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Water pump principle


Introduction of water pump principle


Hydraulic machinery that raises water from low to high by means of power equipment and transmission or by using natural energy. Widely used in farmland irrigation, drainage and agriculture and animal husbandry, industrial and mining enterprises, urban water supply, drainage and so on. The water pump used in farmland irrigation and drainage, agriculture and animal husbandry production process is called agricultural water pump, which is one of the main components of farmland irrigation and drainage machinery.

Water pump type
 

According to different working principles, it can be divided into volumetric pumps, vane pumps and other types. The positive displacement pump uses the change of its working chamber volume to transfer energy, mainly including piston pump, plunger pump, gear pump, diaphragm pump, screw pump and other types. Vane pump is the use of rotary blade and water interaction to transfer energy, centrifugal pump, axial flow pump and mixed flow pump and other types. The pump body part of the submersible electric pump is a vane pump. Other types of water pumps include jet pumps, water hammer pumps, internal combustion water pumps, etc., which work using the principles of jet water hammer and fuel deflagration, respectively. Water turbine pump is a combination of turbine and vane pump. The following types of pumps are more representative.

Centrifugal pump is a kind of pump that uses centrifugal force to increase the pressure of water and make it flow. It is composed of pump casing, impeller and rotating shaft. The power machine drives the rotating shaft, and the rotating shaft drives the impeller to rotate at a high speed in the pump shell, and the water in the pump is forced to rotate with the impeller to generate centrifugal force. Centrifugal force liquid from the impeller around the throw, merged into high-speed high-pressure water flow through the pump shell discharge outside the pump, the impeller center of the formation of low pressure, so as to inhale new water flow, constitute a continuous flow of water transport. The impeller has blades bent in the opposite direction of rotation, and its structural type is closed, semi-closed and open. Most of the agricultural impellers are closed impellers, and the two sides of the blades are closed by discs. The pump body gradually expands into a volute shape along the direction of the outlet pipe. Water from the impeller side of the suction called single suction centrifugal pump, from the impeller side of the suction called double suction centrifugal pump. In order to increase the head, multiple impellers can be installed on the same shaft to become a multi-stage centrifugal pump. The water discharged from the previous impeller enters the water inlet of the next impeller, and is discharged from the next impeller after pressurization, so the more impellers, the higher the pressure. Some centrifugal pumps with can automatically exclude the suction pipe and pump body air device, before starting without filling the pump, said self-priming centrifugal pump, but its efficiency is often lower than the general centrifugal pump.

 

Centrifugal pumps are most widely used in farmland irrigation and water supply for agriculture and animal husbandry. It is mostly used for occasions with high lift and small flow. The head of the single-stage centrifugal pump is 5~125 meters, and the discharge flow is uniform, generally 6.3~400 m 3/h, and the efficiency can reach about 86 ~ 94%.

axial flow pump

It is composed of pump casing, impeller and rotating shaft. Also called propeller pump. There are several propeller-shaped blades on the impeller. When the impeller is driven to rotate with the rotating shaft by the power machinery, each blade pushes the water to one end, and at the same time draws water from the water source at the other end, so that the water is produced along the direction parallel to the rotating shaft. Continuous flow to achieve the purpose of continuously conveying water flow. The pressure of the water flow is increased by the rotation of the impeller. After the rotating water flow from the impeller passes through the fixed guide vane, the rotating speed is eliminated, and part of the kinetic energy is converted into pressure energy due to the diffusion effect, which pushes the water flow in the pump shell to rise along the axial direction and flows out of the outlet pipe. Axial flow pumps are mostly used for occasions with low head and large flow, with a head range of about 1 to 25 meters. The flow rate is 2.7 to 60.0 m 3/s, and the efficiency can reach 85 to 90.5%. There are three kinds of installation methods: vertical, horizontal and inclined, of which vertical axial flow pumps are used more (Figure 2). The installation angle of the propeller blade on the impeller hub of the large axial flow pump can be adjusted, or the rotating shaft of the hydraulic transmission can be adjusted with time in operation to meet the requirements of the head and flow changes and obtain higher productivity, so it is called adjustable axial flow pump.

