lect 6 steam engine

7/28/2019 Lect 6 Steam Engine

1/23

Steam Engine

Converting heat to work or steam to

mechanical action.


2/23

Steam Engine and the Industrial

Revolution

A singular development that accelerated the

Industrial Revolution and the transition from

water-wood-muscle (animal and human)

power to steam power; from cottage

industries to manufacturing; from agrarian to

industrial.


3/23

Extraordinary Growth and Mobility of

Industries

The steam engine was used in numerous

settings from the 18th c: mining, textiles,

pumping, milling, grinding, weaving,

transportation (steam boats, trains), ...

With the use of the steam engine, industries

were no longer bound to locations with water

power.


4/23

Steam Engine

Heat engine that converts heat to work.

Required components:

Fuel as source of heat (e.g. wood, coal, gas, solar,

nuclear)

Working fluid (e.g. water)

Closed cycle including compressor and expansion

unit

Mechanical part to do work (e.g. turbine)


5/23

History

First century AD (wood fuel boiled water;

steam was directed out of jets or nozzles

mounted on a rotating axis. The steam exiting

the jets caused the axel to spin. (aeolipile).

16th and 17th c. experiments on steam engines

focused on studying properties of steam.


6/23

Thermodynamic Cycle

In the study of converting heat (thermo) into

mechanical (dynamic) action or work, many

cycles have been proposed to describe the

relationship between the heat you provide

and the work you get out.

The goal is to maximize the efficiency of the

cycle, i.e. To increase the ratio [workout/heat in].


7/23

Thermodynamic Cycle Relating Heat

in, heat out, Work done

1. Expand gas at constant ThP and V.

I.e., heat, qh or heat in is required.

2. Expand gas with q2 = 0T, P and V.

3. Compress gas at const TcP and V. I.e.,

heat, qc or heat out is required.

4. Compress gas with q4 = 0

T, P and Vto get back to initial state (note cycle).

5. Repeat to extract work by providing qh.


8/23

Analysis of Cycle

During this closed cycle, work is done by the

fluid.

In step 1, we have to provide heat to expand

gas.

In step 3, heat exits the system during the gas

compression.

But q1 q2.


9/23

Efficiency of the Cycle or the 2nd Law

of Thermodynamics

The 2nd Law says that you cannot get

something for nothing. I.e. Efficiency < 100%.

The efficiency depends on the working fluid

(lets choose a gas), the temperature of the

expansion cycle = Th and the compression

cycle = Tc.

Actual efficiencies = @ 40%.


10/23

Thomas Savery (1650-1715)

Military engineer from Devonshire.

1698, Savery patented the first practical steam

engine: "A new invention for raiseing of water

and occasioning motion to all sorts of mill work

by the impellent force of fire, which will be of

great use and advantage for drayning mines,

serveing townes with water, and for the workingof all sorts of mills where they have not the

benefitt of water nor constant windes."


11/23

avery ng nehttp://inventors.about.com/library/invento

rs/blsavery1.htm
http://inventors.about.com/library/inventors/blsavery1.htmhttp://inventors.about.com/library/inventors/blsavery1.htmhttp://inventors.about.com/library/inventors/blsavery1.htmhttp://inventors.about.com/library/inventors/blsavery1.htm


12/23

How did the Savery Engine Work?

Note that there are no moving parts.

Various valves to be opened and closed in

coordination with heating liquid to steam and

condensing steam to liquid.

Water was pumped out of mines due to the

vacuum created when vapor liquid.

1 hp capacity, but prone to explosions.


13/23

Thomas Newcomen

(1663-1729)

Blacksmith from Dartmouth.

1712, Newcomen developed the firstcommercially successful steam engine

Called the atmospheric engine

Based on cylinder and piston arrangement

Used to pump water out of mines and drivingwater wheels. Mine depth increased allowing tonew coal reserves.

5 hp


14/23

Newcomens Steam Engine (Wikipedia)


15/23

How did the Newcomen Engine Work?

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

m_engine

See also locomotive steam engine

http://www.howstuffworks.com/steam1.htm
http://en.wikipedia.org/wiki/Newcomen_steam_enginehttp://en.wikipedia.org/wiki/Newcomen_steam_enginehttp://www.howstuffworks.com/steam1.htmhttp://www.howstuffworks.com/steam1.htmhttp://en.wikipedia.org/wiki/Newcomen_steam_enginehttp://en.wikipedia.org/wiki/Newcomen_steam_engine


16/23

James Watt (1736-1819)

Scottish inventor and mechanical engr.

1758, Watt opened workshop at U. of Glasgow

and eventually started working on steam

engines.

1769, Watt patented the addition of a

separate condenser to Newcomens engine

leading to a 75% fuel reduction because the

entire piston did not have to be cooled.
http://en.wikipedia.org/wiki/James_Watt


17/23

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

att
http://en.wikipedia.org/wiki/James_Watthttp://en.wikipedia.org/wiki/James_Watthttp://en.wikipedia.org/wiki/James_Watthttp://en.wikipedia.org/wiki/James_Watt


18/23

How did the Watt Engine Work?

Instead of cooling the entire cylinder after the

steam expanded, the valve between the boiler

and cylinder was closed and the valve

between the cylinder and second condenserwas opened.

There the steam was cooled and condensed

while the cylinder remained hot.


19/23

Enter Boulton

But Watt had no funds to build his new design

and no skilled machinists to build the parts.

Boulton changed all that and, through their

partnership (1775), made it possible for Watt

to finally and successfully build the new

design in 1776. (capital, skilled workers; Soho

House). Engines were rated at 5-10 hp.


20/23

25 Year Partnership

1775-1800

1781, Watt and Boulton patented a sun and

planet gear in order to create rotary motion

from vertical motion, thus adapting the steam

engine to power industrial machines grinding,milling, weaving.

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

_gear
http://en.wikipedia.org/wiki/Sun_and_planet_gearhttp://en.wikipedia.org/wiki/Sun_and_planet_gearhttp://en.wikipedia.org/wiki/Sun_and_planet_gearhttp://en.wikipedia.org/wiki/Sun_and_planet_gear


21/23

25 Years

The Boulton and Watt firm was enormously

successful. It was established in Birmingham

to manufacture steam engines. By 1800, 500

engines had been produced, and by 1824, thisnumber was 1100.

After Watt retired in 1800, the Watt-Boulton

businesses were transferred to their sons.


22/23

James Watt

Watt made many other improvements to the

steam engine throughout his life.

Watts engineering successes are credited

with driving the IR.

Unit of power = watt = 1/746 horsepower.

Tied for first with Thomas Edison for

technological contributions and impact.

Buried in St. Marys Church, Birmingham.


23/23

Running the Steam Engine in Reverse

Refrigeration

Air Conditioning

Heat Pumps Geothermal Pumps

...

lect 6 steam engine

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