1. Water ring Vacuum Pump
The pump is shown in Figure 10-30. The outer housing 1 is eccentrically equipped with an impeller on which radial blades 2 are arranged. The pump is filled with about half volume of water, and when it rotates, a water ring 3 is formed. The water breaker acts as a liquid seal, and forms many sealed chambers of different sizes with the blades. When the chamber increases, the gas is sucked in from the inlet 4; when the chamber decreases, the gas is discharged from the outlet 5.
The ultimate pressure that the water ring vacuum ticket can cause is about 83.4xl03Pa, and it can also be used as a blower, but the resulting surface pressure does not exceed 98.07x103Pa. When the pumped gas does not come into contact with water, the pump can be filled with other liquids, so it is also called a liquid ring Vacuum Pump.
This type of pump has a simple and compact structure, is easy to manufacture and maintain, has no mechanical friction in the rotating part, has a long service life, and is reliable in operation. It is suitable for pumping gas containing liquid by hand, especially when pumping corrosive or explosive gas. But the efficiency is very low, about 30%~50%, and the degree of vacuum that can be caused is limited by the temperature of the water in the pump body.
2. Jet pump
The jet pump uses the principle of mutual conversion between static pressure energy and kinetic energy when the fluid flows to suck and send fluid. It can not only suck and send gas by hand, but also suck and send liquid by hand. In chemical production, jet pumps are often used to pump air to generate vacuum, so they are also called jet Vacuum Pumps.
The working fluid of jet pump can be steam or liquid. Figure 10-31 shows the steam jet pump. The working steam is ejected from the nozzle 3 at a high speed under high pressure. During the ejection process, the static pressure energy of the steam is transformed into kinetic energy to generate a low pressure, and the gas is inhaled. The inhaled gas mixes with steam and enters the diffuser tube 5, the velocity gradually decreases, the compression increases accordingly, and then it is discharged from the pressure outlet 6.
The jet pump is simple and compact in structure and has no moving parts. However, the efficiency is very low and the steam consumption is large, so it is generally used as a Vacuum Pump instead of a conveying device. Since the transported fluid is mixed with the working fluid, its application range is limited to a certain extent. If several jet pumps are used in series, a higher vacuum degree can be obtained. Shown in Figure 10_32 is a three-stage steam jet pump. The working steam 10 and the gas inhaled by the gas suction port 11 enter the first-stage ejector pump 1 through the condenser.
2. To condense the plain steam, the gas enters the second-stage jet pump 3, and then passes through the condenser 4, the third-stage jet case 5. and the condenser 6 in sequence, and finally is discharged by the jet pump 7. The auxiliary jet pump 8 is connected in parallel with the main jet pump to increase the starting speed. When the system reaches the specified vacuum, the auxiliary jet pump can be cut off from the line. The condensate and cooling water in each condenser flow into the tank.
