| || || |
| || |
| || || |
From the 1924 book, A Popular History of American Invention.
HISTORIANS tell us that the average freeman of ancient Greece had five slaves or “helots.” They were the machines of Greece. Engineers have estimated that every American has thirty slaves working for him, thirty tireless slave-machines that never rebel at the hopelessness of their lot and that feel nothing of the wear and tear of their slavery.
Because the Greek slaves were only human, with human shortcomings, the best flour-mill in Athens, in the time of Pericles, produced but two barrels of flour a day. With slave-machines, a single Minneapolis mill of our time produces in a day 17,000 barrels of flour. There were no helots in the Europe emancipated by the French Revolution, but there was just as much hard backbreaking labor in the towns as ever there was in old Athens.
Before the slave-machines were invented a skilled English workman, during the early part of the last century, could make thirty needles a day. Now a girl, mistress of a slave-machine, produces 500,000 needles a day, and has little to do but watch the slave-machine cut, sharpen, and perforate the needles.
If this is the age of the slave-machine, the steam-engine has made it so. Before the invention of the steam-engine, Europe and America had few machines and few factories, certainly no factories of the kind that now belch smoke from a thousand cities.
Until the coming of the steam-engine it mattered little whether a country possessed coal deposits. Now nations bargain for coal and are even willing to fight for it. Coal means power, industry, and wealth; two hundred years ago, it meant simply fuel to be burned on the hearth.
Because of the steam-engine, Great Britain became the world-dominating commercial nation that she is to-day. Fuel is her life-blood. It is also the life-blood of the United States; for even our waterfalls, numerous as they are, could not supply us with the power we now require if they were all harnessed.
It is difficult to think of the world as it was before the steam-engine. There were no railways, no steamships, no great blast-furnaces where steel is made, no cheap clothes, no electric lights, no machines to till the soil and reap the enormous harvests.
Life was only outwardly different from what it was in the days of Julius Cesar. Greeks and Romans travelled either on wheels or on horseback or in sailing vessels; a method of locomotion which, well into the nineteenth century, had not greatly been improved upon by Englishmen, Frenchmen, or Americans.
The Greek and Roman farmer did his own spinning and weaving, forged his own tools, and with his own hands made everything he needed; so did the European and American farmer up to the introduction of the steam-engine.
| || || |
| || |
| || || |
Steam proved the great liberator of mankind. Before we learned how to use steam, human energy was exploited for thousands of years. The steam-engine enabled men to use the energy locked up in coal, thereby releasing from drudgery, bondage, and misery an army of workmen who, if politically better off than the Greek helots, toiled as long and as hard.
Eight hours is the accepted working-day now, but that working-day would be almost unthinkable without steam-driven, labor-saving machines. Brain is doing more work than brawn. Machines have lightened human labor and given men time to think.
When at last the steam-engine made it possible to use the energy in fuel, invention flourished as never before. Power was given to the world. At once a thousand opportunities of using power suggested themselves.
Then it was that the slave-machines were invented; machines that were nothing but steel fingers, hands, fists, and arms; machines hundreds of times stronger, faster, and surer than human hands and arms; machines that would strike a blow more powerful than a hammer wielded by a Hercules, dig up tons of earth at a single scoop, whisk material from place to place in the twinkling of an eye, and fashion wood and metal for a million purposes with never-failing, uncanny skill.
The steam-engine made the coal-owning countries industrially and even politically great, and made their people machine-inventors, machine-users.
It follows, almost as a matter of course, that because the United States is the largest coal-owning country, the steam-engine proved enormously important in its development; and, in truth, not until the steam-engine was introduced, not until American coal could be converted into energy in American factories, not until American inventors had steam at their command to operate the many machines that they had devised, did the United States take its place in the front rank of great industrial nations.
Not one of the remarkable men to whom we owe the steam-engine could have foreseen how their inventions would change the drift of civilization. They built castles in the air, as inventors do, but their castles were hovels compared with the magnificent structure reared on the foundation of their discoveries.
They thought only of meeting the needs of the moment. And, in the beginning, these needs were merely the pumping of water out of coal-mines.
| || || |
| || |
| || || |
ENGLAND’S NEED OF A PUMP TO KEEP MINES DRY
Long before Columbus discovered America, Englishmen mined coal. They dug with picks and shovels what coal they found at the surface, and when that was burned they dug deeper and deeper. Englishmen still speak of coal-mines as “pits”; the word comes down from a time when great holes had to be made to reach the coal.
When the holes could be dug no deeper, it became necessary to sink shafts—holes with more or less straight sides. Dig a hole or a shaft, and sooner or later a spring is struck and water bubbles up. The pump, a very old invention, had to be applied to draw up the water so that the miners could work.
Sometimes the pumps were driven by hand, but more often by horses. They were crude pumps, so crude that they drew up but little water, and that at great expense in money and in man or animal power. England’s forests had been hewn into for both wood and charcoal.
Even before Queen Elizabeth’s time it had become necessary to pass laws for the protection of timber. England’s plight was, therefore, desperate. Unable to obtain wood enough, confronted with the difficulty of mining coal for lack of adequate pumps, it seemed as if England could save herself only by importing from abroad the fuel that could not be obtained at home.
By the end of the seventeenth century mine after mine had to be abandoned because the water rose faster than the pumps could draw it up.
What England needed was a pump that would draw water as fast as it welled up. The first genius who saw the opportunity but who could not make the most of it, was an impractical schemer and dreamer. He was nimble-witted, restless, attractive Denis Papin, a French physicist, born about 1647, a man who had more ideas than he could possibly carry out in a life-time, and who rarely finished anything that he began.
He invented a method of cooking at temperatures higher than that of boiling water; the safety-valve; a dozen different air-pumps and devices for raising water; and he also wrote about the possibility of travelling in carriages driven by steam.
Not much is known about him. His was a roving spirit. When he tired of Paris he went to London, and when he wearied of London he betook himself to Italy or Germany.
| || || |
| || |
| || || |
PAPIN SHOWS HOW STEAM CAN CREATE A VACUUM
About 1670, when Papin was living as a young man in Paris, the great Dutch mathematician and mechanician, Christiaan Huygens, who lectured there at the time, made him his assistant. Huygens was experimenting with the air-pump, and clever, imaginative Papin was just the man he needed to help him.
These experiments of Huygens gave Papin the idea of pumping water in many ingenious but not very practical ways; for there is not much difference between an air-pump and a water-pump.
In those days the air-pump was discussed as eagerly as we now discuss radium or the latest invention. Scientists marvelled at the air-pump. For generations they had been taught that “nature abhors a vacuum,” and that for this reason water was sucked up as the piston was pulled out of a common syringe—the oldest and simplest form of water-pump.
The vacuum-pump taught them that the air we breathe has weight, that it presses on everything around us, ourselves included, because it has weight, and that when the piston of a syringe is pulled out water rushes up simply because the pressure of the heavy outer air forces it into the empty barrel of the syringe.
Scientists began to measure the air to ascertain its weight. Samuel Pepys in his diary states that Charles the Second once attended a meeting of the Royal Society and laughed uproariously at the silly members “for spending time only in weighing of air and doing nothing else since they sat.” This helps to explain why Charles was popularly called the “merry monarch.”
