Marine Engineering Systems and Machinery
Machinery and systems
Marine propulsion is dominated by slow-speed two-stroke diesels directly coupled to the propeller, with medium-speed four-stroke engines used through gearboxes. Key quantities are MCR, continuous service rating, specific fuel consumption in g/kWh, scavenging and turbocharging, and the propeller law. Support systems include fuel treatment (settling and service tanks, separators, viscosity control for heavy fuel oil, changeover to distillate in emission control areas), lubricating oil, central cooling with sea-water and fresh-water circuits, compressed air, bilge and ballast, exhaust gas economisers and boilers. MARPOL Annex VI covers NOx tiers, sulphur limits, EEDI and SEEMP.
Traps
Distinguish SFOC in g/kWh from fuel rate in kg/h; multiply by power first. Engine margin and sea margin are separate allowances. Include auxiliary engine and boiler fuel when total consumption is requested. Two-stroke engines are typically more efficient at high load but need compatible fuel viscosity and treatment. Do not confuse MCR with normal continuous rating.
Worked example
A 10,000 kW engine at 175 g/kWh burns 10,000 × 175 = 1,750,000 g/h = 1,750 kg/h = 1.75 t/h, or 42 t/day. Rule of thumb: tonnes per day ≈ kW × g/kWh × 24/10⁶; here 10,000 × 175 × 24/10⁶ = 42 t/day.