High efficiency dual-fuel combustion through thermochemical recovery and diesel reforming

A computational system optimization was conducted to explore the potential benefits of diesel reforming in dual-fuel combustion strategies. A comprehensive CFD model, validated against syngas (50/50 H2/CO by mole) metal engine experiments, was used to simulate the engine combustion process. The engine CFD solver was coupled with an equilibrium solver for the reformer process and three different reforming processes were investigated: Partial oxidation, steam reforming, and autothermal reforming. A system level approach was used to evaluate the impact of thermochemical recovery of exhaust energy and reformer losses. A design of experiments of simulations was conducted to explore the combustion system design space and a genetic algorithm was used to search the resulting response surface and find the optimal operating conditions. It was found that fuel reforming can increase engine net indicated efficiencies by as much as 9% due to a shorter combustion duration and reduction in heat transfer losses. The partial oxidation reforming system resulted in the lowest system efficiencies at 44% due to its exothermic nature, while steam reforming and autothermal reforming were able to achieve over 48% system efficiency, an improvement in global efficiency of 8% compared to a diesel baseline due to exhaust heat recovery.