Physical principle of the pump:

　　Power machinery and transmissions or hydro-machines that use natural energy to raise water from low to high. Widely used in farmland irrigation, drainage and agriculture, animal husbandry, industrial and mining enterprises, urban water supply, drainage and other aspects. The pump used in farmland irrigation and drainage and agricultural production is called agricultural pump, which is one of the main components of farmland irrigation and drainage machinery.

　　According to different working principles, it can be divided into volume pump and vane pump. The volumetric 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 so on. The vane pump uses the interaction of the rotary vane and water to transfer energy. There are centrifugal pump, axial flow pump and mixed flow pump. The pump body part of the submersible pump is a vane pump. Other types of pumps include jet pumps, water hammer pumps, internal combustion pumps, etc., which work on the principle of jet water hammer and fuel detonation, respectively. The water wheel pump is a combination of a turbine and a vane pump. The above various types of pumps are more representative of the following types.

　　A centrifugal pump is a pump that uses centrifugal force to increase the pressure of a water body and make it flow. It consists of pump casing, impeller, rotating shaft and so on. The power machine drives the rotating shaft, and the rotating shaft drives the impeller to rotate at a high speed in the pump casing, and the water body in the pump is forced to generate centrifugal force as the impeller rotates. The centrifugal force forces the liquid to be thrown from the periphery of the impeller, and the high-speed high-pressure water flows through the pump casing to discharge the pump. A low pressure is formed at the center of the impeller, thereby inhaling a new water flow, which constitutes a continuous water flow conveying function. The impeller has blades that are curved in the reverse rotation direction. The structure types are closed, semi-closed and open. The agricultural use is mostly closed impeller, and the two sides of the blade are closed by a disc. The pump body gradually expands into a volute shape along the direction of the outlet pipe. A single-suction centrifugal pump in which water flows from one side of the impeller is sucked into the double-suction centrifugal pump from both sides of the impeller. In order to increase the lift, multiple impellers can be mounted on the same shaft to form a multistage centrifugal pump. The water discharged from the former impeller enters the water inlet of the latter impeller, and is pressurized and then discharged from the latter impeller. Therefore, the more the number of impellers, the higher the pressure. Some centrifugal pumps have a device that can automatically remove the suction pipe and the air in the pump body. It is not necessary to fill the pump body before starting. It is called a self-priming centrifugal pump, but its efficiency is often lower than that of a general centrifugal pump.

　　Centrifugal pumps are the most widely used in farmland irrigation and irrigation and agricultural water supply. It is often used in applications where the head is high and the flow is small. The single-stage centrifugal pump has a head of 5 to 125 meters, and the discharge flow is uniform, generally 6.3 to 400 m3/hour, and the efficiency is about 86 to 94%.

Axial flow pump：

　　It consists of a pump casing, an impeller and a rotating shaft. Also known as a propeller pump. There are several propeller-shaped blades on the impeller. When the impeller is rotated by the power machine along with the rotating shaft, each blade pushes the water toward one end, and at the other end draws water from the water source at the other end, so that the water is produced continuously along the direction parallel to the rotating shaft. Flow, to achieve the purpose of continuously conveying water. The water flow pressure is increased by the rotation of the impeller. After the rotating water flowing out of the impeller passes through the fixed vane, the rotational speed is eliminated, and part of the kinetic energy is converted into pressure energy due to the diffusion effect, and the water flow in the pump casing is pushed up in the axial direction and flows out from the outlet pipe. The axial flow pump is mostly used in the case of low lift and large flow, the lift range is about 1 to 25 meters; the flow rate is 2.7 to 60.0 meters 3 / sec, and the efficiency can reach 85 to 90.5%. There are three types of installation methods: vertical, horizontal and inclined. Among them, vertical axial flow pumps are used more. The installation angle of the propeller blades on the hub of the large axial flow pump impeller can be adjusted, or the shaft of the hydraulic transmission can be adjusted with time in operation to meet the requirements of head and flow change, and high productivity is obtained. Flow pump.

The cross flow pump is a type of horizontal axial flow pump. The motor, the speed reducer and the water pump are integrally formed, and are installed in the pit of the underwater dam. The inlet and outlet water passages are located in a straight line, which is approximately straight cylindrical shape, has less hydraulic loss, high water lifting efficiency, and compact structure. Easy installation and maintenance, pump station engineering is simple. The completion pump is a low-lift axial flow pump. Except that the impeller and its outer pump casing are made of metal material, the inlet flow passage and the outlet flow passage are made of masonry or concrete, and the head is below 2 meters. Large, simple structure, low cost and high efficiency. Suitable for drainage and irrigation in low-lying areas.

Mixed flow pump：

　　Construction and working principle A pump with two types of centrifugal pump and axial flow pump. When the impeller is rotated by the power machine, the blade pushes the water body on the one hand, and at the same time drives the water body to rotate to generate centrifugal action. The water body generates flow and increases pressure under the action of the thrust and centrifugal force of the blade. The water flows from the axial direction into the impeller and then flows obliquely along the blades. It is often used for occasions where the displacement is large and the pressure is moderate. There are usually two types of volute and vane. The structure of the volute mixed flow pump is similar to that of the centrifugal pump. The kinetic energy obtained by using the volute-shaped flow passage to pass the water flow through the impeller is converted into pressure energy. Generally, the medium and small mixed flow pumps adopt the volute type structure. The vane type mixed flow pump is also called a diagonal flow pump, and its structure is similar to that of the axial flow pump, and has the characteristics of small radial size, simple structure and light weight. Large mixed flow pumps are mostly guided vanes, and the installation angle of the blades is generally adjustable. The head range of the mixed flow pump is generally 3 to 10.5 meters, the starting power is low, and it can adapt to the change of the water level. The flow rate is 0.1 to 50 m 3 / sec; the efficiency can reach 64 to 86%. Since the 1970s, large-scale mixed-flow pumps have developed at a faster rate, and in many cases there has been a trend to replace large axial-flow pumps.

