First, what is the pump? Pumps are machines that transport liquid or pressurize liquid. It transfers the mechanical energy of the prime mover or other external energy to the fluid, increasing the fluid's energy. Pump is mainly used to transport liquids such as water, oil, acid and alkali, emulsions, suspoemulsion and liquid metal, but also liquid and gas mixtures and liquids containing suspended solids. Pump can usually be divided into working principle of positive displacement pumps, power pumps and other types of pumps three categories. In addition to the principle of classification, but also by other methods of classification and naming. 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 pump; According to the use can be divided into boiler feed pump and metering pump; According to the nature of liquid can be divided into Pumps, pumps and mud pumps. There is a certain interdependence between the various performance parameters of the pump relationship, you can draw a curve to represent, known as the pump characteristic curve, each pump has its own specific characteristic curve. Second, the definition and history of the pump delivery of liquid or pressurized liquid machinery. In a broad sense, a pump is a machine that carries or pressurizes a fluid, including some that convey gas. The pump transmits the energy of the prime mover's mechanical energy or other energy to the liquid to increase the energy of the liquid. Water lifting is very important for human life and production. There are various types of water-lifting appliances in ancient times such as the Egyptian chain pump (formerly 17th century), China's orange cake (former 17th century), the potter's wheel (formerly 11th century), waterwheel (1st century AD) and 3rd century BC Ancient Greece Archimedes invented the spiral rod and so on. About 200 BC, the ancient Greek craftsman Kate Sibius invented the most primitive piston pump - fire pump. As early as 1588, there was a record of 4-vane vane pumps, and various other rotary pumps appeared one after another. In 1689, France's D. Papan invented a 4-bladed impeller centrifugal pump. In 1818, the United States appeared with a radial straight blade, half-open double suction impeller and volute centrifugal pump. 1840 ~ 1850, the United States HR Worthington invented the pump cylinder and steam cylinder direct action opposite the piston pump, marking the formation of the modern piston pump. From 1851 to 1875, multistage centrifugal pumps with guide vanes were successively invented, making it possible to develop high-lift centrifugal pumps. Subsequently, a variety of pumps have come out. With the application of various advanced technologies, the efficiency of the pump is gradually increased, and the performance range and application are also gradually expanding. Third, the pump classification According to a wide range of pumps, according to the working principle can be divided into: â‘ power pump, also known as impeller pump or vane pump, rely on the rotation of the impeller on the dynamic force of the liquid, the energy continuously to the liquid , So that the kinetic energy of liquid (mainly) and the pressure can be increased, and then through the pressure chamber out of the kinetic energy into pressure, can be divided into centrifugal pump, axial flow pump, partial flow pump and vortex pump. â‘¡ positive displacement pumps, relying on the periodic changes in the volume of the sealed working space containing the liquid, the energy is periodically transferred to the liquid, the liquid pressure is increased to force the liquid to be forced to discharge, according to the working elements of the movement can be divided into reciprocating pump And rotary pump. â‘¢ other types of pumps to transfer energy in other forms. For example, the jet pump relies on the high-speed jet working fluid to suck the fluid to be delivered to the pump and then mix it for the exchange of momentum to transfer energy; the water hammer pump uses some water in the flow to ascend to a certain height to transfer energy; Power of the liquid metal in the electromagnetic force generated by the flow and delivery. In addition, the pump can also be transported liquid properties, driving methods, structure, use, etc. for classification. Fourth, the application of the pump in various fields From the performance range of the pump, the flow of giant pump up to hundreds of thousands of cubic meters per hour or more, while the micro-pump flow rate of less than dozens of milliliters per hour; pump pressure from Atmospheric pressure up to 19.61Mpa (200kgf / cm2) above; liquid temperature was transported as low as -200 degrees Celsius, up to 800 degrees Celsius. Pumps deliver a wide variety of fluids, such as delivering water (clean water, sewage, etc.), fluids, acids and alkalis, suspensions, and liquid metals. In the production of the chemical and oil sectors, raw materials, semi-finished products and finished products are mostly liquids, whereas the conversion of raw materials into semi-finished and finished products requires complicated processes that pump to deliver liquids and provide chemical reactions with pressure flow In addition, in many devices also use the pump to adjust the temperature. In agricultural production, pumps are the main irrigation and drainage machinery. A vast rural areas in our country, every year in rural areas require a large number of pumps, agricultural pumps in general account for more than half of total pump output. Pumps are also the most widely used equipment in the mining and metallurgical industries. The mine needs to be drained by a pump. In the process of beneficiation, smelting and rolling, the pump is required to supply water first and so on. In the power sector, the nuclear power station needs a nuclear main pump, a secondary pump, a tertiary pump, and a thermal power plant which require a large number of boiler feed pumps, condensate pumps, circulating pumps and ash pumps. In the national defense building, the regulation of aircraft flaps, tail rudders and landing gear, the rotation of warships and tank turrets, the ups and downs of submarines, etc. require the use of pumps. High pressure and radioactive liquid, some also require the pump without any leakage. In the shipbuilding industry, the