

A rotary vane pump is a type of positive-displacement pump that consists of vanes mounted to a rotor that rotates inside a cavity. In some cases, these vanes can have variable length and/or be tensioned to maintain contact with the walls as the pump rotates.

What’s The Working Principle for Rotary Vane Pumps ?

Rotary vane pumps are types of positive displacement pumps. In a cylindrical housing, the rotor is positioned eccentrically on the shaft so the rotor is positioned near the top of the cylinder. Rotor blades are positioned into numerous rotor slots. When the rotor starts turning, centrifugal force causes the blades to be thrown out and slide against the internal surface of the cylinder. A cell is formed between two blades with a volume that changes constantly during rotation. Air enters from the inlet port into a cell until the rear blade reaches the inlet port, at this point the cell has achieved its maximum air volume.

As the air cell then moves away from the port, its volume becomes smaller and smaller. The air is compressed and the pressure rises. This continues until the pressure in the cell exceeds that in the pressure chamber. The air then exits through the outlet port.

Some models are fitted with exhaust valves that stop the backflow of this discharged air if the maximum pressure has been reached. In a rotary vane vacuum pump, the process is similar, but the air cell gives decreasing pressure and the chamber is at atmospheric pressure.

Uses

Vane pumps are commonly used as high-pressure hydraulic pumps and in automobiles, including supercharging, power-steering, air conditioning, and automatic-transmission pumps[citation needed]. Pumps for mid-range pressures include applications such as carbonators for fountain soft-drink dispensers and espresso coffee machines[citation needed]. Furthermore, vane pumps can be used in low-pressure gas applications such as secondary air injection for auto exhaust emission control, or in low-pressure chemical vapor deposition systems[citation needed].

Rotary-vane pumps are also a common type of vacuum pump, with two-stage pumps able to reach pressures well below 10−6 bar. These are found in such applications as providing braking assistance in large trucks and diesel-powered passenger cars (whose engines do not generate intake vacuum) through a braking booster, in most light aircraft to drive gyroscopic flight instruments, in evacuating refrigerant lines during installation of air conditioners, in laboratory freeze dryers, and vacuum experiments in physics[citation needed]. In the vane pump, the pumped gas and the oil are mixed within the pump, and so they must be separated externally. Therefore, the inlet and the outlet have a large chamber, perhaps with swirl, where the oil drops fall out of the gas. Sometimes the inlet has louvers cooled by the room air (the pump is usually 40 K hotter) to condense cracked pumping oil and water, and let it drop back into the inlet. When these pumps are used in high-vacuum systems (where the inflow of gas into the pump becomes very low), a significant concern is contamination of the entire system by molecular oil back streaming.