CENTRIFUGAL PUMP DESIGN & ANALYSIS
AIM
To perform design and analysis of centrifugal pump.
OBJECTIVES
To show the performance diagram and plot a graph between pressure ratio and mass flow rate.
THEORY
Pump is a device which is used to move fluids which is used to move fluids by mechanical action, typically converted from electrical energy into hydraulic energy.
Centrifugal pumps are the most popular and commonly used type of pump which is used for transfer of fluids. Centrifugal pump is a hydraulic machine which converts mechanical energy into hydraulic energy by the use of centrifugal force acting on the fluid. These pumps are commonly used for transfer of fluids from low level to high level.
Centrifugal pumps are useful as they can handle large quantities of fluid, provide very high flow rates and also have the ability to adjust their flow rates to wide range.
COMPONENTS OF CENTRIFUGAL PUMP
The following are the major components of centrifugal pump
- Impeller
- Casing
- Delivery pipe
- Suction pipe with foot valve and Strainer
IMPELLER
An impeller is a rotating component of a centrifugal pump which transfers energy from the motor that drives the pump to the fluid. Impellers are divided into three types
- Open Impeller
- Semi enclosed impeller
- Enclosed impeller
CASING
Casing is an airtight passage which surrounds the impeller. The impeller is usually enclosed within the casing. It is used to transmit the fluid coming out from the impeller in the same direction of rotation to the delivery pipe.
DELIVERY PIPE
It is a pipe which is connected at its lower end to the outlet of the pump and it delivers the liquid to the required height. Near the outlet of the pump on the delivery pipe, a valve is provided which controls the flow from the pump to the pipe.
SUCTION PIPE WITH FOOT VALVE AND STRAINER
One end of the suction pipe is connected to the inlet of the impeller and the other end is connected to a sump where the fluid is to be pumped. Foot valve and strainer is provided in this end. The strainer is used to filter the unwanted particle present in the water to prevent the pump from any blockage.
WORKING OF CENTRIFUGAL PUMP
The first step in the working of centrifugal pump is priming. Priming is a process in which the impeller is submerged in a liquid without any air trap inside it. When the impeller is made to rotate the fluid particles present around the impeller also rotates. This imparts centrifugal force to the water particles and the water moves radically in outward direction. Since the rotational energy is transferred to the fluid, at discharge side of the impeller both the pressure and kinetic energy of water will rise. At suction side water is been displaced, so a negative pressure will be induced. Such low pressure helps in sucking freshwater stream into the system again and the process continues. This is why priming is necessary. If there is no water present initially, the negative pressure developed by the rotating air will not be sufficient and will be negligibly small to suck a stream of fresh water again.
APPLICATIONS OF CENTRIFUGAL PUMP
The following are some of the major sector which makes use of centrifugal pump
- Oil & Energy sector – pumping crude oil used by refineries, power generation plants.
- Waste management, Agriculture & Manufacturing – Wastewater processing plants, municipal industry, irrigation and flood protection.
- Pharmaceutical, Chemical and Food Industries – Food and beverage production, sugar refining
PROCEDURE
The design of the centrifugal pump is constructed using made up geometry.
The hypothetical model for the centrifugal pump with impeller, casing, suction pipe and delivery pipe is created. The following displays the 3D model of the centrifugal pump.
3D MODEL
FLOW STIMULATION SETUP
- Enable Flow stimulation from Solidworks-Add Ins.
- Click on Wizard icon to create a new project.
- Give the name for the project and click next.
- Specify the unit system and click Next.
- In analysis window, select Internal Flow.
- In the default fluid dialog box select the medium as water and click next.
- Specify the wall conditions and click Finish.
- Specify the boundary conditions. Total pressure at the inlet and velocity at the outlet to 10.
- Click on surface goals and specify the goals as Total pressure at the inlet, Total pressure and mass flow rate at the outlet.
- Click on global mesh and specify the initial level of mesh. Initial mesh size of 4 is used in this project.
- Click on cut plots and specify the contour as velocity and place the plot at the required position.
- Flow trajectories can be used to view how the fluid will move inside the centrifugal pump.
- Run the stimulation.
- Click on new parametric study to run the stimulation for different outlet velocities.
- Select the input variable as Outlet velocity normal to the face. Use range with steps to specify different values for outlet velocities.
- In the output variable select the cut plots and surface goals.
- Run the stimulation.
The following are the results obtained for different outlet velocities.
Velocity plot at 10 m/s
Flow trajectory at 10 m/s
Velocity plot at 12 m/s
Flow trajectory at 12 m/s
Velocity plot at 14 m/s
Flow trajectory at 14 m/s
Velocity plot at 16 m/s
Flow trajectory at 16 m/s
Velocity plot at 18 m/s
Flow trajectory at 18 m/s
Velocity plot at 20 m/s
Flow trajectory at 20 m/s
The values for total pressure at the outlet and mass flow rate for different design points are shown below
The following grpah shows the relationship between mass flow rate at different design points.
Mass flow rate is given a negative sign as the volume is leaving the system.
Pressure ratio is defined as the ratio of total outlet pressure to that of total inlet pressure.
The relationship between pressure ratio and mass flow rate is given below
There is a decrease in pressure ratio when mass flow rate increases.
ANIMATION LINK
PART DRAWING
https://drive.google.com/file/d/16ZxrRvfQ9oM_hPAQhSHCFflxWaZ_HcKj/view?usp=sharing
RESULTS
- The design and analysis of centrifugal pump is successfully carried out and graph is plotted.
- Mass flow rate tends to increase with increase in velocities.
- The velocity of the fluid near the blades of the impeller increases with increase in outlet velocity.
REFERENCES
https://www.powerzone.com/resources/glossary/centrifugal-pump
https://theconstructor.org/practical-guide/centrifugal-pump-working-types/2917/