For thousands of years, people have known that when they boil water, theresulting stearn exerts pressure and moves objects. You might have seen picturesof machines such as the one in Figure 4.1. A Greek inventor named Hero ofAlexandria drew and described this machine. (Historians do not agree on Hero'sbirth date. Some say it was as early as 130 B.C.E. and others say as late as70 C.E.) Hero's "stearn engine" is little more than a toy, but it demonstrates thatpeople understood what steam pressure could do. This knowledge came fromobservation because no one understood the concepts of heat and thermal energy.People observed that when water boiled, the resulting steam created pressure.This pressure could be controlled and directed in a way that would producemechanical motion, as shown in Figure 4.1. A steam engine is any machinethat generates steam and converts the stearn pressure into mechanical motion.

~ The sealed kettle hadtwo pipes that carried steam to ahollow ball. The ball was mountedon the pipes in such a way that itwas free to spin. Steam escapedthrough jets on the ball, causingit to spin.

The First Practical Steam EngineIt was nearly 2000 years after Hero's rime before anyone built a practical steamengine. The need for a powerful engine became critical in England, in the1600s. Wood and charcoal were becoming scarce. More and more fuel wasneeded to heat homes and provide heat for industries such as iron smelting,glassmaking, and firing pottery and bricks. To provide more sources of fuel,industrialists built bigger and deeper coal mines. Water accumulated in the minesand had to be removed so the miners could work. Originally, miners used horsesto pull buckets of water up and out of the mines. At one mine, 500 horses wereneeded to keep the mine free of water. A much more efficient method ofremoving water was needed.

valve CHow Savery's Steam Engine WorkedThomas Savery, of England, built the first practical machine topump water from the mines. In 1698, he received the first patentfor a steam engine. The patent gave Savery the exclusive rightsto make and sell his invention. Savery's engine was quite simplebut effective. The steps in Figure 4.2 explain how the steam engineforced water out of a mine. The process was repeated over and over.

~ This simplified diagram of Savery's steam engine shows how itdischarges water from the mine. The smaller diagram at the top is an originalsketch of Savery's steam engine.

Step 1 Fire boils the water in boiler B producing steam.

Step 2 Open valves C and V2 and close valve V1. Steam fills vessel D.

Step 3 Close valves C and V2 and open valve V1. Steam in 0 condenses andcreates a partial vacuum. Atmospheric pressure above water in the mine isnow greater than pressure in vessel D. Atmospheric pressure pushes waterup into vessel D.

Step 4 Close valve V1 and open valves C and V2. Steam from B pushes waterout of 0 to E and up past F and G. Water is expelled from G.

142 MHR . Unit 2 Energy Flow in Technological Systems

(g) rockingbeam (f) cold water

(d) piston

(a) cylinder

(e) cold watervalve

(c) steamvalve

pump rod-

smaller coldwater pump

(h) mine

pump.(b) boiler

~ Newcomen's steamengine relied on atmosphericpressure to push the piston (d)down and to push water fromthe mine up the pipe and outof the mine.

~

Savery's engine was very inefficient and costlyto operate. Thus, inventors continued to search forbetter engines. In 1712, Thomas Newcomen inventeda much-improved steam engine, called the atmosphericengine. If you study the diagram of N ewcomen's enginein Figure 4.3, you will see that atmospheric pressurealso played an important role in the design of thisengine. The following steps describe one cycle ofNewcomen's engine.

. With steam valve (c) open and cold water valve (e)

closed, steam from the boiler (b) enters the cylinder (a).The steam pressure pushes the piston (d) up.

. The upward motion of the piston (d) moves the

rocking beam (g), causing the piston in the mine pump(h) to go down. Valves (not shown) allow the pistonin the mine pump (h) to go down without pushingany water down. ~

. The upward motion of the piston (d) closes the steam

valve (c) and opens the cold water valve (e). A spray ofwater causes the steam in the cylinder (a) to condense,creating a partial vacuum in the cylinder (a).

. The atmospheric pressure above the piston (d) is now greater than the

pressure inside the cylinder (a) and the atmospheric pressure pushes thepiston back down.

. The downward motion of the piston (d) moves the rocking beam (g), causing

the piston in the mine pump (h) to go up. As the pump rises, it creates a partialvacuum in the pipe. Atmospheric pressure pushes the water in the mine up thepipe. Valves cause water already in the pipe to be expelled from the mine.

