What is a multi stage jet pump?

Multistage jet pump is a special pump type of equipment, its main features and working principle can be summarized as follows:

Definition & Structure

A multistage jet pump consists of two or more injectors and condensers connected in series.
Each injector usually consists of a main part such as a nozzle, a receiving chamber (or a shrinking section before the mixing chamber), a mixing chamber, and a diffuser (diffuser).

How it works

Multistage jet pumps rely on changes in the volume of the pump chamber and the centrifugal force generated by rotation to achieve the process of suction, compression, and exhaust.
As the working steam flows through the nozzle, its velocity rises to supersonic speed, while the pressure decreases, creating a negative pressure that will be drawn in the pumped gas.
The steam is mixed with the pumped gas in a mixing chamber for an energy exchange and then flows to the diffuser.
In the diffuser, the speed of the gas mixture gradually decreases, while the pressure gradually rises, and a positive shock wave may be generated near the throat segment, causing the gas mixture to drop sharply to subsonic speed and the pressure to increase sharply.
After progressive compression, the final gas mixture is discharged at the outlet pressure of the diffuser to atmospheric pressure or the inlet pressure of the next stage injector.

The role of the condenser

In multistage jet pumps, condensers play an important role. It is installed between the ejectors and is used to partially condense and remove the condensable vapors in the mixture to reduce the load on the lower ejectors.
If 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, a condenser is also installed at the first inlet.

Applications & Performance

Multistage jet pumps are widely used in industrial fields that require vacuum or high pressure, such as chemical, petroleum, metallurgy, etc.
Single-stage jet pumps typically have a compression ratio of no more than 10, and in order to achieve lower ultimate pressures, a multistage pump design is required.
In summary, a multistage jet pump is an efficient and versatile pump type of equipment suitable for a variety of industrial applications that require high-pressure or vacuum treatment.