Performance of lignin derived aromatic oxygenates in a heavy-duty diesel engine

The possibility to reduce dependence on fossil fuel resources has led to an increasing interest in the use of bio-fuels. This study builds on earlier work on (aromatic) cyclic oxygenates [1,2], but a far wider window of engine operation has been investigated in this paper. Two parametric variations of engine operation were performed and discussed: (1) non-EGR operation by means of varying the load via injection duration/quantity without EGR and (2) EGR operation by gradually increasing the level of EGR. The aromatic oxygenates in question are anisole, benzyl alcohol and 2-phenyl ethanol. The purpose of this work is to evaluate the feasibility of these lignin-derived bio-fuels in a compression ignition (CI) engine with a wide operation range and to assess the impact of the position of the functional oxygen group relative to the aromatic ring. For a better understanding of the combustion process, Heat Release Rates (HRR) have been compared and emissions of soot, NOx and unburnt products (HC, CO) have also been evaluated. The results demonstrate that both the soot-NOx trade-off and engine efficiency are improved for all oxygenates with respect to diesel. Moreover, the results indicate that EGR plays a very important role in further improving aforementioned tradeoff. With EGR, the improvement in the soot-NOx trade-off correlated to some extent with the position of the functional oxygen group to the ring, with better overall emission behavior observed as the oxygen group was farther removed (i.e. separated by carbon atoms) from the ring in the order anisole → benzyl alcohol → 2-phenyl ethanol. However, with respect to indicated efficiency, benzyl alcohol blend performed best in both non-EGR and EGR operation.