The article describes heavy 2-stroke engine technology, also known as slow engine or cathedral engine, focusing on the state of the art to date, which results from nearly 150 years of constant technical development.
The first part is devoted to the markets served by these engines, and to the specific needs to which they respond. It’s basically the propulsion of large ships of all kinds. Notions of market volume are given as well as the players in these markets, designers, manufacturers, equipment manufacturers, customers and users. Some terrestrial applications in the form of generators exist but are marginal and are not developed here.
It is thus revealed how the technical definition of these engines is driven by demand from the maritime world, in terms of mechanical structure and performance: power, rotation speed, efficiency, level of emissions. The energy transition is mentioned since it is currently at the heart of manufacturers’ R&D activities. Prototypes are being studied, some being tested, to burn bio-fuels, methanol, ammonia or hydrogen. The intrinsic capacity of these engines to burn all types of fuel, liquid or gaseous, is an accelerating factor in the energy transition, the brakes lying more in the availability and logistics of new fuels.
A second part of the article is devoted to the detailed description of the various components and subsystems of the heavy 2-stroke engine (block, combustion chamber, cross-link assembly, electronic injection, supercharging, etc.) by noting what makes them original by compared to their equivalents in 4-stroke engines, better known because they are closer to automobile engines. In the chapter devoted to electronic injection, the various current and future fuels are cited with their implications for the design.
The reader will find a glossary of terms used at the end of the article.