Numerical study of exhaust reforming characteristics on hydrogen production for a marine engine fueled with LNG

When the engine exhaust heat is used for catalytically reforming the mixtures of natural gas and partial exhaust to produce the on-board hydrogen, the hydrogen-rich combustion can be achieved to improve the combustion performance of the natural gas engine. In this work, according to the Exhaust Gas Recirculation (EGR) system of a LNG-fueled engine, an exhaust reforming reaction tube of the reformer with interior coated Ni-based catalyst was modeled with full computational fluid dynamics (CFD) combined with detailed chemical reaction mechanisms to study the reforming characteristics when the EGR ratio ranges from 2.5% to 10% and the molar ratio of water to carbon ranges from 1.0 to 3.5. The simulation results present species formation characteristics in the reforming reactions which involve only steam reforming reaction and partial reforming reaction. Higher mass ratio of water to fuel (W/F) is advantageous for the methane reforming reaction, more hydrogen yield and the inhibition of the coke formation, while higher EGR ratio promotes the conversion of methane and carbon monoxide production. The simulation result also gets a high molar ratio of hydrogen to carbon monoxide ratio for the presence of excess water content. In the given conditions, a more preferable reaction process can be achieved when EGR rate is equal to 5% and W/F gets the value of 3.5.