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INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD , DECEMBER,
Design and Development of Split Case Pump Using Computational Fluid Dynamics
A. V.S. Kadam, B. S.S. Gawade, C. H.H. Mohite, D. N.K.Chapkhane
Abstract Todays requirement regarding Pump is to satisfy specified duty point means
required head and discharge, with less power consumption. For the pump used for water
service applications, periodic maintenance is required to check the wear out parts like wear
ring, shaft sleeves. In such case horizontal split case pumps are more suitable. If the given
duty parameter is unable to satisfy with existing split case pump range, it is necessity to
develop new pump and developed pump should have more efficiency with energy crises
taking into consideration. With the aid of computational fluid dynamics, the complex internal
flow in horizontal split case pump can be well predicted, thus facilitating the design of pump.
The numerical analysis is carried out with multiple frame of reference to predict the flow field
inside the entire pump casing and impeller. Key Words centrifugal pump, computational fluid
dynamics, pump performance
I.
INTRODUCTION
entrifugal pump is a hydrodynamic machine, in which rotating impeller continuously transmits
mechanical work from the driving machine to fluid. The kinetic energy is converted into
potential pressure energy. Computational Fluid Dynamics CFD is one of the Computer Aided
Engineering CAE tool. CFD has recently come up as an alternative approach to investigate
the complex fluid flow phenomenon in pumps. It is rapidly becoming an important tool for
analysis and design in hydraulic engineering. The input to CAE software is meshed geometry
of the model and this geometric modeling is done by using Computer Aided Design CAD
software. II. NEED OF DESIGN OF PUMP FOR NEW SERIES Now a day in most of the
water service applications duty point requirements are of high head and discharge is
between m/hr to m/hr. Current duty point requirement is head H is m and discharge Q is
m/hr. The existing split case pump model range is up to m head for m/hr head. So it is
necessary to develop the pump for new higher head series for given discharge range. With
the same time as the energy crises taking into consideration the developed pump should
consume less power with more efficiency. The various types of pumps like multistage pump,
Vertical Turbine VT pump, mixed flow MF pump can be offered for present required duty of
high head and discharge. The Horizontal Split case pumps are more suitable for water
C
supply scheme projects because of following reasons . Simple in design as compare to
multistage pump and Vertical turbine pump. . Less rotating components and easy to
assemble. . Less cost of production. . Easy for maintenance. Over the last years, CFD has
been increasingly used for a wide variety of engineering applications. In the beginning, the
use of these techniques was customary only in the aerospace and nuclear fields.
Subsequently, the use has spread to a variety of products, physical situations, and
manufacturing processes. In the case of pump industry applications, CFD tools are important
in view of analysis of the hydraulic passage of the pumps. For impeller inlet, CFD can help to
improve the inlet flow distribution by proper designing/checking the quality of flow in pump .
The experimental and theoretical study requires enormous time. Also in experiment actual
physical model of prototype is required to manufacture which is costly. As the CFD analysis
can be carried out on prototype also. CFD tools avoid physical modeling and testing every
time. Better and faster design of pump and its analysis leads to shorter design cycles. III.
FLOW SIMULATION OF PUMP In order to obtain better design in CFD, following procedure
is applied so that fluid flow can easily be modeled in the centrifugal pump impeller.
Fig.. Flow chart of CFD procedure
It is now feasible to use CFD codes for a realistic prediction of the complex three dimensional
D turbulent flow in the entire pump. The D views of hydraulic flow passage of the suction
volute, impeller and delivery volute as
. The appropriate transformation occurs across a sliding interface without any interface
averaging. and tongue geometry . Fig. radial position of the cross section. the traditional
Reynolds Averaged Navier Stoke RANS model. There are five key geometrical parameters in
volute design circumferential variation of the cross sectional area.. Computational Domain.
