Principles of naval engineering - Historic Naval Ships Association

Chapter 22. -DIESEL AND GASOLINE ENGINES4 CENTRIFUGAL VALVESROTATING RESERVOIRPRIMARY ROTOR (IMPELLER:COLLECTOR RINGSECONDARY ROTOR (RUNNER)LUBE OIL FROM ENGINE 3 GPM - 10 PSILUB OIL RETURN TO ENGINE(GRAVITY)SCOOP TUBEPISTON VALVE CONTROL TUBE4 QUICK-EMPTYING PISTON VALVESFigure 22-44.— Scoop control hydraulic coupling.75.262interrupted and the oil in the control tubes willbe discharged through the orifice in the outerend of the piston housing. This releases thepressure on the piston and allows it to moveoutward, thus opening the port for rapid dischargeof oil. Resumption of oil flow from thescoop tube will fill the control tubes; and thepressure will move the piston to the closedposition.When the engine is started and the couplingis filled with oil, the primary rotor turns withthe engine crankshaft. As the primary rotorturns, the oil in its radial passages flows outward,under centrifugal force. (See arrows infig. 22-42.) This forces oil across the gap atthe outer edge of the rotor and into the radialpassages of the secondary rotor, where the oilflows inward. The oil in the primary rotor isnot only flowing outward, but is also rotating.As the oil flows over and into the secondaryrotor, it strikes the radial blades in the rotor.The secondary rotor soon begins to rotateand pick up speed, but it will always rotatemore slowly than the primary rotor because ofdrag on the secondary shaft. Therefore, thecentrifugal force of the oil in the primary rotorwill always be greater than that of the oil in thesecondary rotor. This causes a constant flowfrom the primary rotor to the secondary rotorat the outer ends of the radial passages, andfrom the secondary rotor to the primary rotorat the inner ends.The power loss in the hydraulic clutch issmall (3 percent) and is caused by friction inthe fluid itself. This means that approximately97 percent of the power delivered to the primaryrotor is transmitted to the reduction gear.The loss power is transformed into heat that isabsorbed by the oil— which is the reason forsending part of the oil through a cooler at alltimes.MAINTENANCEKeeping an internal combustion engine (dieselor gasoline) in good operating condition demandsa well-planned procedure of periodic inspection.593