The heart of a large ship is its main engine. The ship diesel engine market focuses on these propulsion units, which can be as tall as a four-story building.
Direct Drive vs. Diesel-Electric
The [LSI keyword: ship diesel engine market] for large vessels (container ships, tankers, bulk carriers) uses direct drive: the engine's crankshaft is connected directly to the propeller shaft. No gearbox. The engine speed is low (50-250 rpm), matched to the propeller's optimal speed. The ship diesel engine market for direct drive is the largest. For vessels with variable speed requirements (ferries, icebreakers, offshore supply vessels), the ship diesel engine market uses diesel-electric propulsion: diesel engines drive generators; electric motors drive the propeller(s). The ship diesel engine market for diesel-electric is growing, as it allows multiple engines to be operated at optimal load, and the electric motor can provide high torque at zero speed (for maneuvering). The ship diesel engine market for "azimuth" thrusters (pods that rotate 360 degrees) is also growing; they are diesel-electric or integrated with a diesel engine.
The ship diesel engine market is segmented by engine speed. Low-speed (2-stroke) are the most efficient (specific fuel consumption as low as 160 g/kWh). The ship diesel engine market for low-speed engines is the largest. Medium-speed (4-stroke) are used in smaller ships and for diesel-electric. The ship diesel engine market for medium-speed is stable. High-speed (4-stroke) are used in fast ferries, patrol boats, and yachts. The ship diesel engine market for high-speed is the fastest-growing.
Scavenging and Turbocharging
The ship diesel engine market for two-stroke engines uses crosshead design (the piston rod is connected to a crosshead, which is connected to the connecting rod, separating the cylinder from the crankcase). This allows the use of low-quality residual fuel (which has high sulfur and ash content) without contaminating the crankcase oil. The ship diesel engine market for "turbocharging" (using exhaust gas to drive a compressor that blows air into the cylinders) is standard, increasing power output and efficiency. The ship diesel engine market for "scavenging" (clearing exhaust gases from the cylinder) can be uniflow (air enters at bottom, exhaust at top) or loop (air and exhaust flow in loops). Uniflow is more common. The ship diesel engine market for "electronic" control of fuel injection (common rail) and exhaust valves (Miller cycle) is standard on modern engines.
As the ship diesel engine market continues to evolve, the focus will be on reducing NOx (through exhaust gas recirculation – EGR, or selective catalytic reduction – SCR), on reducing SOx (through using low-sulfur fuel or scrubbers), and on reducing CO2 (through efficiency improvements and alternative fuels). The ship diesel engine is a masterpiece of mechanical engineering, and it continues to improve.
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