Chapter 14: Turbomachinery
Eric G. Paterson
Department of Mechanical and Nuclear Engineering
The Pennsylvania State University
Spring 2005
Note to Instructors
These slides were developed1, during the spring semester 2005, as a teaching aid
for the undergraduate Fluid Mechanics course (ME33: Fluid Flow) in the Department of
Mechanical and Nuclear Engineering at Penn State University. This course had two
sections, one taught by myself and one taught by Prof. John Cimbala. While we gave
common homework and exams, we independently developed lecture notes. This was
also the first semester that Fluid Mechanics: Fundamentals and Applications was
used at PSU. My section had 93 students and was held in a classroom with a computer,
projector, and blackboard. While slides have been developed for each chapter of Fluid
Mechanics: Fundamentals and Applications, I used a combination of blackboard and
electronic presentation. In the student evaluations of my course, there were both positive
and negative comments on the use of electronic presentation. Therefore, these slides
should only be integrated into your lectures with careful consideration of your teaching
style and course objectives.
Eric Paterson
Penn State, University Park
August 2005
1 These
slides were originally prepared using the LaTeX typesetting system (http://www.tug.org/)
and the beamer class (http://latex-beamer.sourceforge.net/), but were translated to PowerPoint for
wider dissemination by McGraw-Hill.
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Chapter 14: Turbomachinery
Objectives
Identify various types of pumps and
turbines, and understand how they work
Apply dimensional analysis to design
new pumps or turbines that are
geometrically similar to existing pumps or
turbines
Perform basic vector analysis of the flow
into and out of pumps and turbines
Use specific speed for preliminary design
and selection of pumps and turbines
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Chapter 14: Turbomachinery
Categories
Pump: adds energy to
a fluid, resulting in an
increase in pressure
across the pump.
Turbine: extracts
energy from the fluid,
resulting in a
decrease in pressure
across the turbine.
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Chapter 14: Turbomachinery
Categories
For gases, pumps are further broken down into
Fans: Low pressure gradient, High volume flow rate.
Examples include ceiling fans and propellers.
Blower: Medium pressure gradient, Medium volume
flow rate. Examples include centrifugal and squirrelcage blowers found in furnaces, leaf blowers, and
hair dryers.
Compressor: High pressure gradient, Low volume
flow rate. Examples include air compressors for air
tools, refrigerant compressors for refrigerators and air
conditioners.
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Chapter 14: Turbomachinery
Categories
Positive-displacement machines
Closed volume is used to squeeze or suck fluid.
Pump: human heart
Turbine: home water meter
Dynamic machines
No closed volume. Instead, rotating blades supply or
extract energy.
Enclosed/Ducted Pumps: torpedo propulsor
Open Pumps: propeller or helicopter rotor
Enclosed Turbines: hydroturbine
Open Turbines: wind turbine
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Chapter 14: Turbomachinery
Pump Head
Net Head
Water horsepower
Brake horsepower
Pump efficiency
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Chapter 14: Turbomachinery
Matching a Pump to a Piping System
Pump-performance
curves for a centrifugal
pump
BEP: best efficiency
point
H*, bhp*, V* correspond
to BEP
Shutoff head: achieved
by closing outlet (V=0)$
Free delivery: no load on
system (Hrequired = 0)
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Chapter 14: Turbomachinery
Matching a Pump to a Piping System
Steady operating
point:
Energy equation:
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Chapter 14: Turbomachinery
Manufacturer Performance Plot
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Chapter 14: Turbomachinery
Pump Cavitation and NPSH
Cavitation should be avoided due
to erosion damage and noise.
Cavitation occurs when P < Pv
Net positive suction head
NPSHrequired curves are created
through systematic testing over a
range of flow rates V.
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Chapter 14: Turbomachinery
Dynamic Pumps
Dynamic Pumps include
centrifugal pumps: fluid enters
axially, and is discharged
radially.
mixed--flow pumps: fluid enters
axially, and leaves at an angle
between radially and axially.
axial pumps: fluid enters and
leaves axially.
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Chapter 14: Turbomachinery
Centrifugal Pumps
Snail--shaped scroll
Most common type of
pump: homes, autos,
industry.
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Chapter 14: Turbomachinery
Centrifugal Pumps
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Chapter 14: Turbomachinery
Centrifugal Pumps: Blade Design
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Chapter 14: Turbomachinery
Centrifugal Pumps: Blade Design
Side view of impeller blade.
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Vector analysis of leading
and trailing edges.
Chapter 14: Turbomachinery
Centrifugal Pumps: Blade Design
Blade number affects efficiency and introduces circulatory
losses (too few blades) and passage losses (too many blades)
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Chapter 14: Turbomachinery
Axial Pumps
Open vs. Ducted Axial Pumps
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Chapter 14: Turbomachinery
Open Axial Pumps
Blades generate thrust like wing
generates lift.
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Propeller has radial twist to take into
account for angular velocity (=r)
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Chapter 14: Turbomachinery
Ducted Axial Pumps
Tube Axial Fan: Swirl
downstream
Counter-Rotating Axial-Flow
Fan: swirl removed. Early
torpedo designs
Vane Axial-Flow Fan: swirl
removed. Stators can be
either pre-swirl or post-swirl.
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Chapter 14: Turbomachinery
Ducted Axial Pumps: Blade Design
Relative frame of reference
Absolute frame of reference
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Chapter 14: Turbomachinery
Dimensional Analysis
 analysis gives 3 new nondimensional
parameters
Head coefficient
Capacity coefficient
Power coefficient
Reynolds number also appears,but in terms of
angular rotation
Reynolds number
Functional relation is
Head coefficient
Power coefficient
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Chapter 14: Turbomachinery
Dimensional Analysis
If two pumps are
geometrically similar, and
The independent ’s are
similar, i.e.,
CQ,A = CQ,B
ReA = ReB
A/DA = B/DB
Then the dependent ’s
will be the same
CH,A = CH,B
CP,A = CP,B
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Chapter 14: Turbomachinery
Dimensional Analysis
When plotted in
nondimensional form, all
curves of a family of
geometrically similar
pumps collapse onto one
set of nondimensional
pump performance
curves
Note: Reynolds number
and roughness can often
be neglected,
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Chapter 14: Turbomachinery
Pump Specific Speed
Pump Specific Speed is used to characterize the operation of a
pump at BEP and is useful for preliminary pump selection.
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Chapter 14: Turbomachinery
Affinity Laws
For two homologous states A and B, we can use
 variables to develop ratios (similarity rules,
affinity laws, scaling laws).
Useful to scale from model to prototype
Useful to understand parameter changes, e.g.,
doubling pump speed (Ex. 14-10).
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Chapter 14: Turbomachinery