An Elementary Treatise on Steam and the Steam-engine, Stationary and Portable (being an Extension on the Elementary Treatise on Steam of Mr. J. Sewell)...

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C. Lockwood and Company, 1885 - 344 страници
 

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Страница 88 - Te-r part of the pressure at 0" Fahr. for each degree of temperature acquired. Adding 461° to the indicated temperature, the sum, or absolute temperature, varies directly as the total pressure. In brief, 1st, the pressure varies inversely as the volume when the temperature is constant ; 2nd, the volume varies as the absolute temperature when the pressure is constant ; 3rd, the pressure varies as the absolute temperature when the volume is constant. The foregoing enunciation of the relations of temperature,...
Страница 192 - ... and if isolated from air it continues to be invisible and perfectly colourless, like air, but it appears in the form of an opaque-white cloud when first mixed with air, and continues to be visible until it has been dissolved in the air. If a teakettle boils violently, so that the steam issues from the spout in great abundance. it may be observed that the visible cloud is not formed at the very mouth of the spout, but at a small distance before it, when it begins to mingle with the surrounding...
Страница 322 - ... working boilers, the cylinders being purposely set at such a level relatively to the boilers as to allow of this continued circulation by mere gravitation, which is not interfered with by the working of the engine, continuing to act during the intervals of work or as long as steam remains in the boiler. The speed of the engine is regulated by an adjustable cataract : the exhaust valve first and then the steam valve are thrown open by treadle weights, as soon as the catches are detached by the...
Страница 24 - Locomotive, 1688. cock, is mounted " upon little wheels, so as to move easily upon a horizontal plane ; and if the hole be opened, the vapours will rush out violently one way, and the wheels and the ball at the same time will be carried the contrary way.
Страница 267 - ... continues to fall, and the temperature of the steam with it, the curve rises and crosses the normal curve at C in virtue of a partial reevaporation of the steam previously precipitated, caused by the cylinder itself, which, at first colder than the steam, and heated by it in the first stage of the expansion, becomes then relatively hotter, and partially restores the heat of which it had previously robbed the steam. The process of restoration of heat goes on to the end of the expansion, as further...
Страница 131 - ... and the remainder of the tubular surface absorbs it by radiation from the passing gases. Convection. Convection or carrying is the power possessed by fluids of conveying heat acquired at one place to another place. In boilers the heat is thus transmitted amongst the water. In the furnace the air carries the unabsorbed heat to the chimney. When the power of convection is much greater than the power of absorption, then the heat evolved during combustion is carried off without producing its proper...
Страница 269 - ... it allows time for its escape before the piston returns upon it. At the higher speeds, however, the escaping steam may be overtaken and driven before the piston into the atmosphere, should its remaining elasticity prove insufficient, and then an opposing back pressure is established. The wider the lead for the exhaust the less is the back -pressure, on account of the increased facility for escape. For the usual speeds of pistons of stationary engines — from 220 to 300 feet per minute — the...
Страница 144 - Smoke, partly invisible and partly incombustible. Steam is formed from the hydrogen gas given out by the coals combining with its equivalent of oxygen from the air, in the ratio of 2 volumes of hydrogen to 1 of oxygen, or by weight as 1 to 8, as already explained. Carbonic acid is formed from the carbon of the coals combining with its equivalent of oxygen from the air, in the proportion of 2 volumes of oxygen to 1 volume of carbon, or by weight as 16 to 6. Carbonic oxide...
Страница 265 - ... is sufficient. When the lead is excessive, the steam is admitted so readily as to be momentarily compressed, and to cause, in some cases, an unfavourable pulsatory action of the steam. The total absence of lead likewise occasions an unsteady pulsatory action in the cylinder. If lead is deficient or wanting, the maximum pressure of steam in the cylinder is not attained until after a portion of the stroke is traversed by the piston.
Страница 132 - ... 1'279 cubic feet of air 1° per minute, when it is in contact with the glass. Reflecting Power. The reflecting power of different bodies is generally estimated as being inversely as the radiating power, so that if brass reflects 100 parts of heat, silver would reflect 90, and with these others as they stand below. Brass 100 Silver 90 Tinfoil 85 Block tin 80 Steel 70 Lead 60 Tinfoil, softened by mercury 10 Glass 10 Glass, coated with wax 5 Specific Heat. The specific heat, or the comparative capacity...

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