Perhaps he would not have laughed so heartily if he could have known that out of these early air-weighing experiments, conducted by earnest scientists in several countries, would come ways of giving men machines to do their hardest work, of curing their diseases, and of making life easier and happier.
Now Papin knew just how an air-pump worked—knew that the air pressed on everything around us and that its pressure served to explain why water is forced up into an ordinary hand-pump. It has never been possible to obtain a perfect vacuum; it was still less possible in Papin’s day.
Like his master Huygens and many others, Papin was always trying to obtain a better vacuum. In 1687, he turned up in London with a new, startling method, and showed the scientific men of the day a device in which steam produced the vacuum.
The apparatus was simple enough; merely an ordinary upright cylinder in which a piston could rise and fall. Papin placed a little water in the cylinder and heated it with an outside flame, just as he would a kettle. The water boiled away into steam, and the expanding steam forced the piston up and drove out the air through a hole in the piston.
Papin then took away the flame, closed the hole in the piston, and allowed the hot cylinder to cool off. Soon the steam condensed, which meant that it shrank back again into water. There was little or no air in the cylinder, only a little water at the bottom.
The outer air or atmosphere, by its sheer weight, pressed the unresisting piston down to the bottom of the cylinder.
| || || |
| || |
| || || |
|HOW PAPIN CREATED A VACUUM BY CONDENSING STEAM. Papin, in 1690, proposed a thin, open-topped cylinder fitted with a piston provided with a rod on which was a latch. Water in the cylinder was externally heated and steam generated to force the piston up where it was retained by the latch. When the fire was removed the steam condensed so that the piston fell with such force as to enable it by an attached rope to lift a weight. Courtesy Deutsches Museum.|
Papin talked and wrote about the possibilities of thus creating a vacuum by mere steam, but did nothing more. Two hard-headed, practical Englishmen heard about his method of producing a vacuum, and it set them thinking of England’s flooded coal-mines and of a machine which would pump them dry.
One of these Englishmen was Thomas Savery, and the other, Thomas Newcomen; they became friends and partners in business. Their names were so identified with the invention and introduction of the first useful steam-engine that in the old books the one is rarely mentioned without the other.
HOW SAVERY APPLIED PAPIN’S PRINCIPLE
Very little is known about Thomas Savery beyond the fact that he was a military engineer, that he had a mechanical turn of mind, and that he was called “Captain” Savery, although he was never a captain of anything. He is first heard of in 1698, because in that year he received a patent for what he called a “fire-engine.”
Savery’s “fire-engine” was the first practical steam-pump or steam-engine ever invented. It had a vessel into which steam was admitted by a pipe from a boiler to drive out the air. When the air was driven out of the vessel the steam was shut off. Savery then poured cold water over his steam-filled vessel. The steam condensed. Hence a vacuum was created: Papin’s principle.
Savery then opened a pipe leading to the water that was to be raised. At once water rushed into the vacuum, forced up by the sheer weight of the atmosphere. The water valve was now shut off and the steam turned on again to drive the water out of the vessel.
So, the vessel was alternately filled with steam, cooled to condense the steam and produce a vacuum, and filled with water forced up by air-pressure. Savery used two vessels and worked them alternately.
Note that Savery’s pump had no piston and that he pushed the water out of a vessel by the direct pressure of the steam. His process must have been very slow; but he showed how Papin’s discovery might be applied to raise water.
| || || |
| || |
| || || |
Savery explained his steam-engine to mine-owners. They saw it actually pumping water on large estates, but its performance did not convince them that it could pump water out of a mine. It is said that only one mine-owner bought a Savery engine. High steam-pressure was necessary; as much as 150 pounds to the square inch.
Savery did not use safety-valves; hence some of his engines blew up. Perhaps the mine-owners had heard of these explosions and thought it best to keep on using horse-driven pumps.
NEWCOMEN ALSO APPLIES PAPIN’S PRINCIPLE
Thomas Newcomen, about whom few personal facts are known, was born in 1663 and died in 1729. Newcomen was either an ironmonger or a blacksmith, and he conceived the idea of creating a vacuum in much the same way as did Savery, though his engine was much more practical.
He also used steam and not air to force water directly into and out of a vessel, but it was utilized to operate a pump-handle not very different from that still to be found in many a country kitchen. His cylinder or vessel contained a piston, like Papin’s.
Newcomen first drove out all the air in his vessel or cylinder by steam, and then shut off the steam; then he let water spray over the hot cylinder; both ideas were taken from Savery. The steam condensed or shrank back into water. Thus a vacuum was created within the cylinder, whereupon the outer air pressed the piston down.
This piston was connected with one end of a walking-beam, the other end of the walking-beam being connected with a pump-rod. The weight of the pump-rod pulled the piston up. Atmospheric pressure forced it down after the vacuum was created. So the walking-beam would rock and work the pump-rod and draw up water.
By opening and closing the valves at the right time the pump was kept in operation.
One day Newcomen noticed that the engine was working better than usual. He investigated and found that water had leaked directly into the cylinder during the condensing period. At once he saw what had happened. The water did not have to cool first the hot cylinder and then the steam; it could cool and condense the steam directly. After that he always sprayed water into and not on the cylinder.
When Newcomen began to think of selling his engines to mine-owners, he met an obstacle in the form of Savery’s patent. Like a sensible man he proposed a partnership, and Savery readily agreed to the proposal.
Probably Savery was glad enough to make the agreement; the mine-owners would have none of his “fire-engine,” and the one developed by his partner was clearly more practical. Besides, Newcomen’s engine did not work with high-pressure steam that might blow up a boiler, but with steam at a pressure a little greater than that of the atmosphere itself, which is slightly less than fifteen pounds to the square inch at sea-level.
Savery’s engine had to work in the mine itself within a distance of twenty-six feet of the water; Newcomen’s could be erected at the mouth of the mine.
| || || |
| || |
| || || |
The partnership of Savery and Newcomen was successful almost from the beginning. The first Newcomen engine was installed in 1711. It proved so successful that in a few years Newcomen engines were to be found in nearly every mine in England.
The invention restored wealth to dozens of mine-owners who had given up their mines as lost, and saved others from ruin. We are apt to belittle it now because it seems almost ridiculously crude in these days of wonderful machines, but it was one of the greatest achievements of human ingenuity.
Like all inventors, Newcomen had his rivals and opponents who set out to appropriate his ideas and criticise his work. One of these was Desaguliers, who published a book in 1744, entitled Experimental Philosophy, and in this Newcomen’s engine was brushed aside as of no great importance.
It was Desaguliers who spread abroad the story that Humphrey Potter, a boy whose duty it was to control the steam and water by hand, hit on the idea of opening and closing the valves of a Newcomen engine by the simple expedient of strings worked from the beam. Thus the beam, as it rocked, automatically opened and closed the valves at the right time.
Such a contrivance we now call a “valve gear.” It takes more than ordinary engineering ability to design a valve gear which will work in the right way, and it is not likely that a boy possessed that ingenuity.
A picture of a “self-acting” engine, built by Newcomen in 1712, has come down to our time. It clearly indicates an automatic method of opening and closing the valves. Desaguliers’ story may be attributed either to malice or ignorance.
