Performance, Emissions and Exhaust-Gas Reforming of an Emulsified Fuel: A Comparative Study with Conventional Diesel Fuel

The fuel reforming technology has been extensively investigated as a way to produce hydrogen on-board a vehicle that can be utilized in internal combustion engines, fuel cells and aftertreatment technologies. Maximization of H₂ production in the reforming process can be achieved when there is optimized water (steam) addition for the different reforming temperatures. A way to increase the already available water quantity on-board a vehicle (i.e. exhaust gas water content) is by using emulsified fuel (e.g. water-diesel blend). This study presents the effect of an emulsified diesel fuel (a blend of water and diesel fuel with an organic surfactant to make the mixture stable) on combustion in conjunction with exhaust gas assisted fuel reforming on a compression ignition engine. No engine modification was required to carry out these tests. The emulsified diesel fuel consisted of about 80% (mass basis) of conventional ultra low sulphur diesel (ULSD) fuel and fixed water content. Results are compared to those obtained with ULSD fuel based on a) engine performance, b) engine emissions, c) hydrogen production, and d) efficiency of the reforming process. A smoke reduction of about 30–55% throughout all the testing conditions was achieved with the emulsified fuel while the NOx emissions reduction was in the range of 10–50%. As expected, fuel consumption was increased, due to the reduced calorific value of the emulsified fuel, but no negative effect on the brake thermal efficiency was observed. In the fuel reforming process, hydrogen production showed a strong dependence on the steam-to-fuel (S/F) ratio.