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Rothalpy
P M V SubbaraoProfessor
Mechanical Engineering Department
Design variations through Conservation of Rothalpy….
Blade Velocity Vs Tangential Component of Fluid Velocity
Ub
Ub
Vi
Vai
Vfi
2222
2
1bladebladerx UUVVVhI
Vri
In maridional plane at mean radius of rotor & inlet
bladerx UVVVVhIRothalpy 22
1: 222
UbV i
Vai
VfiVri
Ub
V i
Vai Vfi
Vri
V iUb
Vai
Vfi
Vri
22,
22
2
1: bladerelrx UVVVhIRothalpy
22
2
1: bladerel UVhIRothalpy
Relative Angular Velocity
bladeblade
rel UVhU
hIRothalpy 0
2
,0 2:
Constant in an ideal turbo-machine
2222
2
1bladebladerx UUVVVhI
Evolution of Relative Velocity Along Flow Path
For stator path : Ublade =0
constant: 0,0 hhEnthalpyStagnation rel
For rotor Paths :
constant2
: 0
2
,0 bladeblade
rel UVhU
hIRothalpy
For a true axial flow rotor paths: Ublade constant
constant: ,0 relhIRothalpy
Classification of Isentropic Expansion Paths
Turbo-machines working with Vapors/Gas
constant2
: 0
2
,0 bladeblade
rel UVhU
hIRothalpy
constant,2
,0,0
0
2
0
blade
T
pblade
T
p UVdTTpcU
dTTpcIrel
For an ideal gas:
constant2
0,0
0
2
0
blade
T
pblade
T
p UVdTTcU
dTTcIrel
For simple compressible fluid: Like Inert Gas
constant2
: 0
2
,0 bladepblade
relp UVTcU
TcIRothalpy
constant2
0,0
0
2
0
blade
T
pblade
T
p UVdTcU
dTcIrel
Turbo-machines working with Perfect Gas
The Fourth Generation Nuclear Power Plants
An Advanced Nuclear Power Plant
The Ultimate Importance of Invariant Property : Rothalpy
constant2
:2
,0 bladerel
UhIRothalpy
Selection of Stator-Rotor Combinations
From Books of Sir Charles Parson
• In 1884 or four years previously, I dealt with the turbine problem in a different way.
• It seemed to me that moderate surface velocities and speeds of rotation were essential if the turbine motor was to receive general acceptance as a prime mover.
• I therefore decided to split up the fall in pressure of the steam into small fractional expansions over a large number of turbines in series, so that the velocity of the steam nowhere should be great.
• A moderate speed of turbine suffices for the highest economy.
• This principle of compounding turbines in series is now universally used in all except very small engines, where economy in steam is of secondary importance.
• The arrangement of small falls in pressure at each turbine also appeared to me to be surer to give a high efficiency.
• The steam flowed practically in a non-expansive manner through each individual turbine, and consequently in an analogous way to water in hydraulic turbines whose high efficiency at that date had been proved by accurate tests.
Classification of Steam Turbine Flow Paths