PAPIN HEARS OF SAVERY’S SUCCESS
Leibnitz, the great German philosopher, used to write now and then to Papin, then living in Cassel, Germany. In one of his letters, written in 1705, he told Papin of the wonderful success of Savery, and sent him a picture of the original Savery engine—the one which the mine-owners of England could not be induced to use, but which had proved useful on large country estates.
It is easy enough to imagine Papin’s emotions. What a chance he had lost! He knew that Savery’s principle of creating a vacuum by chilling steam in a cylinder was nothing but the practical application of his own idea. He now had nothing to show for a whole life frittered away in experimenting first with this type of vacuum-pump and then with that.
Perhaps it was envy, perhaps regret, perhaps the natural bent of his active mind that prompted him to design an improvement on Savery’s engine. At all events, he made some unimportant changes in it, and showed how the water that it pumped might be used to drive a water-wheel.
| || || |
| || |
| || || |
|IMPROVED PAPIN STEAM ENGINE, EARLY 1700’S.|
He failed to realize that his first piston-engine might still be developed into something highly practical; instead, he took up the Englishman’s abandoned pump. Following his usual practice, Papin was quite content with talking and writing about his perfection of that engine, and proceeded at once to construct a man-driven paddle-wheel boat, in which he hoped to reach the mouth of the river Weser on his way to London.
The boatmen at Münden took his boat from him, claiming that he had infringed their time-honored, exclusive privilege of navigating the river, and left him with so few belongings that, when he finally reached London, he was penniless. The Royal Society gave him some money, but he died in total obscurity, in 1712, just after the first Newcomen engine, embodying his piston and operating on his vacuum principle, had demonstrated its tremendous possibilities.
JAMES WATT’S INTRODUCTION TO THE STEAM-ENGINE
For about seventy years the engines of Newcomen and Savery, unchanged in principle, improved but slightly in proportions, pumped water out of English coal-mines. Then, suddenly, the steam-engine became more than a pump; it became a machine that moved the wheels of industry and revolutionized the whole art of manufacturing.
This sudden conversion of the engine was brought about by James Watt, an instrument-maker by trade, but a real scientist by inclination and self-education. No single man in history did so much to change civilization. With him begins the modern industrial era, the era of the factory, the era of machine-made conveniences. Because of his engine Watt must be regarded as one of the world’s great figures.
James Watt, a Scotchman, was born in 1736. He plied his trade of instrument-maker first in London and then in Glasgow. He had not served a full term of apprenticeship, and therefore could not be admitted as a member of a Glasgow guild; the equivalent of a modern union. Since he was unable to earn his living in the city itself, the university granted him permission to open a shop on its grounds, and appointed him its instrument-maker.
One day a professor of the university gave Watt a classroom model of Newcomen’s engine to repair. As any good mechanic would have done, he soon performed the task.
But James Watt was something more than a skilful mechanic; he was a thinker, a man with a scientific mind that did not rest until it found out the why and the wherefore of things. When he had repaired the damage he put water in the boiler and started the engine.
In a few minutes the water in the boiler had vanished; the engine had consumed it all in the form of steam. Watt was astonished. The engine consumed steam faster than the little boiler could supply it.
It might be that the men who built Newcomen engines had also been astonished at the steam consumption of their engines; if so they certainly never bothered themselves much about it; probably they simply accepted the fact as something from which there was no escape.
Watt, however, investigated. He found that the steam condensed against the cold walls of the cylinder. When fresh steam was turned on, it had first to warm the cylinder again, and in the process more of it was condensed.
Clearly, the cylinder must always be kept hot, so that as little steam as possible would be chilled into water and the cylinder would not have to be warmed again by incoming steam after each stroke of the piston. But how? Watt pondered over this question for weeks.
| || || |
| || |
| || || |
|JAMES WATT, INVENTOR OF THE SEPARATE CONDENSER FOR STEAM-ENGINES.|
One day, as he was walking in the university grounds, the idea flashed upon him. Why not condense the steam in a separate condenser, connected with the cylinder by a short pipe? That ought to make it unnecessary first to cool the cylinder in order to condense the steam, and then to warm it again with new steam.
WATT INVENTS THE SEPARATE CONDENSER
He constructed a model in which this idea was carried out. What a wonderful, tense moment it must have been when he opened the valve between the condenser and the cylinder! He saw the piston forced down by the pressure of the outer air. The separate condenser worked just as he had imagined it would.
|ORIGINAL EXPERIMENTAL MODEL OF THE SEPARATE CONDENSER MADE BY WATF IN 1765. Watt was struck by the enormous steam consumption of Newcomen’s pump, which was due to the fact that the steam condensed against the cold walls of the cylinder. When fresh steam was turned on, it had first to warm the cylinder again, and in the process more of it was condensed. Watt thereupon conceived the idea of condensing the steam in a separate vessel connected with the cylinder by a short pipe. Courtesy South Kensington Museum, London.|
Watt might have stopped then and there and still have gone down in history as a great inventor. But he went farther. He was so concerned with keeping the cylinder hot and the condenser cool that he made improvement after improvement. He actually placed his cylinder within a larger one and filled the space between with steam, thus inventing what we call the steam-jacket, and making it difficult for the cylinder to cool even by exposure to the air.
Moreover, he placed his condenser in a pit filled with cold water, so that it would condense the inrushing steam quickly and not become warm itself. These accomplishments inspired Watt to perform other experiments.
The cylinder of Newcomen’s engine was open at the top. Watt gave it a cover or “head,” through which the piston-rod passed. This enabled him to force the piston down by steam from his boiler, instead of by the pressure of the outer air. Step by step he developed a real steam-engine, a vast improvement on the engine in which the weight of the air pushed the piston.
All these points Watt covered in his first patent, taken out in 1769. He demonstrated them by the use of small models constructed mostly by himself. Too poor to assume the cost of a large engine, he finally persuaded John Roebuck, proprietor of the Carron Iron Works, to go into partnership with him, by offering him two-thirds of all profits.
An engine was partly built; but there were many difficulties to be overcome in construction, particularly the construction of large cylinders of even bore; for in that day there were no accurate iron lathes. Roebuck’s affairs became involved, and work had to be suspended before this engine was ever put to use.
Partly through financing Watt’s steam-engine, Roebuck finally became a bankrupt, and in settling his affairs not one of his creditors considered the invention which had brought about his ruin worth a farthing. Had they only known! Here was an invention worth all the money in England, an invention destined to revolutionize humanity. Instead, they held it of so little worth that Watt was permitted to retain his rights.
| || || |
| || |
| || || |
|EARLY WATT ENGINE WITH SEPARATE CONDENSER. Drawing probably made under Watt’s direction. Courtesy W. and T. Avery, Ltd., London.|
THE PARTNERSHIP OF BOULTON AND WATT
Watt became so discouraged with the difficulty of obtaining properly bored cylinders that for a time he had to abandon the steam-engine. He was now reduced to poverty, and finding it difficult to borrow more money for his invention, he was compelled to seek employment to provide for his family. Then, as good luck would have it, he met Matthew Boulton, a strong-minded man with a good business head, and wealthy.
Boulton was so impressed with the value of the invention that he readily supplied the necessary capital, and the manufacture of engines was begun on a large scale. The engine proved a marked success; and the firm of Boulton & Watt finally made a, large fortune.
