A simulation research of heat transfers and chemical reactions in the fuel steam reformer using exhaust gas energy from motorcycle engine

Onboard fuel steam reformer heated by the exhaust gas of an internal combustion engine has been considered as an effective device to produce hydrogen (H2) for engine application. However, the fuel conversion efficiency of the reformer is strongly dependent on heat transfer characteristics between exhaust gas and the reformer. Heat loss of the gas flow along the exhaust system to ambient and the complicated heat and mass transfer inside the reformer with endothermic reforming reactions strongly affect the reformer’s efficiency. Therefore, modelling study of heat transfer and chemical reactions is thus necessary, as it is a powerful and cost-effective tool for estimating and maximizing the conversion efficiency and hydrogen yield of the reformer. This paper presents the result of numerical study of heat transfer and chemical reactions in the gasoline steam reformer integrated in engine exhaust system. An onboard compact gasoline steam reformer is made and installed in the exhaust pipe of a Honda Wave motorcycle engine to produce hydrogen continuously by using the waste heat of the engine for heating the reformer. The study accounts for all the aspects of major chemical reactions and heat and mass transfer phenomena in the reformer. A computer simulation code has been developed for the study. The predicted result was validated with experiment data. The results show that by taking advantage of engine exhaust energy, the optimum operating conditions of the reformer under engine full load for high hydrogen yield are at mass water/fuel ratio of 3.5:1 under space velocity of 1000/h. Under these conditions, gasoline conversion of up to 80% and H2 wet concentration of up to 46% are achieved.