第5章+真空获得-机械真空泵.ppt

Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology真空物理与技术真空物理与技术第5章真空获得（机械真空泵）Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology第第5章章 真空获得真空获得l真空泵概述l机械式真空泵u旋片泵分子泵罗茨泵l气流泵u扩散泵l俘获泵u吸附泵低温泵升华泵离子泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology真空泵概述真空泵概述Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology什么是真空泵？什么是真空泵？lThis is not a trivial question!u能能对空空间排气（减少气相分子数排气（减少气相分子数,产生低生低压空空间）的）的设备n通通过容容积压缩排气排气(Bulk action)l机械机械压缩n动量量传输(molecular action)l分子直接碰撞分子直接碰撞l夹带：和其他分子碰撞：和其他分子碰撞n降低空降低空间气体分子气体分子浓度度:气体分子气体分子储存在表面存在表面时间 实验时间n所有的真空所有的真空泵都有一定的工作范都有一定的工作范围:l压强l气体种气体种类Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology抽气原理抽气原理l降低空降低空间气体分子气体分子浓度（度（钛泵、低温、低温泵）l排出气体：旋片排出气体：旋片泵l定向运定向运动：扩散散泵、分子、分子泵、罗茨茨泵l“气体二极管气体二极管”u前前进 反向反向 压力差力差u返流返流（back through-put)反反扩散、脱附散、脱附l真空泵：能够维持压力差的设备Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology按照抽气方式分类按照抽气方式分类l压缩性真空泵：将气体由一方压缩到另一方u利用膨胀-压缩-排出原理：旋片泵u利用气体束流牵引作用：蒸汽流喷射泵u利用高速表面牵引分子作用：分子泵l吸附型真空泵：利用各种吸附作用将气体吸掉u利用电离吸气作用：离子泵u利用物理、化学吸附作用：吸附泵、低温泵、吸附剂泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology按照压强范围分类按照压强范围分类l粗真空泵粗真空泵:u大气压大气压-10-3 torrn旋片泵旋片泵n旋转柱塞泵旋转柱塞泵n滑片泵滑片泵n吸附泵吸附泵n罗茨泵罗茨泵l高真空泵高真空泵u10-3 to 10-n torrn扩散泵扩散泵n低温泵低温泵n分子泵分子泵n离子泵离子泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology按照排气压强分类按照排气压强分类l排气压强：泵在此压强下可以排气u往大气排气的泵n前级泵n前级压强n旋片式机械泵u只往低于大气压的环境排气n系统粗抽n需要前级泵（串联）n扩散泵、分子泵、罗茨泵u束缚泵n不需要出气口Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology典型泵组典型泵组粗抽:机械泵主泵:扩散泵前级:机械泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology真空泵性能的基本参数真空泵性能的基本参数l抽气速率S(抽速)u单位时间流入泵内的气体量Q=S.PS=Q/Pl极限压强puu经过足够长时间的抽气后，所能达到的最低平衡压强l最大工作压强u泵能正常工作的最高压强l使用范围u具有抽气能力的压强范围l排气压强u这一压强下,泵可以可以工作排气l超高真空泵参数u抽气选择性、残余气体组分Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology抽速曲线抽速曲线工作压强范围抽速极限压强抽速与气体种类的关系抽速S一般不是常数，随压强变化而变化Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology抽速范围抽速范围1.单级旋片泵(无气镇)2.单级气镇泵 3.罗茨泵4.喷射泵 5.扩散泵 6.分子泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology真空泵的压强范围真空泵的压强范围Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology抽气曲线抽气曲线l被抽容器中压强随时间变化曲线u不随时间变化的压强就是极限压强u抽速大小由达到一定压强所需时间长短来估计n时间越短，抽速越大Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology真空系统时间常数真空系统时间常数l问题：S=60L/s的机械泵，对一个体积为10L的容器排气，是否经过10/60s，能将容器抽至P=0呢？u即使是即使是S=常数的理想真空泵，答案也是否定的常数的理想真空泵，答案也是否定的u容器内压强容器内压强P随抽气降低，同一体积（随抽气降低，同一体积（V）对应的气体量（）对应的气体量（PV）越来越小越来越小u就气体量而言，抽气实际上越来越慢就气体量而言，抽气实际上越来越慢时间常数越大，压强下降越慢，“惰性”反映系统和泵的综合性能时间常数就是压强值将为1/e所需时间压强降低1个数量级需要2.303个时间常数Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology机械泵机械泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology早期机械泵早期机械泵l液体泵u利用液体压缩和排气l往复泵斯普伦杰尔泵水喷射泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology水环泵水环泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology旋转式真空泵旋转式真空泵l容积压缩泵u使用机械方法使一个工作室体积周期性的扩大和缩小达到抽气目的n旋片式n定片式n滑阀式Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology旋片泵旋片泵l最常用的粗真空最常用的粗真空泵u皮皮带泵和直和直联泵u单级泵和双和双级泵u实际上就是一个小型旋上就是一个小型旋转压缩机机Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology旋片泵工作图旋片泵工作图Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology最大抽速最大抽速l几何抽速L：泵腔深度（摩擦力）L=0.5-2.0D1否则电动机功耗太高j：翼片伸缩频率一般j=450转/分D2：不能太小，否则旋片泵的翼片容易断裂或密封不良旋片式旋片式:D2=0.75-0.85D1定片式定片式:D2=0.80-0.90D1滑阀式滑阀式:D2=0.65-0.70D1Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology有害空间有害空间l理想抽速l理论上的极限压强u压缩比（排气口压强与进气口压强比）l机械泵油封1.有害空间 2.定子 3.转子 4.