Numerical simulation of conversion of n-heptane to hydrogen in an inert, porous medium
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The conversion of liquid hydrocarbon fuels, specifically liquid heptane, to a syngas mixture containing hydrogen by means of superadiabatic combustion within a porous inert media is studied computationally over a wide range of rich equivalence ratios, inlet velocities, and in different types of porous material. Parameters of interest include the composition of the exhaust gases and particularly the amount of hydrogen present in the exhaust, conversion efficiency, energy efficiency, reaction front propagation speeds, firing rates, and overall hydrogen production rates. Both a packed bed of 3 mm diameter Al-oxide pellets and a 3.9 pores-per-centimeter reticulated ceramic are studied in depth and compared as the burner material. The computational model used is a one-dimensional, transient code that models the combustion processes as well as the heat transfer processes that occur as the reaction front moves through the porous material. Several different n-heptane chemical kinetics mechanisms are studied and a process is developed that utilizes both the flexibility of a reduced mechanism and the more accurate predictions of a more detailed mechanism. Computational predictions are compared to preliminary experimental data, as well as similar studies performed previously with other fuels types.