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A hydraulic mechanical device that uses natural energy or powered equipment and transmission mechanisms to lift water from a lower place to a higher one. It is widely used in farmland irrigation and drainage, as well as in agriculture and animal husbandry, urban water supply, industrial and mining enterprises, and drainage systems. Pumps used for irrigation and drainage in farmlands, as well as in agricultural and livestock production processes, are known as agricultural water pumps, and they constitute one of the main components of irrigation machinery for farmlands. Type: Based on different working principles, they can be classified into positive displacement pumps, vane pumps, etc. Positive displacement pumps transfer energy by utilizing changes in the volume of their working chamber; the main types include piston pumps, plunger pumps, gear pumps, diaphragm pumps, and screw pumps. Vane pumps utilize the interaction between rotating vanes and water to transfer energy; types include centrifugal pumps, mixed-flow pumps, and axial-flow pumps. The pump body of a submersible pump is a vane pump. Other types of pumps include water hammer pumps, jet pumps, and internal combustion water pumps, which operate based on the principles of jet water hammer and fuel combustion, respectively. A hydraulic pump is a combination of a turbine and a vane pump. Among the various types of water pumps mentioned above, the following formulas are more representative. A tubular pump is a type of horizontal axial flow pump. It consists of a motor, a reduction gear, and a water pump as a single unit, and is installed in a machine chamber inside an underwater dam. Its inlet and outlet flow channels are aligned in a straight line; it has an approximately cylindrical shape, resulting in low hydraulic losses and high pumping efficiency. Additionally, it features a compact structure that facilitates installation and maintenance, making the pump station design simple. A masonry pump is a low-head axial flow pump; aside from the impeller and the pump casing surrounding it, which are made of metal, both the inlet and outlet channels are constructed from brick, stone, or concrete. It has a head of less than 2 meters, offers high flow rates, a simple structure, low cost, and high efficiency. Suitable for drainage and irrigation in low-lying areas. Mixed-flow pump: A type of water pump whose structure and working principle combine the characteristics of both centrifugal pumps and axial flow pumps. When the impeller is rotated by a power machine, the blades push the water while simultaneously causing the water to rotate, thereby creating a centrifugal force. The water flow is generated and the pressure increases under the action of the leaf’s thrust and centrifugal force. The water flow enters the impeller axially and exits obliquely along the blades; it is commonly used in applications requiring a large discharge volume at moderate pressure. Generally, there are two types: volute type and guide-vane type. The structure of a volute-type mixed-flow pump is similar to that of a centrifugal pump; it uses a volute-shaped flow channel to convert the kinetic energy obtained by the water flow after passing through the impeller into pressure energy. Volute-type structures are commonly used in medium and small-sized mixed-flow pumps. The vane-type mixed-flow pump, also known as an inclined-flow pump, has a structure similar to that of an axial-flow pump; it features small radial dimensions as well as a simple and lightweight design. Large mixed-flow pumps are mostly of the vane type, and the installation angle of their blades is generally adjustable as well. The head range of mixed-flow pumps is generally 3 to 10.5 meters; they have a low starting power and can adapt to changes in water level, with a flow rate of 0.1 to 50 cubic meters per second ； The efficiency can reach 64–86%. Since the 1970s, large mixed-flow pumps have developed at a rapid pace, showing a trend of replacing large axial-flow pumps in many applications. Long-shaft deep well pumps are generally vertical single-suction centrifugal pumps. Their impellers are located below the dynamic water level in the well, while the motor is situated above the well. The motor drives the impeller to rotate within the volute casing via a long drive shaft. Water flows through the passage between the volute casing and the impeller, and is then pumped upward to the surface via a delivery pipe. For high head, multi-stage centrifugal pumps with multiple impellers in series can be used. Due to the high requirements for the manufacturing and installation precision of the drive shaft, efficiency decreases significantly as the well depth increases; therefore, it is generally used only in wells with depths of up to 100 meters. Rod-type piston pumps are driven by animal-powered engines, windmills, or internal combustion engines, and are often used to draw water from wells on pastures. It consists of a pump cylinder, piston, inlet and outlet pipes, inlet and outlet valves, tie rods, and a transmission mechanism. The piston is driven by a rod connected to it, moving up and down reciprocally within the pump cylinder. As the piston moves upward, the inlet valve opens, allowing water from the inlet pipe to enter the pump cylinder; at the same time, the outlet valve closes, and the water above the piston is pushed upward ； When the piston moves downward, the inlet valve closes and the outlet valve opens. The water in the pump cylinder then rises above the piston through the outlet valve. This process of continuous water intake and elevation repeats, causing water to be constantly discharged