【机械类毕业论文中英文对照文献翻译】泵的概述
【机械类毕业论文中英文对照文献翻译】泵的概述,机械类毕业论文中英文对照文献翻译,机械类,毕业论文,中英文,对照,对比,比照,文献,翻译,概述
外文资料:Pumps outlineThe pump is the application very widespread general machinery, may say that is place of the fluid flow, nearly has the pump in the work. Moreover, along with sciences and technologys development, pumps application domain is expanding rapidly, according to the over-all state statistics, pumps power consumption approximately composes the national total output of electrical energy 1/5, obviously the pump is natural consumes energy the wealthy and powerful family. Therefore, raises the pump technical level to save the energy consumption to have the important meaning.First. Centrifugal pumps principle of workThe drive leads impeller revolving through the pump spindle to have the centrifugal force, under the centrifugal action of force, the liquid is flung along the leaf blade flow channel to the impeller export, the liquid sends in after the volute collection the eduction tube. The liquid obtains the energy from the impeller, causes the pressure energy and the speed can increase, and depends upon this energy the hydraulic transport to the operating location. while the liquid is flung which exports to the impeller, the impeller eye center has formed the low pressure, has had the differential pressure in the imbibition pot and between the impeller center liquid, in the imbibition pots liquid under this differential pressure function, after inhales the pipeline and pumps suction chamber unceasingly enters in the impeller.Second, centrifugal pumps structure and main spare part A centrifugal pump mainly by the pump body, the impeller, the packing ring, the rotation axis, the axis seals parts and so on box to be composed, some centrifugal pumps are also loaded with the guide pulley, the inducer, the balance disc and so on. 1. Pump body: Namely pumps shell, including suction chamber and delivery chamber. Suction chamber: Its function is enables the liquid to flow in evenly the impeller.Delivery chamber: Its function collects the liquid, and sends in it the subordinate impeller or guides the eduction tube, at the same time reduces the liquid the speed, causes the kinetic energy to further turn the pressure energy. The delivery chamber has the volute and the guide vane two forms. 2. Impeller: It is in the centrifugal pump transmits the energy for the liquid only part, the impeller with the bond fixation on the axis, leads revolving along with the axis by the prime mover, passes to through the leaf blade prime movers energy the liquid.Impeller classification: According to liquid inflow classification: Single suction impeller (in impellers one side has an entrance) and double attracts the impeller (liquid from impellers lateral symmetry liudao impeller passage). Is opposite according to the liquid in centerlines flow direction classification: Runoff type impeller, axial-flow propeller and interflow type impeller. According to impellers structural style classification: Shrouded impeller, open type impeller and semi-opened impeller.3. Axis: Is transmits the mechanical energy the important components, the prime movers torque passes to the impeller through it. The pump spindle is the pump rotors major parts, on the axis is loaded with components and so on impeller, axle sleeve, balance disc. The pump spindle depending on the both sides bearing supporting, makes the high speed rotation in the pump, thus the pump spindle in a big way wants the bearing capacity, to be wear-resisting, to be anti-corrosive. Pump spindles material selects the carbon steel or the alloy steel and after the quenching and retempering treatment generally.4. Packing ring: Is installs in the rotation impeller and the static pump housing (center-section and guide vanes assembly) between packing assembly. It is function is through controls between the two gap method, increases in the pump between the high and low pressure cavity the fluid flow resistance, reduces divulging. 