Definition and classification of centrifugal pumps

1. Definition of centrifugal pump

A centrifugal pump is a mechanical device that converts the mechanical energy of a prime mover into liquid energy. Pumps are used to increase the potential energy, pressure energy, and kinetic energy (high-speed liquid flow) of liquids. The prime mover drives the impeller to rotate through the pump shaft, producing work on the liquid and increasing its energy. As a result, the required amount of liquid is transported from the suction tank to the required height or pressure through the pump’s flow passage components.

The prime mover drives the impeller to rotate, sucking water into the pump from point A and discharging it to point B. The impeller plays the dominant role in the pump, and the blades in the impeller force the liquid to rotate, causing it to be thrown out in all directions under centrifugal force. This situation is similar to the water droplets on a rotating umbrella throwing out in all directions. After the liquid in the pump is thrown out, new liquid enters the pump under atmospheric pressure, continuously supplying water from point A to point B. Before starting the pump, it should be filled with water. If it is not filled with water, the impeller can only drive the air to rotate. Due to the small mass per unit volume of air, the centrifugal force generated is very small, which cannot discharge the air inside the pump and the drainage pipeline, and cannot create a certain vacuum inside the pump, so water cannot be sucked up. The bottom valve of the pump is used for water filling, and the regulating valve on the outlet side of the pump is used to adjust the flow rate.

2. Classification of pumps

There are many types of centrifugal pumps, which can be divided into the following three categories according to their operating principles.

(1) Vane pump

Vane pumps, also known as power pumps, can continuously apply energy to liquids, such as centrifugal pumps, mixed flow pumps, axial flow pumps, etc.

(2) Positive displacement pump

A positive displacement pump is a periodic change that fills the liquid volume through closure. Discontinuously applying energy to liquids, such as piston pumps, gear pumps, screw pumps, etc.

(3) Other types of pumps

The working principles of other types of pumps vary, such as jet pumps, water hammer pumps, electromagnetic pumps, etc.

3. Flow components and structural forms of vane pumps

Overflow components of vane pumps

The main flow components of a vane pump include the suction chamber, impeller, and pressure chamber (including guide vanes).

The suction chamber of the pump is located in front of the impeller, and its function is to guide the liquid towards the impeller. There are three forms: straight cone, bent tube, and spiral

The pressurized water chamber is located on the periphery of the impeller, and its function is to collect the liquid flowing out of the impeller and send it into the discharge pipe. Pressure chambers mainly include vortex chambers (spiral pressure chambers), radial guide vanes, space guide vanes, and axial flow pump guide vanes

The impeller is the most important working component of the pump and the core of the flow passage. The impeller is composed of a cover plate and a middle blade. According to the direction in which the liquid flows out of the impeller, there are three types of impellers: centrifugal (radial flow) and axial flow

In a radial (centrifugal) impeller, the direction in which the liquid flows out of the impeller is perpendicular to the axis, that is, it flows out along the radial direction;

In a mixed flow pump (oblique flow) impeller, the direction of liquid flowing out of the impeller is inclined to the axis;

In an axial flow impeller, the direction in which the liquid flows out of the impeller is parallel to the axis, that is, it flows out along the axis direction.

3.1 Structural form of vane pump

Vane pumps are classified according to their structural form as follows

(1) In the direction of the main axis

1) Horizontal: the spindle is placed horizontally;

2) Vertical: The spindle is placed vertically;

3) Oblique: The spindle is placed at an angle;

(2) By impeller type

1) Centrifugal: equipped with a centrifugal impeller;

2) Mixed flow type: equipped with mixed flow impeller;

3) Axial flow: equipped with an axial flow impeller;

(3) According to inhalation method

1) Single suction: Install a single suction impeller;

2) Double suction: Install double suction impellers;

(4) By level

1) Single stage: Install 1 impeller:

2) Multi stage: Install 2 or more impellers on the same shaft

(5) According to the blade installation method

1) Adjustable blades: The placement angle of the impeller blades is an adjustable structure;

2) Fixed blades: The placement angle of impeller blades is a fixed structure.

(6) According to the shell part method

1) Segmented: The shell is divided into planes perpendicular to the axis;

2) Segmental structure: In a segmented structural form, each stage shell is separated;

3) Split type: The shell is separated on a plane passing through the axis centerline;

4) Horizontal split type: In a split type structure, the dividing surface is horizontal;

5) Vertical split type: In a split type structure, the dividing plane is perpendicular to the horizontal plane;

6) Tilted split type: In a split type structure, the dividing plane is inclined,

(7) According to the form of the pump body

1) Vortex shell type: The impeller discharge side has a shell with a vortex chamber;

2) Double vortex shell type: a shell with double vortex chambers on the discharge side of the impeller;

3) Turbine type: Centrifugal pump with guide vanes:

4) Bag type: The inner shell and outer shell are equipped with cylindrical pressure resistant shells;

5) Double shell type: a pump with a double shell outside of a cylindrical bag type.

(8) According to the pump body support method

1) County style: There are pump feet under the pump body, fixed on the base, and the bearing body is suspended at one end;

2) Bracket type: The lower part of the bearing body is fixed on the base, and the pump body is suspended at one end by the bearing body;

3) Central support type: The pump body is fixed on the base on both sides of the horizontal plane passing through the axis.

(9) Special structure blade pump

1) Submersible electric pump: a pump used in water together with the motor that drives the pump;

2) Cross flow pump: a pump with a driving device such as an electric motor installed inside the pump body;

3) Shielded pump: The pump is directly connected to the motor (using one shaft for vegetables), and the motor is equipped with a shielding sleeve on the inner side to prevent liquid from entering the stator of the pump;

4) Magnetic pump: The motor is equipped with an external magnetic steel support for rotation, which rotates the internal magnetic steel connected to the pump impeller through magnetic induction. There is an isolation sleeve between the internal and external magnetic steel to completely prevent liquid leakage from the pump;

5) Self priming pump: a pump that does not require water injection when restarted;

6) Pipeline pump: As a part of the pipeline, the pump can be installed without special changes to the pipeline;

7) Non clogging pump: a pump that pumps solid substances contained in the liquid without causing blockage inside the pump.

4. The purpose of the medium opening pump

Zhongkai pump is a universal machinery with a wide variety of types. Widely applicable, in various sectors of the national economy, wherever there is liquid flow, there are pumps in operation. Their main application ranges include: agricultural irrigation and drainage, petrochemical industry, power industry, urban water supply and drainage, mining, and shipbuilding industry. In addition, pumps have also been applied in rocket fuel supply and ship propulsion.

Taking the thermal power plant in the power industry as an example to illustrate the application of pumps, the power plant is a steam water cycle process, where the boiler burns water into steam to drive the turbine to rotate and generate electricity. Among them, the boiler feedwater pump is used to supply water from the heater to the boiler. The exhaust gas from the steam turbine needs to be cooled and condensed into water, which needs to be pumped into the heater by a condenser pump for further circulation. The cold circulating water used for the condenser is supplied by a circulating water pump. The pump used for boiler ash discharge is the ash pump, and the boiler smoke contains SO2, which requires the use of a desulfurization pump to send lime slurry for desulfurization.