Heavy 2 stroke engines - Fields of application and structural specific features

This article describes the technology of the heavy 2-stroke engine, also known as the "slow engine" or "cathedral engine", focusing on the state of the art to date, the result of almost 150 years of constant technical evolution.

The first part is devoted to the markets served by these engines, and the specific needs they meet. The main focus is on the propulsion of large ships of all kinds. Market volumes are described, as are the players in these markets: designers, manufacturers, equipment suppliers, customers and users. Some land-based applications in the form of generator sets exist, but are marginal and are not developed here.

It shows how the technical definition of these engines is driven by the demands of the maritime world, in terms of mechanical structure and performance: power, rotation speed, efficiency, emission levels. The energy transition is also mentioned, as it is currently at the heart of manufacturers' R&D activities. Prototypes are being studied, and some tested, to burn biofuels, methanol, ammonia or hydrogen. The intrinsic ability of these engines to burn all types of fuel, whether liquid or gaseous, is a factor that is accelerating the energy transition, while the obstacles lie more in the availability and logistics of the new fuels.

The second part of the article is devoted to a detailed description of the various components and subsystems of the heavy 2-stroke engine (block, combustion chamber, crosshead crankcase, electronic injection, supercharging, etc.), highlighting what makes them different from their equivalents in 4-stroke engines, which are better known because they are closer to automotive engines. In the chapter on electronic injection, the various current and future fuels are mentioned, along with their implications for design.

A glossary of terms is provided at the end of the article.