Definition and classification of centrifugal pumps
1. Definition of centrifugal pumps
A centrifugal pump is a machine that converts the mechanical energy of the prime mover into liquid energy. Pumps are used to increase the potential energy, pressure energy, and kinetic energy of liquids (high-speed liquid flow). The prime mover drives the impeller to rotate through the pump shaft to work on the liquid, increasing its energy, and thus transporting the required amount of liquid from the suction pool 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 a leading 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 the same as the water droplets on a rotating umbrella throwing out in all directions. After the liquid inside 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 first. 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 exhaust the air inside the pump and drainage pipeline, and cannot create a certain vacuum inside the pump, so water cannot be sucked in. The bottom valve of the pump is used for filling water, and the regulating valve on the outlet side of the pump is used to regulate flow.
2. Classification of pumps
There are many types of centrifugal pumps, which can be divided into three categories according to their working 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 in liquid volume that is filled through closure. Continuously 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 passage 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 the guide vanes).
The pump suction chamber is located in front of the impeller, and its function is to guide the liquid towards the impeller. There are three forms: straight conical, curved, and spiral
The water pressure 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. The pressurized water chamber mainly consists of vortex chambers (spiral shaped pressurized water chambers), radial guide vanes, spatial 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 component. The impeller is composed of a cover plate and a middle blade. According to the different directions in which liquid flows out of the impeller, the impeller is divided into three types: centrifugal (radial) and axial flow
In a radial (centrifugal) impeller, the direction of liquid flowing out of the impeller is perpendicular to the axis, that is, flowing out along the radial direction;
In a mixed flow pump (oblique flow) impeller, the direction of liquid flowing out of the impeller is inclined towards the axis;
In an axial flow impeller, the direction of liquid flowing out of the impeller is parallel to the axis, that is, flowing out along the axis direction.
3.1 Structural form of vane pump
Vane pumps are classified according to their structural form as follows
(1) By spindle direction
1) Horizontal: The spindle is placed horizontally;
2) Vertical: The spindle is placed vertically;
3) Oblique: The main shaft is tilted and placed;
(2) By impeller type
1) Centrifugal: Install a centrifugal impeller;
2) Mixed flow type: equipped with a mixed flow impeller;
3) Axial flow type: install an axial flow impeller;
(3) By inhalation method
1) Single suction: Install a single suction impeller;
2) Double suction: Install double suction impeller;
(4) By series
1) Single stage: Install 1 impeller:
2) Multi stage: Install two or more impellers on the same shaft
(5) According to blade installation method
1) Adjustable blade: The placement angle of the impeller blade is an adjustable structure;
2) Fixed blade: The placement angle of the impeller blade 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 structure, each stage of the shell is separated;
3) Split type: The shell is separated on a plane passing through the centerline of the shaft;
4) Horizontal split type: In a split type structure, the dividing plane is horizontal;
5) Vertical split type: In a split type structure, the dividing plane is perpendicular to the horizontal plane;
6) Inclined central opening: In a central opening structure, the dividing plane is inclined,
(7) According to the pump body form
1) Vortex shell type: the impeller has a shell with a vortex chamber on the discharge side;
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) Barrel bag type: The inner shell is equipped with a cylindrical pressure resistant shell outside;
5) Double shell type: A double shell pump other than a cylindrical bag type.
(8) According to the pump body support method
1) County frame type: There is a pump foot 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 supported and suspended at one end by the bearing body;
3) Central support type: Both sides of the pump body are fixed on the base on a horizontal plane passing through the shaft center.
(9) Special structure vane pump
1) Submersible electric pump: a pump that drives the motor of the pump and is used together with the pump in water;
2) Cross flow pump: a pump equipped with a motor and other driving devices inside the pump body;
3) Shielded pump: The pump is directly connected to the motor (with one shaft for vegetable use), 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 outer magnetic steel to rotate, and the inner magnetic steel connected to the pump impeller is rotated through magnetic induction. There is an isolation sleeve between the inner and outer magnetic steel, completely preventing liquid leakage in the pump;
5) Self priming pump: a pump that does not need to be filled with water when the pump is 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 liquid without causing blockage within the pump.
4. The purpose of the split pump
Zhongkai pump is a universal machine with a wide variety of types. The application scope is wide, and in various departments of the national economy, wherever there is liquid flow, there is a pump working. Its main application scope includes: farmland drainage and irrigation, petrochemical industry, power industry, urban water supply and drainage, mining and shipbuilding industry, etc. In addition, pumps have also been applied in rocket fuel supply and ship propulsion.
Taking thermal power plants in the power industry as an example to illustrate the application of pumps, power plants are a steam water cycle process where boilers burn water into steam, driving the turbine to rotate and generate electricity. Among them, the boiler feed 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 condensate pump for further circulation. The cold circulating water used for the condenser is supplied by the circulating water pump. The pump used for boiler ash discharge is an ash pump, and the boiler smoke contains SO2. It is necessary to use a desulfurization pump to send lime slurry for desulfurization.
