What device is installed on the main engine to prevent the leakage of steam from the engine?

Labyrinth seals are specifically designed to prevent the leakage of steam and other fluids from the spaces where they are installed, such as around the main engine. These seals utilize a series of interlocking components that create a complex path, significantly reducing the pressure and flow of steam escaping from the engine. The design of labyrinth seals ensures that there are no direct openings for steam to escape, making them highly effective in high-temperature and high-pressure environments commonly found in steam engines.

In contrast, while options like O-rings, compression seals, and gasket seals can also be used in various sealing applications, they each have limitations. O-rings are typically effective in static and low-pressure applications, whereas gasket seals are generally employed between flat surfaces and may not perform as well under the extreme conditions found in steam applications. Compression seals are used in situations requiring flexibility, but could also allow for more leakage compared to the labyrinth design. Thus, labyrinth seals are the most suitable choice for preventing steam leakage in a main engine context.