Long shaft deep well pump：

　　Most of them are vertical single-suction centrifugal pumps. The impeller is installed below the moving water level in the well. The power machine is placed on the well. The impeller is driven by the long shaft to rotate in the diversion shell. The water flows along the flow path between the diversion shell and the impeller. Lift up to the ground through the water pipe. When the lift is high, a multi-stage centrifugal pump with multiple impellers in series can be used. Due to the high requirements for the manufacture and installation accuracy of the long shaft of the transmission, the efficiency is significantly reduced with the increase of the depth of the well, so it is generally only used for deep wells not exceeding 100 meters.

Submersible pump：

　　Both the pump impeller and the motor that drives the impeller are submersible into a water pump, which is used in both deep wells and working surfaces. The deep well submersible electric pump supplies power to the motor through the cable extending into the well, eliminating the long shaft of the transmission, so the structure is compact, the weight is light, and the installation, use and transfer are convenient. In the power supply area, there is a tendency to replace the long shaft deep well pump, but Not applicable to wells with large sediment content and areas without power. The electric motors for submersible pumps are dry (motors are all sealed), semi-dry (motor stator seals, and rotors running in water), oil-filled (motors are internally filled with oil to infiltrate the windings) and wet (motor interiors) Filled with water, the stator and rotor are all running in water, etc. The first three types need to be sealed and the manufacturing installation accuracy is high. Therefore, the agricultural deep well submersible pump usually adopts a wet motor, and the stator winding adopts water-resistant insulated wire or casts synthetic resin in the end and groove of the stator winding, and the water enters the motor. Not large, the sealing structure can be greatly simplified, only sand control is required. Some deep well submersible pumps have a lift of up to 1400 meters and a maximum flow of 1.4 m3/s.

Jet deep well pump：

　　It is usually composed of a jet pump and a centrifugal pump with corresponding sleeves. Used to extract water from deep wells within 30 meters. The working principle of the jet pump is to spray the pressure through the nozzle to the inlet of the throat. Due to the lateral turbulent diffusion of the jet, the air in the suction pipe is taken away to form a vacuum inside the pipe, and the well water is sucked in and the jet water is in the throat. Mix and exchange energy. At the outlet of the throat, the flow rates of the two are close to each other, and then most of the kinetic energy is converted into pressure energy through the diffusion tube, so that the water pressure is further increased, and finally discharged from the drain pipe.

Jet deep well pumps are available in two combinations:

　　1、The jet pump is connected in parallel with the centrifugal pump. The centrifugal pump sends the pressurized water to the incident flow pump through the pipeline. The jet pump lifts the water together with the water absorption, so that the small flow of high pressure water is converted into a large flow of low pressure water. Mainly used for surface irrigation and channel dredging;

　　2、The jet pump and the centrifugal pump are connected in series and parallel, so that the jet pump pressurizes the centrifugal pump to increase the suction stroke, and the centrifugal pump discharges a part of the water to the jet pump, and the rest is sent to the pressure tank or the pressure line. Its high water pressure is mainly used for sprinkler irrigation equipment and agriculture and animal husbandry water supply. Compared with the submersible pump and the long shaft deep well pump, the jet type deep well pump has the characteristics of simple structure, reliable operation, convenient manufacture and low cost; but the efficiency is low, and the power consumption under the same working condition is high.

Screw pump:

　　A volumetric pump that draws in and transports a body of water by a change in the volume of the pump chamber as the screw rotates. There are single screw, twin screw and multi screw types. A single screw pump is used in agriculture, and the pump chamber is composed of a steel screw and a rubber sleeve fixedly mounted in the pump casing. A screw having a single pitch rotates within a sleeve having a double pitch inner spiral, and a cavity formed therebetween moves from the suction end to the outlet end to form a continuous flow of water. Because of its simple structure, small size, easy assembly and disassembly, reliable work, self-priming performance, it is mostly used in mobile sprinkler irrigation systems.

Manual diaphragm pump：

　　It is used for lifting work with low lift and small flow. It consists of pump body, water inlet and outlet pipe, inlet and outlet valve, diaphragm and push rod. The pump body can consist of one or two pump chambers. A diaphragm pump having two pump chambers, the diaphragm of which is disposed in the center of the pump body, or the two diaphragms are respectively mounted outside the two pump chambers that are separated. During operation, two people manually manipulate the push-pull rod connected to the diaphragm to push the diaphragm into the reciprocating motion of the press-in and the opening, so that the volume of the two pump chambers is alternately enlarged and reduced. When the pump chamber is enlarged, the pressure is reduced, the inlet valve is opened, the outlet valve is closed, and water flows from the inlet pipe into the pump chamber; when the pump chamber is reduced, the pressure is increased, the inlet valve is closed, the outlet valve is opened, and the water in the pump chamber is opened. Outflow from the drain pipe, the two pump chambers alternately absorb water and drain, and can pump 10-20 tons of water per hour.

Pull rod piston pump：

　　Driven by animal prime movers, wind turbines or internal combustion engines, it is often used when lifting water from a well on a pasture. It consists of pump cylinder, piston, inlet and outlet pipe, inlet and outlet valve, tie rod and transmission. The piston is driven by a pull rod connected to the piston to reciprocate 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 closes, the water above the piston is driven upwards; when the piston moves downward, the inlet valve closes and the outlet valve opens. The water in the pump cylinder rises from the outlet valve to the top of the piston, so that the water is continuously fed and lifted, so that the water is continuously discharged from the drain pipe.