The use of fuel reformate
from catalytic processes is known to
have beneficial effects on the spark-ignited combustion process through
enhanced dilution tolerance and decreased combustion duration, but,
in many cases, reformate generation can incur a significant fuel penalty.
In this two-part investigation, we demonstrate that efficient catalytic
fuel reforming can result in improved brake engine efficiency while
maintaining stoichiometric exhaust under the right conditions. In
Part 1 of this investigation, we used a combination of thermodynamic
equilibrium calculations and experimental fuel catalytic reforming
measurements on an engine to characterize the best possible reforming
performance and energetics over a range of equivalence ratios and
O2 concentrations. Ideally, one might expect the highest
levels of thermochemical recuperation for the highest catalyst equivalence
ratios. However, reforming under these conditions is highly endothermic,
and the available enthalpy for reforming is constrained. Thus, for
relatively high equivalence ratios, more methane and less H2 and CO are produced. Our experiments revealed that this suppression
of H2 and CO could be countered by adding small amounts
of O2, yielding as much as 15 vol % H2 at the catalyst outlet for 4 < Φcatalyst <
7 under quasi-steady-state conditions. Under these conditions, the
H2 and CO yields were highest and there was significant
water consumption, confirming the presence of steam reforming reactions.
Analyses of the experimental catalyst measurements indicated the possibility
of both endothermic and exothermic reaction stages and global reaction
rates sufficient to enable the utilization of higher space velocities
than those employed in our experiments. In a companion paper detailing
Part 2 of this investigation, we present results for the engine dilution
tolerance and brake engine efficiency impacts of the reforming levels
achieved.