Diesel Engine Crankshaft Rotational Speed Fluctuation Analysis

Crankshafts drive many accessories such as fuel injection pumps, camshafts, oil- and water pumps, compressors, fans, alternators etc. by using either gears or belts. Since crankshaft rotational speed fluctuates and engine accessories have moments of inertia, belts slip on pulleys and gears hit other gears, which results in noise and wear. This paper describes the mechanism of the rotational speed fluctuations of crankshafts by separating rotational speed fluctuations into those for a rigid and those for a torsional crankshaft for a V-type six-, eight- and ten-cylinder diesel engine. After that, crankshaft rotational speed fluctuations at crankshaft locations are discussed.