It is hard for us to realize, in these days of fine machine-tools, what difficulties had to be overcome by the young firm of Boulton & Watt. No one could bore a cylinder accurately in those days, which is evident from the following account that Watt has given us of one of his early tests:
“A cast-iron cylinder, over eighteen inches in diameter, an inch thick and weighing half a ton, not perfect, but without any gross error was procured, and the piston, to diminish friction and the consequent wear of the metal, was girt with a brass hoop two inches broad. When first tried the engine goes marvellously bad; but upon Joseph’s endeavoring to mend it, it stood still, and that, too, though the piston was helped with all the appliances of a hat, papier-mâché, greases, black-lead powder, a bottle of oil to drain through the hat and lubricate the sides, and an iron weight above all to prevent the piston leaving the paper behind in its stroke. After some imperfection in the valves was remedied, the engine makes 500 strokes with about two hundredweight of coals.”
Boulton, in 1776, wrote that: “Mr. Wilkinson has bored up several cylinders almost without error; that of fifty inches diameter, which we have put up at Tipton, does not err the thickness of an old shilling in any part.”
This would be considered inexcusably coarse work in these days, when errors of more than one ten-thousandth of an inch are not tolerated in the parts of some fine automobiles.
The Mr. Wilkinson, of whom Boulton wrote so approvingly, was John Wilkinson, famous in the history of machine-tools. Wilkinson’s was probably the first metal-working tool capable of doing heavy work with anything like acceptable accuracy.
The Newcomen engine was now doomed. Watt kept on making improvements. He found that it was wasteful to leave the steam-valve open while the piston was pushed from one end of the cylinder to the other. The pressure of the steam, as it came from the boiler, was more than enough to push the piston.
He discovered that the valve could be closed soon after the piston started, and that the steam in the cylinder expanded and continued to drive the piston on. Hence he invented what has ever since been called the “cut-off,” which means that when the piston has completed only about one-fourth of its stroke the steam is automatically cut off from the boiler and permitted to expand so as to drive the piston for the remaining three-quarters of the stroke.
Of course, the steam cools in thus expanding, but it is doing useful work as it cools. Hence the cut-off makes it possible to convert a large amount of heat into work; heat which would otherwise be wasted if it were carried into the condenser or the open air.
| || || |
| || |
| || || |
|MATTHEW BOULTON. Matthew Boulton was James Watt’s partner, financial manager, and disciplinarian. Without him Watt would hardly have been able to perfect the steam-engine. Courtesy W. and T. Avery, Ltd., London.|
LATER IMPROVEMENTS BY WATT
After a time Watt brought out a double-acting cylinder into which steam was admitted and allowed to expand alternately on opposite sides of the piston, as in all modern condensing engines.
The firm found it hard at first to convince a mine-owner just how much work a Watt engine could do. Many of the mine-owners used horses. Indeed, horses had done most of the pulling and lifting of the world up to Watt’s time, so that Boulton or Watt had to interpret their claims in terms of horsepower.
“This engine will do the work of forty horses,” they would say. In order to live up to any such claim Watt first had to find out how much work a horse really could perform. He made some crude measurements which led him to conclude that in one minute a horse could lift 33,000 pounds through a distance of one foot.
A horse-power, then, is 33,000 foot-pounds per minute, as engineers say. This measure of engine performance has been used ever since, although engineers are not satisfied with its accuracy.
Boulton was a good salesman. He sold engines on the strength of the fuel they would save. Mine-owners wanted to keep their fuel bills low. Newcomen’s best engines consumed thirty-five pounds of coal in one hour for each horsepower.
By studying heat and how to make the most of it, by inventing the separate condenser, and by making other improvements, Watt reduced this coal expenditure to eight pounds. In our best engines of to-day the coal consumed amounts to little more than a pound an hour for a horse-power hour. Even this is considered wasteful, because not more than thirteen per cent of the energy in the coal is utilized.
| || || |
| || |
| || || |
|WATT’S OLD BESS STEAM ENGINE OF 1777.|
|WHERE WATT’S ENGINES WERE MADE. In January, 1796, the Soho Foundry, still in existence, was dedicated with considerable ceremony and a “rearing feast” given to the engine-smiths and other workmen. On this occasion Matthew Boulton made the following speech:
“I come now as the Father of Soho to consecrate this place as one of its branches; I also come to give it a name and a benediction.
“I will therefore proceed to purify the walls of it by the sprinkling of wine, and in the name of Vulcan and all the Gods and Goddesses of Fire and Water, I pronounce the name of it Soho Foundry. May that name endure forever and ever, and let all the people say Amen, Amen.” Courtesy W. and T. Avery, Ltd., London.
THE INVENTION OF THE COMPOUND ENGINE
As the steam expands and cools in a cylinder the cylinder also cools. It ought to be hot, otherwise the next measure of steam will waste some of its heat in warming the cylinder again. Here we have exactly the same situation that Watt found in the Newcomen engine. If Watt could keep the cylinder of a Newcomen engine warm by leading the steam into a separate condenser, the same principle should apply to his own engine.
In other words, allow the steam to enter one cylinder without cutting it off, and, after it has pushed the piston as far as possible, let it pass into a second, larger cylinder, there to cut it off and let it expand and push a second piston. This probably occurred to Watt; but he was prejudiced against high-pressure steam, and the idea could be carried out only if the pressure were high.
So it was that Jonathan Hornblower, in 1781, saw that if two cylinders could be used in this way, he could save, by means of the cut-off, even more heat than Watt had done. He built engines on that principle which were very successful. Hornblower apparently came of a steam-engine family.
One of his ancestors, Joseph Hornblower, is referred to in old books as Newcomen’s “operator,” and he was employed by Newcomen to superintend the erection of engines. Jonathan Hornblower threatened to become so formidable a rival that Boulton sued him for patent infringement and won the case. Boulton & Watt also drove other rivals out of business, and collected large sums in royalties and damages.
After Watt’s patents expired Hornblower’s excellent idea was called to life again, in 1804, by Arthur Woolf, another Englishman. If a second cylinder can make steam expand more, why not a third and fourth? This was first tried by Doctor A. C. Kirk, in 1874, who found that it was indeed possible to reduce the coal bill and get more work out of the heat in steam by thus adding more cylinders.
There is a limit to the number of cylinders, however, and the limit seems to be four. By the time it has left the fourth cylinder the steam has given up so much of its heat that there is little left for a fifth. Even if there were a fifth, the cost of constructing and operating the extra parts is greater than any saving in coal that can be effected.
To use one cylinder after another in this way the steam must leave the boiler at high pressure. At first, 100 pounds to the square inch was regarded as very high pressure; now it is not uncommon to carry anywhere from 150 to 250 pounds. With pressure in excess of 250 pounds to the square inch, difficulty is encountered in packing and lubricating the first cylinder.
| || || |
| || |
| || || |
|HORNBLOWER’S COMPOUND STEAM ENGINE.|
OLIVER EVANS INVENTS THE FIRST HIGH-PRESSURE ENGINE AND PUTS IT TO WORK
Like Savery and Newcomen, Watt thought at first only of pumping water. To be sure, after he made steam instead of air do the work of moving a piston, he had produced an engine which could turn a shaft and therefore drive factory machines and railway-carriages and vessels.
