Propulsion shafting vibration and exhaust emission gas derived from marine diesel engine are main subjects after development by Rudolf Diesel in 1893 until a recent date. Looking backward above two thesis are separately managed based on individual focused interesting without each other association because generally exhaust emission gas is focused on combustion process optimization.
It was came true quite a change for both high speed vessel and large vessel because of the change of global ocean market and worldwide ship transportation volume increasing. As a consequence marine diesel engine was changed with long stroke and fuel economic type and then both emission air pollution and vibration issue were keep in front not mechanical performance but environmental development subject.
Recently as appearance of electric control diesel engine, it was developed advantage marine diesel engine with eco-friendly, fuel saving, low vibration, low noise and finally low exhaust emission gas comparing conventional marine diesel engine during up to recent. Special regarding latest competed ocean market for propulsion ship and recognition change for global environmental issue, high efficient propulsion ship including marine diesel engine was appeared due to forced international legislation for the prevention of air pollution from ship like MARPOL 73/78 and US EPA. In the results both bigger propulsion ship and bigger marine diesel engine were designed and constructed to satisfy for environmental requirement and to get better fuel efficiency .
Therefore the new vessel main engine or retrofitted main engine of operating vessel are required applicable internal or external application strategies where former is increasing firing pressure, miller cycle like optimal combustion and latter is after treatment like using catalytic or particle filters. Within recent 10 years, retrofitted trend for main engine of operating vessel specially adopted slow steaming to reach both better fuel efficiency and environmental development through internal application like de-rating, low load tuning, turbocharger cut-off, dynamic cylinder cut-out, alternating firing deactivate and above applications mixture.
Eco friendly large marine diesel engine targeted better fuel efficiency via applicable internal measures has often big vibration influence at propulsion shafting system or large construction like gas receiver or wheel house due to increasing cylinder compression and firing pressure in the low load operating range. In case of direct coupled 2 stroke marine diesel engine operating whole range it was difficult to arrange propulsion shafting system due to large barred range relatively, limited performance of torsional vibration damper and coupling or misfiring.
In this paper, Nitrogen Oxides and vibration response characteristic for large 2 stroke marine diesel engine applying eco technologies for operating vessel in 4 different cases due to recently ultra-high oil price have been reviewed and are summarized as below.
First, exhaust NOx characteristic from operating vessel main engine adopted eco-friendly technologies according to international legislation is reviewed trade off common relationship between fuel consumption and NOx increasing with difference at load condition through NOx Technical Code 2008.
Second, torsional excitation change from main engine using emulsion fuel including 30% water comparing conventional HFO is reviewed. Used excitation from HFO determined applying for torsional vibration calculation because the excitation changes are disregard or lower.
Third, de-rating main engine adopted reducing cylinder number and increasing cylinder bore is reviewed for narrow barred speed range, higher torsional vibration level relatively. Specially the performance for torsional vibration damper within normal operating range is examined and suggested for function change.
Fourth, torsional vibration influence for conventional main engine adopted automatic exhaust valve closing adjustment with turbocharger cut-off is examined due to high torsional excitation and then reverse calculated torsional vibration for the propulsion shafting system.
Fifth, recently a respected turbocharger cut-off of the most effective methods in the slow steaming strategies for the operating vessel was presented a studying for vibration response characteristic at propulsion shafting system and then engine body, large construction like gas receiver and hull vibration response characteristic by second excitation through propulsion torsional vibration.