Design and construction of heat engines (Google eBook)

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McGraw-Hill, 1920 - History - 704 pages
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Page 136 - ... The expansion and compression curves are taken as hyperbolas, because such curves are ordinarily used by engine builders in their work, and a diagram based on such curves will be more useful to them than one where the curves are constructed according to a more exact law. In cases where there is a considerable loss of pressure between the boiler and the engine, as where steam is transmitted from a central plant to a number of consumers, the pressure of the steam in the supply main should be used...
Page 135 - Diagram Factor. The diagram factor is the proportion borne by the actual mean effective pressure measured from the indicator diagram to that of a diagram in which the various operations of admission, expansion, release, and compression are carried on under assumed conditions. The factor recommended refers to an ideal diagram which represents the maximum power obtainable from the steam accounted for by the indicator diagrams at the point of cut-off, assuming first that the engine has no clearance;...
Page 683 - Ordinary clay and dry sand mixed with clay 2 Dry sand and dry clay 3 Hard clay and firm coarse sand 4 Firm coarse sand and gravel 5 Shale rock 8 Hard rock..
Page 477 - ... solids. The elongation theory is employed by some writers of great authority on the subject of elasticity as confidently as if it were a statement of observed facts, and has been greatly developed in connection with the elastic properties of matter which is not isotropic. An addition to the .tenacity of a material, consequent on the application of a lateral tension, can, however, hardly be considered as intrinsically probable, and such direct experimental evidence as exists is against the supposition...
Page 104 - The frictional resistance is nearly proportional to the normal pressure between the two surfaces. 2. The frictional resistance is nearly independent of the speed for low pressures. For high pressures it tends to decrease as the speed increases.
Page 137 - ... and as such is what may be called the theoretical mean pressure. In an actual engine, however carefully designed and manufactured, there will be certain causes of loss of pressure, so that the actual indicator-diagram will show a mean pressure considerably less than that due to the initial pressure and the rate of expansion. The...
Page 325 - ... valve stem guide mechanism. The eccentric itself is a circular disk keyed to the shaft. E is the center of the eccentric and O is the center of the shaft. The eccentric is really a crank pin large enough to include the shaft. The distance OE is known as the eccentricity and corresponds to the distance from the center of the shaft to the center of the crank pin on a crank of the ordinary kind. In our diagrams we will usually represent the eccentric by the center line of the equivalent crank. When...
Page 129 - The Point of Cut-off. The term "cut-off" as applied to steam engines, although somewhat indefinite, is usually considered to be at an earlier point in -the stroke than the beginning of the real expansion line. That the cut-off point may be defined in exact terms for commercial purposes, as used in steamengine specifications and contracts, the Committee recommends that, unless otherwise specified, the commercial cut-off, which seems to be an appropriate expression for this term, be ascertained...
Page 344 - The curve is properly calibrated by drawing horizontals through these points, repeating them and subdividing the intervals as much as may be required. The curve shows that the force at the top, dead centre, is about 51 tons, and on the bottom centre 31 tons, that when the crank is at right angles to the line of stroke it is 10 tons ; in fact, the disturbing force for this particular cylinder is known for any assigned position of the crank belonging to it. 108. Derivation of...
Page 159 - ... low-pressure piston must be at the beginning of its return stroke. The steam in the receiver and high-pressure cylinder is now admitted to the other end of the low-pressure cylinder, its volume increases as shown in Fig. 290, and its pressure falls accordingly, as shown by the line EF, which is a part of the back-pressure line of the highpressure diagram, and the steam line of the low-pressure diagram. The pressure at F has already been found to be 22.2 pounds, and the terminal pressure at T...

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