. The downward motion of the piston (d) closes the cold water valve (e) and

opens the steam valve (c). The cycle begins again.

Newcomen's pump relied on atmospheric pressure to push the piston downbut all pumps rely on atmospheric pressure to push the water up from a mine.People often incorrectly say that a vacuum "pulls" water up. However, the lowpressure caused by a partial vacuum cannot pull. Pressure only pushes. You candetermine the direction that pressure will push on water in a pipe by comparingthe pressure on the water inside the pipe with that outside the pipe. The pressurethat is highest will push on the water. To better understand the way that apressure difference can move water up a pipe, carry out the following activity.

Chapter 4 Thennal Energy and Work. MHR 143

4. When the water has nearly boiled away,invert the test tube and put the top of thetest tube in the water in the beaker.

Safety Precautions

onlmlmJ. Do not touch hot surfaces with your skin.

. Take care not to burn yourself with the steam.

. Tie back long hair to keep it out of the flame.

. Do NOT use an ordinary glass test tube

because it will break.

5. Watch the test tube and the water whilethe test tube cools.

What Did You Find Out?

1. What happened to the water as the testtube cooled?

2. What was the origin of the force that causedthe water to move?

Procedure - r~[:J!iii:l; ill'! i[ ~lll~ i~::J:~:I:.i~'-l~]

3. What stage of action of the Savery engine didthis activity simulate?2. Put approximately 0.5-1.0 mL of water in the

test tube.4. What stage of the action of the Newcomen

engine did this activity simulate?3. While holding the test tube with a test tubeholder, place the test tube in the flame untilthe water boils.

Although Newcomen's atmospheric engine was a dramatic ,mprovementover Savery's engine, it still had some fundamental flaws. With every cycle ofmotion, the piston and the cylinder were heated with steam and then cooledwith a spray of water. This constant heating and cooling caused rapid wear onthe engine's parts. As well, it took time for the cylinder to heat and cool withevery cycle, which slowed the process. Therefore, inventors continued to lookfor ways to improve the Newcomen engine.

Pause&Re lect

Outline the technological problem-solving strategy that led to theNewcomen engine. Identify thechallenge, design requirements,and construction. Evaluate thetechnology in your own words.

Watt's Improvement of the Steam EngineIn 1757 ,James Watt (1736-1819) went to work as an instrument maker for theUniversity of Glasgow, in Scotland. Several years lateF, as part of his job, Wattwas asked to repair a Newcomen steam engine. While working on the engine,Watt became aware of its limitations. He began thinking about ways to designa more efficient engine. Mter much designing and testing, Watt developed anengine that became the model for all steam engines for many years to come.In 1796, Watt received a patent for his modifications of the steam engine. Asimplified diagram of the essential parts of Watt's engine is shown in Figure 4.4.

Follow the arrows in the diagrams to see how steam pushed the piston intwo directions. In Figure 4.4A, you can see that the steam (red arrows) movedthrough a valve that directed the steam to the left side of the piston. As the steampushed the piston to the right, the exhaust steam from the previous cycle (bluearrows) was pushed out through a valve that directed it out of the cylinder. Whenthe piston reached the right side of the cylinder, as shown in Figure 4.4B, thevalve rod slid to the left. The valve's movement changed the direction of thesteam's flow. Then the steam from the boiler (red arrows) flowed through the

?The design for Watt's crankshaft isstill the most common mechanicaltransfer mechanism in use today- it is used in cars, trucks, and

other machinery. All internal.combustion engines convert heatinto rotary motion to drive wheels.

144 MHR . fnit 2 Energy Flow in Technological Systems

1. Fill the 250 mL beaker with cold tap water.Set it beside the burner.

Watt's design for the steam engine is sometimes called the "double-acting"engine because steam pressure pushed the piston in both directions.

This textile factory was powered by oneof Watt's steam engines. Imagine the deafening noisecaused by all of the belts and turning wheels.

valve to the right side of the cylinder. The steam pressure pushedthe piston to the left. It also pushed exhaust steam (blue arrows)through the valve and out of the cylinder. When the steam flowedout of the exhaust tube, it went to a chamber (not shown in thediagram). Here, it was condensed by a spray of water. The pistonand the cylinder remained hot at all times, thus avoiding thedamage caused by constant heating and cooling. In addition, the .

steam pressure produced was higher than atmospheric pressure.At first, the piston in Watt's engine was attached to a rocking

beam much like the one in the Newcomen engine. This designis effective for pumping water from wells. Watt realized, however,that the steam engine could provide power for many other uses. -He not only continued to improve his engine but also designedsystems of gears and levers so that the piston could turn a wheel.This design made it possible for the steam engine to providepower for many of the machines used in small industries. For example, in textilefactories (like the one shown in Figure 4.5), a steam engine turned a wheel thathad a long belt wrapped around it. The belt was attached to another wheel nearthe ceiling of the factory. A long shaft connected the wheel near the ceiling tomany more wheels above many machines in the factory. A belt would run downfrom the wheel above the machine and power the machine.

