Turbomachinery Aero-Thermodynamics - Crans

49 Pages·2015·1.72 MB·English

Turbomachinery Aero-Thermodynamics
Aero-Thermodynamics 0D-2D
Alexis. Giauque1
1LaboratoiredeM´ecaniquedesFluidesetAcoustique
EcoleCentraledeLyon
Ecole Centrale Paris, January-February 2015
AlexisGiauque (LMFA/ECL) TurbomachineryAero-ThermodynamicsII EcoleCentraleParis 1/48
And now what are the stakes and technologies?
Sustainable progress
Propulsion – Contra-Rotative Open Rotors (CRORs)
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Table of Contents
1. Vues and Analysis surfaces
Meridional view
Cascade view
2. Thermodynamics
Relative total/stagnation variables
3. Transformations
Transformation types
Transformation representation
Evolution of the main variables during compression/expansion
4. Efficiency
Isentropic efficiency
Polytropic exponent
Polytropic efficiency
Link between Polytropic and isentropic efficiency for a compression
Polytropic efficiency and aerodynamics
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Views and Analysis surfaces
In order to understand and design compressors and turbines, it is necessary
to simplify the flow representation without losing the main physical
features.
Views and Analysis surfaces
Two types of views are most commonly used:
the meridional view
the blade-to-blade view
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Meridional view
The definition of the meridional view is best understood by the next
picture which represents an axial turbine stage
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Meridional view – How we use it
Let’s consider an axial stage.
r is the mean radius and h is the blade height. Obtaining
m
m˙ = 2πρV hr
z m
Assuming uniform ρ and V , the mass flow rate can therefore be obtained
z
directly by using informations available from the meridional view in the
case of an axial stage
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Meridional view in a centrifugal compressor
In the case of a centrifugal compressor, the meridional view is a bit more
complex
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Difference between meridional view and meridional surface
It should not be confused with the meridional surface which is a plane
projection of this surface. Note that in axial machines, both view and
surface are identical.
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Cascade view
The cascade view or blade-to-blade view is very important because it
comprises all the necessary informations related to the work exchange in
the machine.
The definition of the cascade view is best understood by the next picture
which represents an axial turbine stage
AlexisGiauque (LMFA/ECL) TurbomachineryAero-ThermodynamicsII EcoleCentraleParis 9/48
Cascade view in axial machines
The following picture presents the notation used in axial machines
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