The basic knowledge of the pump

First, the definition of the pump:
A pump is a machine that delivers or pressurizes a liquid. It transmits the mechanical energy of the prime mover or other external energy to the liquid, increasing the liquid energy.

Second, the pump's main use:
Pumps are used to transport liquids including water, oils, acids, alkalis, emulsions, suspoemulsions, and liquid metals, as well as liquids, gas mixtures, and liquids containing suspended solids.

Third, a brief history of the development of the pump:
The rise of water is very important for human life and production. In ancient times, there have been various water lifting devices, such as the Egyptian chain pump (17th century BC), China's Jupiter (17th century BC), Sui (11th century BC) and the waterwheel (1st century AD). More famous also in the third century BC, Archimedes invented the spiral rod, can smoothly and continuously raise the water to several meters high, the principle is still used by modern screw pump. Around 200 BC, the fire-extinguishing pump invented by the ancient Greek craftsman K克ticíbius was one of the most primitive piston pumps with the main components of a typical piston pump, but the piston pump only developed rapidly after the appearance of a steam engine. .

From 1840 to 1850, Worthington, the United States, invented a piston pump that directly opposed the pump and steam cylinders, and marked the formation of modern piston pumps. The 19th century was the climax of the development of piston pumps. It was already used in various machines such as hydraulic presses. However, with the dramatic increase in water demand, from the 1920s onwards, low-speed, high-displacement piston pumps have gradually been replaced by high-speed centrifugal pumps and rotary pumps. However, the reciprocating pump still occupies a major position in the field of high pressure and small flow, especially the diaphragm pump and the piston pump have unique advantages and their applications are increasing. The emergence of rotary pumps is related to the increasingly diverse industrial requirements for liquid transport. As early as 1588, there was a record for a four-blade vane pump. Afterwards, various other rotary pumps appeared one after another. However, there were still disadvantages such as large leakage, large wear, and low efficiency during the 19th century. At the beginning of the 20th century, people solved problems such as rotor lubrication and sealing, and they were driven by high-speed motors. The rotary pumps suitable for higher pressures, medium and small flow rates, and various viscous liquids developed rapidly. The types of rotary pumps and the types of liquids that can be transported are not as great as those of other types of pumps. The idea of ​​using centrifugal force to transport water first appeared in Leonardo da Vinci's sketch.

In 1689, the French physicist Papan invented a four-blade impeller volute centrifugal pump. But what is closer to modern centrifugal pumps is the so-called Massachusetts pump that appeared in the United States in 1818 with a radial straight blade, a semi-open double suction impeller and a volute. From 1851 to 1875, multi-stage centrifugal pumps with guide vanes were invented, making it possible to develop high-lift centrifugal pumps. Although as early as 1754, the Swiss mathematician Euler proposed the basic equation of the impeller-type hydraulic machinery and laid the theoretical foundation for the design of the centrifugal pump. However, it was not until the end of the 19th century that the invention of the high-speed motor enabled the centrifugal pump to obtain the ideal power source. The superiority of the game can be fully realized. Based on the theoretical research and practice of many scholars such as Renault in the United Kingdom and Pflerdrel in Germany, the efficiency of the centrifugal pump has been greatly improved, and its performance range and field of use have also been expanding. It has become the most widely used in modern applications. The largest output pump.

Fourth, the pump's classification:
Pumps are usually divided into displacement pumps, power pumps and other types of pumps according to their working principle, such as jet pumps, water hammer pumps, electromagnetic pumps, and gas lift pumps. Pumps can be classified and named according to other methods, in addition to classification according to working principles. For example, according to the driving method can be divided into electric pumps and water wheel pumps; according to the structure can be divided into single-stage pumps and multi-stage pumps; according to the use can be divided into boiler feed pumps and metering pumps; according to the nature of the liquid can be divided into Water pump, oil pump and mud pump.