Steam Engines and the Industrial RevolutionWatt's steam engine was soon adapted to drive many types of machinery thatwere previously powered by other means. Two such means were horses andflowing water. For example, flowing water powers the mill shown in Figure 4.6.The late 1700s marked the beginning of a tremendous change in Westernsociety called the Industrial Revolution. People were moving from farms tocities to work in the new flour mills, sawmills, and textile industries. Morethan any other single invention, Watt's steam engine was responsible for therapid development of the Industrial Revolution, first in England and then inNorth America and Europe.

! Imagine turning thiswater wheel by hand to cause amillstone to grind flour. This is an"undershot" water wheel - the

water flows under it.

Chapter 4 Thennal Energy and Work. MHR 145

~ The steam cylinder is located in the box, just above the two smallwheels on the front of the locomotive. The cylinder and its partner on theopposite side provide more than enough thrust to turn the wheels. The bulkof the engine is the boiler, which produces the steam used in the cylinders.

~ Farmers no longer useTo feed the growing populations in the cities during the illdustrial Revolution,

fanners needed to produce more food. The steam engine became an importantnew tool for fanners. %th a steam-powered tractor such as the one shown inFigure 4.7, fanners could cultivate much more land than they could with horses.

ill order for steam engines to power larger machines, they had to producehigher steam pressures. These higher pressures required the development ofstronger boilers and cylinders and better seals around the piston rods. By theearly 1800s, high-pressure steam engines were powering huge locomotives likethe one in Figure 4.8. ill 1836, the first railway was built in Canada betweenMontreal and the Richelieu River. By 1864, railway tracks spanned the country.Steam locomotives opened up the western Prairies.

Tractors and trains were not the only vehicles powered by steam engines.In the early 1800s, paddle-wheel steamboats, similar to the one shown inFigure 4.9, travelled the major rivers of North America. Steamboats carriedpeople, supplies, lumber, furs, and sometimes even entertainment. The pistonson the steam engines turned large paddle wheels mounted on the sides or atthe back of the boats. Paddle-wheel steamers were a common sight on the FraserRiver in British Columbia. The Hudson's Bay Company used steamboats alongthe North and South Saskatchewan rivers to carry supplies to fur trappers. Thesteamboats also carried the furs back to markets in Eastern Canada. .

, DidYouKnow?,

Steam TurbinesToday, steam engines no longer power locomotives or tractors. Most paddle-wheel steamers are merely tourist attractions. However, a type of steam enginecalled a steam-turbine engine still powers giant ocean liners and cruise ships.Several inventors had attempted to design a steam-turbine engine. Finally,British engineer Charles Parsons (1854-1936) perfected the steam-turbineengine in 1884.

146 MHR . Unit 2 Energy Flow in Technological Systems

steam-driven tractors. What designcriteria would favour a tractor withan internal combustion engine,such as those used today?

There were many steam cars inproduction by the beginning of the1900s. The "Stanley Steamer" wasthe best known. Brooks also madesteam cars between 1923 and 1927.It was the best-selling (after theStanley) steam car in Canada andwas assembled in Stratford, Ontario.

Steam-turbine engines do not use pistons. Instead, steampasses through a set of curved blades similar to fan blades (seeFigure 4.10). Some of the blades are stationary. They direct thesteam toward blades attached to a central axle that turns. Steamturbine engines are somewhat cone-shaped. This shape allowsthe steam pressure to decrease gradually. As the pressure decreases,a larger set of stationary blades directs the steam to a larger wheelwith more blades. These blades add to the forces that turn theaxle. By the time the steam leaves the turbine, the temperatureand the pressure of the steam have dropped greatly. In theinvestigation on the next page, you can experiment withsteam engines of your own design.