through the drain pipe. Performance parameters: The technical parameters used to evaluate the performance of water pumps include flow rate, suction lift, head, shaft power, hydraulic power, efficiency, etc.; for vane-type water pumps, speed and specific speed are also relevant parameters. ①Suction lift. That is, the suction height of the water pump. It refers to the vertical distance from the center of the pump to the water level source; when water is drawn in using the vacuum created within the pump, the allowable suction height is generally not more than 7.5 meters. ②Head. That is, the lifting height of the water pump. It refers to the value of the energy increase per unit weight of water after passing through a water pump. The height difference between the water surfaces in the inlet and outlet basins of a pumping station is generally referred to as the actual head ； The head loss caused by the pump station piping and its accessories (such as foot valves, elbows, gate valves, etc.) is referred to as the total head. The head indicated on the water pump’s nameplate refers to the head achieved when the pump operates at its highest efficiency at a certain speed; it is the sum of the actual head and the loss head. ③Traffic. It refers to the amount of water that a water pump can transport in a unit of time, also known as the water delivery volume. Common units of flow rate include liters per second, cubic meters per second, cubic meters per hour, kilograms per second, tons per hour, and so on. ④Shaft power. It refers to the power delivered by the power machine to the pump shaft, that is, the input power of the pump. ⑤Water power. Also known as apparent power. It refers to the actual power consumed by the water pump for water transportation per unit time; in other words, it is the output power of the water pump. ⑥Efficiency. The ratio of water power to shaft power is the efficiency of the water pump, which is usually expressed as a percentage. It is an indicator used to measure the efficiency with which power machinery transfers energy to water pumps, reflecting the quality of the pump’s performance. ⑦Specific speed. A comprehensive parameter representing the characteristics of the water pump. It is usually expressed in nS. nS=3.65nQ1/2H-3/4. In the formula, n represents the rotational speed (revolutions per minute), Q represents the flow rate (cubic meters per second); for double-suction pumps, Q/2 should be used in place of Q. H represents the head (meters). The specific speed of a water pump is closely related to various parameters of the pump. Generally, centrifugal pumps have a relatively low specific speed; this is because they have a large impeller diameter, narrow outlet width, high head, and low flow rate ； Axial flow pumps have a relatively high specific speed; therefore, they exhibit low head and high flow rate ； Mixed-flow pumps fall between the two. The specific speed of common centrifugal pumps ranges from 30 to 300, that of mixed-flow pumps from 300 to 600, and that of axial flow pumps from 500 to 1800. Two geometrically similar vane pumps must have the same specific speed. Therefore, the test data from geometrically similar models can be used to predict the performance parameters of large pumps. Submersible pump: A type of water pump in which both the impeller of the pump body and the motor that drives the impeller operate underwater; it comes in two types: those for deep wells and those for use at the work site. Submersible pumps for deep wells are powered to their motors via cables extending into the well, eliminating the need for a long drive shaft; as a result, they have a compact structure, low weight, and are easy to install, use, and transport. In areas with power supply, they tend to replace deep-well pumps with long drive shafts, but they are not suitable for wells with high sediment content or in areas without power supply. Electric motors for submersible pumps come in various types, including dry-type (where the entire motor is sealed), semi-dry-type (where the stator of the motor is sealed while the rotor operates in water), oil-filled type (where oil is filled inside the motor to prevent moisture from reaching the windings), and wet-type (where water is present inside the motor, with both the stator and rotor operating in water). The first three types all require sealing and have high demands regarding manufacturing and installation precision; therefore, agricultural deep well submersible pumps typically use wet-type motors, whose stator windings are made from water-resistant insulated wires, or synthetic resin is poured into the ends of the stator windings as well as within the slots. Water entering the motor has little impact, so the sealing structure can be simplified – only protection against sand is required. Some deep-well submersible pumps have a head of up to 1400 meters, with a maximum flow rate of 1.4 cubic meters per second. Centrifugal pump: A pump that utilizes the force of centrifugal action to increase the pressure of water and cause it to flow. It consists of a pump casing, impeller, shaft, etc. (Figure 1). The power engine drives the shaft, which in turn causes the impeller to rotate at high speed inside the pump casing; as a result, the water within the pump is forced to move along with the impeller, generating centrifugal force. The centrifugal force forces the liquid to be ejected from the periphery of the impeller, forming a high-speed, high-pressure flow that is discharged outside the pump through the pump casing. A low pressure is created at the center of the impeller, which draws in new fluid, thus enabling continuous flow of water. The impeller has blades that are curved in