Development of Next-Generation Engines as a Component of Society

Engines, starting with automobiles, are used in various applications, and the performance required of them is diverse. The ideal "ultimate engine" is not only one that can produce high output with less fuel but also, and importantly, one whose exhaust gases do not harm the environment.

At the Iida Laboratory at Keio University, we are exploring the future of engines by analyzing combustion through computer-based combustion simulations and combustion experiments using experimental apparatus.

Currently, we are focusing on research and development of ultra-lean premixed compression ignition engines that achieve higher efficiency than gasoline and diesel engines.

Ashley classifies engine combustion using the matrix shown in Table 1. He categorized the ignition method into "spark ignition" and "compression ignition," and the formation of the fuel-air mixture into "homogeneous" and "heterogeneous."

A gasoline engine is a combustion system where a homogeneous premixed gas is supplied to the combustion chamber, combustion is initiated by "spark ignition," and it undergoes "flame propagation combustion." A diesel engine is a combustion system where fuel is injected into compressed, high-temperature, high-pressure air, and it undergoes "spray combustion," where the fuel spray "ignites" and "burns" during the process of evaporation, diffusion, and mixing in the air.

The HCCI engine is based on "premixed charge compression ignition," which is known as the third type of combustion. It is an engine where air and fuel are premixed, introduced into the combustion chamber, and then ignited and burned by piston compression. This combustion method allows for ignition and combustion even with a premixed gas that was traditionally considered impossible to burn through flame propagation. It can burn even a premixed gas with a low fuel concentration (ultra-lean) or a premixed gas diluted with a large amount of EGR gas (ultra-diluted). Low-temperature combustion is achieved, and harmful exhaust gases such as nitrogen oxides (NOx) and soot (PM) are not produced during the combustion process. Low-temperature combustion can prevent heat from being lost through the walls of the engine's combustion chamber, so it is expected to enable the realization of high-efficiency engines with low heat loss.

Whether this can be realized depends on whether we, as engine researchers, can take on the challenge with new ideas. Why don't you join us in the quest for engine technologies that challenge the effective use of energy and resources and the reduction of environmental impact, aiming for the construction of a sustainable society?