Combustion Characteristics and Exhaust Gas Emissions of a Diesel Engine Supplied with Reformed EGR

The Reformed EGR (REGR) technique involves the injection of hydrocarbon fuel (e.g., diesel) into a catalytic reformer fitted into the engine EGR system, so that the produced hydrogen containing gas mixture is fed back to the engine as REGR. Thus, in effect the engine operates in a similar way to a dual fuelled engine with standard EGR. Depending on the reforming conditions, the composition and the calorific value of the REGR may vary and this affects the engine performance and emissions. In the present study, simulated REGR with different H₂/CO ratios has been examined. The combustion of REGR with maximum H₂ and minimum CO contents resulted in the highest reduction of NO_x emissions. This case simulated the reformer operation where the CO is fully converted to H₂ by promoting the exothermic water gas shift reaction (WGSR). The highest reductions of both smoke and fuel consumption were achieved in the case of simulating the reformer operation where the CO is not fully converted to H₂. In all the examined cases, the use of REGR resulted in reduced NO_x and smoke emissions. Improved fuel economy was achieved only at middle and high load engine operation compared to the standard operation with diesel fuel only.