Introduction

IUBAT- International University of Business Agriculture and Technology Founded 1991 by Md. Alimullah Miyan

COLLEGE OF ENGINEERING AND TECHNOLOGY(CEAT)

Course Title: TurbomachineryCourse Code : MEC 437

Course Instructor: Engr. Md. Irteza Hossain

1The Power God : Steam Power

~1760 : James Watt~1820 : Sadi CarnotGeorge Brayton & W Rankine ~ 1860Power Gods : Gas Power

George Brayton

Nicolaus A. Otto

Rudolf DieselPower Gods : Hydro Power

Lester Allan Pelton

James B. Francis

Viktor KaplanDefinition of a Turbomachine

The word turbo is a Latin origin and implies that which spins or whirls aroundA turbomachine is a device in which energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rowsA rotating blade row, a rotor or an impeller changes the stagnation enthalpy of the fluid moving through it by either +ve or ve work. The changes in enthalpy are linked with pressure changes.A pump: work is done on fluid A turbine: work is done by fluidThe definition precludes consideration of positive displacement machines such as piston pumps and piston steam engines. Introduction and Classification of Fluid MachinesMachines for Doing Work on a Fluid

7Introduction and Classification of Fluid MachinesMachines for Doing Work on a Fluid

8Introduction and Classification of Fluid MachinesMachines for Extracting Work (Power) from a Fluid

9Classification of TurbomachinesMajor subdivisions

A. Power classifications (power is added or extracted from the fluid)

Pumps are power addition machines and include liquid pumps, fans, blowers and compressors.Fluids are water, fuels, air, steam, refrigerants.

Turbines are power extraction devices and include windmills, water wheels, hydroelectric turbines, automotive engine turbochargers, gas turbines.Fluids; gases, liquids, mixtures.Applications to Fluid SystemsMachines for Doing Work on a FluidFans, Blowers, and Compressors

11Classification of TurbomachinesB. The manner in which the fluid moves through and around a machine

Open flowNo casing or enclosure for the rotating devicesExamples: propeller is an open flow pumping device.Windmill is an open flow turbine

Enclosed or encased flow devices

Classification of TurbomachinesC. Flow-path or through-flow

Axial through-flow machines. The flow moves on streamlines parallel to the axis.

Predominantly radial flow.

Mixed flow machines.Classification of Turbomachines

Classification of TurbomachinesD. Compressibility of the fluidIncompressibleThe density is constant through the entire flow process; liquid pumps.

Compressible; Gas flows: compressors.

E. Impulse or reaction machinesImpulse: pressure changes are absent in the flow through the rotor. In an impulse machine, all the pressure change take place in nozzlesEx. Pelton wheel

Reaction: pressure changes in rotor are absent

Classification of TurbomachinesPelton wheel

IMPACTS OF JETSWater jet experiences some force as it hit a fixed plate This force is equal to the rate of change of momentum of the Jet Newton Second law of motion: The rate of change of momentum is directly proportional to the impressed force and it takes place in the same direction in which the force acts

TRASH RACK

Uses the velocity of the water to move the runner and discharges to atmospheric pressureThe water stream hits each bucket on the runner No suction downside, water flows out through turbine housing after hittingHigh head, low flow applications. Types : Pelton wheel, Cross Flow Impulse Turbine

Runner of a Pelton TurbineSPLITTERBUCKETS OR VANESRUNNERCombined action of pressure and velocity of moving water Runner placed directly in the water stream flowing over the blades rather than striking each individually

lower head and higher flows than compared with the impulse turbines. Reaction Turbine

It is a reaction turbine developed by an English born American Engineer, Sir J.B. Francis.

The water enters the turbine through the outer periphery of the runner in the radial direction and leaves the runner in the axial direction, and hence it is called mixed flow turbine.

It is a reaction turbine and therefore only a part of the available head is converted into the velocity head before water enters the runner.

The pressure head goes on decreasing as the water flows over the runner blades. Francis Turbine

The static pressure at the runner exit may be less than the atmospheric pressure and as such, water fills all the passages of the runner blades.

The change in pressure while water is gliding over the blades is called reaction pressure and is partly responsible for the rotation of the runner.

A Francis turbine is suitable for medium heads (45 to 400 m) and requires a relatively large quantity of water.Francis Turbine

The Francis TurbineIMPACTS OF JETSWater jet experiences some force as it hit a fixed plate This force is equal to the rate of change of momentum of the Jet Newton Second law of motion: The rate of change of momentum is directly proportional to the impressed force and it takes place in the same direction in which the force acts FORCE EXERTED BY FLUID JET ON A STATIONARY FLAT PLATE