What is the difference between low-speed and high-speed Marine Diesel Engines?

Low-speed diesel engines are mostly two-stroke engines medium-speed diesel engines are mostly four-stroke engines, and high-speed diesel engines have both. The scavenging forms of low-speed marine two-stroke diesel include reverse scavenging and opposed piston air-intake scavenging. Large-capacity medium and low-speed diesel engines widely use heavy oil as fuel, high-speed diesel engines still mostly use light diesel oil.

Low-speed marine diesel engines directly drive the propeller. In order to achieve high propulsion efficiency of the prop, a lower speed is required. Medium and high-speed diesel engines drive the propeller through a gear reducer. The gearbox is also generally equipped with a reverse mechanism to reverse propeller rotation, but low-speed diesel engines and some medium-speed diesel engines can reverse by themselves. Medium and high-speed diesel engines can also achieve electric transmission generators, motors, and propellers.

Low-speed marine diesel engines have the advantages of large power, high efficiency, long life, good reliability, and simple operation and maintenance They are the main propulsion power for ocean-going ships and are mainly used for ocean-going cargo ships, oil tankers, and container ships from 2000 to 500,000 tons. According to statistics, 90% of the world's maritime traffic is driven by low-speed engines. Medium- marine diesel engines are mainly used for fishing boats, cargo ships, tugboats, and auxiliary machinery for ocean-going ships. High-speed marine diesel engines are mainly used forachts, official boats, leisure fishing boats, small transport boats, pumps, auxiliary machinery for power generation, and compressors, etc.