Fig. 17 6th order vibration levels (%) of diesel power plant
5. CONCLUSION
In this paper, three methods to control and optimize X-mode vibration of 2 stroke low speed diesel engine for diesel power plant are introduced which can be summarized as the belows.
1) For diesel power plant using four sets of 12K90MC-S, uneven crankshaft arrangement was considered to decrease 5th, 6th X-moment most likable to be X-mode resonance. As the result, X-mode vibration was evidently decreased at synchronized speed, but 4th torsional resonance was almost coincident with generator synchronized speed which resulted in high torsional stress at crankshaft in one cylinder misfiring condition. To prevent this misfiring condition, torsional vibration monitoring system was provided.
2) For diesel power plant adapting one 9K80MC-S unit, to control X-mode vibration by dynamic vibration absorber was considered. As a result, though resonance of X-mode vibration is not exactly same as generator synchronized speed, vibration could be satisfactorily controlled. And if the stiffness of foundation is calculated/decided more delicately, dynamic vibration absorber can be more efficiently designed.
3) For diesel power plant adapting two 9K80MC-S units, the structural vibration of main engine and adjacent buildings were influenced on phase angle between two engine units. As a countermeasure, top bracing and synchrophaser were applied by which phase angle was controlled. The final and optimum phase angle was decided based on vibration measurement for engine and adjacent buildings.
Reference
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[3] D. C. Lee, B. W. Lee, U. K. Kim and H. J. Jeon. "X-mode vibration Vibration Controls of Large Two Stroke Low Speed Diesel Engine", APVC'97 (1997), p151.
[4] D C Lee B W Lee, U. K. Kim and H.J. Jeon, "Vibration Controls of Two Stroke Low Speed Diesel Engine for Large Scale Container Vessel" , ISME'95 (1995), p51.
[5] Hyundai heavy industries Engine and machinery division, Dynamic Characteristics and Performance of Tuning Torsional Vibration Damper for Hyundai-MAN B&W Two Stroke Low Speed Diesel Engine, MAN B&W Diesel A/S Meeting of Licensees (1993)
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