What does a vacuum pump consist of?

Ring vacuum pump (water ring pump for short) is a kind of rough vacuum pump, and the limit pressure of single-stage pump is 2.66 ~ 9.3 1 kPa. The two-stage pump is 0. 133 ~ 0.665 kPa. The water ring pump can also be used as a compressor, which belongs to a low-pressure compressor. The pressure range is (1 ~ 2) x 105 Pa gauge pressure (under certain conditions). Water ring pumps are used in petroleum, chemical industry, machinery, mining, light industry, paper making and other industries. Such as vacuum filtration, vacuum feeding, vacuum degassing, vacuum evaporation, vacuum concentration and vacuum moisture regain. , has been widely used. Because the process of gas compression by water ring pump is isothermal, flammable and explosive gas, dust and water-containing gas can be pumped out. Therefore, the application of water ring pump is increasing. Water ring pump is composed of impeller, pump body, suction and exhaust disk, water ring formed by water on the inner wall of pump body, suction port, exhaust port and auxiliary exhaust valve. The impeller is eccentrically installed in the pump body. When the impeller rotates in the direction shown in the figure, the water entering the pump body is thrown around by the impeller. Due to the centrifugal force, water forms a closed water ring with a thickness similar to that of the pump cavity. The upper inner surface of the water ring is just tangent to the impeller hub, and the lower inner surface of the water ring is just in contact with the tip of the blade (in fact, the blade has a certain insertion depth in the water ring). At this time, a crescent-shaped space is formed between the impeller hub and the water ring, which is divided into several small cavities with the same number of blades by the impeller. If the upper part of the impeller is 0 as the starting point, when the impeller rotates180, the volume of the small cavity gradually increases from small to large (that is, from I-I section to II-II section), and the pressure decreases continuously, and it is communicated with the suction port on the suction and exhaust disk. When the pressure in the small cavity space is lower than that in the pumped container, the pumped gas is continuously pumped into the small cavity according to the principle of gas pressure balance, and at this time it is in the process of pumping. When the suction is completed, the volume of the small cavity decreases gradually and the pressure increases continuously. At this point, it is in the process of compression. When the compressed gas reaches the exhaust pressure in advance, it is discharged from the auxiliary exhaust valve in advance. From section III-III to I-I, the volume of the small cavity communicating with the exhaust port is further reduced and the pressure is further increased. When the gas pressure is greater than the exhaust pressure, the compressed gas is discharged from the exhaust port. During the continuous operation of the pump, suction, compression and discharge are continuously carried out, so as to achieve the purpose of continuous discharge. In the water ring pump, the auxiliary exhaust valve is a special structure, and rubber ball valves are generally used to eliminate the over-pressure and under-pressure phenomena during the operation of the pump. Both phenomena will cause excessive power consumption. Because the water ring pump has no direct exhaust valve, the exhaust pressure is always fixed, so the compression ratio of the water ring pump depends on the end position of the air inlet and the start position of the air outlet. But these two positions are fixed, so they can't meet the demand of suction pressure change. In order to solve this problem, a rubber ball valve is generally installed below the air outlet, so that when the pump cavity reaches the exhaust pressure prematurely, the ball valve will automatically open and the gas will be exhausted, eliminating the phenomenon of over-compression. This problem can be solved by determining the compression ratio with the lowest suction pressure in the design of general water ring pumps, so as to determine the initial position of the air outlet.