 

Tubular pump is a kind of horizontal axial flow pump. It is composed of a motor, a deceleration device and a water pump, and is installed in the machine pit inside the underwater dam. The inlet and outlet flow channels are located in a straight line, which is approximately straight and cylindrical, with less hydraulic loss, high water lifting efficiency, and compact structure, convenient installation and maintenance, and simple pumping station engineering. Masonry pump is a low-lift axial flow pump. In addition to the impeller and its peripheral pump shell made of metal materials, the inlet and outlet channels are made of masonry or concrete structures, and their lift is less than 2 meters. Simple structure, low cost and high efficiency. Suitable for drainage and irrigation in low-lying areas.

mixed flow pump

Structure and working principle of both centrifugal pump and axial flow pump two types of characteristics of a pump. When the impeller is driven by the power machinery to rotate, the blade pushes the water body on the one hand, and at the same time drives the water body to rotate to produce centrifugal effect. The water body generates flow and increases pressure under the thrust and centrifugal force of the blades. The water flows into the impeller from the axial direction and then flows out obliquely along the blades, which is often used in occasions with large conveying displacement and medium pressure. There are usually two types of volute type and guide vane type. The structure of the volute mixed flow pump is similar to that of the centrifugal pump. The kinetic energy obtained by the water flow through the impeller is converted into pressure energy by the volute shaped flow passage. Generally, the medium and small mixed flow pump adopts the volute structure. The guide vane mixed flow pump is also called diagonal flow pump. Its structure is similar to that of axial flow pump. It has the characteristics of small radial size, simple structure and light weight. Large mixed-flow pumps are mostly guide vanes, and the installation angle of their blades can generally be adjusted. The lift range of the mixed flow pump is generally 3~10.5 meters, the starting power is low, and it can adapt to the change of water level, and the flow rate is 0.1~50 m 3/s; the efficiency can reach 64 ~ 86%. Since the 1970 s, the development of large-scale mixed-flow pumps has been rapid, and there is a trend to replace large-scale axial-flow pumps on many occasions.

long shaft deep well pump

Most of them are vertical single-suction centrifugal pumps. The impeller is installed below the dynamic water level in the well. The power machine is arranged on the well. The impeller is driven by the long shaft to rotate in the guide shell. The water flow follows the flow channel between the guide shell and the impeller and rises to the ground through the water delivery pipe. When the head is high, a multi-stage centrifugal pump with multiple impellers in series can be used. Due to the high requirements of manufacturing and installation accuracy of the transmission shaft, the efficiency decreases significantly with the increase of the well depth, so it is generally only used for deep wells not exceeding 100 meters.

electric submersible pump

The pump body impeller and the motor driving the impeller are submerged into the water to work a pump, there are deep well and working surface with two. The submersible electric pump for deep well supplies power to the motor through the cable extending into the well, thus eliminating the long shaft of transmission. Therefore, it has compact structure, light weight, convenient installation, use and transfer. It has a tendency to replace the long shaft deep well pump in areas with power supply, but it is not applicable to wells with large sand content and areas without power supply. The motors used in submersible electric pumps are dry (the motors are all sealed), semi-dry (the stator of the motor is sealed, and the rotor runs in water), oil-filled (the motor is filled with oil to prevent moisture from invading the windings) and wet (the motor is filled with water, The stator and rotor are running in water) and other types. The first three kinds need to be sealed and the manufacturing and installation accuracy requirements are high. Therefore, agricultural deep well submersible electric pumps usually use wet motors. The stator windings are made of water-resistant insulated wires or synthetic resin is poured into the ends and slots of the stator windings. Water enters the motor. The internal impact is not large, the sealing structure can be greatly simplified, and only sand control is required. Some deep well submersible pump head up to 1400 meters, the maximum flow of 1.4 m 3/sec.

