Low Speed 4-stroke Diesel Engine

About Low Speed 4-stroke Diesel Engine

This is an engine that carries out one cycle consisting of intake, compression, combustion, and exhaust, for 2 crankshaft revolutions, or 4 piston strokes.

The low speed 4-stroke diesel engine tends to have larger external dimensions than medium and high speed engines. However, it can exhibit outstanding ease of handling and reliability.

With improvements in the propulsion efficiency of propellers in recent years, the transition to even lower speeds of revolution are progressing, thus enabling these engines to have a longer stroke.

As their name indicates, low speed 4-stroke diesel engines have a lower speed of revolution than medium speed engines.

Therefore, there are cases where they may be equipped with an intermediate reversing gearbox or CPP, but they can basically be directly connected to a propeller.

On the other hand, medium speed engines have a high revolution speed , so they must be connected to a propeller via a reduction gearbox to lower their revolution speed.

Advantages

One advantage of the low speed 4-stroke diesel engine is a reduction in engine revolution speed due to the longer stroke. High thermal efficiency is achieved by the lower revolution speed which provides a sufficient combustion period, and the longer stroke which provides a larger combustion space. The lower revolution speed leads to a reduction in sliding frequency, and the elimination of the need for a reduction gearbox decreases the number of parts, allowing it to attain high reliability. This high reliability can reduce the frequency of failure, extend the maintenance interval, and achieve a low running cost due to a decrease in the number of parts for replacement.

Life cycle cost

Compared to a medium speed diesel engine, the low speed 4-stroke diesel engine is larger in size which leads to a higher engine price.

Since it does not need a reduction gearbox, the price of the stern will be lower, but the initial cost will still be higher than a medium speed diesel engine even with a reduction gearbox.

However, due to the low running cost, which is an advantage of the low speed 4-stroke diesel engine, it can result in a higher cost advantage the longer the period it is used, such as 5, 10, or 15 years.