It was an American who realized perhaps more keenly than Watt how tremendously helpful the steam-engine could be in doing most of the world’s hard, wearying work. This American was Oliver Evans, born in Newport, Delaware, in 1755.
Evans was a farmer boy who, like many a great American inventor, had to educate himself. What he knew of history, politics, and mechanics he learned out of books at night by the light of burning shavings. His brothers were millers, and, because of his mechanical ability, they took him into partnership with them.
|OLIVER EVANS. Inventor of the high-pressure steam-engine.|
The United States of Evans’s time was a land of infinite possibilities. It had a territory so immense that even men like Franklin, Washington, and Hamilton did not know exactly where it ended west of the Appalachian Mountains. There were forests to be hewed down; coal and iron to be mined; untold, even unsuspected, riches were in the earth. What America needed was men to develop these resources, and there were fewer men in the original thirteen States than there are now in Chicago and New York.
Evans could not have known how rich the new republic was, but he did know that there were not enough men to till the soil or mine the earth. His inventive mind naturally turned toward machines that would do the work of men. Even at twenty-two we find him inventing a machine for making the teeth used in carding cotton and wool: a purely labor-saving device.
In his brothers’ flour-mill he was constantly struck with the need of machinery that would grind flour faster than was possible with the crude water-wheel of the day, and carry it away automatically to be sacked. The United States granted him one of the three patents it issued in the first year of its existence; a patent on flour-mill machinery.
One day a book which described Newcomen’s engine fell into his hands. He knew nothing about engines, but his inventive mind saw at once that while the pressure of the atmosphere worked the piston. Newcomen did nothing with the steam beyond producing a vacuum by condensation.
Why had not Newcomen used the elastic force of steam? He asked himself the question over and over again. Constructed so as to employ and utilize its steam, an engine could be used for other purposes than pumping water; it would be a real power-generator, something that would drive other machines and thus do the work of hundreds of hands.
Evans thereupon resolved to invent a steam-engine, a real steam-engine and not a mere pump. His drawings of a high-pressure engine, which could actually be used to drive other machines, and which was the first steam-engine of the kind ever invented, he sent to England in 1787. Richard Trevithick, an Englishman, the first man to build a locomotive, came out soon afterward with a high-pressure steam-engine, but there is good reason to believe that he saw these drawings of Evans’s.
Watt was prejudiced against high pressures; and yet, unless they were used, the steam-engine could not be employed to the utmost advantage in factories. Hence, to Evans belongs the credit of having produced an engine, independently of Watt, which made it possible to drive factory machinery.
Evans built a high-pressure engine and showed how machines could do the work of the men the United States lacked. In 1801 he gave public exhibitions to prove that his engine could drive machines that ground plaster and sawed marble. Evans found it hard to convince business men that new ideas are worth carrying out. His efforts to introduce his engine almost ruined him.
| || || |
| || |
| || || |
|OLIVER EVANS HIGH PRESSURE STEAM ENGINE OF 1801.|
Undaunted, he kept on. He applied his engine in his flour-mill. At the same time he invented flour-mill machinery which, in principle, is the same as that we find to-day in the great mills of the Middle West.
In 1803 he became a regular builder of engines. Philadelphia ordered a steam-dredge from him with which to clean the city docks. His shop was a mile and a half away from the Schuylkill River. Resourceful, practical man that he was, he mounted one of his engines within the scow and ran the scow on rollers by steam to the river. That was the first steam-wagon.
But Evans did more than this. When he had reached the river, he substituted a stern paddle for the rollers and steamed away on the water to Philadelphia. The scow, christened by Evans, Oruktor Amphibolos (“Amphibious Digger”) was, therefore, not only the first automobile, but also one of the first steamboats. Indeed, the Mississippi stern-wheeler is nothing but a steam-driven scow, with cabins and cargo spaces, but larger than the one made by Oliver Evans.
| || || |
| || |
| || || |
|THE “AMPHIBIOUS DIGGER” OF OLIVER EVANS—THE FIRST AUTOMOBILE. Philadelphia ordered a steam-dredge from Oliver Evans in 1804. His shop was a mile and a half away from the Schuylkill River. He mounted one of his engines within the dredge-scow and ran the scow on rollers by steam to the river. This was the first steam-wagon or automobile. When he reached the river Evans substituted a paddle for the rollers and steamed away to Philadelphia. Hence the invention was also one of the first steamboats. Evans named this craft “Oruktor Amphibolos”, or “Amphibious Digger.” This is a picture of the Baltimore & Ohio Railway Company’s reconstruction of the Amphibious Digger.|
Evans intended to write a long, learned book about his steam-engine, profusely illustrated with explanatory drawings, and to be called “The Young Engineer’s Guide.” But his disappointments, and the straits into which he had been plunged by his first attempt to build and sell engines, forced him to compromise on the book, which was considerably reduced and grimly renamed The “Abortion of the Young Engineer’s Guide.”
He wrote other books and pamphlets, in which he described his flour-mill machinery and foretold with remarkable accuracy what might be expected of power-machines. In an “Address to the People of the United States,” in which he poured forth all his troubles as an inventor, he says:
“The time will come when people will travel in stages moved by steam-engines from one city to another almost as fast as birds fly—fifteen to twenty miles an hour. Passing through the air with such velocity—changing the scene in such rapid succession—will be the most exhilarating, delightful exercise. A carriage will set out from Washington in the morning; arid passengers will breakfast at Baltimore, dine at Philadelphia and sup at New York the same day.”
He was not referring to ordinary steam-driven road coaches, such as Sir Goldsworthy Gurney introduced in England years later, but to railway carriages; for he goes on to describe rails on which the carriages are to run. “And the passengers will sleep in these stages as comfortably as they now do in steam stage-boats.”
The worries which beset him and which prompted him to pour out his woes in this amazing “Address,” led him to destroy the drawings and records of no fewer than eighty inventions. The final blow came when a fire destroyed his factory in 1819. He died a few months later, a bitter, discouraged man, yet a great pioneer inventor in the annals of American industry.
CORLISS AND HIS DROP CUT-OFF
Evans was the first of a line of American inventors who helped to make the steam-engine what it is to-day, and certainly the first in America to apply it industrially. We have to wait until 1849 before another man appears with improvements that heightened the usefulness of the steam-engine.
In that year an American, George H. Corliss, received a United States patent for an engine which has not been greatly bettered to this day. Engineers rank Corliss with Watt when they trace the history of the steam-engine.
Corliss, a born inventor, had to teach himself the rudiments of mechanics, but, like his predecessors, Watt and Evans, his mechanical ideas were inexhaustible. How fertile was his mind is revealed by the fact that even when scarcely more than a boy he performed a feat that civil engineers had declared impossible.
A freshet had swept away the bridge near the village of Greenwich, New York, where he lived. Unless this bridge were rebuilt the village would practically have been cut off from supplies. There was no time to wait for the water to subside. The bridge must be reconstructed at once. “Impossible,” said the engineers. Corliss set to work and rebuilt the bridge in ten days at a cost of fifty dollars.
