柴油机培训资料Chapter5Theory.ppt

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Engine oiling Oil pumps Driven by distributors, gear on camshaft, or crankshaft Engine oiling Oil pumps with pressure relief valves Gear type pump Rotor type pump Engine oiling Full flow oil filtering system Oil pump output flows through filter first Bypass circuit for restricted filters will allow oil to flow to engine Engine oils API, SAE, and ASTM “S” - Spark ignition “C” - Compression ignition Engine oil additives Viscosity index improvers To reduce viscosity change with heat Detergents To dissolve varnish and sludge Dispersants To keep sludge, carbon and other materials from recombining and suspends them in oil to be drained Scuff inhibitors To reduce friction and wear Antifoam and antioxidants To prevent foaming and to slow oxidation in oil Engine measurements Bore Diameter of cylinder Stroke Distance between TDC BDC Engine measurements Displacement per cylinder ? r2 S Displacement for the engine Disp per cylinder times the Number of cylinders Engine measurements Compression ratio D + CV CV To calculate clearance volume D . CR-1 Engine measurements Deck clearance Top of piston to top of block deck Measured with dial indicator or depth mic Engine measurements Deck height Center line of crank to block deck Fits and clearances Running fit Clearance between bearing and shaft Clearance for oil Listed as diametral Fits and clearances Interference (press) fit OD is larger than ID Example is piston pin pressed into rod Fits and clearances of pistons Full floating .0003 - .0005 clearance in rod .0001 - .0003 clearance in piston Oscillating .0008 - .0012 interference in rod .0003 - .0005 clearance in piston Rod offset Beam offset to center of cylinder Enlarged chamfers to clear fillets Pin offset Offset to major thrust side Quieter engine, less cylinder wear Cooling sys