. American engineer and railroad journal . ilable pressure for the different speeds,and by this we mean the mean effective pressure, with thefriction of the engine deducted, or the net effective pressureon the pistons. Diagram No. 2 of the Master Mechanics Association reportabove mentioned [this diagram is reproduced here as Fig. 3,and Fig. 1 from the same report is reproduced as Fig. 4. Theywill be found also in our issue of July, 1897, page 251.—Editor]gives the ratio of mean effective pressure to initial pressurefor various speeds and cut-offs, and allowing in addition 5 percent, drop from
. American engineer and railroad journal . ilable pressure for the different speeds,and by this we mean the mean effective pressure, with thefriction of the engine deducted, or the net effective pressureon the pistons. Diagram No. 2 of the Master Mechanics Association reportabove mentioned [this diagram is reproduced here as Fig. 3,and Fig. 1 from the same report is reproduced as Fig. 4. Theywill be found also in our issue of July, 1897, page 251.—Editor]gives the ratio of mean effective pressure to initial pressurefor various speeds and cut-offs, and allowing in addition 5 percent, drop from boiler pressure to initial pressure, and 8 percent, for engine (internal) friction, we have the results of thediagram multiplied by 0, , with which to con-struct the line B-B, which shows the maximum mean availablepressures which can be obtained at the various speeds. Thisallows for the internal friction of the engine, but not for thejournal and rolling friction. It is to be noted, that a strict interpretation of the line. Miles p«r hour to Fig. 1. d=evaporation rate under the assumed conditions, from andat 212 degrees. Then the maximum quantity of steam which the boiler cansupply in pounds per hour, =vxbxcxd, from and at 212 degrees. (The values of these factors under different conditions maybe obtained from the report on Grate Area and Heating Sur-face, made last year to the Master Mechanics Association,see page 218 of the proceedings for 1897.) Let x=cut-off ratio in the cylinders;y=rrevolutions per minute; a=weight in pounds of a cubic foot of steam at cut-offpressure;then, allowing for the factor of evaporation (from 212 de-grees to working pressure), and 25 per cent, for cylinder con-densation, we have the weight of steam used per hour, inpounds; = vXxX2XyXaXl-2X 1-25 X 60, from and at 212 deg. Fig. 2. A-A of maximum cut-offs, would require the left-hand end tobe slightly dropped, as at slower speeds, the cut-off pressureand weight of steam would be
Size: 2546px × 982px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
