Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGTOTAL VOLUMEAT TOO.il==:TOTAL VOLUMEAT B DC.A -START OF UPSTROKE(COMPRESSION OR EXHAUST)B-START OF OOWNSTROKE(POWER OR INTAKE)14.7-ONE-HALF CRANKSHAFT REVOLUTION -— TOTAL VOLUME (BDC)C-CYCLEDIAGRAMFigure 22-6.— Pressure-volume diagram, Otto 4-stroke cycle.54.19Bthe line represent compression. The bottomhorizontal line provides a means of representingcylinder volume and piston movement. Thevolume line has been divided into six partswhich correspond to the divisions of volumeshown in illustration A. Since piston movementand volume are proportional, the distance betweenO and 6 indicated the volume when thepiston is at BDC, and the distance from O to 1the volume with the piston at TDC. Thus, thedistance from 1 to 6 corresponds to total pistontravel and units of the distance may be used toidentify changes in volume resulting from thereciprocating motion of the piston.The curved lines of illustration C representthe changes of both pressure and volume whichtake place during the four piston strokes ofthe cycle. To conform to the discussion on therelationship of strokes and events (see fig.22-1), the cycle of operation starts with intake.552