A type of engine that has evolved in Japan distinct from mainstream design principles - nicknamed the ‘Galapagos engine’ after the island home of several uniquely evolved species - has been updated to develop a new modern engine.
Unlike other four strokes, Galapagos eninges are low-speed. They are therefore simpler than other four-stroke engines in a similar power range because they drive the propeller directly without a reduction gear. They can also use lower quality fuel than other four-stroke engines, while the slow speed gives greater engine stability and longer life of components. Although they are also big and heavy relative to their power output, their virtues have found a niche with domestic Japanese bulk carrier, oil tanker and fishing vessel owners.
Japanese enginebuilder Niigata used design concepts nomally found in medium-speed engines to improve on the engine design, the company’s representative Tatsuya Kitajima told delegates at CIMAC World Congress this week. The design has increased the compression ratio and maximum cylinder pressure by lengthening the engine stroke, deploying a turbocharger with a high pressure ratio turbocharger and high-pressure fuel injection, and optimising intake and exhaust timings.
Uniquely for low-speed engines, the resulting 6M34RT deploys a hanger bearing design which enables a reduction in the size of the engine, allowing it to be mounted in the same space as other conventional engines with a similar power output. The new engine will be designed for IMO Tier II NOx limits and will also aim to minimise smoke, noise and oil mist.
The resulting Niigata 6M34RT engine has a 340-mm bore, a stroke of 630 mm and rated output of 1,471 kW. It will be commercially available from next year.