14-11-2012, 01:14 PM
COMPUTATIONAL ANALYSIS ON PERFORMANCE OF A
CENTRIFUGAL PUMP IMPELLER
COMPUTATIONAL ANALYSIS ON PERFORMANCE OF A.pdf (Size: 1.2 MB / Downloads: 66)
ABSTRACT
Centrifugal pump is a most common pump used
in industries, agriculture and domestic applications.
The design of a centrifugal pump impeller
demands a detailed understanding of the internal
flow during design and off-design operating
conditions. The present paper describes the
simulation of the flow in a centrifugal pump
impeller at five different flow coefficients viz.
0.0146, 0.0346, 0.0546 (designed flow coefficient),
0.0746 and 0.0946. The numerical solution of the
deiscretized three-dimensional, incompressible
Navier-Stokes equations over an unstructured grid
is accomplished with CFD package Ansys-CFX.
For each flow co-efficient, performance results,
static pressure contours, absolute velocity vectors,
blade loading plots, mass averaged total pressure
and static pressure, area averaged absolute
velocity, pressure variation in blade to blade
passage are presented.
INTRODUCTION
The complexity of the flow in any
turbomachine is due to the three dimensional blade
geometry, turbulence, secondary flows,
unsteadiness etc. Computational fluid dynamics
(CFD) has successfully contributed to the
prediction of the flow through pumps and the
enhancement of their design. Various researchers
have considerably contributed to reveal the flow
mechanisms inside centrifugal pump impellers
with spiral volute or vaned diffuser volute aiming
to the design of high performance centrifugal
turbomachines.
GOVERNING EQUATIONS:
The incompressible flow through the rotating
impeller is solved with a moving frame of
reference with constant rotational speed. 3-D
incompressible Navier-Stokes equations with the
rotational force source term are solved to analyze
the flow in centrifugal pump. Turbulence is
modeled with k-ε turbulent model.
BOUNDARY CONDITIONS
Centrifugal pump impeller closed type domain
is considered as a rotating frame of reference with
a rotational speed of 925 rpm anti clockwise
direction. The working fluid through the pump is
water at 25oC. casing is not taken into the account
for analysis. k- turbulence model with turbulence
intensity of 2% is considered. Non slip boundary
conditions have been imposed over the impeller
blades, hub and shroud. Roughness of all walls is
considered 100"m. Inlet static pressure and outlet
mass flow rate are given based on flow
coefficients. Convergence precision of residuals
was considered as 10-5. Three dimensional
incompressible N-S equations are solved with
Ansys-CFX Solver.
RESULTS
Centrifugal pump impeller is solved for five
different flow coefficients. The performance
results for different flow coefficients are presented
in Table No.3. The head obtained by the CFD
analysis for designed flow coefficient is 9.45m
WG and static efficiency is 61.22%. These results
are compared with the Bcharoudis et al., 2008
experimental results.