Vacuum pump classification
According to the working principle of vacuum pump, vacuum pump can basically be divided into two types, namely, gas transmission pump and gas trap pump. With the vacuum application technology in the field of production and scientific research more and more wide range of its application pressure, most of the need to be composed of several vacuum pump vacuum exhaust system together to meet the production and scientific research process requirements, therefore Selection of different types of vacuum pump composed of vacuum extraction unit more often. For the sake of convenience, it is necessary to classify these pumps in some specific detailed categories according to their working principle or their structural features. Now described as follows: First, the gas transmission pump Gas transmission pump is a gas can continue to inhale and discharge, in order to achieve the purpose of pumping vacuum pump, there are basically two types of pumps: 1) variable capacity vacuum pump capacity Vacuum pump is the use of cyclical changes in the volume of the pump to complete the process of inhalation and exhaust of a vacuum pump. The gas is compressed before being discharged. This pump is divided into two types of reciprocating and rotary: ⑴ reciprocating vacuum pump: reciprocating piston pump is used to make the gas inhalation, compression and discharge. Therefore, also known as piston vacuum pump. ⑵ rotary vacuum pump: the use of the pump cavity to make rotary motion piston, the gas inhalation, compression and discharge. Rotary vacuum pump and the following types: ①oil-sealed vacuum pump: It is the use of oil seals between the moving parts of the gap, reducing the harmful space of a rotating varactor vacuum pump. This pump is usually equipped with gas ballast, it is also known as gas-town vacuum pump. According to its structural characteristics are divided into the following five types. a) Rotary vane vacuum pump: The rotor is installed in the pump casing with a certain eccentricity and is close to the fixed surface of the inner surface of the pump casing. Two (or more than two) rotary vanes are provided in the rotor groove. When the rotor rotates Slides reciprocate along their radial grooves and are always in contact with the inner wall of the pump housing. This vane rotates with the rotor to divide the pump chamber into several variable volumes. b) Spool vacuum pump: a spool is mounted on the outside of the eccentric rotor, the rotor rotates to bring the spool to slide and roll along the inner wall of the pump housing, the spool rod on the upper part of the spool can slide in the swingable spool guide and the The pump chamber is divided into two variable volumes. c) Fixed-disc vacuum pump: An eccentric rotor near the inner surface of the pump is installed in the pump housing. A radial vane always contacts with the rotor surface is provided on the pump housing. When the rotor rotates, the vane can slide up and down Divide the pump chamber into two variable volumes. d) trochoidal vacuum pump: eccentric in the pump chamber is equipped with a trochoid trochanter rotor, which along the inner wall of the pump chamber rotation and the pump chamber is divided into two variable volume. e) Multi-Chamber Rotary Vane Vacuum Pump: A rotary vane vacuum pump with multiple independent chambers driven by the same motor in parallel in a pump housing. ② Dry vacuum pump: It is a non-oil (or liquid) sealed varactor vacuum pump. ③ liquid ring vacuum pump: rotor with a multi-blade eccentrically installed in the pump housing, when it is rotating, the liquid (usually water or oil) thrown into the pump housing to form a concentric liquid ring, the liquid ring with the rotor blades Formed a few small volume changes in volume, it is also known as rotary varactor vacuum pump. ④ Roots vacuum pump: pump equipped with two opposite directions synchronous rotation of the double-leaf or multi-lobed rotor, between the rotor, the rotor and the pump housing to maintain a certain gap between the inner wall. It belongs to the rotating vacuum pump. Mechanical booster pump is the type of vacuum pump. 2) Momentum transfer pump This pump is to rely on high-speed rotating blades or high-speed jet, the momentum transfer to the gas or gas molecules, the gas from the pump inlet to the outlet continuously. Specific can be divided into the following types. ⑴ molecular vacuum pump: It is the use of high-speed rotating rotor to transfer energy to gas molecules, so that compression, exhaust a vacuum pump. It has the following types: ①traction molecular pump: gas molecules and high-speed rotor collision to obtain momentum, was sent to the exit, therefore, is a momentum transfer pump. Turbomolecular pump: Pump equipped with a grooved disc or rotor with a blade, it is rotating between the stator disc (or stator). The linear speed of the rotor circumference is high. Such pumps usually work in molecular flow conditions. ③ composite molecular pump: It is a combination of turbocharged and towed molecular pump in series a composite molecular vacuum pump. ⑵ jet vacuum pump: It is the use of Venturi (Venturi) effect of the pressure drop generated by high-speed jet to the gas delivered to the export of a momentum transfer pump, suitable for viscous flow and transition flow state work. This pump can be divided into the following detailed: ①liquid jet vacuum pump: liquid (usually water) as the working medium jet vacuum pump. ② gas jet