Turbomachinery: Industrial Pump Design Optimization

TURBOMACHINERY DESIGN
WITH CFD OPTIMIZATION
ARNAUD GIRIN

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TURBOMACHINE DESIGN
What is a turbomachine?
A turbomachine acts as an energy converter
between kinetic energy (to/from the
impeller) and pressure energy ( to/from the
fluid).
If the work is done to the fluid, then the
turbomachine is classified as a pump or fan.
If the work is done by the fluid then the
turbomachine is classified as a turbine.
Pelton Turbine Wheel

USING CFD TO ASSESS A TURBOMACHINE DESIGN
TOPIC OVERVIEW
Looking at improving the design of
turbomachinery, the key factor is reducing
losses ( recirculation, friction etc.).
Many parameters on the different
components of the machine can be altered
and their effects on the performance can be
measured.
CFD provides a great solution for carrying
out fast iterations in order to converge on an
optimum design without the need for
excessive physical prototyping.
Fluid flow simulation of a water turbine design

TURBOMACHINE DESIGN EFFICIENCY
The efficiency of a turbomachine is defined as:
Where:
● ⍴: density in m3/kg
● g: gravity magnitude m/s²
● Q: is the flow rate m³/s
● H: pressure head (m)
● Pin: mechanical power input from the shaft defined by
At a set rotating speed, each pump design will reach a best efficiency point for a certain Q and H value,
this is what we are looking for.
For instance, increasing the impeller diameter of a certain pump will increase the pressure head
achieved but will also increase the mass to be moved; it is all about trade off!

DESIGN PARAMETERS
For the impeller:
● Number of blades
● Outer diameter
● Eye diameter
● Leading edge blade angle
● Trailing edge blade angle
For the volute/housing:
● Position and size of cutwater
● Inlet diameter, outlet diameter
● Shroud gaps
● Volute cross section area

THE SIMSCALE CFD SIMULATION WORKFLOW
3) Design Decision
Simulation insights to make better design
decisions faster and earlier
2) Simulation Setup
Structural mechanics, fluid dynamics or
thermal analysis—all in one application.
1) CAD Import
CAD model upload or import from other
cloud services

OUR CASE: CENTRIFUGAL PUMP
Objectives
● Observe the velocity and pressure
distribution inside the cavity of the
pump
● Identify areas in the design that
contribute to lower performance
● Quantify the performance scalars
such as the torque, the axial thrust,
and the velocity of the flow

What CAD geometry do we need
for this analysis?
Impeller volume
Rotating region volume
Fluid flow volume

Rotating Region
● Using the MRF method,
we can input an angular
velocity of 350 rad/s to
the volume surrounding
the rotating blades
MRF volume
½ between
the housing
and impeller

MESH GENERATION
Mesh Generation: Hex Dominant and Refinement
● Cylinder region, feature refinement, propeller
surface, rotating region (with cell zone), inflate
boundary layer
● 1.6 million cells
● 13 minutes on 16 processors 13.9 core hours

Analysis Type
● Incompressible analysis
● Steady state
● K-omega SST turbulence model
Known Inputs
● Water at 20°C
● Inlet
○ Volumetric Flow Rate = 0.004m³/s
● Outlet
○ Pressure = 0 Pa
● Impeller
○ MRF Rotating zone = 350 rad/s
THE SIMULATION SETUP

FLOW VELOCITY PATTERN
Sudden decrease of
velocity = lower efficiency
Acceleration of the velocity
at the tip of the blades
Cutwater region sees a rapid drop in velocity
and possible recirculation in the vicinity

VELOCITY STREAMLINES
Notice the acceleration and swirl of the flow
as it enters the impeller region.
The rotation of the impeller induces a vortex
at the inlet duct which uses energy and does
not participate in the pressure energy.
Some inlet housing are equipped with fins in
order to limit this effect.

PRESSURE DISTRIBUTION
Gradual build up of pressure as the flow
enters the volute spiral region.
Similarly to what is happening with
velocity, efficiency will improve with a
smooth increase of the pressure.

Turbomachinery: Industrial Pump Design Optimization

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