Abstract
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.
Highlights
Policy makers and the general public alike are increasingly aware of, and concerned by, the negative impacts of IC engine exhaust gas species on urban air quality and human health [1]
Recent attention has focused on levels of both nitrogen oxides (NOx) and particulate matter (PM) emitted by diesel engine powered vehicles, with higher mortality rates being attributed to PM emissions alone in urban cities
In addition to oxygen bearing fuels, a further approach that has been considered for the reduction of PM in particular has been the partial displacement of fossil diesel or biodiesel with fuels of lower carbon content, for example with cocombustion of natural gas [19] or hydrogen [20e22]
Summary
Policy makers and the general public alike are increasingly aware of, and concerned by, the negative impacts of IC engine exhaust gas species on urban air quality and human health [1]. The often locally rich but globally lean stoichiometry of diesel combustion [10] results in elevated levels of PM and excess oxygen in engine exhaust gases that necessitate the use of several after-treatment systems in series for effective reduction of pollutant emissions. Studies utilising potential biofuels containing a higher proportion of oxygen than long chain fatty acid esters, for example ethers and short chain alcohols, in blends with fossil diesel and biodiesel have reported simultaneous reductions in both PM and NOx [17,18]. In addition to oxygen bearing fuels, a further approach that has been considered for the reduction of PM in particular has been the partial displacement of fossil diesel or biodiesel with fuels of lower carbon content, for example with cocombustion of natural gas [19] or hydrogen [20e22]
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