UNDER THE SKIN JESSE CROSSE
IN JULY LAST year, Chinese manufacturer GAC announced it had been working with Toyota on using ammonia as a substitute for fossil fuel and had successfully run a combustion engine on the carbon-free chemical.
We have got used to hearing about methanol, hydrogen and synthetic fuels as potential replacements for petrol and diesel, but ammonia? A household cleaning product or fertiliser, yes, but the idea of ammonia being flammable seems almost bizarre. However, it is being investigated for all kinds of transport use, including ships, trucks and cars.
More recently, Sophia University in Tokyo has been working on making ammonia burn efficiently inside an engine’s combustion chamber. An ammonia molecule contains three atoms of hydrogen and one of nitrogen so it is flammable, but not that easy to ignite. Its use as a combustion engine fuel is actually as old as the hills so it’s fitting that the thrust of the new research focuses on a fundamental of engine development: increasing swirl in the intake tract to improve combustion efficiency.
Using ammonia cut with petrol has been the default method of ensuring efficient combustion, but the aim now is to use ammonia on its own, eradicating fossil fuel. Since 2019, the team at Sophia University has been focusing on the intake ports to promote swirl in the mixture before it arrives in the combustion chamber.
‘Swirl’ describes the way the air-fuel mixture is encouraged to form a vortex that combines the two into a homogeneous mixture, improving combustion and reducing emissions. Mixing fuel and air creates the same efficiency benefits in a combustion engine whether the fuel is ammonia, petrol, diesel or an
