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Centrifugal pump
1.Working principle of centrifugal pump
Both the pump and inlet piping are filled with water before the pump starts. After the pump is running, under the influence of the centrifugal force generated by the rapid rotation of the impeller, the water in the flow channel of the impeller is thrown around and pressed into the insect shell, forming a vacuum at the impeller inlet. Water from the pool is drawn along the absorber tubes at outside atmospheric pressure to replenish this space. Then the inhaled water is thrown out by the impeller, and enters the outlet pipe through the worm shell. It can be seen from this that if the impeller of the centrifugal pump continues to rotate, it can continuously absorb and press water, and the water can be continuously lifted from a low place to a high place or far away. In short, due to the centrifugal force generated by the high-speed rotation of the impeller, the centrifugal pump is called a centrifugal pump.
2.Characteristics of centrifugal pumps
(1) The water flowing along the direction of the centrifugal pump is sucked in the axial direction of the impeller, and flows out perpendicular to the axial direction, that is, the directions of inflow and outflow flow at 90° to each other.
(2) Since the centrifugal pump absorbs the water in the vacuum through the impeller inlet, the water must be poured into the pump and the suction pipe before starting, otherwise the vacuum pump must be used to pump out the air to form a vacuum. In addition, the pump casing and suction pipe must be strictly sealed without leakage. Otherwise, a vacuum cannot be formed and water cannot be absorbed.
(3) Since the impeller inlet cannot form an absolute vacuum, the suction height of the centrifugal pump cannot exceed 10 meters. In addition, the actual allowable installation height (pump shaft height from the suction water surface) is far away from the water flow loss through the suction line. Less than 10 meters. If the installed water is too high, it will not absorb water; in addition, because the atmospheric pressure in mountainous areas is lower than that in plains, if the same water pump is installed in mountainous areas, especially in high mountain areas, its installation height should be lowered, otherwise it cannot absorb water.
Axial flow pump
The working principle and characteristics of the axial flow pump
1.Working principle of axial flow pump
The working principle of the axial flow pump is different from that of the centrifugal pump. It mainly uses the thrust generated by the high-speed rotation of the impeller to lift water. When the blades of the axial flow pump rotate, the lifting force generated by the water pushes the water from bottom to top.
The blades of the axial pump are generally immersed in the pool to be absorbed. Due to the high-speed rotation of the impeller, under the lift force generated by the blades, the water is continuously pushed upwards, so that the water flows out along the outlet pipe. The impeller rotates continuously, and the water is continuously pressed high.
2.Characteristics of axial flow pump
(1) The flow direction of water in the axial flow pump is sucked in along the axial direction of the impeller and flows out axially, so it is called an axial flow pump.
(2) Low head (1-13 meters), large flow, high efficiency, suitable for irrigation and drainage of plains, lakes and rivers.
(3) There is no need to irrigate before starting construction, and the operation is simple.
Mixed flow pump
1.Working principle of mixed flow pump
Because the impeller shape of the mixed flow pump is between the impeller of the centrifugal pump and the impeller of the axial flow pump, the working principle of the mixed flow pump has both centrifugal force and lift force. Through the combined action of the two, the water flows out of the impeller at an angle to the impeller shaft. Lifts the water through the volute chamber and pipes.
2.General characteristics of mixed flow pumps
(1) Compared with the centrifugal pump, the mixed flow pump has a lower head and a larger flow. Compared with axial flow pumps, mixed flow pumps have higher head and lower flow. It is suitable for drainage and irrigation in plains and lake areas.
(2) It sucks in water at a certain angle with Huangzhou and flows out along the flow direction of the mixing pump, so it is also called inclined pump.
Commonly used agricultural pumps
Centrifugal pump
Centrifugal pump models, in various sizes and variants, are the most common among agricultural pumps. According to the way water flows into the impeller, the number of impellers, whether the pump body can be filled automatically, and the size and power of the supporting power, centrifugal pumps have single-stage single-suction centrifugal pumps, single-stage double-suction centrifugal pumps, and multi-stage centrifugal pumps. and self-priming centrifugal pumps. pumps, electric pumps and diesel water pumps.
1.Single-stage single-suction centrifugal pump
The old pump types include BA and B type single-stage single-suction centrifugal pumps. In the 1980s, according to international standards and the actual situation of drainage and irrigation machinery, my country updated and developed centrifugal pump products, and produced IB and IQ single-stage centrifugal pump series products, which were listed as national professional standards and industry standards.
