Study of particulate matter and gaseous emissions in gasoline direct injection engine using on-board exhaust gas fuel reforming

Gasoline Direct Injection (GDI) engines provide advantages over preceding spark ignition engine technologies in terms of reduced fuel consumption, increased power output and CO2 depletion. However, the main drawback is the increased level of Particulate Matter (PM) emissions, which is associated with the adverse effects on human health and the environment.
GDI engine’s fuel economy can further be enhanced by exhaust gas fuel reforming, a thermochemical recovery technique, which utilizes the engine exhaust gas heat, CO2 and H2O to produce a hydrogen-rich gas named reformate. Furthermore, additional benefits in gaseous emissions can be achieved through the combustion of reformate. In this investigation, a prototype on-board fuel reformer has been employed in a GDI engine to study the effects of reformate combustion as a supplementary fuel to gasoline on PM and gaseous emissions. Between 5% and 6% reduction in the engine fuel consumption was achieved by using the fuel reformer. The different effects (i.e. dilution, thermal, chemical, etc.) of the reformate combustion on the PM nature and gaseous emissions has been identified. It was found that the reformate combustion can decrease notably the engine PM emissions, however, the reduction is dependent on the PM nature. Reformate combustion was found to remove soot cores more efficiently than the volatile PM. The study has shown that the three-way catalytic converter (TWC) can reduce PM emissions. The possible interactions between the reformate and the TWC operation have also been analyzed. For the studied conditions, fuel reforming technology has not shown significant detrimental influence on the TWC operation.