Meshed model for CFD analysis The general parameters and boundary conditions used for
the D flow simulation of the pump are summarized in Table. kg/s Pressure outlet Standard
kepsilon model Second order upwind RSM Parameter D b D Su z Parameter b D outlet Flow
simulation domain Grid Fluid Inlet Outlet Turbulence Model Discretization Maximum residual
conversions criteria Table. Three criteria influence the choice of a turbulence model the
physical nature of the problem. whereby the impeller flow field is solved in a rotating frame
and the casing in a fixed one . this choice is always crucial when using CFD codes..
Simulation Parameters used in Fluent. All periodic grid surfaces are defined as periodic
boundary conditions. The pump main dimensional parameters are presented in Table. Finally
mesh file is imported in fluent software. metric unit is used. The two frames of reference are
connected in such a way that they each have a fixed relative position throughout the
calculation. and computing power. The impeller with specific speed . shown in Fig... The flow
solver of the CFD code employs for incompressible turbulent flow the continuity equation.
NUiCONE Conditions The first task to accomplish on numerical flow simulation is the
definition of the geometry. shape of the crosssection. Several numerical calculations are
carried out to predict the flow pattern inside the entire impeller and casing. Parameters
Description Extended Inlet and outlet. The grid of total flow domain passages has nodes.
Grid Generation and boundary The simulation domain at the inlet and outlet sections was
sufficiently extended to allow inlet recirculation and the elliptic influence of the flow . A design
requirement is to make the circumferential pressure distribution uniform. position of the
volute inlet. Nevertheless. The transport equations are discretized using the conservative
finite volume method. Depending on the flow complexity. Table. INTERNATIONAL
CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY. Delivery volute and impeller
Structured Water at room temperature Mass flow m/hr. Geometrical Parameters of the pump
It has found that a good volute design could improve the pump performance and operating
range .. Suction volute. the quality of attended results. Flow domains of pump for CFD A D
flow simulation is carried out for hydraulic flow passage. followed by the grid generation.
standard k viscous model is used .. For the present study the advection terms in the integral
equations are modeled employing a second order accurate skewed upwind . A structured
grid is created using the HyperMesh software as shown in Fig. Impeller Value Description
mm Impeller outside diameter Blade inlet angle Blade outlet angle mm Impeller Outlet Width
mm Impeller Eye Diameter mm Blade Thickness Number of Blades Volute Value Description
mm Volute inlet width mm Cut water diameter mm Volute outlet diameter Fig. The blades..
The walls are modeled using a loglaw wall function.. hub and shroud surfaces and casings
surfaces are modeled as solid walls. Volute studies have been performed on existing
geometries and can be categorized into two groups volute flow analysis and flow interactions
between volute and impeller.
Path lines colored by velocity magnitude Fig. Even though the effect of the volute tongue is
appreciable. the flow in the volute encounters a dividing plane. point. The CFD simulation
offers a virtual image of the internal flow in the machine allowing the analysis and
comprehension of more complex phenomena .. Parameters Discharge Total head Pump
input Efficiency CFD Analysis m/hr m . The blades. the mass flow rate in the absolute frame
of reference . above which the flow enters the volute. AHMEDABAD . According to Fig. The
leading edge of the tongue is analogous to that of an airfoil.. All periodic grid surfaces are
defined as periodic boundary conditions. the total pressure distribution shows some
negligible circumferential non uniformity at the impeller outlet. kW . .INSTITUTE OF
TECHNOLOGY.. This difference manifests itself as a design tradeoff. NIRMA UNIVERSITY.
Fig. DECEMBER. while a volute with a round tongue has better offdesign performance .. m .
The fringed contours of total pressure and velocity distributions at mid span of the impeller
and volute casings at the design point are shown in Fig. is obtained by numerical analysis.
