Laminar Flame Speed Characteristics and Combustion Simulation of Synthetic Gas Fueled SI Engine 2008-01-0965
As the real-time supplying of hydrogen-rich gas becomes possible by the advances in the on-board fuel reforming technologies, utilizations of synthetic gas in IC engines are actively studied. However, due to the lack of fundamental studies on the combustion characteristics of synthetic gas, there is no precedent for the simulation of combustion process in synthetic gas fueled SI engine.
In this study, the laminar flame speeds of synthetic gas and its mixture with iso-octane were calculated under extensive initial conditions of 3,575 points derived by combinations of temperature, pressure, fraction of lower heating value of synthetic gas and air-excess ratio variations. In order to investigate the effect of EGR on the laminar flame speed of synthetic gas mixture, additional calculations were performed with various fractions of burnt gas up to 0.5 in volume fraction, and the effect of variations on the fractions of H2 and CO in the reformer-out gas were also investigated for the understanding of the roles of H2 and CO in the chemical reaction paths.
By using the results of laminar flame speed calculations, the effect of synthetic gas addition on the combustion characteristics was investigated by multi-dimensional computational fluid dynamics with modified FAE (flame area evolution) combustion model. The aspect of flame propagation was analyzed in a two-dimensional planar mesh, and the potential benefits of synthetic gas utilizing in an SI engine was confirmed by the combustion simulations in a three-dimensional engine mesh.