旋片Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology机械泵油机械泵油l功能u润滑剂u密封剂u热传导/冷却u腐蚀防护l基本要求u化学稳定性u热稳定性u适当的润滑能力u适度的粘性u低饱和蒸汽压l矿物油u各种馏分混合u棕色-5/literu白色-20/literu氧化l合成泵油u炭氟化合物n惰性n500/literVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology典型的直联式旋片泵典型的直联式旋片泵l电机和机和泵直接相直接相连 j提高提高 1450转/分分钟 l7 cfm（cubic ft per minute）=鞋盒尺寸鞋盒尺寸l60 cfm=中等大小的狗尺寸中等大小的狗尺寸lEssentially all rotary vane pumps in research laboratories are now Direct DriveVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology双级旋片泵双级旋片泵l两个串两个串联压缩腔腔l更低的极限真空更低的极限真空 10-4Torrl低返油低返油Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology抽速曲线抽速曲线l压强较高时，抽速稳定l压强较低时，抽速显著下降l极限压强时，抽速为0单级双级Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology气镇气镇l抽除冷凝蒸汽（如水蒸汽）u饱和蒸汽且温度较高-立刻凝结u蒸汽压缩-压强增大-凝结u凝结液体与泵油混合u低压侧蒸发，限制极限压强l气镇阀u定时将一定量空气放入压缩区u压缩气体-蒸汽混合物u提前喷射20C水蒸气 Pv=17.5Torr60C水蒸气 Pv=149Torr压缩比9:1Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology可抽除的蒸汽压可抽除的蒸汽压lVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology返油返油l油的返流u油蒸汽逆着气流的方向进入泵入口，并进入真空室u返油量随着真空度的降低而增加u最轻的馏分l防止返油u吸附阱u低返油的泵油（贵）u打开气镇Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology使用使用l启启动泵u一定的一定的转向和向和转速速u冷却冷却l关关泵u回油回油u放气放气u电磁磁阀lGreat for pumping on airu2X-2（2L/s）1500u维护费用低l防止水汽、杂物(尤其腐蚀性物质)进入泵油Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology旋片泵小结旋片泵小结l压强范围u大气压-10-3Torrl优点u可靠u价廉u抽大气l缺点u噪音u脏u油u大且重Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology分分 子子 泵泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology分子牵引分子牵引l基本原理：动量传输u分子流条件下，碰撞运动表面的分子，离开表面时具有和运动表面速率u相近的切向速率u气体分子从具有运动的表面得到定向动量Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology牵引分子泵牵引分子泵-Gaede泵泵lhl特点：u分子平均速度越大，S越大10000转/分uUBUL和气导相关，反比M1/2，M越大，S越大l优点：u启动时间短u容易抽重气体分子l缺点：u密封间隙太小(hp2)UL:缝隙漏率UDC:逆时针返流Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology涡轮分子泵涡轮分子泵轴向交错排列的转子和定子,转速16000-40000叶轮很薄（3mm)，单极压差很小，但数量很多（多级）转子直径越大，要求叶片数量越多倾角越小，压缩比越大，但抽速小 一般20度 单极压缩5开缝（间隙1mm)具有实用价值Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology抽速曲线抽速曲线10-2Torr 取决于前级泵取决于前级泵几乎与种类无关几乎与种类无关,M较小时较小时S略降低略降低但对氢抽速比空气抽速大但对氢抽速比空气抽速大20%逆扩散，极限压强逆扩散，极限压强10-10Torra:抽速45m3/h前级泵b:抽速10m3/h前级泵稳态(S=0)时M越大,压缩比越大H2 1000N2 108Ar 109重氢化合物 1010Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology涡轮分子泵基本结构涡轮分子泵基本结构Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology以中型涡轮分子泵为例以中型涡轮分子泵为例横式:中部为高真空端,两端为前级高真空端定子和转子各12片,每片开槽48条,=30o前级端定子8片,转子7片,每片开槽20条,=15o转速16000转/分(外沿线速度150m/s)最大抽速140L/s压缩比k=5x10-7经过300度烘烤后,极限压强pu10-10TorrVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology横式和立式分子泵比较横式和立式分子泵比较横式横式立式立式泵体T型双端，造价贵异物落入时不损伤叶片寿命长噪声大泵体直圆筒型，造价低异物落入引起损伤平衡轻微变化会造成不稳定轴承损伤后不易更换Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology涡轮分子泵系统涡轮分子泵系统Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology应用应用l最高工作压强u10-2-10-1Torr之间u需要前级泵l电源u专用中频电源u启动电机，5min后转速稳定，泵正常工作u强迫冷却l极限压强u取决于最轻气体成分nHeVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology涡轮分子泵小结涡轮分子泵小结l启动压强10-2Torrl极限压强10-10Torrl优点u无油泵，干净u排出气体l缺点u振动u价格昂贵u相相对效率低效率低u对He抽速较低u机械损坏灾难性损坏Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology罗茨泵罗茨泵l原理u容积压缩分子牵引l结构u两个双叶型转子u相反方向运转u运转过程中紧密配合，不互相触及，也不触及泵体u压缩比低,返流大（前级真空）u无摩擦,转速高,相对抽速大Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology罗茨泵工作图罗茨泵工作图Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology特性特性l抽速曲线l低压下效率高u间隙流导减小u10-2Torr最高必须配备前级泵必须配备前级泵Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and Technology Vacuum Science and TechnologyVacuum Science and Technology Va