No abstract

No abstract

Hydrogen production through fuel reforming can be used to improve IC (internal combustion) engines combustion characteristics and to lower vehicle emissions. In this study, a computational fluid dynamics (CFD) model based on a detailed kinetic mechanism was developed for exhaust gas reforming of biogas to synthetic gas (H 2 and CO). In agreement with experimental data, the reactor's physical and chemical performance was investigated at various O 2 /CH 4 ratios and gas hourly space velocities (GHSV). The numerical results imply that methane reforming reactions are strongly sensitive to O 2 /CH 4 ratio and engine exhaust gas temperature. It was also found that increasing GHSV results in lower hydrogen yield; since dry and steam reforming reactions are relatively slow and are both dependent on the flow residence time. Furthermore, the hot spot effect, which is associated to oxidation reforming reactions, was investigated for catalyst activity and durability.

No abstract

New renewable fuels have been developed for diesel engines, contributing to the reduction of carbon emissions and to fuel security. However, the combustion characteristics of these fuels and emissions still remain unclear. A study to investigate diesel engine performance integrated with biogas and hydrogen has been carried out. Biogas is principally a mixture of methane (CH4) and carbon dioxide (CO2) along with other trace gases. In this study the simulated gaseous biogas (60% CH4 and 40% CO2 vol.) and hydrogen (2% vol.) fuels were fed into the engine intake manifold and diesel fuel was injected into cylinder as a pilot ignition fuel. The effects of biogas and hydrogen showed reduced PM compared with diesel combustion. In addition, up to 39 and 33% reduction in total particulate mass and smoke, respectively, was seen. However, there was a slight increase in particle number when gaseous fuel addition was used, where the particulate size distributions have moved towards the nucleation region thus benefitting the after-treatment systems. Reduced thermal efficiency was observed for the gaseous fuel addition.