Axial Flow Turbines, 3-D Flow theories Notes | EduRev

: Axial Flow Turbines, 3-D Flow theories Notes | EduRev

 Page 1


1
Lect 25
Page 2


1
Lect 25
2
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
Axial Flow Turbines
3-D Flow theories
Page 3


1
Lect 25
2
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
Axial Flow Turbines
3-D Flow theories
3
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
• It is assumed that radial motion takes place in 
the blade passage only
C
r
<< C
a
;   C
r
<< C
w
• The stream surface has a cylindrical shape
•simplified radial equilibrium equation is valid
2
w
dp
11
= .C
?r
dr
r
m
Page 4


1
Lect 25
2
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
Axial Flow Turbines
3-D Flow theories
3
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
• It is assumed that radial motion takes place in 
the blade passage only
C
r
<< C
a
;   C
r
<< C
w
• The stream surface has a cylindrical shape
•simplified radial equilibrium equation is valid
2
w
dp
11
= .C
?r
dr
r
m
4
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
Following Three 3-D flow models in axial turbines 
are often used for design and analysis
1) Free Vortex flow
2) Constant nozzle exit angle, a
2
3) Arbitrary vortex case, C
w
= r
n
Page 5


1
Lect 25
2
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
Axial Flow Turbines
3-D Flow theories
3
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
• It is assumed that radial motion takes place in 
the blade passage only
C
r
<< C
a
;   C
r
<< C
w
• The stream surface has a cylindrical shape
•simplified radial equilibrium equation is valid
2
w
dp
11
= .C
?r
dr
r
m
4
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
Following Three 3-D flow models in axial turbines 
are often used for design and analysis
1) Free Vortex flow
2) Constant nozzle exit angle, a
2
3) Arbitrary vortex case, C
w
= r
n
5
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect 25
1) Free Vortex Flow model 
C
w
. r = constant, applied on the rotor flow
which normally entails a few assumptions :
At turbine rotor entry , 
dH
02
/dr = 0 ; C
w2
.r = constant; C
a2
= const
Rotor specific work done :
H
02
– H
03
= U (C
w2
+ C
w3
)= ?(r
2
.C
w2
- r
3
.C
w3
)
= constant
With C
w3
.r = constant, it follows C
a3
= const
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