5. Axle sleeve: The axle sleeve is uses for to protect the pump spindle, causes it not to corrode and the attrition. When necessity, the axle sleeve may replace. 6. Axis seals: The pump spindle and around packing box between end covers installs short for axis to seal, mainly prevents in pumps liquid divulging and the air enters in the pump, achieves seals and prevents the air admission to cause the pump cavitation goal. the axis seals form: Namely has skeletons rubber seal, the packing seal and the mechanical seal.7. axial force balancing unit.Third. Centrifugal pumps prime task parameter 1. Current capacity: Namely the pump in unit of time discharges the liquid quantity, usually indicated with the Unit of volume that mark Q, the unit has m3/h, m3/s, l/s and so on, 2. Lifting: The transportation unit weights liquid (pump suction flange) (pump discharge flange) from the pump inlet place to the pump exit, its energys increment, indicated with H, the unit is m. 3. Rotational speed: Pumps rotational speed is the pump each minute revolving number of times, expressed with N. Electrical machinery rotational speed N generally about 2900 n/min. 4. Net positive suction head: Centrifugal pumps net positive suction head is expressed that pumps performances main parameter, uses the symbolic representation. 5. Power and efficiency: Pumps power input is shaft power P, is also electric motors output. Pumps output is the active power.Fourth, pump proper energy loss Pump mechanical energy which obtains from the prime mover, has a part to transform into the liquid energy, but another part because in the pump consumes loses. In the pump all losses may divide into the following several items: 1. Hydraulic loss by the liquid in pump impact, the turbulent flow and the surface friction creates. The impact and the eddy current loss are because the liquid flow change direction produces. The liquid flows through the flow channel general meeting which contacts to present the surface friction, from this produces the energy loss is mainly decided by flow channels length, the size, the shape, the surface roughness, as well as liquid speed of flow and characteristic.2. Volumetric loss: volumetric loss was already obtained the energy liquid to have a part to flee the result which in the pump the class and leaked outward. Pumps volumetric efficiency is 0.930.98 generally. Improves the packing ring and the seal structure, may reduce the leakage, raises the volumetric efficiency. 3. Mechanical loss mechanical loss refers to the impeller lap side and the pump housing friction loss between the liquid, namely the disc loses, as well as pump spindle when packing, bearing and balancing unit and so on mechanical part movement friction loss, generally before primarily.Fifth, pumps speed change-Proportionality law 1. Centrifugal pumps speed change: A centrifugal pump, when its rotational speed change, its rated flow, lifting and the shaft power will have the change according to the certain proportion relations. At present, uses the frequency conversion velocity modulation electrical machinery to realize centrifugal pumps speed change, is a new important energy conservation way. 2. proportionality law expression: In the formula, Q, H, N- pumps rated flow, lifting and shaft power The subscript 1,2 express the different rotational speed separately n- rotational speedSixth, centrifugal pumps ratio rotation Compared to the rotation is the comprehensive parameter which derives by the law of similarity, it is the operating mode