Hydrogen-diesel Fuel Co-combustion Strategies in Light Duty and Heavy Duty CI Engines

The co-combustion of diesel fuel with H2 presents a promising route to reduce the adverse effects of diesel engine exhaust pollutants on the environment and human health. This paper presents the results of H2-diesel co-combustion experiments carried out on two different research facilities, a light duty and a heavy duty diesel engine. For both engines, H2 was supplied to the engine intake manifold and aspirated with the intake air. H2 concentrations of up to 20% vol/vol and 8% vol/vol were tested in the light duty and heavy duty engines respectively. Exhaust gas circulation (EGR) was also utilised for some of the tests to control exhaust NOx emissions.
The results showed NOx emissions increase with increasing H2 in the case of the light duty engine, however, in contrast, for the heavy duty engine NOx emissions were stable/reduced slightly with H2, attributable to lower in-cylinder gas temperatures during diffusion-controlled combustion. CO and particulate emissions were observed to reduce as the intake H2 was increased. For the light duty, H2 was observed to auto-ignite intermittently before diesel fuel injection had started, when the intake H2 concentration was 20% vol/vol. A similar effect was observed in the heavy duty engine at just over 8% H2 concentration.