Basic theory of water pump and diesel engine water pump stat

Article provenance：Hai Rui ZhonglianPopularity：Publication time：2020-03-25 09:40

Basic theory of water pump and diesel engine water pump (diesel engine fire pump) station

Classification and definition of pumps

Pump: it is a kind of hydraulic machinery, which transfers the external energy to the pumped liquid to increase the liquid energy, so as to achieve the purpose of lifting and conveying the liquid.

Classification: vane pump, positive displacement pump, other types of pump

Centrifugal pump, mixed flow pump, axial flow pump - three vane pumps

Main components of water pump:

Pump shaft: the main part that drives the impeller to rotate. It must be strong enough to transmit torsion.

Impeller: centrifugal pump impeller is divided into closed, semi closed, open;

The impeller of axial flow pump can be divided into fixed type, semi regulating type and full regulating type according to whether the blade can adjust the installation angle of impeller.

The impeller of mixed flow pump is between centrifugal pump and axial flow pump

Mouth ring: also known as leakage ring, sealing ring, to prevent leakage.

Shaft seal device:

Stuffing box: it is composed of stuffing box, stuffing box, condensation cap, packing, etc. stuffing box is composed of packing, stuffing cap and water seal ring.

Water seal ring (note) function: water seal, cooling, lubrication.

Mechanical seal: static ring and dynamic ring.

Bearing:

Centrifugal pump: the function of bearing is to support the weight of rotating parts, as well as the axial force and radial force of pump in operation.

Axial flow pump: the function of the guide bearing is to guide the rotating part of the unit to precisely rotate around the axis and bear the radial force of the rotating part.

Pressure chamber: used to install impeller. Type: guide vane type and axial flow type.

Pump shell: there are two types of worm shell, guide leaf type.

Guide vane function: diffusion of water flow, recovery of part of kinetic energy, change of flow direction.

Structure of diesel engine water pump

Characteristics of centrifugal pump (see P3): high head, small flow

Mixed flow pump

Features of axial flow pump: large flow, low head

Tubular pump: it is a kind of horizontal axial flow pump, composed of motor, reducer and water pump. It is installed in the pit of underwater dam, which is approximately straight cylinder, with small hydraulic loss and high water lifting efficiency.

It can be divided into: axial extended flow, axial flow, spherical bubble flow and full tubular flow.

centrifugal pump

This product is a centrifugal pump, which uses centrifugal force generated by impeller rotation to transport and lift liquid.

Features: high lift and small flow

Principle: when the motor drives the impeller to rotate through the pump shaft at high speed, due to the inertial centrifugal force, the water in the impeller sweeps from the center of the impeller to the outer edge of the impeller, and is collected into the pump body, and the water used to obtain the potential energy and kinetic energy is guided to the water outlet. , along the water outlet pipe to the water outlet.

Its structure and type are as follows: 1. Single stage single suction centrifugal pump (B / BA) 2, single stage double suction centrifugal pump (s / SH) 3, multistage pump.

Single stage single suction centrifugal pump:

Features: only one impeller, only one side of the impeller has a suction port.

Structure: composed of impeller, pump body, pump shaft and bearing, shaft seal, etc.

Impeller: the rotating body with blades transfers energy to the liquid, which is called impeller.

Pump impeller can be divided into closed, semi closed and open.

Pump body: the pump body enters the water, the spiral pressure chamber and the water outlet pipe form the water flow of the pump together with the impeller.

Pump shaft and bearing:

Pump shaft: it is the main part to drive the impeller to rotate, and it must have sufficient strength. One end of the pump is fixed on the impeller and the other end is equipped with a coupling or pulley to form the rotating part of the pump.

Bearing: it is a part of supporting pump rotor, bearing axial force and radial force.

Shaft seal: packing seal is the most common form of shaft seal. It consists of packing, packing gland, water sealing ring (packing ring), packing box, etc.

Single stage single suction centrifugal pump features: high head, small flow, simple structure, convenient maintenance, small volume, convenient movement.

Single and double suction centrifugal pump

This product is a double suction impeller, symmetrical in shape, as if it is connected back to back by two identical single suction impellers, and water enters the impeller from both sides.

Multistage pump

Definition: when the water pump is running, the water flow is discharged from the first stage impeller, then through the guide vane into the second stage impeller, then from the second stage impeller, then through the guide vane into the third stage impeller, and so on. The more impeller series, the greater the energy obtained through flow, the higher the water head.

Axial flow pump is divided into vertical (ZL) horizontal (ZW) inclined (ZX)

Definition: water is driven by the thrust generated by the impeller rotating in the water.

Features: large flow, low lift.

Principle: the blade of vertical axial flow pump is installed below the lowest water surface of the re-entry pool. When the motor drives the blades to rotate through the pump shaft, the blades generate thrust (also known as lifting force) in the water, so that the water can be lifted. The water flows out along the axial direction after passing through the guide vanes, and then it is delivered to the water outlet tank through the outlet elbow and outlet pipe.

Structure: it is composed of intake horn, impeller, guide vane, outlet elbow, pump shaft, rubber bearing, sealing device, blade regulating mechanism, etc.

Intake horn: the intake horn is a one-line horn shaped intake pipe. Its function is to make the water flow uniform, to cause the minimum loss of impeller smoothly, and to be made of cast iron.

Impeller: the main working part of axial flow pump, usually composed of blade, hub and guide vane cone.

According to whether the blade can adjust the installation angle on the impeller, it can be divided into fixed, semi adjustable (b) and fully adjustable (q).

Hub body: it is used to install the blade, blade adjusting mechanism and other components. There are three types: cylindrical, conical and spherical.

Guide vane body: composed of guide vane, guide vane hub and impeller shell. The guide vane body and the impeller shell of the large axial flow pump are separated and installed above the impeller, which is cone-shaped.

Function: convert the rotating movement of water flowing out of impeller into axial movement.

Outflow elbow: used to change the outflow direction. The outlet elbow of large pump station is a plane circular section, and there is tongue separation near the outlet.

Pump shaft: made of high quality carbon steel, used to transmit torque. The lower end of the shaft is connected with the hub body, and the upper end is connected with the coupling shaft of the motor.

On the journal where the pump shaft contacts the guide bearing, there is usually a layer of stainless steel and spraying stainless steel to improve the smoothness, wear resistance and corrosion resistance.

Bearing: there are two kinds of guide bearing (rubber bearing) and thrust bearing.

Guide bearing: its function is to guide the rotation of the unit in the case of inaccurate rotating shaft and bearing the radial force of rotating parts. The guide bearing can be divided into water lubricated bearing and oil lubricated bearing. The most common is rubber bearings.

Thrust pump: it is used to bear the axial pressure of the blade, maintain the axial invisible position of the rotation through the water flow and the weight of the rotating parts of the pump and motor, and penetrate the axial pressure into the foundation.

Sealing device: composed of packing box, packing gland, packing, etc.

Blade adjustment mechanism: hydraulic and mechanical.

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