jet type deep well pump

It is usually composed of jet pump and centrifugal pump with corresponding casing. Used to lift water from deep wells within 30 meters. The working principle of the jet pump is to make the pressure spray to the entrance of the throat pipe through the nozzle. Due to the horizontal turbulent diffusion of the jet, the air in the suction pipe is taken away, and a vacuum is formed in the pipe. The well water is sucked in and mixed with the jet water in the throat pipe for energy exchange. At the outlet of the throat, the flow rate of the two approaches the same, and then most of the kinetic energy is converted into pressure energy through the diffusion pipe, so that the water pressure is further improved, and finally discharged from the drain pipe.

There are two combination types of jet deep well pumps: ① the jet pump is connected in parallel with the centrifugal pump, the centrifugal pump sends pressure water to the jet pump through a pipeline, and the jet pump lifts this part of water upward together with the absorbed water, thus converting the small flow of high pressure water into large flow of low pressure water, which is mainly used for ground irrigation and channel dredging, etc.; ② The jet pump and the centrifugal pump are connected in series to pressurize the centrifugal pump in parallel to increase its suction range, the centrifugal pump will be part of the water provided to the jet pump, the rest into the pressure pool or pressure pipeline, the water pressure is higher, mainly used for sprinkler irrigation equipment and agriculture and animal husbandry water supply. Compared with submersible electric pumps and long-axis deep well pumps, jet deep well pumps have the characteristics of simple structure, reliable work, convenient manufacture, and low cost; but they have lower efficiency and higher power consumption under the same working conditions.


(II) of water pump principle

screw pump

A volumetric pump that relies on changes in the volume of the pump chamber when the screw rotates to inhale and transport water. There are single screw, twin screw and multi screw types. In agriculture, single screw pumps are used, and their pump chambers consist of a steel screw and a rubber sleeve fixedly installed in the pump housing. A single-pitch screw rotates in a sleeve having a double-pitch inner spiral, and the cavity formed therebetween moves from the suction end to the outlet end, thereby forming a continuous flow of water. Because of its simple structure, small size, easy disassembly and assembly, reliable work, and good self-priming performance, it is mostly used in mobile sprinkler irrigation systems.

Manual diaphragm pump

It is used for lifting water with low lift and small flow. It is composed of pump body, inlet and outlet pipes, inlet and outlet valves, diaphragm and push-pull rod. The pump body may consist of one or two pump chambers. In a diaphragm pump having two pump chambers, the diaphragm is arranged in the center of the pump body, or the two diaphragms are respectively arranged outside the two pump chambers. When working, two people manipulate the push-pull rod connected with the diaphragm by hand to push the diaphragm to press in and open the reciprocating motion, so that the volume of the two pump chambers is alternately expanded and reduced. When the pump cavity expands, the pressure decreases, the inlet valve opens, the outlet valve closes, and the water flows into the pump cavity from the inlet pipe; when the pump cavity shrinks, the pressure increases, the inlet valve closes, the outlet valve opens, and the pump cavity Water flows out from the drain pipe, the two pump chambers alternately absorb water and drain water, and can lift 10-20 tons of water per hour.

pull rod piston pump

Driven by animal power prime movers, wind turbines or internal combustion engines, etc., often used when lifting water from wells on grazing grounds. It is composed of pump cylinder, piston, inlet and outlet pipes, inlet and outlet valves, pull rods and transmission devices. The piston is driven by the pull rod connected to it and reciprocates up and down in the pump cylinder. When the piston moves upward, the inlet valve opens, the water in the inlet pipe enters the pump cylinder, and the outlet valve is closed at the same time, and the water above the piston is driven upward; when the piston moves downward, the inlet valve is closed and the outlet valve is opened. The water in the pump cylinder rises to the top of the piston from the outlet valve, so that the water is repeatedly fed and lifted, so that the water is continuously discharged from the drain.


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