Thermal engines - Next-generation reciprocating engines

Reference is made to the fantastic diversity and creative ingenuity of engine manufacturers who have marked the country's technological history since the first industrial revolution [BM 2 593] . While many of these achievements now seem obsolete, the virtues of old concepts are being rediscovered and reappearing in the palette of new internal combustion engines. The opposed-piston engine, free-piston generators and the Wankel engine are all topical examples in the decarbonized energy context that characterizes the 21st century.

In this article, we focus on the new technological challenges and the associated energy mix that are driving innovation and progress in internal combustion engines, which in Europe now prohibit the use of hydrocarbons.

We refer briefly to two eminent contemporary French climate specialists, Jean Jouzel, who stated in May 2020 that "we need to completely change our approach to economic development and detoxify from fossil fuels". Valérie Masson-Delmotte also skilfully retraces the visionary genesis already imagined by a few scientists of the time, and unequivocally notes the worsening climate disorder.

The combination of internal combustion, electric and pneumatic engines with a range of alternative fuels, including biomass, dihydrogen and e-fuels such as ammonia and e-methanol, has become essential. These and other green fuels are in the spotlight in the 21st century.

There are five preferred routes for decarbonizing mobility: electricity, pure or additivated hydrogen, gaseous fuels such as biomethanization and its liquid and gaseous derivatives, biomass, synthetic fuels obtained by combining hydrogen with CO ₂ , which represent an alternative technological route in the making [BM 2 697] .

Innovative research and development work on e-fuels and second-generation biofuels should be highlighted, as they offer an alternative to hydrocarbons for piston engines, as well as for mobility applications that are difficult to electrify, such as the aeronautical and maritime sectors. The integration of decarbonated hydrogen in the production...