Centrifugal pump design and analysis

INTRODUCTION – CENTRIFUGAL PUMP:

Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are a sub-class of dynamic axisymmetric work-absorbing turbomachinery. A centrifugal pump is a mechanical device designed to move fluid through the transfer of rotational energy from one or more driven rotors, called impellers. Fluid enters the rapidly rotating impeller along its axis and is cast out by centrifugal force along its circumference through the impeller's vane tips.

Mass Flow rate: mass flow rate is the mass of a substance that passes per unit of time.

AIM:

To create a centrifugal pump geometry to perform the flow simulation using Solidworks and obtaining the analysis results to view the relationship between the mass flow rate and pressure ratio.

Note: Pressure ratio = Outlet total pressure/ Inlet total pressure

OBJECTIVE:

• To obtain the relationship between the mass flow rate and pressure ratio.
• Reviewing the obtained results.

PROCEDURE:

3D MODEL:

• To create the centrifugal pump geometry, starting the sketch from the top plane in Solidworks.
• Two circles that are concentric with the origin are sketched with dia 0.04m and dia 0.08m respectively.
• Constructing two arcs between the two circles for the vanes of the impeller that are concentric.
• Trimming the extra outer circle and patterning the vanes as 5 concerning the origin.
• Now extruding the sketch from midplane to get the profile. From the top plane, drawing another circle from its origin and extruding from the midplane to get the geometry.

*Merge results are unselected.

• From the top plane, a new circle is sketched and extruded.
• With the centreline, draw a tangent over the circle from the top plane and a line is drawn parallel and equal to the centreline inside the circle.
• A reference plane is drawn on the endpoint of the line drawn and a circle is drawn on that plane and sweeper into the circle.
• From the top face of the profile, the circle is drawn and extruded for the inlet cavity.
• Using the direct editing tab, combining the profile into a single geometry.
• Using the shell, the thickness is provided to the geometry.
• Now from the top plane, the circle is drawn outside the edges of vanes end extruded up to 0.011m in the midplane.

Part File-Centrifugal Pump:

Part file with Transparency: shows the vanes of the impeller inside the compressor pump.

BASELINE SIMULATION:

For the watertight body, the lid is created on both the circular profile of the centrifugal pump. In the wizard menu, the following are provided as inputs for the baseline simulation for the centrifugal pump.

Units: SI units

Simulation Type: Internal Flow

Fluid: Water

To perform the flow simulation inside the centrifugal pump, the rotation is included with the local region averaged.

Boundary Conditions:

Environment Pressure = 101325 pa

Outlet Velocity = 10 m/s

Rotating Region = Outside the vanes (Boss Extrude 4) with 1000 rad/s

In the component control, boss extrude is excluded from selection, and in the Calculation control options, only Iterations are selected and value is provided at 500.

Avg Total Pressure = Outlet Profile (LID2)

A mass flow rate is provided for both the lids.

Global Mesh is refined at level 3 and advanced channel refinement.

Then the simulation is performed. After the completion of the baseline simulation, the parametric study is calculated.

Flow Trajectory Velocity - Baseline Simulation:

Flow Trajectory Pressure - Baseline Simulation:

PARAMETRIC STUDY:

To perform the parametric study on the compressor pump, the followings are provided:

Input parameters = Velocity normal to face (outlet velocity)

The input values are ranged from 10m/s to 30m/s with number of values 5 (i.e.) 10m/s, 15m/s, 20m/s, 25m/s, & 30m/s.

Output Parameters = All goals and all results are inserted.

Running the simulation, we get the following results.

RESULTS:

CASE 1: @ 10m/s:

Velocity Contour-cut plot:

Pressure Contour-cut plot:

Flow Trajectory Velocity Contour:

Flow Trajectory Pressure Contour:

CASE 2: @ 15m/s:

Velocity Contour-cut plot:

Pressure Contour-cut plot:

Flow Trajectory Velocity Contour:

Flow Trajectory Pressure Contour:

CASE 3: @ 20m/s:

Velocity Contour-cut plot:

Pressure Contour-cut plot:

Flow Trajectory Velocity Contour:

Flow Trajectory Pressure Contour:

CASE 4: @ 25m/s:

Velocity Contour-cut plot:

Pressure Contour-cut plot:

Flow Trajectory Velocity Contour:

Flow Trajectory Pressure Contour:

CASE 5: @ 30m/s:

Velocity Contour-cut plot:

Pressure Contour-cut plot:

Flow Trajectory Velocity Contour:

Flow Trajectory Pressure Contour:

PLOT:

Pressure Ratio vs Mass flow rate:

CONCLUSION:

Thus the Pressure ratio vs Mass flow rate was obtained by sketching and performing the flow simulation for the centrifugal pump. The following are observed during the analysis of the centrifugal pump:

• The increase in velocity results in an increase in mass flow rate. From the plot, we conclude that as an increase in mass flow rate, the pressure ratio value increases respectively is obtained in the above plot.
• The negative sign indicates the flow of the fluid at the outlet port.
• Generally, for the compressor pump, the pressure ratio will decrease in an increase in velocity at the outlet.
• Here the variation is not linear as because the geometry of the centrifugal pump is not sketched with the standard centrifugal pump i.e. with dimensions and values. If the standard values are used, the resulted plot will be linear and accurate i.e. the pressure ratio will decrease in an increase in velocity at the outlet.