What Is Turbo-Machine ? Classification Of Turbo-Machine & Difference Between Positive Displacement Machine & Turbo-Machine - SKengineers

 

TURBO – MACHINE

·        It is a device in which the energy transfer occurs between the fluid and a rotating element in a steady flow process due to dynamic action and results into change in pressure and momentum of the fluid.

 

FEATURES:-

1.      ROTOR/RUNNER –

Ø  Rotor is used for axial flow gas turbines runner is used for radial flow hydraulic turbines.

2.      STATIONARY ELEMENT OR GUIDE VANES OR NOZZLES –

Ø  These are used for controlling the flow direction of fluid for energy conversion process without any pressure changes except in case of nozzles stationary element is not a necessary component of every turbo-machine. E.g. in case of ceiling fan which is used to circulate air in a room.

3.      SHAFT –

Ø  Shaft is a rotating member however in power transmitting machines we have input and output shaft as in case of torque converter and fluid couplings.

4.      HOUSING OR CASING –

Ø  It is not a necessary component in certain types of turbomachine.

5.      DIFFUSER –

Ø  It is a passage of increasing cross-sectional area in the direction of fluid flow. Its function is to convert the kinetic energy in the pressure energy .

Ø  E.g. in case of centrifugal compressors.

6.      DRAFT TUBE –

Ø  It is similar in an action of diffuser. It is placed at the outlet of a hydraulic reaction turbine.

Ø  E.g. in case of francis and Kaplan turbine.

 

v  CLASSIFICATION OF TURBO-MACHINE –

Ø  According to direction of energy :-

a)      Fluid to rotor (for turbine)

b)     Rotor to fluid (for pump)

Ø  According to type of energy :-

a)      Hydraulic (fluid water)

b)     Thermal (gas used)

Ø  According to dynamic action :-

a)      Impulse turbine (pelton turbine)

b)     Reaction turbine (francis turbine)

Ø  According to direction of flow :-

a)      Tangential (pelton turbine)

b)     Radial (centrifugal turbine)

c)      Axial (Kaplan turbine)

d)     Mixed (francis turbine)

 

COMPARISON BETWEEN POSITIVE DISPLACEMENT MACHINE & TURBO-MACHINE

Sr. No.	POSITIVE DISPLACEMENT MACHINE	TURBO-MACHINE
1.	Fluid is subjected to a change in volume resulting into change in pressure.	Fluid is subjected to a pressure and momentum changes resulting into energy transfer.
2.	Fluid action is nearly static.	Fluid action is dynamic.
3.	It has pure reciprocating motion of mechanical elements.	It has pure rotary motion of mechanical elements.
4.	It has unsteady flow of fluid.	It has steady flow of fluid.
5.	It has high energy conversion efficiency due to static energy transfer.	It has low efficiency due to dynamic energy transfer.
6.	Volumetric efficiency is low.	Volumetric efficiency is 100%.
7.	Fluid handling capacity is low.	Fluid handling capacity is large.