A pump is a machine that transports or pressurizes liquid。It transfers the mechanical energy or other external energy of the prime mover to the liquid, making the liquid energy increase。The pump is mainly used to transport liquids including water, oil, acid lye, emulsion, suspension emulsion and liquid metal, etc., and can also transport liquids, gas mixtures and liquids containing suspended solids。 The ascension of water is very important for human life and production。Various water-lifting devices existed in ancient times, such as the Egyptian chain pump (17th century BC), the Chinese Shadof (17th century BC), pulley (11th century BC), and water wheel (1st century AD).。In the third century BC, Archimedes invented the screw, which can smoothly and continuously lift water to a height of several meters, and its principle is still used by modern screw pumps。 Around 200 BC, the ancient Greek craftsman Ctesibius invented the fire pump is a primitive piston pump, which has the main components of a typical piston pump, but the piston pump has only been rapidly developed after the emergence of the steam engine。1840-1850, Worthington invented pump cylinder and steam cylinder opposite, steam direct action piston pump, marking the formation of modern piston pump。The 19th century was the climax of the development of piston pumps, which were used in a variety of machinery such as hydraulic presses。However, with the rapid increase in water demand, from the 1920s, the low-speed piston pumps with greatly limited flow were gradually replaced by high-speed centrifugal pumps and rotary pumps。However, reciprocating pumps still occupy a major position in the field of high pressure and small flow, especially the advantages of diaphragm pumps and plunger pumps, and their applications are increasing。 The emergence of rotary pumps is related to the increasingly diverse requirements for liquid transportation in industry。As early as 1588, there were records on the four-blade sliding vane pump, and other rotary pumps have appeared since, but until the 19th century, rotary pumps still have the shortcomings of large leakage, wear and low efficiency。At the beginning of the 20th century, people solved the problems of rotor lubrication and sealing, and used high-speed motor drive, suitable for high pressure, small and medium-sized flow and various viscous liquids rotary pump has been rapidly developed。The types of rotary pumps and the types of liquids suitable for transport are as many as other types of pumps。 The idea of using centrifugal force to transport water appeared in sketches made by Leonardo Da Vinci。In 1689, the French physicist Papin invented the volute centrifugal pump with a four-blade impeller。But closer to the modern centrifugal pump, it is the so-called Massachusetts pump with radial straight blades, semi-open double suction impeller and volute appeared in the United States in 1818。From 1851 to 1875, multistage centrifugal pumps with guide blades were successively invented, making it possible to develop high-lift centrifugal pumps。 Although as early as 1754, the Swiss mathematician Euler proposed the basic equations of impeller hydraulic machinery, laying the theoretical basis for the design of centrifugal pumps, it was not until the end of the 19th century that the invention of high-speed motors made centrifugal pumps obtain an ideal power source, and its advantages were fully developed。On the basis of the theoretical research and practice of many scholars such as Renault in the United Kingdom and Pfledreer in Germany, the efficiency of centrifugal pumps has been greatly improved, and its performance range and application fields have also been expanding, and it has become a pump with a wide range of modern applications and large output。Pumps are usually divided into positive displacement pumps, power pumps and other types of pumps according to the working principle, such as jet pumps, water hammer pumps, electromagnetic pumps, gas lift pumps。In addition to the classification according to the working principle, the pump can also be classified and named according to other methods。For example, according to the driving method can be divided into electric pump and hydraulic pump;According to the structure can be divided into single-stage pump and multi-stage centrifugal pump;According to the use can be divided into boiler feed pump and metering pump;According to the nature of the liquid can be divided into pumps, oil pumps and mud pumps。 Positive displacement pump is to rely on the working elements in the pump cylinder for reciprocating or rotating movement, so that the working volume alternately increases and decreases, in order to achieve the suction and discharge of liquid。The positive displacement pump with reciprocating movement of the working element is called the reciprocating pump, and the rotary movement is called the rotary pump。The suction and discharge processes of the former are carried out alternately in the same pump cylinder, and are controlled by the suction valve and the discharge valve.The latter is through the rotating action of working elements such as gears, screws, blade rotors or sliders, forcing the liquid to transfer from the suction side to the discharge side。 Positive displacement pump at a certain speed or reciprocating number of flow is certain,It hardly changes with pressure;The flow and pressure of the reciprocating pump have large fluctuations，It is necessary to take corresponding measures to reduce pulsation;Rotary pumps generally have no pulsation or only small pulsation;It has self-priming ability，The air suction liquid in the pipeline can be removed immediately after the pump starts;The discharge line valve must be opened when starting the pump;Reciprocating pump is suitable for high pressure and small flow;Rotary pump is suitable for small flow and high pressure;Reciprocating pumps are suitable for transporting clean liquids or gas-liquid mixtures。In general, positive displacement pumps are more efficient than power pumps。 The dynamic pump relies on the force of the rapidly rotating impeller on the liquid to transfer the mechanical energy to the liquid, so that its kinetic energy and pressure can increase, and then through the pump cylinder, most of the kinetic energy is converted into pressure energy to achieve transmission。Power pump is also known as impeller pump or vane pump。Centrifugal pump is a common power pump。 There is a limited value of the head generated by the power pump at a certain speed,The head changes with the flow;Job stability，Transmission continuity，No pulsation of flow and pressure;Generally no self-priming ability，It is necessary to fill the pump with liquid or pump the pipeline into a vacuum before starting to work;Wide range of applicable performance;Suitable for conveying clean liquids with small viscosity，Specially designed pumps can transport mud, sewage, etc., or water transport solids。The power pump is mainly used for water supply, drainage, irrigation, process liquid transport, power station energy storage, hydraulic transmission and Marine jet propulsion。 Other types of pumps are pumps that transmit energy in a different way。Jet pumps, for example, rely on high-speed ejections of working fluids，The fluid to be delivered is sucked into the pump，The energy is transferred by the momentum exchange through the mixing of two fluids.Water hammer pumps use the energy produced when the flowing water is suddenly stopped，To raise some of the water pressure to a certain height;Electromagnetic pump is to make the energized liquid metal under the action of electromagnetic force，Produce flow to achieve transport;The gas lift pump delivers compressed air or other compressed gases through a conduit to the bottom of the liquid，To form a lighter liquid mixture of gas and liquid fluid，The mixed fluid is then pressed up by the pressure of the liquid outside the pipe。 Pump performance parameters are mainly flow and head