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