Page images
PDF
EPUB

room was used in its construction, the to a full stop and begins over again steam turbine generates nearly fifty per twice in every revolution—as in a recipcent more power than one of the big rocating engine-for it has no piston, no engines. Without audibly proclaiming cross-head, no crank pin, no connecting its achievement, the steam turbine yields rod, no valves and no eccentrics. It has a third more power for every pound of nothing which can be adjusted with a coal consumed than the noisy giants monkey-wrench, nothing which will yield sprawled over the rest of the engine to a soft hammer, nothing susceptible to There is no heavy odor of hot' the insinuation of the steel bar. The

steam turbine is tool-proof.

The cosmopolitan character of the steam turbine is rounded out by a capacity for increase in size which, like the capital stock of a modern corporation, is limitless. While reciprocating engines are by their very nature limited in size, turbines of 7,000 horsepower are common, a number of 16,000 horsepower have been constructed and there are no practical difficulties in the way of building them of 50,000 horsepower if need be.

To the extent that power is generated by the impact of a fluid upon buckets or vanes on the periphery of a wheel a steam turbine is like a water turbine ; but there the resemblance ends. In a water turbine the fluid always has the same volume and temperature, and so the energy it exerts is always the same. Steam, on the other hand, varies within wide limits as its temperature and pressure change. For instance, 141 cubic feet of saturated steam at 200 pounds pressure produces 1,647 cubic feet at atmospheric pressure, and if the pressure be reduced to six-tenths of a pound, one-fourth of the steam would be condensed and the volume of steam

and water combined would be 25,500 MEDIUM PRESSURE ROTAR, WITH BUCKETS READY TO GO INTO 120-INCH TURBINE.

cubic feet. In a water turbine, if the

water were delivered upon the wheel oil hanging about it to remind the owner under a head of 150 feet its velocity of an important item in his operating would be 96 feet in a second and a cubic expenses, for the steam turbine doesn't foot of it would have a kinetic energy take oil, thank you. It sticks to cold of 9,000 foot pounds. A cubic foot of water with a steadfastness which should steam at 50 pounds pressure has so small win the admiration of the W. C. T. U. a mass that in order to produce the same and thereby reduces friction to the van- amount of energy it must move at the ishing point.

rate of 2,200 feet in a second. If steam The steam turbine is not only Japanese at a pressure of 150 pounds is allowed to in efficiency, but it is also a very China- expand into a 28-inch vacuum, which is man for perversity. All accepted ideas as near a perfect vacuum as it is possible regarding the essential features of steam to obtain in ordinary work, it will move engines must be discarded in considering at the rate of 4,010 feet in a second, or the steam turbine. That which an engine 45.6 miles a minute. If it were possible has, the turbine has not. In a steam to produce a perfect vacuum between turbine there are no “dead centers" New York and Chicago along the shortwhere the development of power comes est rail route a jet of steam introduced at one end of the line would travel in speed had to be reduced by a ten to one 21 minutes the distance the fastest trains gearing to make the power available at in the world require 18 hours to traverse. all. In the larger sizes the turbine wheel

[graphic]

It was this property of steam which revolves with a peripheral velocity of prevented the perfection of the steam tur- 1,200 feet per second. De Laval solved bine long ago. Some idea of the diffi- but half the problem, for he could not culty of mastering the problem as well control the steam. It has not been found as the vast amount of effort bestowed practical to build De Laval steam turupon it may be gathered from the fact bines of more than 300-horsepower and that in the last 120 years no fewer than its field of usefulness is restricted. 429 patents relating to steam turbines A year after De Laval obtained his were granted in England alone; yet it patent, C. A. Parsons, of England, found was not until 1883 that a steam turbine that he could control the speed of rotation which would work was produced, and up of a steam turbine by using the same to the present but three types have been steam upon a number of wheels in sucable to attain any degree of commercial cession. This meant that turbines of any success.

size and for any purpose could be built. The first successful steam turbine was The problem was finally solved. produced in 1883 by Dr. Carl Patrick Roughly speaking, the Parsons turbine Gustaf de Laval, a Swedish scientist. De

