Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . in the theoreticalcurve. It will now be an easy matter to trace thecurve through these points. If, on the other hand, itbe desired to compare the curves toward the exhaustend of the diagram, draw lines E D and E T, Fig. 88,also T R, locating R near where release commences,after which draw line R D, completing the parallelo-gram E T R D, fixing R as a point in the theoretical DIAGRAM ANALYSIS 251 curve started at E. After drawing the diagonal T V,proceed in the same manner as before to locate thein
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . in the theoreticalcurve. It will now be an easy matter to trace thecurve through these points. If, on the other hand, itbe desired to compare the curves toward the exhaustend of the diagram, draw lines E D and E T, Fig. 88,also T R, locating R near where release commences,after which draw line R D, completing the parallelo-gram E T R D, fixing R as a point in the theoretical DIAGRAM ANALYSIS 251 curve started at E. After drawing the diagonal T V,proceed in the same manner as before to locate theintermediate points. It will be observed that in order to ascertain theperformance of the steam near the beginning of thestroke, the starting point of the isothermal curve mustbe near the point of release, and conversely, if thestarting point of the curve is located near the point ofcut off and coincident with the actual curve, the testwill apply towards the end of the stroke. It is not tobe expected that the expansion curve of any diagramtaken in practice will conform strictly to the lines of. figure 88. the isothermal curve, especially towards the latter endof the stroke, owing to the reevaporation of waterresulting from the condensation of steam which wasretained in the cylinder by the closing of the exhaustvalve. This reevaporation commences just as soon asthe temperature of the steam, owing to reduction ofpressure due to expansion, falls below the temperatureof the cylinder walls, and it continues at an increasing-rate until release occurs. The tendency of thisreevaporation or generation of steam within thecylinder during the latter portion of the stroke is to ENGINEERING raise the terminal pressure considerably above what itwould be if true isothermal expansion took terminal pressure may also be augmented by aleaky steam valve, while, on the other hand a leakypiston would cause a lowering of the terminal and anincrease in the back pressure. The Adiabatic Curve. If
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