Steam Engine

SYSTEM

• Objective: Objective: Describe the basic cycle and Describe the basic cycle and design features of a modern Steam design features of a modern Steam propulsion system propulsion system

Specific Objectives:Specific Objectives: • Define the theory of steam turbine propulsionDefine the theory of steam turbine propulsion

• Sketch and describe a steam propulsion plant Sketch and describe a steam propulsion plant layout arrangementlayout arrangement

• Describe functions of major componentsDescribe functions of major components• Describe the type and arrangement of steam Describe the type and arrangement of steam

turbine engineturbine engine• Sketch and identify the steam turbine engine Sketch and identify the steam turbine engine

partsparts

Major Components Boiler Turbine Condenser Extraction Pump Feed Pump Economiser Superheaters

Steam propulsion plant layout arrangement

Condenser

Condensate pump

Deaerator

Main feed pump

Heater stages

Economizer

Boiler Superheater

Saturated steam

Superheated steam

HP turbine

LP turbineAstern turbine

Gearing & propeller shaft

Ranking Cycle

T

2’

3’4

s

3

2

1

6 5

1-2 –> Water heated in boiler 2`-2->wet steam heated in

superheated boiler 2-3->HP dry steam expand in

turbine to obtain much work 3-4->LP steam coming out of

turbine is condensed into water in condenser

4-1-> water from the condenser heated return back to boiler drum- this complete the cycle

Components function Boiler

To produce steam from water Superheater

To dry the wet steam produced in the boiler Turbine

Converts heat energy of steam into mechanical work

Condenser To condense exhaust steam from turbine for

re-use in boiler

Components function

Feed Pump To transfer high pressure feed water

De-aerator & economizer To raise the temperature of feed water before

entry into the boiler drum so that less heat will be required to transform water into steam

Boilers Main propulsion boilers are water tube types

C Steam rate of main boilers is 40-60 bar,

5000C and 60-90 tons/hr Auxiliary steam boilers are Fire tube boilers

of low steaming capacity

ESD I Boiler

•Super Htr located in low temp region exhaust gas path

•Both Primary and Secondary have contra flow heating

•Metal temp of secondary high

•Air attemperator less efficient

•Burner front fired

•Flame impingement reduced not eliminated

•Response to sudden load is slow

STEAM TURBINE

ENGINE

INTRODUCTION The Steam turbine is a device for obtaining

mechanical work from the energy stored in steam.

Steam enters the turbine with high energy content and leaves after giving up most of it.

The high pressure steam from the boiler is expanded in nozzles to create a high velocity jet of steam.

In any type of steam engine, it is the VELOCITY of the liberated steam, and NOT the pressure, which produces the force which causes rotation of the shaft.

The nozzle acts to convert heat energy in the steam into kinetic energy.

Commencing with a high pressure, a high velocity can be produced, and it is the kinetic energy which provides the motive force of the turbine engine.

The amount of energy or force available from steam is directly proportional to the amount of heat available from the steam.

Heat available is proportional to the mass flow of steam times change in velocity…….

Mass flow (kg/s) X Velocity (m/s) = Force (kgm/s2) 

This is the operating principle of all steam turbines, although the arrangements may be vary considerably.

The heat is available only when the steam remains in gaseous state

If condensation takes place during passage through the turbine, then the part which changes state to water will not be capable of producing further motive power. So the steam should therefore enter DRY and theoretically remain dry until it is exhausted.

When dry saturated steam passes through the normal working cycle of a turbine, condensation will take place throughout many stages, but if SUPERHEATED steam is used this condensation is reduced considerably.

Types of Turbines

Impulse Turbine

Reaction turbine

IMPULSE TURBINE The impulse arrangement is made up of a ring of

nozzles followed by a ring of blades. In the pure impulse turbine the high energy steam

is expanded only through fixed nozzles, with a decrease in pressure and an increase in velocity.

Energy in the steam is converted to kinetic energy when the jet of steam impinges/ directed onto the moving blades and leaves in a different direction.

The changing direction and therefore velocity produces an impulsive force which mainly acts in the direction of rotation of the moving turbine blades causing rotation and mechanical work.

The passage between the blades is of parallel section, no expansion or change of pressure takes place between the inlet and outlet sides of the blading.

Impulse Turbine Blades

•Flow area between two blades is constant

•No pressure drop when steam flows over blade

•Flow velocity constant

Two stage impulse turbine with diaphragm blades to change direction of steam flow to enter next stage of turbine

Impulse turbines were classified as below:

Single Stage Velocity compounded Pressure compounded Pressure-velocity compounded Velocity-pressure compounded