De is a horizontal cylinder within which is Laval directed jets of steam, expanded a shaft on which are a number of steel by being introduced through the small wheels from fourteen inches to three feet end of a cone-shaped nozzle, like the in diameter and an inch to two inches in nozzle of a garden hose turned wrong thickness, with little concave brass buckend to, upon a row of tiny buckets upon ets or vanes set close together upon their a single small wheel enclosed in a cham- rims. Between each pair of wheels is a ber. The velocity of this small wheel stationary raised ring of buckets on the

so tremendous that it had to be inside of the cylinder, with their concave mounted upon a flexible shaft and the surfaces facing in the opposite direction

was

[graphic]

A CONTRAST IN SIZES. In foreground, 27-inch turbine with top laid bare; in background, 120-inch turbine.

from the buckets on the wheels. Jets of ets. Notwithstanding this the steam tursteam are introduced through nozzles set bine is wonderful for the long-sustained at an acute angle to the first wheel of service without attention of which it is the series. The jet of steam on striking capable. A 500-horsepower Westinga bucket pushes the wheel around until house-Parsons steam turbine at the St. the opening is opposite the opening of Louis World's Fair ran without stopping one of the stationary buckets, through at a uniform speed of 3,600 revolutions which it passes, and on its way is de- a minute, from 9:40 a. m., June 20, to flected to the proper angle to be effective 12 m., December 2, 1904. In that time on the buckets of the next wheel, and it made 776,522,000 revolutions, and the so on until it has traversed the entire periphery of the generator, at a speed of

[graphic][subsumed][ocr errors][merged small]

length of the cylinder in a spiral course. 7,000 miles a day, traveled 1,155,000 As the steam expands the size of the miles without a moment of time or a wheels is increased to correspond with penny of expense for adjustment or rethe high pressure, intermediate and low pairs. Even this remarkable record was pressure cylinders of a reciprocating exceeded by a Parsons, steam turbine engine, and the buckets are enlarged pro- driving a fan at the Howdon Lead portionately.

Works at Wellington-Quay-On-Tyne, A Westinghouse-Parsons steam tur- England, which ran continuously for five bine, which is the Americanized type of

years. the Parson turbine, of 500-horsepower, Several other steam turbines, such as has 58 rings of buckets. Each bucket the Stumpf, the Seger and the Schulz, contributes about one ounce toward the are passing through the experimental total of 500 horsepower. From this it stage in Europe, but none have yet atmay be seen that it requires an enormous tained practical success except the one number of pieces to make up a steam tur- invented by Professor A. Rateau, of bine of this type. The 18,000 horsepower France, which is in commercial use to a steam turbines to be installed in the new limited extent. Cunarders will each have 1,250,000 buck- The newest and the most advanced type of steam turbine yet produced was ond row on the wheel, and then passes patented some six years ago by C. C. out of the chamber, through nozzles simCurtis, of New York City, and developed ilar to the first set, though larger, to the by the inventor in collaboration with W. next chamber, and so on to the conL. R. Emmet, of Schenectady. The Cur- denser. tis steam turbine differs radically from Now that the development of the steam others, in many particulars. The tur- turbine has been accomplished in these bine wheels or disks are much larger in two notable types, the first really great diameter and fewer in number than in improvement in the steam engine since the Parsons type and they revolve hori- the days of Watt has been achieved. Not zontally instead of vertically. This ar- only are the turbines now in use doing rangement affords an opportunity for a their work 30 per cent cheaper than it most ingenious method of reducing fric- can be done by the best types of reciprotion almost to the vanishing point. The cating engines, but there is also a great turbine shaft which bears the full weight saving in the original cost. It has been of the heavy steel wheels and also the shown that in a big plant each turbine moving parts of the dynamo does not of 7,000 horsepower can be set up for rest on a bearing at the bottom, but, approximately $80,000 less than the cost instead, is actually floated on a layer of of reciprocal engines of equal power. water half an inch deep, which is pumped The saving of space, particularly by the into the chamber at the rate of 300 gal-, Curtis vertical turbine, is very great. A lons a minute, at a pressure of 400 pounds Curtis steam turbine of 5,000 horseto the inch. One of these Curtis steampower requires but 35-1,000th of a square turbines of 7,000 horsepower has three foot of foor area per horsepower as solid steel wheels, 14 feet 7 inches in compared with 7-10ths of a square foot diameter and from 1/2 inches thick at per horsepower required by a vertical retheir circumference to six inches at their ciprocating engine. center, revolving in a chamber 5 feet 6 True, the steam turbine has its limitainches high. So nearly is friction elim- tions. From its very nature it never can inated and so perfectly are the wheels be adapted to the locomotive. The effibalanced that if all the load be taken off, ciency of the steam turbine lies in its one of these great turbines will continue high speed. Locomotives may be reto revolve for two hours after the steam quired to attain high speed, but first they is turned off. By a steady pull to overcome inertia the huge mass

