Ch.5-1 Introduction to Turbomachinery
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What is “Turbomachinery” ?
“turbo” or “turbinis” is Latin in origin
and implies that which spins or whirls
around.
A turbomachine is a rotating (as opposed
to reciprocating) device that extracts
energy from or adds energy to fluids.
There are two main categories of
turbomachines, i.e.
• those absorbs power (e.g., pumps, fans,
compressors), and
• those generates power (e.g. hydraulic,
steam, and gas turbines)
A turbomachine changes the enthalpy of
the working fluids.
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Review: Why “enthalpy”?
First Law of Thermodynamics for an open system (based on
control volume analysis)
1 2 2



 ( h 2  h1 )  (c2  c1 )  g(z 2  z1 )
QW  m
2


Therefore,
 m
 (h1  h2 )
W
What is enthalpy ?
h  u  pv
u: internal energy
pv: flow work
Important:
All these parameters (h, u, p, v) are properties of a substance.
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Example 1a (system): Steam Power Plant
Siemens Steam Plants (SSP™)
Reference:
http://www.powergeneration.siemens.com/products-solutions-services/power-plant-soln/steam-turbinepower-plants/
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Example 1b (system): Steam Turbine
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Example 2a: Tidal Stream Turbine
Tidal power is the only form of energy which
derives directly from the relative motions of
the Earth-Moon system. Tidal power is
practically inexhaustible and classified as a
renewable energy source. Tidal energy is
periodical and predictable. In contrast, wind
and solar energies cannot be well-predicted.
SeaGen is the world's first large scale commercial tidal stream generator. It is four
times more powerful than any other tidal stream generator in the world.
Reference: http://en.wikipedia.org/wiki/SeaGen
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Example 2b: Tidal Stream Turbine
Click the following weblink:
http://www.youtube.com/watch?v=qRUl1mJQHmc&list=PL994CD8692F04FA15&index=2
http://www.youtube.com/watch?v=tSBACzRE3Gw&feature=related
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Example 3: Turbo Engines
Click the following weblink:
http://www.youtube.com/watch?v=p1TqwAKwMuM&list=PL17E887C02E1576E6
http://www.youtube.com/watch?v=Y0uQzLC851c&feature=PlayList&p=17E887C02E1576E6&index=3
http://www.youtube.com/watch?v=CXSi4GXUojo
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Classification of Turbomachines
According to the function:
• Pumps/compressors
Absorbing power
• Turbines
Generating power
According to the flow direction:
• Axial-flow turbomachine
Flow path parallel to axis of rotation
• Radial-flow turbomachine
Flow path perpendicular to axis of rotation
• Mixed-flow turbomachine
Both radial and axial flow components
According to the pressure change in a rotor:
• Impulse (zero-reaction) turbomachine
Pressure changes across the nozzle/diffuser;
Pressure does not change across the rotor (or blades).
• Reaction (zero impulse) turbomachine
Pressure changes across both the nozzle/diffuser and the rotor.
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Example 4a: Centrifugal Compressor
Jet engine
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Example 4b: Centrifugal Turbines
Turbine and nozzles
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Shaft and turbine
Example 4c: Centrifugal Turbomachine
Nozzles and compressor blades
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Example 5a: Axial Compressor
4-stage compressor
A blade wheel (single stage)
Jet engine
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Example 5b: Axial Turbine
Axial gas turbine (rotor)
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Wind turbine
Tidal turbine
Example 5c: Axial Compressor
Rotor
(To transfer mechanical energy to kinetic energy
of gas; to partially increase the pressure.)
Stator
(To increase the pressure;
to transfer kinetic energy to
potential/pressure energy.)
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1 stage
= 1 stator blade wheel
+1 rotor blade wheel
Example 6: Impulse Turbines
Simplest example
Pelton hydraulic turbines
No pressure changes across the blades
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