FLUID MACHINES

FLUID MACHINES

There are various fluid machines in which the fluid flows and energy conversion takes place. The machines may convert hydraulic energy to mechanical energy and vice versa, e.g. turbines, pumps, compressors, fans, hydraulic couplings and torque converters etc.

TURBINES: are prime movers in which change of momentum of a fluid is utilized to create rotation of a shaft. Rotary motion is obtained by centrifugal forces resulted by change in direction of motion of high velocity jet.

Classification of turbines:

1. On basis of process of energy conversion

a) Impulse turbine b) Reaction turbine

a) Impulse turbine: In Impulse turbine hydraulic energy available is first converted in kinetic energy by means of efficient nozzles. The high velocity jet from nozzle strikes a series of buckets fixed on rotor shaft. The buckets are designed to split the change of direction of motion of jet. It results the change in moment of momentum of rotor shaft and shaft rotates. Examples are pelton wheel, Girad turbine, Banki turbine, Jonval turbine etc.

b) Reaction turbine: In reaction turbines some part of the total available energy is converted into kinetic energy, and remaining part still in form of potential energy. As the water flows through the runner, the water under pressure goes on changing pressure energy to kinetic energy. Examples Francis, Kaplan, Propeller,Fourneyron turbines etc.

2. On basis of direction of flow of water in the runner:

a) Tangential flow turbine (Pelton Wheel)

b) Axial or parallel flow turbine (Kaplan Turbine)

c) Mixed-radial & axial turbine (Modern Francis Turbine)

d) Outward radial flow turbine (Fourneyron Turbine)

e) Inward radial flow turbine (Old Francis Turbine)

Construction details are to be discussed in BME Lab.

· Specific Speed of turbine:

· Specific Speed (Ns) N√P/H⁵⁄⁴

· Where N= Speed of actual turbine

P= Power in kw

H= Head in metres

Refer classification of pumps on this Blog