can be turned with a man's little finger.

The large size of the wheels in the Curtis turbine is one of the means of reducing speed to practical limits. Each wheel revolves in a separate chamber. Each has two rows of buckets on its periphery which bestride a stationary ring of buckets on the inner wall of the chamber. The steam, on being admitted through the nozzles in the wall of the chamber, acts on the first row of buckets, passes from this to the stationary ring, is deflected against the sec

INTERIOR OF SHELL OF A CURTIS STEAM TURBINE.

[graphic]
[ocr errors]

must start a heavy load by a slow pull speed of the turbine and how to change upon which their maximum power must the pitch of the propeller blades to adapt be exerted. But the very thing that dis- it to a swifter gait, and now steam-turqualifies the steam turbine for the loco- bine-driven ships are making wonderful motive makes it peculiarly serviceable for records. the development of electric energy. For The British Government built four generating an electric current, high speed cruisers exactly alike, equipping two with is required. Heretofore, it has been nec- the usual type of marine engines and two essary to drive dynamos with belts in with steam turbines, and set them to

steaming about to see what they could do. It was found that the turbine ships could make 1.9 knots an hour greater speed on 10 per cent less coal than the vessel with the old-style engines. In addition to their economy the turbine caused so little vibration that the vessels plowed through the water as quietly as a sailing ship.

Altogether the marine steam turbine has made so good a showing that the ultra conservative Cunard Company has let contracts for building two steamships, 800 feet long, larger

than any yet constructed, ROTARS ON SHAFT READY TO GO INTO 120-INCH TURBINE.

to be equipped with steam

turbines. These ships are order to get the speed; or, if the dynamos to have a speed of 26 knots an hour, were on the same shaft with the engine

two and half knots faster "direct connected,” it is called—it has than the swiftest vessels now in service. been necessary to have the revolving field. The Carmania, the first Cunarder very large in order to get the peripheral to be equipped with turbines, has been velocity needed. The problem with the able to develop a knot more speed steam turbine has been to reduce the than her sister ship, the Caronia, which speed sufficiently to use it in driving a has quadruple expansion engines, with 5 dynamo. The high speed of the steam per cent less weight of machinery and 15 turbine makes it practicable to have the pounds less steam pressure. The vibraelectric generator very compact and tion, as recorded by instruments, is explaced directly upon the shaft of the ceedingly slight. engine. As electricity is adapted to King Edward has been so impressed nearly everything nowadays, the useful- with the performance of the steam turness of the steam turbine is pretty wide. bine that he is having a yacht built which

In the marine field, in particular, the is to be provided with that kind of steam turbine has a great future. It took engine. lots of hard thinking to utilize the steam

Even the United States Government, turbine for driving a propeller, for at notwithstanding Admiral Melville's adfirst the thing went so fast that the water verse report two years ago, has decided thrown out by the propeller blades did to build two turbine ships. not have a chance to flow back again, and So successful has the steam turbine the wheel was left spinning impotently been on shipboard that already marine around in a hole in the water. Patient turbines of an aggregate capacity of 150,experiments showed how to reduce the 000 horsepower are in use, and one of the

[graphic]

or

а

« PreviousContinue »