function, to a pump, the different operating mode has differently compared to the rotation, for ease of carries on the comparison to the different type pumps performance and the structure, the application optimum condition (the peak efficiency spot) the ratio rotation represents this pump. When chooses the pump, may according to job requirement Q, H and unifies electrical machinerys rotational speed, calculates the ns number, determines pumps type approximately. At that time, used the positive displacement pump generally, at that time, used the centrifugal pump, the interflow pump, the axial flow pump and so on.Seventh,centrifugal pumps cavitation andinspirationcharacteristic 1.Cavitation phenomenons The pumping station transportation mediums liquid condition and the gas are can transform mutually, the transformed condition is the pressure and the temperature. Under certain temperature, the liquid starts the critical pressure which vaporizes for the vaporization pressure. The temperature is higher, the liquid vaporization pressure is higher. Pump when revolution, if its overflow part local region (for example impeller blade import later somewhere), the liquid absolute pressure drops when pulled out delivers the liquid at that time under the temperature vaporization pressure, the liquid then in this place starts to vaporize, the bubble formation (air bubble internal pressure approximately was equal to vaporization pressure). When these air bubbles along with liquid flow forward motion to high pressure region, down to around the air bubble high-pressured liquid causes the air bubble to reduce suddenly congeals. While air bubble vanishing, the liquid particle by the high speed packing hole, occurs hits mutually forms the intense pressure surge, causes the overflow part to receive the corrosion and the destruction. The above process is called the cavitation. 2. Cavitation will cause serious results: (1). has the vibration and the noise. (2). is influential to pumps operating performance: When the cavitation develops the certain extent, the steam bubble produces massively, will stop up the flow channel, will cause pumps current capacity, lifting, the efficiency and so on obviously to drop. (3). will have the destruction to flow channels material quality: Is mainly nearby the leaf blade entrance the metal weary disintegration.3. centrifugal pumps inspiration characteristic: (1). Pump has the cavitation basic condition is: Under leaf blade entrance lowest liquid flow pressure Pump not cavitation = The pump starts the cavitation 泵不汽蚀 = 泵开始汽蚀 泵严重汽蚀 (5).对于一台泵,为了保证其安全运行而不发生汽蚀,对于泵的必须汽蚀余量还应加一个安全裕量,于是,泵的允许汽蚀余量为: =4.提高离心泵抗汽蚀性能的方法有: (1).改进机泵结构,降低,属机泵设计问题。 (2).提高装置内的有效汽蚀余量.最主要最常用的方法是采用灌注头吸入装置. 此外,尽量减少吸入管路阻力损失,降低液体的饱和蒸汽压,即在设计吸入管路时尽可能选用管径大些,长度短些,弯头和阀门少些,输送液体的温度尽可能低些等措施,都可提高装置的有效气蚀余量。5.轴向力的平衡装置(1).轴向力的产生原因 叶轮前后两侧因流体压力分布情况不同(轮盖侧压力低,轮盘压力高)引起的轴向力A1,其方向为自叶轮背侧指向叶轮入口。 流体流入和流出叶轮的方向和速度不同而产生的动反力A2,其方向与A1相反,所以总轴向力A=A1-A2,方向一般与A1相同(一般A2较小)。(2).轴向力的平衡 采用双吸式叶轮:叶轮两侧对称,流体从两端吸入,轴向力自动抵消而达到平衡。开平衡孔或装平衡管: A:在叶轮轮盘上相对于吸入口处开几个平衡孔。 B:为避免开平衡孔后,因主流受扰动而增加水力损失,可设平衡管代替平衡孔,即采用一小管引入口压力至轮盘背侧。采用平衡叶片:在叶轮盘背面铸几条径向筋片,筋片带动叶轮背面间隙内的流体加速旋转,增大离心力,从而使叶轮背面压力显著降低。利用止推轴承承受轴向力。一般小型的单吸泵中止推轴承可以承受全部的轴向力,防止泵轴窜动。八、离心泵的操作方法1.离心泵启动前的检查(1)电机检修后,在连接联轴器前,先检查电机的转动方向是否正确。(2)检查泵出入口管线及附属管线,法兰,阀门安装是否符合要求,地脚螺栓及地线是否良好,联轴器是否装好。(3)盘车检查,转动是否正常。(4)检查润滑油油位是否正常,无油加油,并检查润滑油(脂)的油质性质。(5)打开各冷却水阀门,并检查管线是否畅通。注意冷却水不宜过大或过小,过大会造成浪费,过小则冷却效果差。一般冷却水流成线状即可。(6)打开泵的入口阀,关闭泵的出口阀,并打开压力表手阀。(7)检查机泵的密封状况及油封的开度。注意:热油泵在启动前要均匀预热。2.离心泵的启动(1)全开入口阀,关闭出口阀,启动电机。(2)当泵出口压力大于操作压力时,检查各部运转正常,逐渐打开出口阀。(3)启动电机时,若启动不起来或有异常声音时,应立刻切断电源检查,消除故障后方可启动。(4)启动时,注意人不要面向联轴器,以防飞出伤人。3.离心泵的停泵操作(1)慢慢关闭泵的出口阀。(2)切断电机的电源。(3)关闭压力表手阀。(4)停车后,不能马上停冷却水,应泵的温度的降到80度以下方可停水。(5)根据需要,关闭入口阀,泵体放空。4.离心泵操作时的注意事项(1)离心泵在
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