vacuum pump: non-condensable gas as the working medium jet vacuum pump. ③ steam jet vacuum pump: to steam (water, oil or mercury vapor) as the working medium jet vacuum pump. ⑶ diffusion pump: low-pressure high-speed steam flow (oil or mercury vapor) as the working medium jet vacuum pump. Gas molecules diffuse into the vapor jet and are sent to the outlet. The molecular gas density in the jet is always low, and this pump is suitable for operation in molecular flow conditions. Can be divided into: ①self-purification diffusion pump: pump volatile impurities by mechanical transport to the export without returning to the boiler in an oil diffusion pump. ② fractionation diffusion pump: This pump has a fractionation device, so that the vapor pressure of the lower working pressure vapor into the work of high vacuum nozzle, and high vapor pressure of the working liquid vapor into the low vacuum nozzle work, it is a more Grade oil diffusion pump. ⑷ diffusion jet pump: It is a diffusion pump characteristics of single-stage or multi-stage nozzle with jet vacuum pump features a single or multi-stage nozzle in series consisting of a momentum transfer pump. Oil booster pump that belongs to this type. ⑸ ion transfer pump: it is ionized gas will be in the electromagnetic field or the role of the electric field, delivered to the export of a momentum transfer pump. Second, the gas trap pump This pump is a gas molecules are adsorbed or condensed on the pump's inner surface, thereby reducing the number of gas molecules in the container to achieve the purpose of pumping the vacuum pump, the following types. 1) Adsorption Pumps It is a trapping vacuum pump which relies mainly on the physical adsorption of adsorbents with a large surface, such as porous substances. 2) Getter pump It is a vacuum pump that uses a getter to capture gas chemically. Getters are usually metals or alloys that exist in the form of lumps or deposited fresh films. Sublimation pump that belongs to this type. 3) getter ion pump It is the role of ionized gas through the electromagnetic field or electric field adsorption on the surface of the gettering material, in order to achieve the purpose of pumping. It has the following types. ⑴ evaporative ion pump: the pump is ionized gas adsorption in an intermittent or continuous manner sublimation (or evaporation) and covered in the pump wall suction material, in order to achieve a vacuum pump. ⑵ sputter ion pump: ionized gas pump is adsorbed by the continuous sputtering cathode from the gettering material to achieve the purpose of pumping a vacuum pump. 4) cryogenic pump use of low-temperature surface to capture gas vacuum pump 3.1.3 vacuum pump performance parameters and the use of 3.1.3.1 vacuum pump performance parameters 1) the ultimate pressure pump vacuum pump ultimate pressure unit is Pa, refers to the pump installed at the entrance A standard test hood and work according to the specified conditions, the gas does not work under normal circumstances, the trend toward the lowest pressure. 2) Suction rate of the vacuum pump Pump suction rate unit is m3 / s or l / s, is the pump equipped with a standard test cover, and work according to the provisions of the conditions, the gas flows from the test cover and the test cover The ratio of the equilibrium pressure measured at the specified location. Pump pumping speed. 3) Vacuum pump suction volume Vacuum pump suction unit is Pa m3 / s or Pa l / s. It refers to the pump inlet gas flow. 4) starting pressure of the vacuum pump vacuum pump starting pressure in units of Pa, it refers to the pump start without damage and the pressure when pumping. 5) Pump's Pre-Pressure The vacuum's pre-pressure unit is Pa, which is the outlet pressure of a vacuum pump with an exhaust pressure lower than one atmosphere. 6) The maximum pressure before the vacuum pump The maximum pressure unit before the vacuum pump port is Pa, which means more than the previous pressure can damage the pump. 7) The maximum working pressure of the vacuum pump The maximum working pressure of the vacuum pump unit is Pa, which refers to the inlet pressure corresponding to the maximum pumping capacity. Under this pressure, the pump can work continuously without deterioration or damage. 8) Compression Ratio The compression ratio is the ratio of the pump outlet pressure to the inlet pressure for a given gas. 9) Coefficient of Ho coefficient The ratio of the actual pumping speed on the pumping channel area to the theoretical pumping speed calculated on the basis of molecular effusion. 10) Pumping Coefficient The actual pumping speed of the pump is calculated as the ratio of the theoretical pumping speed calculated by molecular diarrhea at the pump inlet. 11) Backflow rate The pump backflow rate unit is g / cm2.s. It refers to the pump when the required conditions work, through the pump inlet unit area pump flow mass flow rate. 12) Allowable amount of water vapor The allowable amount of water vapor is kg / h. It refers to the mass flow rate of water vapor that can be extracted by the gas-pumping pump under continuous operation under normal environmental conditions. 13) The maximum allowable water vapor inlet pressure The maximum allowable water vapor inlet pressure unit is Pa. It refers to the maximum inlet pressure of water vapor that can be extracted by the gas-operated pump under continuous operation under normal environmental conditions.
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