Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGSEA WATER INLETEXHAUSTfflIDINLET PIPEFLEXIBLEPIPEEXHAUSTSILENCER^:*P> EXHAUST ANDSEA WATEROUTLETIBiOWATER LINEWATERJACKETOVERBOARDDISCHARGEEXHAUSTMAN! FOLDAIR INTAKEPORTSTAKESILENCERAIRBOXAIRSCREENFigure 22-20.-Air systems of a 2-stroke cycle engine.75.151Xis called scavenge ( or scavenging ) air and theports through which it enters are called scavengeports .The process of scavenging must be accomplishedin a relatively short portion of the operatingcycle; however, the duration of the processdiffers in 2- and 4-stroke cycle engines. In a2-stroke cycle engine, the process takes placeduring the later part of the downstroke (expansion)and the early part of the upstroke (compression).Ina4-stroke cycle engine, scavengingtakes place when the piston is nearing and566