the direction opposite to its rotation. There are three structural types: closed, semi-closed, and open. For agricultural applications, closed-type impellers are commonly used; both sides of their blades are enclosed by discs. The pump body gradually expands into a volute shape along the direction of the discharge pipe. A centrifugal pump that draws water in from one side of the impeller is called a single-suction centrifugal pump; one that draws water in from both sides of the impeller is called a double-suction centrifugal pump. To increase the head, multiple impellers can be mounted on the same shaft to form a multi-stage centrifugal pump. The water discharged by the preceding impeller enters the inlet of the subsequent impeller, is pressurized, and then discharged from the latter impeller; thus, the more impellers there are, the higher the pressure. Some centrifugal pumps are equipped with devices that can automatically remove air from the suction pipe and inside the pump, eliminating the need to fill the pump with water before starting; such pumps are known as self-priming centrifugal pumps. However, their efficiency is usually lower than that of ordinary centrifugal pumps. Centrifugal pumps are most widely used in farmland irrigation and drainage as well as in water supply for agriculture and livestock farming. It is commonly used in applications requiring high head and low flow rate. The head of a single-stage centrifugal pump ranges from 5 to 125 meters, and the flow rate it delivers is consistent, typically between 6.3 and 400 cubic meters per hour; its efficiency can reach around 86 to 94%. Axial flow pump: It is composed of components such as the pump casing, impeller, and shaft. Also known as a propeller pump. The impeller is equipped with several propeller-like blades; when the impeller rotates together with the shaft driven by a power mechanism, these blades push water toward one end while simultaneously drawing water from the source at the other end, thereby creating a continuous flow of water in a direction parallel to the shaft, thus enabling the continuous transport of water. The water flow pressure increases due to the rotation of the impeller. The rotating water flow exiting the impeller loses its rotational component of velocity after passing through the fixed vanes; as a result of diffusion, part of its kinetic energy is converted into pressure energy, which drives the water flow within the pump casing upward along the axial direction and out through the outlet pipe. Axial flow pumps are commonly used in applications requiring low head but high flow rates, with a head range of around 1 to 25 meters ； The flow rate ranges from 2.7 to 60.0 m3/second, with an efficiency of 85–90.5%. There are three installation types: vertical, horizontal, and inclined, among which vertical axial flow pumps are the most commonly used (Figure 2). The installation angle of the propeller blades on the hub of the impeller in large axial flow pumps can be adjusted, or it can be adjusted over time during operation via a hydraulically driven rotating shaft. This allows the pump to adapt to changes in head and flow rate, thereby achieving higher productivity; hence, these pumps are known as adjustable axial flow pumps. Jet deep well pumps are usually composed of a jet pump and a centrifugal pump, along with the corresponding casing. Used to pump water from deep wells within 30 meters. The working principle of a jet pump is to force pressure to be ejected through a nozzle at the inlet of the throat. Due to the lateral turbulent diffusion of the jet, air within the suction pipe is removed, creating a vacuum in that pipe. Well water is then drawn in and mixes with the jet water inside the throat, where energy exchange takes place. At the outlet of the throat, the flow velocities of both become nearly equal; thereafter, most of the kinetic energy is converted into pressure energy through the diffuser, further increasing the water pressure. Finally, the water is discharged via the drain pipe. There are two types of combinations for jet deep well pumps: ① The jet pump is connected in parallel with a centrifugal pump; the centrifugal pump sends pressurized water to the jet pump through pipes, and the jet pump lifts this water along with the water to be pumped upward, thereby converting high-pressure water with a low flow rate into low-pressure water with a high flow rate. This setup is mainly used for surface irrigation and dredging channels ； ②The jet pump and centrifugal pump are connected in series and parallel such that the jet pump pressurizes the centrifugal pump, thereby increasing its suction lift. A portion of the water discharged by the centrifugal pump is supplied to the jet pump, while the remaining portion is directed to a pressure tank or pressurized pipeline. The resulting water pressure is relatively high; this system is mainly used for sprinkler irrigation systems and water supply in agriculture and animal husbandry. Compared with submersible pumps and long-shaft deep well pumps, jet-type deep well pumps feature a simple structure, reliable operation, easy manufacturing, and low cost ； However, its efficiency is lower, and the power consumption is higher under the same operating conditions. Screw pump: A positive-displacement pump that draws in and transports water by utilizing the change in volume within the pump chamber as the screw rotates. There are types such as single-screw, twin-screw, and multi-screw. In agriculture, single-screw pumps are used, whose pump chamber consists of a steel screw and a rubber sleeve fixed inside the pump casing. A screw with a single pitch rotates inside a sleeve with a double-pitch internal