With a weight of 2300 tons and a height of 13.5 meters, the world's largest engine, why is the rated speed only 102 rpm?

At present, the propulsion system of modern large-scale civil ships is usually a two-stroke low-speed diesel engine, which is generally slow in speed and huge in size. Looking at medium and high-speed diesel engines, their volume is smaller than that of low-speed diesel engines. From the comparison of the two, we can see that the size of diesel engines seems to have a certain relationship with their rotational speed.

Today we will talk about whether the size of the diesel engine is related to its speed.

First of all, let's take a look at the difference between high, medium and low speed marine diesel engines. In marine diesel engines, the speed range above 3000 rpm is a high-speed diesel engine, 1500-3000 rpm is a medium-speed diesel engine, and below 1500 rpm is a low-speed engine; most low-speed diesel engines are two-stroke engines, and medium-speed diesel engines are four-stroke engines. All kinds of diesel engines use heavy oil as fuel, while high-speed diesel engines have both, and light diesel fuel is mostly used for fuel; in addition, low-speed diesel engines can directly drive propellers to work, while medium- and high-speed diesel engines drive propellers through gear reduction boxes.

Engines on large ships often weigh thousands of tons

After understanding the difference between them, let's analyze why ships use low-speed diesel engines. The efficiency of a ship is related to its propeller, the larger the diameter of the propeller, the lower the speed, the higher the efficiency. Earlier we mentioned that the low-speed diesel engine can directly drive the propeller to work, which means that the use of the low-speed diesel engine in the ship can save the gear reduction box and simplify the ship's propulsion system. As long as the speed of the low-speed diesel engine can match the propeller, the ship's propulsion can be greatly improved. The efficiency of the system, and the diesel combustion speed is slow, and the economy is higher.

piston

The speed of the propeller of the ship is generally around 600-800. The low-speed diesel engine should match this speed as much as possible from two aspects. One is to reduce the speed of the piston, but at the same time, in order to ensure the power of the diesel engine, it is necessary to increase the cylinder bore and increase the piston's speed. Effective area; the second is to increase the stroke of the piston without reducing the speed of the piston. For example, it is also a stroke of 200 meters. If a circle is exactly 200 meters, you only need to run one circle. If the circle is only 100 meters, then you need to run Run two laps, so increasing the piston stroke can effectively reduce the speed of the diesel engine.

4 story high engine

Whether it is to increase the cylinder bore or increase the piston stroke, it means that the volume and weight of the diesel engine also increase. At present, the world's largest marine diesel engine 14RT-flex96C is manufactured by the Finnish company Wärtsilä. It is 27.3 meters high, 13.5 meters high, rotates at 102 rpm, and has a total weight of 2,300 tons. It is mainly used for large container ships.

From the above point of view, the volume and weight of the diesel engine are closely related to the low speed.

Although most ships currently use diesel engines as power, some large destroyers do not use diesel engines. The large size is one of the reasons. After all, the land on the warship is expensive, and the equipment and materials are carefully considered. In addition, the diesel engine starts slowly. The acceleration is not good, and it is too noisy during operation, which is easy to be detected. Therefore, generally large destroyers use diesel engines as power, or they will be mixed with other power engines.