Centrifugal Pump Design and its CFD Analysis

OBJECTIVE :

1. To make CAD model of a centrifugal pump and perform its flow simulation.
2. To obtain and plot the relationship between pressure ratio and mass flow rate.

SOLVER USED : SOLIDWORKS Flow Simulation

INTRODUCTION :

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 electric motor. They are a sub-class of dynamic axisymmetric work-absorbing turbomachinery. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from which it exits.

CAD MODEL :

ROTOR SKETCH :

CASING SKETCH :

FINAL CAD MODEL:

SECTIONAL VIEW OF EXTRUDED GEOMETRY :

FLOW SIMULATION :

Flow Setup :

• Temperature = 293.2 K
• Wall type is real.
• Gravity is considered in negetive X direction with g = 9.81 m/s2.
• Cavitation is not considered.
• Flow type is 'Laminar and Turbulent'.
• Water is used as working fluid.
• Boundary Condition at inlet: Environmental Pressure = 101325 Pa.
• Boundary Condition at outlet : Velocity = 8 m/s.
• Rotor speed = 300 rad/s

Solution Preview :

Pressure Plot :

Velocity Plot :

Flow Trajectory :

Flow Trajectory Animation :

It can be observed from the trajectory animation that a small amount of water outflows from the inlet itself, this is because this geometry is just an arbitrary geometry. Actual pumps have more intricate geometry to prevent such problems.

PARAMETRIC STUDY :

A 'parametric Study' or 'What if analysis' is done to obtain a relationship between pressure ratio and mass flow rate.

The flow analysis is performed at different values of outlet velocity and corresponding pressure ratio is calculated.

Following Results wew obtained :

Goal (Value)	Design Point 1	Design Point 2	Design Point 3	Design Point 4	Design Point 5
Velocity normal to face (Outlet Velocity 2) [m/s]	8	7	6	5	4
SG Average Total Pressure 1 [Pa]	1485602.355	915277.3168	630146.2566	1368698.526	145620.6295
Inlet Pressure	101325	101325	101325	101325	101325
Pressure ratio	14.66	9.03	6.22	3.5	1.44
SG Mass Flow Rate 2 [kg/s]	3.944598066	3.451912453	2.959329229	2.46521445	1.973341678

CONCLUSION :

1. The performance of centrifugal pump is very sensitive to the geometry.
2. Blue region at the downstream of inlet shows that it is the least pressure region and thus is more prone to cavitation.
3. Reddish region in the casing shows pressure of the fluid increases suddenly as it enters into the volute casing.
4. Pressure increase and velocity decreases gradualy as it flows over the impeller due to its diverging cross section.
5. As mass flow rate increases pressure rato also increases.

REFERENCE :

1. https://www.iitism.ac.in/~shibayan/MMC%2016101%20Fluid%20Machines/MMC%2016101_centrifugal%20Pump_01.pdf
2. Introduction to Fluid Mechanics and Fluid Machines - S.K. SOM and G. BISWAS.
3. https://nptel.ac.in/courses/112/105/112105206/
4. https://nptel.ac.in/courses/112/105/112105206/

======================Thankyou=======================