While the combustion engine is staying strong, with the possibility of extending it with e-fuels or hydrogen, Sophia University in Tokyo prefers to target ammonia. It can be burnt effectively by interfering with the air intake and causing a swirling effect on the cylinder.

We know that ammonia is a possible carrier for hydrogen. That’s precisely why we could see ships carrying hydrogen in this form in the future. However, it is more unusual to see it used in a combustion engine, because it is difficult to burn and generally has to be mixed with petrol. Since 2019, Professor Mitsuhisa Ichiyanagi, from the Department of Engineering and Applied Sciences at Sophia University’s Faculty of Science and Technology, has been working with other colleagues to design engines in which ammonia can be used as the sole fuel. Their work focuses on the intake system, to improve the mixing of the air with the fuel inside the engine cylinder for more efficient combustion.

Fluids dynamic

The idea is to create a swirling* effect, similar to a vortex. The tests were carried out on a single-cylinder diesel engine, with a glass cylinder and a piston. It featured a spiral duct left permanently open to let in swirling air, and a tangential duct with a normal air inlet with an adjustable opening. And it was by altering this opening by more than 25% that it was possible to redirect the swirling air/ammonia mixture in the cylinder to improve combustion during the intake and compression phases. The researchers were able to determine the right dosage, using silica particles injected into the combustion chamber and filmed by a high-speed CMOS camera (active pixel sensor) to better track the flows.

A detailed explanation can be found in this article.

Easier storage

In conclusion, the observation of vortex flows in the cylinder opens the door to efficient combustion of ammonia in the engine. Following this study, the researchers will be working on the combustion of an ammonia-petrol mixture or just ammonia in the engine. They believe that ammonia is in any case more practical than hydrogen, because its storage is far easier.

“The development of ammonia-fueled engine vehicles is expected to not only reduce carbon dioxide emissions from engines but also contribute to realizing a hydrogen energy society,” stated Professor Ichiyanagi.

*In fluid dynamics, the swirl is an aerodynamic phenomenon used in internal combustion engines. It involves giving the fresh gases introduced into the engine’s combustion chamber during the intake phase a speed of rotation around an axis perpendicular to that of the cylinder.

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Article written by Laurent Meillaud and translated by Mariem Ben Tili