~ Paddle-wheel steamboats were usuallywide and shallow so they could navigate rivers. Thesteam engines had to provide enough power so thatthe boats could travel upriver against the cJjrrent.

rotation

tr- ~~:m

~ In this turbine, steam hits the first set of stationary blades. The steamis then deflected by the first set of stationary blades to the next set of rotating blades.Only two sets of blades are shown here. Large turbines have many sets of blades.This action continues to the last set of rotating blades. Although the steam losespressure as it passes through each set of blades, steam at its original pressureand temperature continues to enter the turbine. Thus, the rotation of the axle iscontinuous. Modern turbines may have as many as 20 sets of rotating andstationary blades attached to a single shaft.

Technology Paves the Way for ScienceWhile Savery, Newcomen, and Watt were designing, building, and marketingsteam engines, scientists still did not understand the nature of heat. Inventorsbased their work entirely on what they observed, not on scientific theories orlaws. They knew that when wood or coal was burned, the fire was hot enoughto boil water. They also knew that when water boiled into steam, the volumeof the steam was much greater than the volume of the liquid water. If the steamwas contained in a boiler and not allowed to increase in volume, the steamcreated very high pressures. Inventors used this pressure to propel pistons andto turn turbines. However, they did not know the scientific principles relatedto heat. As the Industrial Revolution - based on the steam engine - took

place throughout England, Europe, and North America, scientists becamemore and more curious about the basic nature of heat.

Chapter 4 Thermal Energy and Work. MHR 147

You have been reading about step-by-step improvements in steam engines.Now apply what you have learned to design and test a steam-powered hoistto lift an object. How large a mass can your steam turbine lift?

ChallengeDesign a steam-powered turbine that will lift a 50 g mass a distance of 10 Cffi.

Design SpecificationsA. The turbine must be able to lift a mass

a distance of at least 10 cm.

MaterialsThe materials required for this project are thosedetermined by your design and must be readily available.For example, the bottom of an aluminium pie plate mightprovide the turbine blades for your hoist. A flask fittedwith a rubber stopper could be used as your steamboiler (see diagram of steam generator assembly).

B. The most effective design will lift the massin the shortest period of time.

Plan and Construct -0 Your group should provide a design that enables

you to lift a mass in the shortest possible time.Start testing your hoist with a 50 g mass. Testsmaller and smaller masses until you find onethat your hoist can lift. This will depend on theshape and angle of your turbine blades. It willalso depend on the position of the nozzle thatpropels the steam onto the blades. CAUTION:Be careful when cutting and bending the edgesof the turbine blades. The metal can be sham.

test-tube clampmounted on

\iron stand

rubber stopper\

rubber hose

rubber tube

rubber stopper

ring stand

mounted on

an iron stand

/

~turJne

Iblades

steamnozzle

gauze screenTo create the most effective hoist, friction mustbe reduced. Take special note of the methodby which the axle of the turbine is mounted.Note also the method by which the energyis transferred to the string that lifts the mass.

Bunsen burner(or hot plate)

. The nozzle from the boiler can effectivelyincrease the speed at which the steam isprojected onto the turbine blades. CAUTION:The steam boiler and nozzle will be very hot.Use protective clothing and eye protection.

Safety Precautions

-~~--. Take care when handling boiling water, steam,

and open flames. Avoid contact with your skin,

148 MHR . Unit 2 Energy Flow in Technological Systems

Section 4. 1 SummaryIn this section, you learned about the development of the steam engine. Peopleused steam to power toys over 2000 years ago but no one invented a practicalsteam engine until the 1600s. Thomas Savery invented the first useful steamengine to draw water from coal mines.SoQ~, Newcomen developed a morepractical steam engine. The improvements that James Watt made in the steamengine were essential for the rapid development of the Industrial Revolutionin Europe and North America. Watt's engine became the standard for manyyears. Very few steam-powered piston engines are still in use but steamturbines still power large ocean liners.

Check Your Understanding

1. How is sucking on a straw to drink pop or water similar to the way thatSavery's steam engine pumped water from a mine? "\iVhat really causesthe liquid to move up the straw?

2. What exerted pressure on the piston in Newcomen's steam engine,causing it to move?

3. State two ways in which Watt's steam engine was an improvement overNewcomen's steam engine.

4. How do steam-turbine engines differ from piston engines?

5. Apply Explain how Watt's steam engine influenced the IndustrialRevolution.

6. Thinking Critically In 130 B.C.E., people knew how to operate toysteam engines. Why do you think it took 2000 years before anyonemade a useful and practical steam engine?

Chapter 4 Thermal Energy and Work. MHR 149