number of pumps used on each ocean going wheel is generally more than 100 and its type is also varied. Others, such as urban water supply and drainage, steam locomotive water, lubrication and cooling in machine tools, transporting drifts and dyes in the textile industry, transporting pulp in the paper industry, and transporting milk and sugar foods in the food industry, require large quantities Pump. In any case, pumps, pumps, running pumps, tanks, submarines, or drilling, mining, trains, ships, or everyday life are needed everywhere. This is the case, so the pump as a general machinery, it is a kind of mechanical industry in the product. Fifth, the basic parameters of the pump characterization The main performance of the pump the following basic parameters: 1, the flow rate Q is the amount of liquid delivered in a unit of time (volume or mass). Volume flow Q said, the unit is: m3 / s, m3 / h, l / s and so on. Mass flow Qm said, the unit is: t / h, kg / s and so on. The relationship between mass flow and volume flow is: Qm = ÏQ where Ï is the density of the liquid (kg / m3, t / m3) and Ï = 1000 kg / m3 at room temperature. 2, head H head is pumping unit weight of liquid pumping from the pump inlet (pump inlet flange) to the pump outlet (pump outlet flange) the value of energy. Which is the effective energy of a Newtonian liquid through the pump. The unit is N? M / N = m, that is pumping the liquid column height, used to refer to as meter. 3, speed n speed is the number of revolutions of the pump shaft unit time, with the symbol n said unit is r / min. 4, NPSH NPSH NPSH, also called net positive nozzle, is the main parameter of cavitation performance. Naphthenic margin used domestic Δh said. 5, power and efficiency Pump power usually refers to the input power, that is, the prime mover shaft pump power, it is also known as shaft power, with P said; pump the effective power, also known as the output power, said Pe. It is the unit of time delivered from the pump liquid in the pump to obtain effective energy. Since the head is the unit of fluid that the pump outputs, it is the effective energy obtained from the pump so that the product of the head and the mass flow and the acceleration of gravity is the effective energy obtained from the liquid output from the pump per unit of time - the pump The effective power of the pump: Pe = ÏgQH (W) = γQH (W) where Ï - pumping liquid density (kg / m3); γ - heavy pumping liquid (N / m3) Flow rate (m3 / s); H - pump head (m); g - acceleration of gravity (m / s2). The difference between the shaft power P and the effective power Pe is the loss power in the pump, which is measured by the efficiency of the pump. Pump efficiency for the effective power and shaft power ratio, expressed with η. Sixth, what is the flow? What alphabet is used? How to convert? The volume of liquid discharged by the pump per unit time is called the flow rate and the flow rate is expressed by Q. The unit of measure is m3 / h, l / s, L / s = 3.6 m3 / h = 0.06 m3 / min = 60L / min G = QÏG is the weight Ï is the liquid specific gravity Example: a pump flow 50 m3 / h, when pumping pumping hourly weight? The specific gravity of water Ï is 1000 kg / m3. Solution: G = Qp = 50 × 1000 (m3 / h? Kg / m3) = 50000kg / h = 50t / h Seven, what is the lift? What alphabet is used? What unit of measurement? And pressure conversion and formula? The weight per unit weight of liquid obtained through the pump is called head. Pump head including the suction stroke, approximately pump outlet and inlet pressure difference. Head with H said, in meters (m). The pressure of the pump is expressed by P in units of Mpa (MPa), H = P / Ï, H = 1kg / cm2 / 1000kg / m3 if P is 1kg / (1000 kg / m3) = (10000 kg / m2) / 1000 kg / m3 = 10m 1Mpa = 10kg / c m2, H = (P2-P1) / Ï (P2 = outlet pressure P1 = inlet pressure) NPSH What is suction stroke? The respective units of measure that letters? Pump at work at the impeller inlet at a certain vacuum pressure will produce a vapor, vaporization of bubbles in the liquid particle impact movement, the impeller and other metal surface erosion, thus undermining the impeller and other metals, the vacuum pressure at this time Vapor pressure, NPSH refers to the excess energy of vaporization pressure per unit weight of liquid at the suction inlet of the pump. Units marked with meters, with (NPSH) r. Suction stroke is required NPSH Δh: That is, the degree of vacuum that the pump allows liquid to be sucked in, that is, the allowable installation height of the pump, in meters. Stroke = standard atmospheric pressure (10.33 meters) - NPSH - safe amount (0.5 meters) Standard atmospheric pressure can depress the pipeline vacuum height of 10.33 meters. For example: a pump required NPSH is 4.0 meters, suction Δh? Solution: Δh = 10.33-4.0-0.5 = 5.83 meters Nine, what is the pump cavitation phenomenon and its causes 1, the cavitation liquid at a certain temperature, reducing pressure to the temperature of the vaporization pressure, the liquid will produce steam bubble. The phenomenon of bubbles is called cavitation. 2, cavitation collapse Cavitation bubbles generated when the flow to high pressure Department, its volume decreases so that burst. This phenomenon of bubble disappearing in liquid due to pressure increase is called cavitation collapse. 3, the causes of cavitation and hazards Pumps in operation, if the over-flow part of the local area (usually the impeller blade inlet somewhere later) for some reason, pumping the absolute pressure of the liquid reduced to the current temperature When the liquid evaporates, the liquid begins to vaporize there, generating a large amount of steam and forming bubbles. When the liquid containing a large amount of bubbles is pushed forward through the high-pressure area inside the impeller, the high-pressure liquid around the bubbles causes the bubbles to rapidly shrink and break. At the same time as the bubbles are broken and condensed, the liquid particles fill the cavities at a very high speed, which causes a very strong water hammer at this moment and impacts the metal surface with a very high impact frequency with an impact stress of several hundreds to several thousands of atmospheres , The impact frequency up to tens of thousands of times per second,