vacuumpump真空泵ppt課件(編輯修改稿)
2025-06-01 18:28 本頁面
【文章內(nèi)容簡介】 ns 3) Content of pump chamber is already so far pressed that the vapor condenses to form droplets – overpressure is not yet Reached 4) Residual air only now produces the required overpressure and opens the discharge valve, but the vapor has already condensed and the droplets are precipitated in the pump. Without gas ballast 05/10/2022 Title 18 Gas ballast 1) Pump is connected to the vessel, which is already almost empty of air (70 mbar) – it must thus transport mostly vapor particles 2) Pump chamber is separated from the vessel – now the gas ballast valve, through which the pump chamber is filled with additional air from outside, opens – this additional air is called gas ballast 3) Discharge valve is pressed open, and particles of vapor and gas are pushed out – the overpressure required for this to occur is reached very early because of the supplementary gas ballast air, as at the beginning the entire pumping process condensation cannot occur 4) The pump discharges further air and vapor With gas ballast 05/10/2022 Title 19 Root’s pump The Root’s pump consist of two doublelobe impellers. These are rotated in opposite within the pump housing. The directions of rotation being those shown in the below figure. The impellers have identical cross sections and are dimensioned and arranged so that a large enough part of the surface of R1 is a close fit to a part of the surface of R2 through the rotation. The impellers are also a close fit inside the pump housing. The rotating impellers do not, however, touch one another, nor do they touch the housing, but there is a small clearance (about mm) at the points 1, 2 and 3. As point 1 moves around the inside wall of the pump housing, points 2 and 3 move correspondingly. Root’s pump 05/10/2022 Title 20 Action of Root’s pump Since the inlet port is isolated in fact from the outlet by a narrow gap (clearance between parts) there is a back flow of gas from the exhaust region to the inlet region, and therefore the efficiency of pression is much lower than in the case of oil sealed pumps. However, the absence of rubbing contacts means that higher speeds of rotation (10004000 rpm) are possible, leading to much higher pumping speeds. Processing 05/10/2022 Title 21 1. Cover 2. Wear plate 3. Rotary lobe 4. Casing 5. Shaft 6. Gear box 7. Sealing monitor Root’s pump schematic 05/10/2022 Title 22 Pumping speed curve of Root’s pump 05/10/2022 Title 23 Root’s pump ? Doublelobe impeller 雙葉轉(zhuǎn)子 ? Housing 框架，泵體 ? identical 相同的 ? close fit ? clearance, narrow gap ? back flow 回流 ? efficient, effective ? oil sealed pump ? Rubbing contact ? Conductance 流導(dǎo) 05/10/2022 Title 24 ? molecular drag pump 牽引分子泵 ? Directional velocity 定向速率 ? Impart 傳遞 ? Turbomolecular pump ? Alternate ? Roting/stationary disc/plate ? Preferentially 優(yōu)先的 ? Running clearance ? pitch angle 螺旋角
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