Low-Temperature Ethanol Reforming: A Multi-Cylinder Engine Demonstration 2011-01-0142
It has been previously reported that ethanol can be reformed at
around 300°C to a mixture of hydrogen, carbon monoxide, and methane
using copper-plated nickel catalyst. This low reforming temperature
enables heat to be supplied from the engine exhaust.
Single-cylinder engine testing demonstrated that this gaseous
mixture of "ethanol reformate" enhances engine combustion
and part load dilution capability, which decreases fuel consumption
while also reducing feedgas NOx emissions. In addition,
excellent cold start capability with significantly reduced
hydrocarbon emissions was observed. Thus, ethanol reformate has the
potential to address two major barriers to wider use of ethanol as
an engine fuel: ethanol's low heating value per volume and
higher hydrocarbon emissions at startup relative to gasoline.
In this study, the dilute capability of a multi-cylinder engine
was assessed using a mixture of 50% reformate and 50% E85 on a mass
basis at several key part load operating points. A strategy
combining lean-burn with internal residual dilution was used to
maximize thermal efficiency while maintaining adequate exhaust gas
temperature for reformer operation. The resulting feedgas
NOx emissions are low enough to enable the use of a
reasonably sized lean NOx trap with low regeneration
frequency for minimal impact to the fuel consumption benefit.
Cold start testing at 20°C showed that 50% reformate mass
fraction is sufficient to provide significantly reduced start-up
emissions and fuel consumption compared to an E85 baseline. The
retarded spark timings incorporated in the test engine's
production calibration enabled 300°C exhaust temperatures for
three-way catalyst light-off after 15 seconds of operation. The
results indicate that a reasonably sized reservoir tank could
supply enough reformate for vehicle start.
While most of the results of this study were acquired using
simulated ethanol reformate from gas bottles, data at one part-load
engine operating point was obtained using a working prototype
reformer utilizing engine exhaust heat.