While he was still a country storekeeper, Corliss invented a sewing-machine; and this before Howe. Dreaming of the wealth that would be his if he could manufacture and sell this machine, Corliss set out for Providence to raise the needed money. There he arranged with the steam-engine building firm of Fairbanks & Bancroft to perfect the machine. Corliss had an attractive personality and his ingenuity pleased the firm.
Fairbanks & Bancroft had no particular faith in his invention, but they had a great deal of faith in Corliss. They offered him a position on condition that he would give up the foolish machine. Poor as he was he accepted the offer. One year later he became a partner.
The sewing-machine was abandoned, but Corliss thought of other machines. He made a profound study of the engines of his day. By this time the steam-engine had taken its place in thousands of factories in Europe and in hundreds in the United States.
These factory engines had to adapt themselves to the machines they drove; in other words, sometimes all the machines were running, so that the engines were taxed to the utmost to deliver power, and sometimes only a few machines were in operation. It was clearly impossible, when men and women in the factory called “more power,” or “my machine is shut off,” for the engineer to regulate his engine in accordance with their demands.
Hence, Watt invented the “ball-governor,” a sleeve which can slide up and down a rod or pipe, and which is connected with two whirling balls. When some of the factory machines were shut off, the engine would naturally speed up, whereupon the balls would whirl around faster and would be flung out farther. This raised the sleeve and cut off some of the steam supplied to the engine.
As more and more machines were thrown into operation, the balls would whirl more slowly and fall slightly; consequently the sleeve would drop and permit more steam to reach the engine. Thus Watt made it possible for an engine automatically to speed up or slow down in accordance with the factory demands.
Ingenious as the ball-governor was, it had its faults. The engine had to speed up or slow down before the big steam-valve could be moved by the ball-governor and its sleeve. In a textile mill the spindles of a spinning-machine run very fast. The slightest variation in speed of the engine that drives the machine is multiplied many times at the spindle.
If the spindle runs too fast the work produced is spoiled; if it runs too slow the output is low. It was difficult to make a Watt ball-governor that would be responsive enough to meet this situation.
Corliss invented a much more sensitive governor, a “valve gear,” one that seemed so complicated to engineers of the day that they poked fun at it, and at first refused to take Corliss engines seriously:
“Levers, links, and motions various
Endless jimcracks all precarious.”
Thus ran a couplet composed to express the current opinion of the mechanism that was offered as a substitute of the Watt ball-governor.
| || || |
| || |
| || || |
|CORLISS ENGINE. The original Corliss valve-gear was invented in 1849 by G. H. Corliss. The leading features of the invention are: The employment of separate steam and exhaust valves at each end of the cylinder, so that any alteration of the point at which steam is cut off can be made without interfering with the action of the exhaust-valve; and separate adjustment for each of the cylindrical valves. The two exhaust-valves which are at the bottom of the cylinder are rocked by a single eccentric, while the two steam-valves at the top are rocked by another eccentric. The steam eccentric swings an arm provided with a cylindrical end upon which are two hardened steel plates; as the arm swings these plates engage with similar plates attached to flat levers that proceed from cranks on the spindles of the two steam-valves. As the arm reciprocates, the steam-valves are alternately opened, but, at certain points, determined by the speed of the governor, the lever of the steam-valve then opening slips off the corresponding driving-plate; the valve then left free is rapidly turned into a closed position by a coiled spring.|
What was this new device that seemed so strange? The Watt engine had what is called a “D” slide valve, and it was so named because it was shaped like the letter “D.” The slide valve opens and shuts just like a sliding door, to admit and shut off the steam. The “D” slide valve for a large engine is massive, and steam pressure keeps it tightly closed. This produces friction and wastes power.
Corliss invented a valve that worked like a revolving door: a rotary valve. He used these revolving-door valves at each end of the cylinder, one to admit the steam, and one to control the exhaust. A slight motion of one of these valves was sufficient to open or close the steam port or doorway almost without friction.
To open and close his rotary valve, or revolving steam-door, automatically, Corliss invented a governor which was apparently composed of “endless jimcracks all precarious.”
By a system of parts, certainly more complicated than the simple ball-governor and sleeve of Watt, a weight was made to drop and suddenly cut off the steam as it entered the cylinder and not, as in the Watt engine, some moments later. For that reason this invention by Corliss is called the “drop cut-off.”
If only a few machines in the factory happened to be running, the drop cut-off would shut off the steam after the piston had moved only a few inches. This was not only a saving of steam, but also of fuel. The cut-off acted like an attendant who holds a revolving door when he wants to hold back a crowd and helps to turn it when he wants to hurry it up.
Finding it difficult to convince business men that his engine was any better than Watt’s, Corliss had to take risks in selling it. He knew his engine would save coal, and therefore he adopted a plan similar to that which Boulton & Watt had found successful: the plan of installing an engine free of charge and of receiving in payment part of the money saved in coal.
He sold one of his first engines with the understanding that he was to be paid all the money it saved in five years. At the end of five years he had pocketed $19,734.22—several times what the engine was really worth. This shrewd business policy made Corliss rich and gave him the necessary money to fight infringers. One of his patent-infringement suits lasted fifteen years, and cost him $100,000.
When the Philadelphia Exposition of 1876 was planned, Corliss suggested that one large double engine was enough to furnish all the power required to drive the machines in the Machinery Hall. But no one could build the engine. “Impossible,” said the engineers again.
Then Corliss decided that he would build the engine himself. When he set it up it was the mechanical marvel of the exposition. It was afterward bought by the Pullman Company and ran in its shops until 1910.
| || || |
| || |
| || || |
|HUGE ENGINE BUILT BY CORLISS FOR THE PHILADELPHIA EXPOSITION OF 1876. It was afterward bought by the Pullman Company and did service in its plant for over a generation. Courtesy Pullman Company.|
THE INVENTION OF THE STEAM-TURBINE
In the steam-engine, as Watt handed it down to us, the piston moves back and forth, or up and down, in the cylinder, just as it does in an automobile engine. This is called a “reciprocating” motion, and engines in which pistons thus move are therefore known as “reciprocating engines.”
This back and forth, or reciprocating motion, cannot be used to drive a wheel or a shaft directly. It must be changed to a turning or rotary motion. For this purpose cranks are used. They are found in the reciprocating engines of automobiles, and by their means a shaft is turned and the wheels of the automobile are made to revolve.
Why was it not possible to make the steam turn a wheel directly, just as the wind turns a windmill or a stream a water-wheel? Some of the earliest engines of which we have any record were built on this principle. There was the engine of Hero, a mathematician, who lived in Alexandria, Egypt, about 130 B. C., an engine which was little more than a toy, but in which there was a wheel that was whirled around by steam escaping from bent tubes.
In 1629, Giovanni Branca, of the great Italian University of Padua, also succeeded in moving wheels by blowing steam against their paddles. Watt, too, thought so much of this principle that he tried to apply it, but he soon abandoned it because of the many mechanical difficulties he encountered. For generations inventors had tried to do away with the to-and-fro motion of the piston.
| || || |
| || |
| || || |
Literally, hundreds of patents had been granted to inventors in England and the United States for rotary engines, not one of them of any practical value, when, toward the end of the nineteenth century, the dynamo, or electric generator, was introduced. The generator is a high-speed machine, and by comparison the reciprocating engine is slow. But it was difficult to adapt the slow engine to the fast generator, and unless that was done neither could be used economically.
