. Annual report of the American Institute, of the City of New York. Science. POLYTECHNIC ASSOCIATION: 831 Suppose, for instance, the steam is cut off at mid stroke, the diagram of work will be such as is here shown : The rectangle cor- responding to the work of the second half stroke is reduced by the area C H H', but the remaining area, CBY IP, still exceeds the triangle P B C, which repre- sents the work of the first half stroke. Let, now, through the point, B; another line be drawn, as P' B Y', and suppose such a weight given the reciprocating parts of the engine that P' O may suffice to im
. Annual report of the American Institute, of the City of New York. Science. POLYTECHNIC ASSOCIATION: 831 Suppose, for instance, the steam is cut off at mid stroke, the diagram of work will be such as is here shown : The rectangle cor- responding to the work of the second half stroke is reduced by the area C H H', but the remaining area, CBY IP, still exceeds the triangle P B C, which repre- sents the work of the first half stroke. Let, now, through the point, B; another line be drawn, as P' B Y', and suppose such a weight given the reciprocating parts of the engine that P' O may suffice to impart to them the neces- sary initial acceleration, then PP'BC will be the diagram of work for the first quadrant, and CBY' II' the corresponding diagram for the second quadrant. It is obvious that such a position may be found for P' Y' as to make these two diagrams equal. It is to be noticed, however, that if we wish the engine to perform, when worked with cut-off, the same amount of work which we have supposed it to perform when working with full head of steam (viz.: that represented by the rectangle P O G II), the initial pressure will have to be increased to a degree which is a function of the part of stroke performed before cut-off. And as it is usual to compute roughly the work of expansively working engines by means of hyperbolic logarithms,* we may find the pressure P, which would do * If it were important to the object of this inquiry that the elastic force of expand- ing' steam, and the work done during exhaustion, should be very exactly stated, it would hardly be proper to depend, in this part of the investigation, upon the hyper- bolic theory, or the law of Marriotte. The formula of Poisson for expanding gases, viz.: though not strictly true of vapors which, like steam, partially condense during exhaustion, would give results nearer the truth. Pambour's formula, now generally accepted, is the formula of Marriotte, with a negative term annexed, increasing with the exh
Size: 1821px × 1373px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecad, bookpublisherslsn, booksubjectscience