Fifth, the pump works:
The positive displacement pump relies on the reciprocating or rotating motion of the working element in the pump cylinder to alternately increase and decrease the working volume to achieve the suction and discharge of liquid. The volumetric pump for the reciprocating motion of the working element is called a reciprocating pump, and the rotary motion is called a rotary pump. The suction and discharge processes of the former are alternately performed within the same cylinder and are controlled by suction and discharge valves; the latter are driven by the rotation of working elements such as gears, screws, leaf rotors or vanes, forcing liquids from inhalation. Side transfer to discharge side. The volumetric pump has a certain amount of flow at a certain speed or number of reciprocations and hardly changes with pressure; the flow and pressure of the reciprocating pump have large pulsations, and corresponding pulsation measures need to be taken; the oscillating pump is generally not pulsating or has only small Pulsating; With self-priming ability, the pump can start to pump the air in the suction liquid after starting; When the pump is started, the discharge line valve must be fully opened; The reciprocating pump is suitable for high pressure and small flow; The rotary pump is suitable for medium and small flow And higher pressure; reciprocating pump suitable for the delivery of clean liquid or gas-liquid mixture. In general, positive displacement pumps are more efficient than powered pumps. Powered pumps rely on the force of a rapidly rotating impeller on the liquid, transferring mechanical energy to the liquid, increasing its kinetic energy and pressure, and then passing the pump cylinder to convert most of the kinetic energy to pressure energy for delivery. Power pumps are also called impeller pumps or vane pumps. Centrifugal pumps are the most common powered pumps. The power pump has a limited lift value at a certain speed. The head changes with the flow rate. The work is stable, the flow is continuous, and the flow and pressure are pulseless. Generally, there is no self-priming capability. The pump must be filled with liquid or pumped first. It can work after being vacuumed; it has a wide range of applicable properties; it is suitable for delivering clean liquids with very low viscosity; specially designed pumps can deliver mud, sewage, or water to transport solids. Power pumps are mainly used for water supply, drainage, irrigation, process fluid delivery, power station energy storage, hydraulic transmission, and ship injection propulsion. Other types of pumps refer to a type of pump that transfers energy in another way. For example, the jet pump relies on the working fluid jetted at high speed, sucks the fluid to be pumped into the pump, and transfers the momentum through the momentum exchange of two fluids; the water hammer pump is generated when the water in the flow is suddenly braked. Energy, so that part of the water pressure rose to a certain height; electromagnetic pump is to enable the liquid metal under the action of the electromagnetic force, flow to achieve delivery; gas lift pump through the catheter to send compressed air or other compressed gas to the liquid At the bottom layer, it forms a gas-liquid mixed fluid that is lighter than the liquid, and then the pressure of the mixed fluid is boosted by the pressure of the liquid outside the tube.

Six, the pump's main performance parameters:
The performance parameters of the pump are mainly flow and head, in addition to shaft power, speed, and necessary cavitation margin. Flow refers to the amount of liquid that is output through the pump outlet per unit time. Generally, volume flow is used. Head is the increment of energy per unit weight of pumped liquid from the pump inlet to the outlet. For positive displacement pumps, the energy increase is mainly reflected in the increase in pressure energy. , so usually expressed in increments of pressure instead of lift. The efficiency of the pump is not an independent performance parameter. It can be calculated from other performance parameters such as flow, head, and shaft power. On the contrary, the shaft power can also be obtained by knowing the flow rate, head and efficiency. There is a certain interdependence between the various performance parameters of the pump, which can be tested by the pump, and the parameters are measured and calculated, and plotted as curves. These curves are called pump characteristics. Each pump has a specific characteristic curve that is provided by the pump manufacturer. The recommended performance section is also usually indicated on the characteristic curve given by the plant and is called the working range of the pump. The actual operating point of the pump is determined by the intersection of the pump curve and the pump characteristic curve. To select and use the pump, the operating point of the pump should fall within the working range to ensure economical and safe operation. In addition, when the same pump delivers liquids with different viscosities, the characteristic curve also changes. In general, the characteristic curve given by the pump manufacturer mostly refers to the characteristic curve when delivering clean cold water. For the power type pump, as the viscosity of the liquid increases, the head and efficiency decrease, and the shaft power increases. Therefore, the viscosity of the liquid with a large viscosity is sometimes heated in the industry to reduce the viscosity to improve the transportation efficiency.