A Memoir of John Elder, Engineer and Shipbuilder, Glasgow

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University Press, 1883 - Marine engineering - 89 pages
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Page 70 - Perplext in faith, but pure in deeds, At last he beat his music out. There lives more faith in honest doubt, Believe me, than in half the creeds.
Page 15 - ... load. The useful work is, as before, the gross work done during expansion ; and, thus adjusted, the net useful work and the efficiency are nearly proportional to log, r. This conclusion is obviously true, whatever the value of n or the character of the expansion-line. Thus, as stated by Rankine, " the greatest useful work is obtained by making the expansion cease when the forwardpressure is just equal to the back-pressure, added to a pressure equivalent to the friction of the engine.
Page 20 - The remedy for this cause of loss is to prevent that spontaneous liquifaction of the steam during its expansive working, in which the process just described originates ; and that is done either by enclosing the cylinder in a jacket or casing supplied with hot steam from the boiler, or by superheating the steam before its admission into the cylinder ; or by both those means combined.
Page 19 - ... expands in a nonconducting cylinder, and during its expansion performs mechanical •work, its pressure falls — (1) On account of increase of volume; (2) because of liquefaction. The performance of work by the steam causes an equivalent loss of heat, and the amount of heat transformed into work, is sufficient, not only to lower the temperature of the steam to that corresponding to its reduced pressure, but also to cause liquefaction of a portion of it. When a small portion liquefies, it liberates...
Page 14 - ... back pressure, exerted by the steam " which has already done its work, and which the piston is expelling " from the cylinder ; and hence it follows that in order to realise the " greatest quantity of work which the steam is capable of performing " the expansion ought to be carried on until the forward pressure of the " steam behind the piston has fallen so low as to be just sufficient to
Page 42 - Company; and during many years' subsequent service the consumption of coal in those steamers was from two and one-half to three pounds per indicated horse-power per hour, a degree of economy never before realized in marine engines, amounting as it did to a saving of from thirty to forty per cent, of the coal previously burned by steamers of the same class.
Page 49 - The superior economy of fuel, as compared with indicated power, in the Constance is, of course, to be accounted for by a higher initial pressure and a greater rate of expansion than those used in the other vessels, combined possibly with better jacketing and greater superheating.
Page 23 - The advantage of employing the compound engine is connected with those causes which make the actual indicated work of the steam fall short of its theoretical amount, and also with the strength of the engine and its framing, the steadiness of action, and the friction of its mechanism.
Page 50 - D mechanism — in other v/ords, in economy of indicated power as compared with effective power — can be accounted for only by the comparative smallness of the friction in the engines of the Constance; and when it is considered that the engines of the Octavia...
Page 15 - ... falls below the pressure which is just sufficient to overcome the friction, the work done is no longer partly useful and partly wasteful, but is wholly wasteful ; whence it follows that, although in order to obtain the greatest indicated work from a given weight of steam the expansion should be continued until the forward pressure becomes just equal to the...

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