helix; the cavity formed between them moves from the inlet side to the outlet side, thereby creating a continuous flow of water. Due to its simple structure, small size, easy assembly and disassembly, reliable operation, and good self-priming capability, it is widely used in mobile sprinkler systems. Manual diaphragm pump – Used for lifting water with low head and low flow rates; it consists of a pump body, inlet and outlet pipes, inlet and outlet valves, a diaphragm, and a push-pull rod. The pump body can consist of one or two pump chambers. A diaphragm pump with two pump chambers, in which the diaphragm is located at the center of the pump body, or the two diaphragms are installed on the outside of the two separate pump chambers. During operation, two people manually operate the push-pull rods connected to the diaphragm, pushing the diaphragm to perform reciprocating movements of compression and expansion, thereby causing the volumes of the two pump chambers to alternate between expansion and contraction. As the pump chamber expands, the pressure decreases; the inlet valve opens while the outlet valve closes, allowing water to flow into the pump chamber from the inlet pipe ； As the pump chamber contracts, the pressure increases; the inlet valve closes while the outlet valve opens, allowing the water in the pump chamber to flow out through the drain pipe. The two pump chambers take turns drawing in water and discharging it, and can lift 10 to 20 tons of water per hour. The appropriate power matching for water pumps: A proper combination of water pumps and power sources is crucial for ensuring their normal operation, thereby achieving high efficiency and low energy consumption. The power of the accompanying power unit is calculated using the following formula, based on the pump’s head H (in meters) and flow rate Q (in cubic meters per second): (kilowatts). The head H consists of the geometric head Hj and the pipeline loss HS; during preliminary selection, HS can be estimated as HS=(0.1～0.2)Hj. Once the piping layout is determined, the values are calculated using hydrodynamic methods or obtained from tables, based on the type or size of the pipes and fittings. In the formula, K is the power reserve coefficient; commonly, K ranges from 1.05 to 1.3, with a smaller value being used when the power is high. η1 represents the transmission efficiency, and it is equal to 1 when the power engine is connected directly to the water pump ； η2 is the pump efficiency, which is determined based on the pump type and operating conditions. The diameter D of the inlet and outlet pipes for water pumps, as well as those connected to the water tank, is determined using the following formula: D = 1.13Q^(1/2)V^(-1/2) (in meters). Here, V represents the flow velocity inside the pipes; generally, the flow velocity in the inlet pipes is ≤ 2 meters per second, while it is ≤ 3 meters per second in the outlet pipes. When a tapered tube with varying diameter is used, the length of the tapered section should be 5 to 7 times the average diameter. The inlet openings of the centrifugal pumps and axial flow pumps are located at a distance h1 below the water surface of the inlet tank, where h1 = (1.4～1.6)D1, and D1 is the diameter of the inlet pipe. The centerline of the impeller in the axial flow pump is located at a distance h3 below the water surface of the inlet tank, with h2 ≥ (0.75～D)D0, where D0 is the diameter of the impeller. The height h0 of the water inlet from the bottom of the tank is (0.5～1)D0. The width of the water inlet tank for a single water pump is (2–3)D1. In the water intake tank equipped with multiple water pumps, the distance between adjacent inlet pipes is (3–3.5)D1. The distance from the water inlet pipe to the back wall of the water inlet tank is (1～1.5)D1. To avoid wasting head, the outlet pipe is usually installed below the water surface of the outlet tank. The distance from the lower edge of the outlet pipe of small and medium-sized water pumps to the bottom of the tank is approximately 10–20 centimeters ； The vertical distance from the upper edge of the outlet pipe to the water surface is (1–2)v1/2g, where v1 is the outlet flow velocity (meters per second) ； The length of the water outlet tank is (6–12)D2. D2 is the diameter of the outlet pipe; the distance between the outlet pipe and the pool wall is 0.2 to 0.5 meters. Development trends: The requirements for developing agricultural water pumps are to improve efficiency, reduce energy consumption, and make full use of natural energy. Replacing multiple small pumps with one large pump can improve the efficiency of the system, save materials, reduce energy consumption and construction costs, and facilitate automated management. As a result, various large-scale axial flow pumps and mixed-flow pumps have developed rapidly, with the maximum impeller diameters reaching 4.6 meters and 6.2 meters respectively, and the accompanying power capacity reaching up to 12,500 kilowatts. Mixed-flow pumps show a tendency to replace some high-head axial flow pumps and low-head centrifugal pumps. For water pumping from deep wells, submersible pumps have been primarily developed; their maximum diameter has reached 1 meter, and some are equipped with 6000-volt high-voltage motors, achieving a maximum power of 2500 kilowatts. Water turbine pumps, wind-driven rod pumps, screw pumps, various diaphragm pumps powered by human or animal power, piston pumps, and pumps designed specifically for use with irrigation equipment are also given varying degrees of attention in China and some other countries. Experts in wear-resistant repair, Luoyang Napute New Materials Technology Co., Ltd. 13603889856 0379-60679266