Catalytic Exhaust Gas Recirculation-Loop Reforming for High Efficiency in a Stoichiometric Spark-Ignited Engine through Thermochemical Recuperation and Dilution Limit Extension, Part 2: Engine Performance

This is the second part of a two-part investigation of on-board catalytic fuel reforming to increase the brake efficiency of a multicylinder, stoichiometric spark-ignited (SI) engine. In Part 1 of the investigation, we analytically and experimentally characterized the energetics and kinetics of a candidate reforming catalyst over a range of reforming equivalence ratios and oxygen concentration conditions to identify the best conditions for efficient reforming. In the present part of our investigation, we studied an engine strategy that combined exhaust gas recirculation (EGR)-loop reforming with dilution limit extension of the combustion. In our experiments, we found that, under an engine operating condition of 2000 rpm and brake mean effective pressure (4 bar), catalytic EGR reforming made it possible to sustain stable combustion with a volumetric equivalent of 45%-55% EGR. Under this same operating condition with stoichiometric engine exhaust (and no reforming), we were only able to sustain stable combustion with EGR under 25%. These results indicate that multicylinder gasoline engine efficiency can be increased substantially with catalytic reforming combined with and higher EGR operation, resulting in a decrease of more than 8% in fuel consumption, compared to baseline operation.