Steam Engine - System

7/23/2019 Steam Engine - System

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Steam Engine

SYSTEM



General Learning Objective: Describe thebasic cycle and design features of amodern Steam propulsion system

Specific Learning Objectives:

• Define the theory of steam turbine

propulsion• Sketch and describe a steam propulsion

plant, parts and layout arrangement• Describe functions of major components• Describe the type and arrangement of

steam turbine engine



Major Components (Pleaser efer

to page 61(ME) Boiler

Turbine

Condenser Extraction Pump

Feed Pump

Economiser Superheaters



Steam propulsion plant layout arrangement

Condenser

Condensate pump

Deaerator

Main feed pump

Heater stages

Economizer

BoilerSuperheater

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 is heated in boiler

2`-2->wet steam heated in superheated boiler

2-3->HP dry steam expand in turbine to obtainmuch 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 forre-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



Steam Plant Auxiliary System

However, these system require auxiliary system. i.e

the turbine require LO System

The condenser require cooling circulating system which use

pumping system

The condensate or feed pump require power source

The boiler require fuel oil pump and forced draft fans

The pumps and the blower can be motor driven with electric

power supply from generator driven off the shaft of turbine The turbine driven generator can also have its own auxiliary



Other Auxiliaries

Additional equipment like air ejector is also

required to remove the air and non

condensate vapors that leaks into the part

of the system – this to prevent creation of

partial pressure that impair the condenservacuum

The turbine also require sealing and gland

leadoff steam The system also require storage (surge

tank) for unneeded working fluid



Power Equation

E

Q p Heat Power

vf

778

144)(

The power input is the heat equivalent of feed pump work

Where Pvf is the total pump head in feet water Q is the quantity of heat pumped per hour

E- Mechanical efficiency

The weight of fuel require = Net heat added/ fuel heating x boiler efficiency

Net heat added = Total heat – heat entering the boiler/

Heat rate = net heat added / horsepower produced



Boilers Main propulsion boilers are water tube types

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 andSecondary have

contra flow

heating

•

Metal temp ofsecondary high

•Air attemperator

less efficient

•Burner frontfired

•Flame

impingement

reduced not

eliminated

•Response to

sudden load is

slow



Water Tube Boiler

http://en.wikipedia.org/wiki/File:Water_tube_boiler_schematic.png



Typical Fire Tube Boiler



Fire tube and Waterside Boiler

B il S l ti id ti

http://en.wikipedia.org/wiki/File:Steam_Boiler_3_english.png



Boiler Selection consideration To design boiler to produce required quantity of steam at

required temperature and pressure the following design

consideration are necessary: Efficient operation when burning various fuel

Fit easily and conveniently in engine room space and be

accessible for operation , inspection and maintenance

Rugged enough to with stand adverse sea condition Redundant control and automation system

Reliability of thermal and structural design

Compliance to regulation

Cycle requirement

Heat balance

Fuel and firing method

Boiler for marine vehicles- space, weight , and regulation



Fuel combustion systemBoiler Design

- fuel analysis, combustion air, efficiency

Furnace – exit gas temperature, radiant heat absorbing surface,heat absorption rate, tube metal temperature

Boiler tube bank- from type boiler, header type, boiler delivery

superheating steam

Superheater-Types and characteristics,, arrangement of steampasses, tube temperature material and attachment of headers,

supports, location of headers, slagging ad high temperature

corrosion, reheater

Air heater and economizer- air heater, economizer Desuperheater and atemperature

Circulation and steam baffle-circulation, heated down comers,

steam drum baffle

Burner



Boiler Design Consideration Page 94) Combustion

Heat absorption rate

Circulation

Pressure drop

Duty cycle

Design limitation-Construction and physical requirement: according to Lloyd,

ABS…etc- Drums, headers, casing

-Boiler mounting:stop valve, fed check valves, feed water

regulator, safety valve, sentinel valve, high and low water levelalarm,

Pressure guage, vent and drain valve, lowdown valves, water

level indicator, water sampling connections, soot blowers

burner flame scanner and ignitors, instrumentation and control

o er pera on an



o er pera on anMaintainaceConsideration (Page129)

Water treatment Feed water

Boiler water

Initial preparation Normal operation

Boiler cleaning

Boiler storage



STEAM

TURBINE

INTRODUCTION



INTRODUCTION

The Steam turbine is a device for obtainingmechanical work from the energy stored in steam.

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

The high pressure steam from the boiler isexpanded 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, whichproduces 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 massflow of steam times change in velocity…….



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

Velocity (m/s)

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 ofproducing 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 ifSUPERHEATED 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 ofnozzles 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 invelocity.

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 ofparallel section, no expansion or change of

pressure takes place between the inlet and

outlet sides of the blade.

http://en.wikipedia.org/wiki/File:Turbines_impulse_v_reaction.png






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



Reactive turbine

They are turbines develop torque by reacting

to the gas or fluid's pressure or mass.

http://en.wikipedia.org/wiki/Torque


http://en.wikipedia.org/wiki/Torque



Efficiency calculation

Efficiency of turbine bade = work in blade /

energy in steam

E

Q p Heat Power vf

778

144)(



Summary

• Steam propulsion plant, parts and layout

•

Major components• arrangement of steam turbine propulsion

Steam Engine - System

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