Steam Gauge
an instrument at tached to a boiler to indicate the pressure of steam. There are many varieties. into the cylinder above the piston. The admission of steam into the cylinder 's regulated by a side valve worked by a lever, and the force of the stroke can be controlled to such an extent by regulating the admission of steam, that the largest hammer can be made to crack a nut, or to come down on a mass of iron with a momentum of many hundred foot tons. The weight of the hammer ranges from about 200 pounds to 25 tons; and the object to be struck is placed on an anvil consisting of a slab of iron resting on a huge mass of piles and concrete, which frequently descends a great depth STEAM HAMMER STEAM TURBINE into the ground. There are numerous impact of particles of steam upon a mov other forms.
STEAM NAVIGATION. In 1815 a steamboat made a passage from Glasgow to London, and in 1818 one plied from New York to New Orleans. In 1819 the "Savannah," an American vessel of 380 tons burden, with side wheels, built at Corlear's Hook, N. Y., by Crocker and Fickett, made the first trip by steam across the Atlantic, sailing from the United States to England and thence to St. Petersburg. At Liverpool she made a great sensation, being mistaken at one time for a vessel on fire. Canvas was able vane.
The next invention on these lines, after Branca's, was that of Wolfgang de Kempelen, who produced a reaction turbine in the year 1784, James Watt constructing a similar machine almost simultaneously. It was not, however, until the comparatively recent date of 1883 that the steam turbine received practical application. In that year De Laval designed a turbine which he used to turn an early model of the cream separator which is still associated with his In his machine, which is of the name. impulse type, a specially constructed used during the last part of the voyage, nozzle causes a jet of steam to impinge because after about 12 days out the engine had consumed all the coal which could be carried. There was no room for cargo when she was stored with coal.
It was not till 1820 that steam packets were established between Holyhead and Dublin. The year 1838 is memorable in the history of steam navigation. The steamer "Sirius" sailed from Cork on packets April 4, the "Great Western" from Bristol on the 8th of the same month, both arrived in New York on the 23d, the "Sirius" being only 12 or 14 hours ahead of the "Great Western," the latter having made the trip in about 14 days. The passage is now often made from Queenstown to New York in less than five days. The opening of the Suez Canal greatly promoted swift steam communication with India, China, and the East, and Australia. Steam vessels are now to be found on all seas and lakes and navigable streams. See STEAMBOAT; SHIP AND SHIPPING.
STEAM TURBINE. The principles underlying the steam turbine are very simple, much more so, indeed, than those of the reciprocating engine. It is, therefore, not surprising that turbines of a single and crude type were invented very early in history. The first steam turbine is believed to have been constructed by Hero of Alexandria, in the year 120 в. c. He boiled water in a cauldron, caused the steam to pass through pipes to two jets, fixed at opposite edges of a disc, the jets being turned at right angles to the plane of the disc and in opposite directions. The force of the escaping steam caused the disc to revolve. Nearly eighteen hundred years later, in 1629 A. D. Branca turned a wheel by impinging a jet of steam on to paddles fixed to the circumference. These two simple turbines illustrate the two types now in use the reaction turbine and the impulse turbine, motion being produced in the former by the reaction of steam escaping from an orifice, and in the latter by the on to buckets arranged on the rim of a revolving cylinder. The velocity of the steam is very high, as much as 2,500 feet per second, and the cylinder revolves at from 10,000 to 30,000 revolutions per minute, the higher speed being used in machines of smaller size. Owin machines of smaller size. Owing to this high velocity, this type of turbine is not used for marine engines, but finds a common application for driving dynamos.
C. A. Parsons, of England, built the first large turbine in 1884. This was capable of producing about 10 horse power and made use of both the impulse and the reaction principle. It consisted of a cylindrical case, containing a shaft or spindle, the diameter of this spindle being less than the internal diameter of the cylinder. An annular space was thus left between the two. On the inside of the cylindrical case were numerous rings of inwardly projecting blades, while, on the shaft, were mounted corresponding outwardly projecting blades. These two sets of blades occupied the space between the cylinder and the spindle. When steam was admitted it met a ring of fixed blades on the wall of the cylinder. These blades deflected it in such a manner that it impinged upon the corresponding blades of the spindle, and imparted to them a rotary motion. The diameter of the cylinder increased in successive stages toward the exhaust. The blades in the first few rows are of copper, the others of a special brass alloy. The Curtis turbine is similar to the Parsons, but depends upon the impulse principle, steam being admitted through a series of nozzles. The steam is expanded almost to exhaust pressure in the nozzles, so that there is no appreciable difference of pressure between the front and back end. It follows that the end thrust, which has to be taken care of in the Parsons turbine, is almost entirely avoided in this engine. Moreover, owing to the expansion of steam in the STEAM TURBINE nozzles, the front blades are not subjected to the action of superheated steam and so do not require to be constructed of special metal for resisting high temperatures. Regulation of speed is obtained by closing one or more nozzles.
Other types of turbine are the Riedler- Stumpf, the Rateau, the Melins and Pfenniger, the Schulz, and the Zölly.
While each one has its special features , they all follow the general principles outlined above. As an indication of the speed at which the shafts run in different engines, the following figures may be taken as representative. The velocity of the tips of the rotating blades in the Parsons turbine is 100-150 feet per second at the front end, and at the back end, where the diameter of the shaft increases, 300-350 feet per second. In the Rateau, the speed is 350-400 feet per second, and in the Curtis a little higher.
On the other hand, the buckets in the De Laval and the Riedler-Stumpf turbines reach a velocity of 1,000 feet per second.