On the Development and Transmission of Power: From Central StationsLongmans, Green, 1894 - 312 páginas |
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adiabatic air mains air motor alternate current atmospheric boilers brake cable cent central station coal compressed air compressors condensing conductors constructed cost cubic feet curves destructor direct current discharge distance driving dynamos effective h.p. hour efficiency energy erected expansion fall feet per second flow friction fuel full load gas engines Geneva h.p. per annum heat hydraulic i.h.p. hour impulse turbines inches in diameter Indicated h.p. indicator diagram jacket leakage lighting gas Lord Armstrong loss of pressure low pressure machinery mechanical mechanical efficiency Messrs miles motive power NON-CONDENSING obtained ordinary P₁ Paris Pelton wheel pipes piston pound power purposes pressure turbines pressure water Professor Riedler pulleys pumping quantity re-heated reservoir revolutions per minute Rhône river rope Schaffhausen shaft sluices speed square inch steam engine steam power storage stored stroke supply temperature town transmitted utilised valve varying volts waste water power wheel Zürich
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Página 233 - The reason of this is that the heat supplied to the air is used nearly five times as efficiently as an equal amount of heat employed in generating steam. In certain cases the air-motor cylinder has been jacketed by hot air. This increases again the amount of work obtained per pound of air used. It can hardly be considered a thermodynamically advantageous process, but it may have advantages practically in raising the exhaust-temperature.
Página 243 - If the air is used oold the power obtained will be as follows : — If the air is reheated to 300° Fahrenheit as assumed in the previous case — Here the efficiency of the whole arrangement— calculated on the indicated power, the air being delivered at a distance of 20 miles, and including all losses — is 40 to 50 per cent. if the air is used cold, and 59 to 73 per cent. if the air is reheated. The results are based absolutely on efficiencies already obtained in similar cases, and the sole...
Página 222 - Loss of Pressure per Mile of Pipe. — In order to indicate what kind of results this formula leads to, the following cases have been calculated. 1. Given the diameter of the pipe, and the initial pressure and velocity of the air entering the main, it is required to find the loss of pressure in 1 mile of transmission. By simple transposition, putting L = 5,280...
Página 239 - As to the efficiency of the process of compression, this varies greatly with the type of compressor. In some of the older singlestage compressors it is as low as 0-5. But taking the best of those tried by Professor Riedler and slightly rounding off the values — For single-stage compressors . . . i/2 = 0 • 7 „ two-stage „ . . . i/2 = 0-9 The loss in the main must be calculated for each special case.
Página 235 - In the later machines, arranged to work expansively, the efficiency ranges from 0 - 58 to 0 - 87, results remarkably good for motors so small. The coefficients are rather higher with reheated air, showing that the work done is increased even in a rather higher ratio than T3/T2.
Página 7 - Its full effect was only gradually felt, and water continued to be economically the better agent during the first quarter of the nineteenth century; but eventually as a consequence of Watt's invention, water-falls became of less value. Instead of carrying the people to the power, employers found it preferable to place the power among the people at the most convenient trading centres.
Página 233 - It was using about 31,000 cubic feet (reckoned at atmospheric pressure) or about 2,376 pounds of air per hour. This air was heated to a temperature of about 300° Fahrenheit by the expenditure of only 15 pounds of coke per hour. On a favourable assumption a steam-engine working to the same power would have required ten times this consumption of fuel at least.
Página 233 - Prof. Riedler tried an old 80 horse-power steam engine in Paris which had been adapted to work as an air motor, and which was actually giving 72 indicated horse-power with compressed air at 5% atmospheres.
Página 218 - Eeduced, as shown in the last line, the results are consistent if it is assumed that the leakage was really greater in the sections included in I, II, and IV than in the other sections. Now, with an initial gauge-pressure of 6 atmospheres and an initial velocity of 30 feet per second, the main would deliver about 600,000 cubic feet of air per hour, reckoned at atmospheric pressure. Then the percentage of loss by leakage per mile per hour would be as follows: Per cent~| I.