Stringent European carbon dioxide (CO2) emission regulations have stimulated the
development of alternative technologies such as Dual Fuel (DF), which involves
partially replacing fossil fuel with a low-carbon alternative. Hydrogen
represents an ideal candidate for DF due to its properties, including the
absence of carbon, high flame propagation speed, and high diffusivity. This
study analyzes the combustion and performance of a 1.0L, naturally aspirated,
three-cylinder in-line compression ignition off-road engine with a 17.5:1
compression ratio, originally equipped with a conventional diesel system and
modified for diesel-hydrogen dual fuel operation. Three Port Fuel Injectors
(PFI) are installed in the intake manifold for hydrogen injection. Additionally,
they are strategically positioned to minimize the volume between the intake
valve and injector tip. Tests were conducted at a fixed engine speed of 2000
rpm, varying the engine load from 30% to 85% of maximum torque. The diesel
contribution was maintained at 10%, while hydrogen provided the remaining
energy, achieving a substitution ratio up to 72%. The analysis showed that
hydrogen without diesel doesn't burn efficiently, and the combustion of the
air-hydrogen mixture is influenced by diesel injection and excess air in the
engine. Subsequently, with the load fixed at 70%, the effect of hydrogen start
of injection (SOI) on the engine's air intake flow was studied. The injection
window was shifted by 112° crank angle step, avoiding injection near the intake
valve closing. The results showed that injections too close to the compression
phase, (end of injection equal to 163° crank angle before top dead center), can
cause irregular combustion problems.