HYDROGEN COMBUSTION ENGINES: WILL THEY EVER BECOME VIABLE?

摘要

HYDROGEN HAS SO far struggled to meet its early promise as an alternative road transport fuel, but it's a subject that just refuses to go away. Its use in hydrogen fuel cells to generate emissions-free electricity still has huge potential, but the impetus behind running internal combustion engines on it has dwindled. Interest remains, though, an example being Toyota's development of a hydrogen-powered three-cylinder racing engine taken from the GR Yaris and used to power a specially developed Corolla Sport entered in the Fuji 24 Hours (see separate story, left). Although hydrogen is a clean fuel compared with petrol or diesel, it's only completely emissions free when converted in a fuel cell system to generate electricity. When burned in a combustion engine it isn't - quite. Although no unburned hydrocarbons (HC), carbon monoxide (CO) or CO_2 are produced, nitrogen oxides (NO_x) are. Air is 78% nitrogen, and in combustion it's oxidised to produce the toxic NO_x - but how much depends on how hot things get in the combustion chamber, and that's where hydrogen engines can have an advantage.