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1、CENTRIFUGAL PUMPS IN THE CHEMICAL INDUSTRYAbstract : A centrifugal pump converts the input power to kinetic energy in the liquid by accelerating the liquid by a revolving device - an impeller. The most common type is the volute pump. Fluid enters the pump through the eye of the impeller which rotate
2、s at high speed. The fluid is accelerated radially outward from the pump chasing. A vacuum is created at the impellers eye that continuously draws more fluid into the pump . This article stresses on a series of centrifugal pumps，From a brief introduction to the principles.Keywords : centrifugal pump
3、 ,Introduction ,Working principle , Cavitation ， Mechanism of Cavitation ，Solution and Remedies1. Introduction Pump ,device used to raise ,transfer ,or compress liquids and gases .Four general classes of pumps for liquids are described below .In all of them ,steps are taken to prevent cavitation (th
4、e formation of a vacuum) ,which would reduce the flow and damage the structure of the pump .Pumps used for gases and vapors are usually known as compressors .The study of fluids in motion is called fluid dynamics. Water pump ,device for moving water from one location to another ,using tubes or other
5、 machinery .Water pumps operate under pressures ranging from a fraction of a pound to more than 10,000 pounds per square inch .Everyday examples of water pumps range from small electric pumps that circulate and aerate water in aquariums and fountains to sump pumps that remove water from beneath the
6、foundations of homes . One type of modern pumps used to move water is the centrifugal pump .Early version of the centrifugal pump ,the screw pump ,consists of a corkscrew-shaped mechanism in a pipe that ,when rotated ,pulls water upward .Screw pumps are often used in waste-water treatment plants bec
7、ause they can move large amounts of water without becoming clogged with debris .In the ancient Middle East the need for irrigation of farmland was a strong inducement to develop a water pump .Early pumps in this region were simple devices for lifting buckets of water from a source to a container or
8、a trench .Greek mathematician and inventor Archimedes is thought to have devised the first screw pump in the third century BC .Later Greek inventor Ctesibius develop the first lift pump .During the late 17th and early 18th Centuries AD ,British engineer Thomas Savery ,French physicist Denis Papin ,A
9、nd British blacksmith and inventor Thomas Newcomen contributed to the development of a water pump that used steam to power the pump piston .The steam-powered water pumps first wide use was in pumping water out of mines .Modern-day examples of centrifugal pumps are those used at the Grand Coulee Dam
10、on the Columbia River .This pump system has the potential to irrigate over one million acres of land . Also known as rotary pumps ,centrifugal pumps have a rotating impeller ,also known as a blade ,that is immersed in the liquid .Liquid enters the pump near the axis of the impeller ,and the rotating
11、 impeller sweeps the liquid out toward the ends of the impeller blades at high pressure .The impeller also gives the liquid a relatively high velocity that can be converted into pressure in a stationary part of the pump ,known as the diffuser .In high-pressure pumps ,a number of impeller may be used
12、 in series ,and the diffusers following each impeller may contain guide vanes to gradually reduce the liquid velocity .For lower-pressure pumps ,the diffuser is generally a spiral passage ,known as a volute ,with its cross-sectional area increasing gradually to reduce the velocity efficiently .The i
13、mpeller must be primed before it can begin operation ,that is ,the impeller must be surrounded by liquid when the pump is started .This can be done by placing a check valve in the suction line ,which holds the liquid in the pump when the impeller is not rotating .If this valve leaks ,the pump may ne
14、ed to be primed by the introduction of liquid from an outside source such as the discharge reservoir .A centrifugal pump generally has a valve in the discharge line to control the flow and pressure .For low flows and high pressures ,the action of the impeller is largely radial .For higher flows and
15、lower discharge pressure ,the direction of the flow within the pump is more nearly parallel to the axis of the shaft ,and the pump is said to have an axial flow .The impeller in this case acts as a propeller .The transition from one set of floe conditions to the other is gradual ,and for intermediat
16、e condition , the device is called a mixed-flow pump . 2.The Centrifugal Pump The centrifugal pump is by far the most widely used type in the chemical and petroleum industries .It will pump liquids with very wide ranging properties and suspensions with a high solids content including ,for example ,cement slurries ,and may be constructed from a very wide rang of corrosion resistant materials .The whole pump casing may be constructed from plastic such as p