It was not easy to design and build an engine according to the ideas of Watt and Corliss which would turn the generator continuously at high speed; the generator had to be made large to suit the speed of the engine, and power-wasting belting or gearing had to be used in order that the generator might turn at two and three times the speed of the engine.
A faster engine was needed. Rotary engines were fast; accordingly inventors tried once more to solve the old, seemingly hopeless problem of building them.
THE DE LAVAL STEAM-TURBINE
In 1889, Doctor Gustaf De Laval, a Swedish engineer, brought out the first practical rotary engine: a turbine. He took a disk or solid wheel and cut vanes in its rim. Against these vanes, nozzles, properly placed, shot jets of steam. After having struck the vanes the steam was allowed to escape. De Laval’s disk was something like a pinwheel.
Because it cost too much in steam, and therefore in fuel, to blow steam against vanes in the open air, De Laval enclosed his disk in a tight cylinder, rather flat. Everything depended on the shape of the nozzles and the vanes. The nozzles had to shoot the steam at the highest possible speed, and the vanes had to be so shaped that they would let the steam do its work most effectively and not waste its force by recoiling upon itself.
| || || |
| || |
| || || |
|DE LAVAL TURBINE. This remarkable machine owed its success to the discovery by Doctor Gustaf De Laval in 1889 of the fact that the velocity of the particles of an escaping jet of steam is increased by discharging through an expanding orifice, the conversion of the energy of the steam into momentum being so complete that when applied to a form of Pelton wheel or impulse turbine a high efficiency is obtained.|
About the time that De Laval was conducting his experimenting, an English engineer, Charles A. Parsons, since knighted, invented a turbine entirely different in character. Unlike most inventors Parsons was a rich nobleman’s son. His father was the Earl of Rosse, famous in his time because he built one of the largest telescopes in the history of astronomy, an instrument that was one of the wonders of the world.
Parsons spent his boyhood in a moated castle under the influence of a father noted for his public spirit and his scientific attainments. To build the big telescope a foundry and machine-shops had been fitted up in the castle grounds. Here young Parsons spent much of his time.
Sir Robert Ball, who was his private tutor—the Earl of Rosse had a deep-rooted prejudice against all schools—said that Parsons was forever in the shops making machines or tinkering. Later, the young man was sent to the University of Cambridge where he graduated with high honors.
Parsons then apprenticed himself to the firm of Armstrong & Whitworth, famous in English naval history for its guns and battleships. Here, under the eye of Whitworth, one of the most ingenious mechanics and engineers of our time, Parsons learned the art of successfully attacking a mechanical problem.
After he had served his apprenticeship and had become junior partner in an engineering firm, Parsons began to think seriously of a steam-turbine. In 1884, he took out his first patent; so that he began work even before De Laval.
| || || |
| || |
| || || |
|SIR CHARLES A. PARSONS. Inventor of the Parsons steam-turbine.|
Parsons used more than a single wheel or disk. He strung a large number of disks in a row on a shaft and enclosed them all in a cylinder or drum. It must not be inferred that he blew an individual jet of steam against each set of blades. Instead, he blew a single current of steam from one end of the cylinder to the other, and subdivided it into little jets, each playing upon successive blades. Therein lay the novel feature of his great invention.
He subdivided the steam current by studding the inner surface of the long, enclosing casing with rings of blades, fitting or dovetailing between the shaft blades. The casing blades were fixed; the shaft blades turned. The fixed blades guided the tiny streams of steam to the moving shaft blades at just the right angle, so that the steam would not get in its own way.
The blades of both casing and shaft were curved so that although the steam entered the casing parallel with the shaft it was shot against the blades just as you would blow air against the vanes of a pinwheel. The steam literally writhed through the turbine, worming its way from fixed blade to moving blade, until its energy was spent in a parting kick administered to the last ring of shaft or moving blades.
| || || |
| || |
| || || |
|THE FIRST POWER-HOUSE EQUIPPED WITH PARSONS TURBINE. Turbo-generators in the plant of the Newcastle and District Electric Lighting Co., Limited. Courtesy C. A. Parsons & Company.|
The turbine invented by Parsons proved successful almost from the beginning. If the old reciprocating engine was too slow this new engine was too fast. It ran faster than any dynamo or generator, indeed ten and even fifteen times as fast.
Instead of being a fault this proved a virtue. It became possible to build smaller, faster dynamos that would deliver just as much current as the old, bigger, slower dynamos.
Soon Parsons’s turbines were introduced not only in power-houses, but also on ships. Some of the fast transatlantic liners, among them the Mauretania, are driven by Parsons’s turbines, and some of the great fighting ships that won the day for England at Jutland were turbine-propelled.
|COURSE OF STEAM-JET BETWEEN FIXED AND MOVING BLADES—PARSONS TYPE TURBINE-ENGINE. (Right) THE “ROTOR” OR MOVING BLADES OF A WESTINGHOUSE-PARSONS STEAM-TURBINE. Courtesy Westinghouse Electric and Mfg. Co.|
|PLAN AND ELEVATION SHOWING STEAM PASSAGE IN A FOUR-STAGE CURTIS STEAM-TURBINE. Curtis’s turbine consists of a set of disks, each turning in a separate compartment. After the steam has acted on the first disk it is shot into a compartment where it accumulates and produces back pressure. This has the effect of slowing up the shaft. The steam next passes to another set of nozzles and is discharged against a second disk at a lower pressure. Here, again, it accumulates and discharges against a third disk, and so passes through perhaps a dozen stages.|
CURTIS COMBINES THE IDEAS OF DE LAVAL AND PARSONS
Difficulties are encountered in the manufacture of both De Laval’s and Parsons’s turbines. It is difficult to balance parts properly that turn at 15,000 revolutions a minute, and thousands of little blades have to be fitted very carefully.
Charles E. Curtis was an electrical manufacturer in Brooklyn, New York, when he first thought of his turbine. He helped to invent the electric fan now used in every office and home. With the money that he made he pushed his conception of a turbine to success.
In the De Laval turbine the steam blows against one set of blades on a disk and expands in a single jump; in the Parsons turbine the steam blows against one set of blades, then against set after set, each time expanding a little, until finally it leaves the machine expanded to the utmost and with scarcely any energy left.
Curtis combined the ideas of De Laval and Parsons. De Laval’s steam jets shot against the blades at a speed of 4,000 feet a second—nearly twice as fast as a rifle-bullet. The steam was travelling so much faster than the blades could turn that energy was lost.
On the other hand, Parsons had trouble with his blades. There were literally millions of them in the turbines of a great powerhouse or steamer, all carefully set by hand. Moreover, the fixed blades and the moving blades had to dovetail so closely that not more than three-hundredths of an inch was left between some of them; so that if the steam was turned on suddenly some blades would be stripped off as the shaft turned, because they had expanded unevenly and touched dovetailing blades.
By combining the principles of De Laval and Parsons, Curtis invented a machine which had the good features of both without their faults. His turbine consists of a set of De Laval disks, each turning in its separate compartment.