For a single-stage single-suction centrifugal pump, water enters the impeller from the shaft to a single surface, and there is only one impeller, so it is called a single-stage single-suction centrifugal pump. Its characteristics are that compared with mixing pumps and shaft pumps, it has high lift, low flow rate, simple structure and convenient use.
The IQ type single-stage single-suction centrifugal pump (also known as light and small centrifugal pump) is designed according to national conditions, meets user requirements, has simple structure, light weight, low price, good performance and convenient support. There are 84 products. 3 derivative series, 413 specifications.
(1) The diameter of the pump is 50-200 mm, the flow rate is 12.5-400 cubic meters per hour, and the head is 8-125 meters. The supporting power includes diesel engine direct connection, belt drive, motor direct connection, power 1.1-110 kW, speed 1450-2900 rpm /point.
(2) The structural type of light and small centrifugal pumps is axial suction single-stage single-suction suspension centrifugal pump. The pump body is opened behind the door, the outlet is located in the center, the back cover is pressurized, the bearing body is directly connected with the pump body, and the pump foot is located under the pump body. The bearings are lubricated with grease. There are three types of shaft seals: soft packing, mechanical seal and rubber oil seal. The impeller is closed, and the transmission mode is divided into coupling transmission and double-ring transmission. Pump impeller direction: From the direction of the pump inlet, the impeller rotates clockwise, and when the pump is directly driven by the diesel engine, it rotates counterclockwise. The pump outlet can be equipped with a manual pump, and the bottom valve can be removed to reduce hydraulic loss and make the pump dry by itself.
2.Single-stage double-suction centrifugal pump
It is a single-stage double-suction centrifugal pump that supplies water from both sides of the impeller. Since the pump cover and pump body are assembled by horizontal joints, it is also called a horizontal open centrifugal pump. Compared with single-stage single-suction centrifugal pumps, it has the characteristics of high efficiency, large flow and high lift. However, it is bulky and heavy and is often used for stationary work. Suitable for hilly and plateau irrigation areas, also suitable for factories, mines, urban water supply and drainage.
There are several types of single-stage double-suction centrifugal pumps: S type, SH type, SA type and SLA type. The difference between S-type and SH-type is that the S-type pump rotates clockwise, while the SH-type pump rotates counterclockwise. SLA is a vertical single-stage double-suction centrifugal pump.
The performance range of the s-type pump is 160 to 18,000 cubic meters per hour, the lift is 12 to 125 meters, the inlet diameter is 150 to 1400 mm, the speed is 2950, 1450, 970, 730, 585, 485, and 360 revolutions per minute.
(1) D-type pump performance range: flow rate 6.3~720 cubic meters per hour, lift 16~600 meters, inlet diameter: 50, 75, 100, 125, 150, 200mm, among which the pump type is 50~125mm high speed 2950 rpm, 150-200mm pump speed 1480 rpm.
(2) The D-type multi-stage centrifugal pump is horizontal multi-stage (2-12 stages), the impeller is single-suction, and the pump body is segmented. When the first impeller is double suction, it is expressed by ds. When two speeds are specified at the same time, the low speed is represented by da, and the multistage boiler feed water centrifugal pump is represented by dg.
3.Self-priming centrifugal pump
The self-priming pump is a single-stage single-suction centrifugal pump, relying on the special structure of the pump itself to generate self-priming force. It is called a self-priming centrifugal pump. Compared with ordinary centrifugal pumps, the structure of the pump body is significantly different: one is to increase the pump inlet position, and sometimes install a suction valve; the other is to set an air and water separation chamber on the water outlet side.
Self-priming pumps outside the pump are equipped with self-priming devices, such as vortex pumps, water ring vacuum pumps, jet pumps and manual pumps.
Compared with ordinary centrifugal pumps, self-priming pumps are compact in structure and easy to operate. It not only eliminates the trouble of diverting a large amount of water before starting, but also eliminates the low valve of the water inlet pipe, reduces the water inlet resistance, and increases the output of the pump. However, the efficiency of self-priming pumps is 3%-5% lower than that of ordinary centrifugal pumps of the same specification. Self-priming pumps are mainly used for light and small sprinkler irrigation units and pipeline irrigation units.