Sr. turbulence intensity. The inlet velocity vector is in the axial direction. differencing scheme
with physical advection correction. The fluid variables like outlet pressure and velocity are
extrapolated at the outlet of the discharge nozzle sectional plane. Contours of Total Pressure
field on middle plane The tongue of a volute is located corresponding to a joint of the volute
smallest area. At this . below which the flow exits the pump. Comparison between CFD
analysis and Experimental testing Fig. Contours of Total Pressure Fig. The flow pattern in
casings also affects the performance of the pump . while a wellrounded leading edge has
large blockage but is insensitive to incidence... a relatively uniform pressure distribution is
obtained around the impeller. and Fig. and exit cone.. hub and shroud surfaces and casings
surfaces are modeled as solid walls . largest area. At the inlet of the computational domain.
volute and circular casings. Table. kW Experimental Results m/hr . Velocity Vectors Colored
by Velocity Magnitude m/s Comparison between CFD analysis and Experimental testing
Comparison between the CFD analysis and experimental results for the hydraulic
performance of the Pump is as shown in Table. A sharp volute tongue provides the absolute
peak efficiency. length scale and the reference pressure at one grid point are specified.
RESULTS The entire threedimensional flow field in the centrifugal impeller. IV. . a sharp
leading edge has low blockage but is sensitive to angle of attack.
. Numerical method for flow analysis and blade design in centrifugal pump impeller. Ross. S.
Val S. Journal of Experimental Thermal and Fluid Science .. . Jaico publishing house. . .
Craig Hornsby. Experimental and Finite Element Method FEM failure analysis and
optimization of centrifugal pump volute casing. . L.K. required head and discharge. Spence.
NUiCONE John S. Tata McGrawHill Book Company. This shows that CAD and CAE tools
are very useful in hydraulic design. ChuaThe flow patterns within the impeller passages of a
centrifugal pump model. World Pumps Magazine. W.. Computer simulation helps design
more efficient water pumps. with the use of advanced fluid modeling tools. pp. . Impeller
pumps. World Pumps Magazine May . Design and Application. pp. . John D. pp. World
Pumps Magazine. R. Centrifugal and Axial flow pumps Theory. Traditional volute design is
based on twodimensional analysis. HQ characteristics using CFD and Experimental testing
Performance found satisfactory as per the Acceptance standard IS . Journal of Engineering
Failure Analysis . INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN
TECHNOLOGY. Dr. Chris Reeves. and the emphasis is on collection Impeller and less on
the diffusion Volute function. . Journal of Computers and Fluids . Ing Friedrich. . and
Mischeke C. June . A. by which it is confirmed that CFD analysis is clearly validated. pp. pp.
Journal of Medical Engineering and Physics . Centrifugal Pumps design and application.R.
VI. V. Mechanical Engineering Design. pp. Computational Fluid DynamicsThe Basics with
Applications Taylor and Francis Publications. Considering economic incentive for operating
range and efficiency is gained by better understanding of the influence of the tongue. J. pp.
August . . Fig. Anderson.P. . it is possible to design a volute using threedimensional analysis.
. The volute design and analysis presented is indeed part of a new product in development at
Kirloskar Brothers Limited. Lobanoff and Robert R. CFDdriving pump design forward. Chan.
Troskolanski. . However. CONCLUSION The impeller of the existing closer range pump has
been modified by increasing the diameter to mm from mm to suit the higher efficiency. .
Pergramon Publication. .E. . The CFD analysis of the pump with modified impeller diameter
is carried out to check the performance and efficiency of the pump. Anagnostopoulos. .
Efficiency of the pump from CFD results is coming and by actual performance test efficiency
is coming . Shigley J. REFERENCES Ahmad Nourbakhsh Experimental study of
characteristic curves of centrifugal pumps in different specific speeds. Stephen Lazarkiewicz
and Adam T. Ahmad Nourbakhsh. CFD for parametric study of geometrical variations on the
pressure pulsations and performance characteristics of a centrifugal pump. Stepanoff. . .
John Wiley and Sons. Pump with higher efficiency and greater stable operating region is
designed. Journal of Computers and Fluids . Economic development of efficient centrifugal
pump impellers by numerical methods.