The steam acts on the first disk, just as it does in the De Laval turbine, but, instead of being discharged into the open air or into a condenser, it is shot into a compartment where it accumulates and produces back pressure. This has the effect of slowing up the steam jets so that the shaft does not need to run so fast as in the De Laval turbine.
The steam next enters another set of nozzles and is discharged against a second disk at a lower pressure. Here, again, it accumulates and afterward discharges against a third disk, and so through perhaps a dozen stages. To reduce the speed of a Parsons turbine the engineer reduces the steam pressure, which results in waste.
| || || |
| || |
| || || |
|Curtis steam turbine. Nozzles and both moving and stationary blades result in less waste of steam.|
To reduce the speed of a Curtis turbine the engineer simply cuts off steam from one or more nozzles, so that the machine can run economically at low speed as well as at high.
The steam-turbine of Curtis is a very great invention, the last word in steam-engines. It has been so successful that even in England it is competing with Sir Charles Parsons’s invention. It was not developed overnight. Curtis spent $60,000 on it, and then sold his patent rights to the General Electric Company, in the research laboratories of which over $3 million were paid out in bringing his turbine to its present stage of perfection.
Three million dollars is more money than there was in all England in the time of Richard the Lion Heart. That huge sum was an investment in an engineering idea, an investment that has paid rich dividends when it is considered that Curtis’s turbines on land generate 15 million horse-power, on sea 20 million horse-power, and that the British navy uses Curtis’s turbines having a combined horse-power of 5 million.
The Curtis turbine was brought to commercial perfection by Mr. W. L. R. Emmett of the General Electric Company. To his efforts is it due that our battleships are now electrically driven; that is, the steam-turbines drive not the propeller directly but electric generators and motors with which the propeller-shafts are connected.
With the development of the Curtis turbine it seemed as if the story of the steam-engine had been brought to a close. And yet Emmett saw further than the Curtis steam-turbine. As an engineer he knew that the steam-engine is a heat-engine, and that its chief purpose is to convert the energy liberated by burning fuel into useful work.
The more heat that one can obtain, the more work results. From Watt to Curtis all efforts had been directed toward utilizing more and more heat. Temperatures had been raised to the utmost. Water cannot exist in a boiler above the critical temperature of 706 degrees Fahrenheit, and even then the pressure will be over 3,000 pounds to the square inch, which is quite outside the range of ordinary practice.
Water has its limitations. Can any other liquid be used? Emmett determined to experiment with quicksilver or mercury. Water boils at 212 degrees Fahrenheit; mercury at 677 degrees Fahrenheit. Therefore it can store up more heat and do more work.
Emmett began to experiment with mercury about 1912. With the financial resources of a great manufacturing organization behind him, he was able to spend hundreds of thousands of dollars in experiments.
Finally, in 1923, he had reached a point where he was able to drive electric generators of the Hartford Electric Light and Power Company with mercury vapor. Even this experimental installation cost $500,000. It was the fifteenth that Emmett had designed up to that time.
| || || |
| || |
| || || |
|THE EMMETT MERCURY-STEAM POWER-PLANT. Water boils at 212 degrees Fahrenheit; mercury at 677 degrees Fahrenheit. Hence mercury can store up more heat (energy) and do more work. W. L. R. Emmett after twelve years of experimenting successfully applied the idea in this mercury-steam plant of the Hartford Electric Light and Power Company. Mercury is vaporized in a special boiler, B, with ordinary fuel—coal or oil. The mercury vapor, at a temperature of 677 degrees and pressure of 35 pounds, is supplied to a single-stage turbine, G, which drives an electric generator, M. After leaving the turbine it still has a temperature of 455 degrees—hot enough to boil water. It is passed through a condenser, H, where it boils water and raises steam, which is fed through a pipe, K, to a Curtis steam-turbine coupled with an electric generator. Thus the vaporized mercury not only drives a turbine but raises steam which drives another turbine. Courtesy Scientific American.|
Let us examine this 6,000 horse-power Hartford installation with the aid of the illustration on this page. Mercury is boiled in a special boiler with ordinary fuel—coal or oil. Vapor is given off at 677 degrees Fahrenheit at thirty-five pounds pressure. It is supplied to a single-stage turbine which drives an electric generator. After having spun the turbine it still has a temperature of 455 degrees.
If the vapor were to be discharged or collected then and there, mercury would show no improvement over water. This hot, condensed liquid mercury can do much more work. Emmett passes it through a condenser and makes it serve exactly the same purpose that glowing coals serve under a boiler. He heats water with it—raises steam.
So this condenser is really a kind of steam-boiler. The mercury passes through a series of tubes; water surrounds the tubes; hence the intensely hot liquid mercury boils the water and raises steam which is fed to a Curtis steam-turbine coupled to another electric generator.
Mercury costs about a dollar a pound. Moreover, its vapor is poisonous. For these two reasons it must not be allowed to escape. From the condenser-boiler the liquid mercury flows to a heater right in the path of the hot fuel gases of the mercury-boiler. Thus it is preheated and finally passed back to the main mercury-boiler. The cycle then begins all over again.
Thus the fuel gases are used to the utmost before they escape up the smoke-stack; and the mercury is not allowed to escape at all. The vaporized mercury is made to do double work—to drive a mercury-vapor turbine and to generate steam for a steam-turbine. Because mercury condenses at a temperature more than twice that of boiling water and stores up more heat from a fire than water, the efficiency of the Emmett power system is unprecedented.
Hartford has a population of 175,000. It costs $ 1.5 million annually for coal to supply this population with electric light and power. With the mercury process the coal bill is cut in half; for the Hartford plant, with steam at 200 pounds pressure, can produce with mercury vapor at thirty-five pounds pressure, fifty-two per cent more electric energy for each pound of fuel consumed.
“And if,” Emmett adds, “in such a plant the steam-boiler were re-equipped with furnaces and mercury apparatus arranged to burn eighteen per cent more fuel, the station capacity, with the same steam-turbines and auxiliaries, would be increased about eighty per cent.”
With Emmett, the American inventor, we bring the story of the steam-engine, probably the greatest of all inventions, to a close. Watt, Evans, Corliss, Parsons, Curtis—their work centralized industry in single huge factories and towns, gave us the fabric of modern civilization, and raised the standard of living to a degree undreamed of only a century and a half ago.
The great revolutions of England, America, and France gave men political freedom; but Watt and his successors gave them the machine that meant freedom of a different kind, a freedom that has expressed itself in the slave-machines that now do so much of the world’s work.
Millions of horse-power, thousands of millions of tons of coal, billions of barrels of oil are the measure of our country’s wealth; a measure that meant little or nothing before the invention of the steam-engine. Now our engines generate every hour in the day and night 125 million horse-power, of which over eighty-two per cent must be credited to steam.
Perhaps Boulton had an inkling of what was to come when he aptly crystallized the significance of the steam-engine in a conversation with George the Third:
“In what business are you engaged ?” asked the king.
“I am engaged, your Majesty,” said Boulton, “in the production of a commodity which is the desire of kings.”
“And what is that? What is that?”
“Power, your Majesty,” replied Boulton.
And he was right. The steam-engine is king of the world.
| || || |
| || |
| || || |
|MODERN STEAM TURBINE POWER PLANT. Courtesy Commonwealth Edison Company.|