vacuumpump真空泵ppt課件-資料下載頁
2025-05-05 18:28本頁面
【正文】 e acquiring an additional velocity ponent in the direction of the moving surface. 05/10/2022 Title 33 Orientation of rotors and stators in a turbomolecular pump The orientation of the moving (rotor) blades and stationary (stator) blades to the axial direction in a turbomolecular pump is as shown Figure. The molecule shown incident on a rotor blade and its pitch(斜度） . The stator blades are also pitched. Their pitch direction is such that they preferentially transmit molecules that have left the rotors and are moving axially down the pump. Molecules moving in the reverse direction (backdiffusion) are likely to be reflected back. 05/10/2022 Title 34 More detailed description of turbomolecular pump For the blades to be effective with rapidly moving molecules, the blade speeds must approach the molecule speeds。 otherwise the molecules will pass through the rotor regions without being struck. Lighter molecules are more difficult for turbomolecular pumps to pump, because they are more likely to pass through the rotors without being hit by a blade, increasing the likelihood of back diffusion of the gas. Pump performance depends on blade design as well as rotor speed. Variables include the pitch angle, blade width and the distance between blades. Overall performance is optimized by varying the blade geometry through the pump. Ingestion（ 攝 ?。? of foreign objects into any turbomolecular pump during operation will cause severe damage to the rotor and stator blade. In order to reduce this risk most pumps are provided with a wire mesh inlet guard. 05/10/2022 Title 35 Pumping selectivity Pumping speed depends on the types of gas (molecular weight, momentum transfer) for the operation principle 05/10/2022 Title 36 ADVANTAGES 1. Fast recovery from “Dumping” 2. Fast startup 3. Constant speed 4. Clean ( No oil ) 5. Operating costs 6. High throughput 7. Small to large size DISADVANTAGES 1. Sensitive to particulates 2. Requires mechanical pump 3. High rpm ( Noise/Vibration ) 4. Low speed for hydrogen and helium 5. High maintenance cost 6. 1 ? 103 Torr upper limits 7. High initial cost Advantages and disadvantages of the turbomolecular pump 05/10/2022 Title 37 ? Vapor pump: ejector pump and diffusion pump ? Distinction： mean free path at the intake port vs. throat width ? In relation to 關(guān)于 涉及 ? boiler ? Mercury ? Chimney ? Deflect 偏轉(zhuǎn) ? Umbrella 傘形鐘罩 ? Pressure gradient ? viscous drag and turbulent mixing ? Diminish, crosssection ? Orifice 孔 ? vapor booster pump: bination the diffusion and ejector pump 05/10/2022 Title 38 1 Nozzle (Laval) 2 Diffuser nozzle (Venturi) 3 Mixing chamber 4 Connection to the vacuum chamber 1 Steam inlet 2 Jet nozzle 3 Diffuser 4 Mixing region 5 Connection to the vacuum chamber
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