2. WHAT IS CENTRIFUGAL PUMP ?
• Convert the mechanical energy into hydraulic
energy by centrifugal force on the liquid
• Constitute the most common type of pumping
machinery
• Used to move liquids through a piping system
• Has two main components:
1. Stationary componets, casing, casing cover
and bearings
2. Rotating components, impeller and shaft
• Classified into three categories ; Radial Flow,
Mixed Flow, Axial Flow
3. WORKING MECHANISM OF A CENTRIFUGAL
PUMP
• Simplest piece of equipment in any
process plant
• Energy changes occur by virtue of
impeller and volute
• Liquid is fed into the pump at the
center of a rotating impeller and
thrown outward by centrifugal force
• The conversion of kinetic energy into
pressure energy supplies the
pressure difference between the
suction side and delivery side of the
pump Liquid flow path inside a
centrifugal pump
4. PUMP SELECTION
The amount of fluid
The properties of the fluid
Type of power supply
Cost and mechanical
efficiency of the pump
5. BACKGROUND
• Centrifugal pumps are used in a variety of
applications, such as, water supply and irrigation,
power generating utilities, flood control, sewage
handling and treatment, process industries,
transporting liquid-solid mixtures.
• Conventional design method of centrifugal pump
are largely based on the application of empirical
and semi-empirical rules along with the use of
available information in the form of different
types of charts and graphs as proposed by
successful designers .
6. INTRODUCTION OF CFD MODEL
• Computational fluid dynamics (CFD) is being
increasingly applied in the design of the centrifugal
pumps. 3-D numerical computational fluid dynamics
tool can be used for simulation of the flow field
characteristics inside the turbo machinery
• To overcome the difficulties of Conventional design
method , some simplifications in the geometry are
often considered many hydrodynamic models are
reported in two (2D) and three dimensional (3D) by
using the CFD code.
7. CFD in the turbomachinery
IMPELLER 3D FLOW
SIMULATION
A 3D CFD flow simulation was carried out on an isolated impeller
of a mixed-flow centrifugal pump with specific speed
of 32 (impeller NS32).
9. Turbulence models
.
• Figure 6 shows the influence
of the three turbulence
models on the calculated
pump head. The calculated
head H varies very slightly (less
than 0.02%). The same
tendency is observed in
Figures 7 and 8, where no
significant influence of the
turbulence model on the
meridional velocity field and
velocity profile near the wall is
observed
11. Static pressure field of pump NS32 at the best efficiency point
(Q/Qbep = 1) for different relative positions of impeller-volute
tongue.
12. NON UNIFORM PREESUR
DISTRIBUTION
The non uniform pressure
distribution around the
impeller periphery is the
origin of periodic loads
causing the radial thrust.
This fundamental parameter
affects the life cycle of the
pump shaft and bearings as
well as the vibration
behavior of the machine.
The pressure distribution
around the impeller
periphery is shown in Figure
for α = 0◦ and different flow
rates.
13. Radial thrust
The radial thrust can be determined
from the pressure distributions
by carrying out the integration of the
elementary forces around the impeller
periphery
14. CONCLUSIONS
• In this research work, an integral procedure for the optimization of
centrifugal pumps has been developed based on 3D quasi-unsteady
flow simulation using CFX-TASC flow and CFX 5.5 codes.
• The sensitivity study performed on the isolated impeller has shown
two relevant aspects.
• (i) The numerical solution is stabilized with grids containing more
than 40 000 nodes.
• (ii) All turbulence models used (k − ε, k ω, k − ω, SST) gave almost
identical results, for the same simulating conditions.
• The impeller-volute assembly requires the addition of two
extended computational domains; one at the impeller inlet and the
other at the volute outlet. The Frozen-Rotor interface model (quasi-
unsteady) is considered for the study of the impeller-volute
assembly since it represents the best accuracy of computing time
tradeoff.
