Centrifugal pump design and analysis

AIM : To design and analyse a Centrifugal Pump.

OBJECTIVES :

1. To create a 3D model of a centrifugal Pump.
2. To obtain the relationship between Pressure ratio and mass flow rate using Performance diagram.

THEORY : Centrifugal Pumps are the most popular and commonly used type of pump for the transfer of fluids. In simple words, it is a pump that uses a rotating impeller to move water or other fluids by using centrifugal force. These are the undisputed pump choice especially for delivering liquid from one location to another in numerous industries including agriculture, municipal (water and wastewater plants), industrial, power generation plants, petroleum, mining, chemical, pharmaceutical, and many others. Centrifugal Pumps are useful since they can generally handle large quantities of fluids, provide very high flow rates (which may vary with the changes in the Total Dynamic Head (TDH) of the particular piping system) and have the ability to adjust their flow rates over a wide range. Centrifugal pumps are generally designed and suitable for liquids with a relatively low viscosity that pours like water or light oil. More viscous liquids such as 10 or 20 wt. oils at 68-70 deg F will require additional horsepower for centrifugal pumps to work. For viscous liquids of more than 30 wt. oils, positive displacement pumps are preferred over centrifugal pumps to help lower energy costs.

Working of a Centrifugal Pump - Let us understand in detail, how a Centrifugal pump works. Centrifugal pumps are used to induce flow or raise a liquid from a low level to a high level. These pumps work on a very simple mechanism. A centrifugal pump converts rotational energy, often from a motor, to energy in a moving fluid. The two main parts that are responsible for the conversion of energy are the impeller and the casing. The impeller is the rotating part of the pump and the casing is the airtight passage which surrounds the impeller. In a centrifugal pump, fluid enters into the casing, falls on the impeller blades at the eye of the impeller, and is whirled tangentially and radially outward until it leaves the impeller into the diffuser part of the casing. While passing through the impeller, the fluid is gaining both velocity and pressure.

PROCEDURE :

• Geometry Modelling of Pump -
• At first 3D model of the pump is made using ideas from the video. It comprises sketching of impeller,casing,inlet and outlet channels and a rotating extrusion for flow simulation.

• Parameters for Baseline Simulation

  Internal analysis

  Fluid: Water

  Laminar and turbulent type of flow

  Boundary Condition at Inlet - 1 bar [Pressure]

  Boundary Condition at Outlet - 10 m/s

  Local Region Averaging

  Procedure

  • Create a 3D Model in Solidworks CAD Software.
  • Modify the Components in the Components Control.
  • The Computational Domain is created.
  • The Rotating Region is selected and the speed is set to 1000 rpm.
  • The Inlet Boundary Condition is set as Environmental Pressure of 1 bar.
  • The Outlet Boundary Condition is the Exit Velocity of 15 m/s.
  • The Surface Goal is set in the Inlet and the Outlet faces.
  • Then the Mesh is created for the model and the Automatic mesh level is set into 3 and Advanced Chanel refinement is selected.
  • Run the Simulation and the cut plots are created for the Pressure and Velocity and get the values for the goals.

  Results-Grid Dependency test

  For this test, I have set the input variables as output velocity and the values are 10 m/s, 15 m/s, 20 m/s, 25 m/s, 30 m/s. The Level of mesh is set as 3. The number of Iteration for the solver is set as 500 in the calculation control option. The mesh is refined to advanced channel refinement.

  RESULTS :

  • Case 1 (For outlet velocity as 10ms">10m/s)-
  • Velocity Surface Flow Trajectory -
  • Pressure Surface Flow Trajectory -
  • Case 2 (For outlet velocity as 20ms">20m/s)-
  • Velocity Surface Flow Trajectory -
  • Pressure Surface Flow Trajectory -
  • Case 3 (For outlet velocity as 30ms">30m/s)-
  • Velocity Surface Flow Trajectory -
  • Pressure Surface Flow Trajectory -
  • Case 4 (For outlet velocity as 40ms">40m/s)-
  • Velocity Surface Flow Trajectory -
  • Pressure Surface Flow Trajectory -
  • Case 5 (For outlet velocity as 50ms">50m/s)-
  • Velocity Surface Flow Trajectory -
  • Pressure Surface Flow Trajectory -
  • Case 6 (For outlet velocity as 60ms">60m/s)-
  • Velocity Surface Flow Trajectory -
  • Pressure Surface Flow Trajectory -
  • Case 7 (For outlet velocity as 70ms">70m/s)-
  • Velocity Surface Flow Trajectory -
  • Pressure Surface Flow Trajectory -
  • Pressure Ratio = Pressure 1/Pressure 2,
  • The negative sign in mass flow rate indicates that mass is leaving the control volume, and for performance curve it's been removed.
  • Performance diagram between Pressure ratio and mass flow rate -

  CONCLUSION :

  1. It is clearly shown in the pressure and velocities flow trajectories that at inlet pressure is high and velocity is low and vice-versa at outlet.
  2. From the performance diagram between Pressure ratio and mass flow rate, it can be concluded that as the pressure ratio increases, mass flow rate of water coming out from outet also increases and vice-versa and it helps in achieving the desired purpose of the pump as it pumps to a high pressure from low pressure and more amount of mass rate coming out from outlet.
  3. A pump does not create pressure it only creates flow. Pressure is a measurement of the resistance to flow.
  4. so from the above plots and graphs we can conclude that the above project is executed proplerly and the plots are upto the given conditions.