A pump is a machine that transports liquids or pressurizes liquids. It transfers the mechanical energy of the prime mover or other external energy to the liquid to increase the energy of the liquid. The pump is mainly used to transport liquids including water, oil, acid-base liquids, emulsions, suspoemulsions and liquid metals, etc. It can also transport liquids, gas mixtures and liquids containing suspended solids. The improvement of water is very important for human life and production. There have been various water-lifting appliances in ancient times, such as the Egyptian chain pump (17th century BC), China's Jugai (17th century BC), pottery (11th century BC) and waterwheel (1st century AD). There is also the screw rod invented by Archimedes in the third century BC, which can smoothly and continuously lift water up to several meters high. The principle is still used by modern screw pumps. Around 200 BC, the fire extinguishing pump invented by the ancient Greek craftsman Ketzibius was a primitive piston pump, which already had the main components of a typical piston pump, but the piston pump developed rapidly only after the appearance of the steam engine. From 1840 to 1850, Worthington in the United States invented a piston pump in which the pump cylinder and the steam cylinder were opposed, and the steam directly acted on the piston pump, marking the formation of the modern piston pump. The 19th century was the climax of the development of piston pumps. At that time, it was used in hydraulic presses and other machinery. However, with the rapid increase in water demand, starting from the 1920s, low-speed, highly restricted piston pumps have gradually been replaced by high-speed centrifugal pumps and rotary pumps.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 diversified requirements for liquid transportation in the industry. There was a record of four-blade sliding vane pumps as early as 1588, and various other rotary pumps appeared one after another. However, until the 19th century, rotary pumps still had shortcomings such as large leakage, large wear and low efficiency. At the beginning of the 20th century, people solved the problems of rotor lubrication and sealing, and adopted high-speed electric motors to drive. Rotary pumps suitable for higher pressure, medium and small flow rates and various viscous liquids have developed rapidly. The types of rotary pumps and the types of liquids that are suitable for delivery are beyond the reach of other types of pumps. The idea of ​​using centrifugal force to transport water has long appeared in Leonardo da Vinci's sketches. In 1689, French physicist Papin invented a volute centrifugal pump with a four-blade impeller. But closer to modern centrifugal pumps are the so-called Massachusetts pumps with radial straight blades, semi-open double-suction impellers and volutes that appeared in the United States in 1818. From 1851 to 1875, multi-stage centrifugal pumps with guide vanes were invented one after another, 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 and laid the theoretical foundation for the design of centrifugal pumps, but it was not until the end of the 19th century that the invention of high-speed motors made centrifugal pumps an ideal source of power. The superiority can be brought into full play. Based on the theoretical research and practice of many scholars such as Renault in the United Kingdom and Pfleidrell in Germany, the efficiency of centrifugal pumps has been greatly improved, and its performance range and application fields have also been expanding. It has become a modern application with a wide range of output. Big pump. Pumps are usually divided into positive displacement pumps, power pumps and other types of pumps according to their working principles, such as jet pumps, water hammer pumps, electromagnetic pumps, and gas lift pumps. In addition to the classification of pumps according to their working principles, they can also be classified and named according to other methods. For example, according to the driving method, it can be divided into electric pumps and water turbine pumps; according to the structure, it can be divided into single-stage pumps and multi-stage centrifugal pumps; according to purposes, it can be divided into boiler feed water pumps and metering pumps; according to the nature of the liquid to be transported, it can be divided into These are water pumps, oil pumps and mud pumps. Positive displacement pumps rely on working elements to reciprocate or rotate in the pump cylinder to alternately increase and decrease the working volume to achieve the suction and discharge of liquid. Positive displacement pumps with reciprocating working elements are called reciprocating pumps, and rotary pumps are called rotary pumps. The suction and discharge processes of the former are alternately carried out in the same pump cylinder and are controlled by the suction valve and discharge valve; the latter is the rotation of working elements such as gears, screws, vane rotors or sliding vanes to force liquid from the suction The side shifts to the discharge side. The flow rate of the positive displacement pump at a certain speed or the number of reciprocations is constant, and it hardly changes with the pressure; the flow and pressure of the reciprocating pump have large pulsation, and corresponding measures to reduce the pulsation need to be taken; the rotary pump generally has no pulsation or only small Pulsation; With self-priming ability, the pump can suck the air in the pipeline after the pump is started; the discharge pipeline valve must be opened when the pump is started; the reciprocating pump is suitable for high pressure and small flow; the rotary pump is suitable for small and medium flow and Higher pressure; reciprocating pump is suitable for conveying clean liquid or gas-liquid mixture. In general, the efficiency of positive displacement pumps is higher than that of power pumps. The power pump relies on the force of the rapidly rotating impeller on the liquid to transfer mechanical energy to the liquid to increase the kinetic energy and pressure energy, and then through the pump cylinder, most of the kinetic energy is converted into pressure energy to achieve delivery. Power pumps are also called impeller pumps or vane pumps. Centrifugal pumps are common power pumps. The head produced by the power pump at a certain speed has a limit value, and the head changes with the flow; the work is stable, the delivery is continuous, the flow and pressure are not pulsating; generally there is no self-priming ability, the pump needs to be filled with liquid or the pipeline is pumped It can only start to work after it is in a vacuum; it has a wide range of applicable performance; it is suitable for transporting clean liquids with small viscosity. The specially designed pump can transport mud, sewage, etc. or water transport solids. Power pumps are mainly used for water supply, drainage, irrigation, process liquid transportation, power storage, hydraulic transmission, and ship jet propulsion. Other types of pumps refer to a type of pump that transfers energy in another way. For example, jet pumps rely on high-speed injection of working fluid, suck the fluid that needs to be transported into the pump, and transfer energy by mixing two fluids for momentum exchange; water hammer pumps are produced when the flowing water is suddenly braked Energy makes a part of the water pressure rise to a certain height; the electromagnetic pump causes the energized liquid metal to flow under the action of electromagnetic force to achieve delivery; the gas lift pump sends compressed air or other compressed gas to the liquid through the pipe At the bottom layer, a lighter gas-liquid mixed fluid is formed, and the pressure of the mixed fluid is increased by the pressure of the liquid outside the tube. The performance parameters of the pump mainly include flow and head