Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts . does take place—often to an enor-mous extent, and always to an important degree—by which means the practical curve of expansion isusually raised to or above the hyperbolic curve, it follows that the latter practically represents allthe conditions better than the adiabatic curve; for which reason, and to secure simplicity, the hyper-bolic curve will be herein considered as the theoretical curve of expansion. For various reasons hereafter explained, it is desirable to lay down the theore
Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts . does take place—often to an enor-mous extent, and always to an important degree—by which means the practical curve of expansion isusually raised to or above the hyperbolic curve, it follows that the latter practically represents allthe conditions better than the adiabatic curve; for which reason, and to secure simplicity, the hyper-bolic curve will be herein considered as the theoretical curve of expansion. For various reasons hereafter explained, it is desirable to lay down the theoretical curve uponindicator diagrams for the purpose of comparing it with the indicated curve, and thereby ascer-taining the condition of the engine. This may be done in several ways, two of which will beexplained in connection with Fig. 2390. The first step is to lay down the perfect vacuum line Q ITat a distance below the atmospheric line df, by the scale of pressures equal to the barometric pres-sures at the time, or usually lbs. A perpendicular Q Qi should also be erected to lengthen the diagram, in the same proportion that the spaces in clearances and passages increase the capacity ofthe cylinder. For instance, if the clearances, etc., equal .07 of the displacement of the piston (or ofits area multiplied by the length of stroke), then Q R = .07 x R IT. If it be desired that the curve ofexpansion pass through a particular point of the indicated curve, z2 for instance, by multiplying thedistance of z2 from Q Qx in any scale by the total pressure at aa (viz., above Q U), the productwill be a constant which, divided by the distance of any vertical line from Q Qx in the same scalepreviously employed, will give the total pressure at the point where the theoretical curve crosses thatvertical line. For instance, QS x Sz2 -=- Q U= lTzu; and the points z10, z9, etc., may be found ina similar manner. There are many methods of laying down the curve graphically. The follow
Size: 2387px × 1047px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbenjaminpark18491922, bookcentury1800, bookdecade1880
