Performance and emissions of a direct injection internal combustion engine devised for joint operation with a high-pressure thermochemical recuperation system

This paper presents the results of an experimental study on performance and pollutant emissions of a direct-injection spark-ignition engine devised for joint operation with a high-pressure thermochemical recuperation system based on methanol steam reforming. A comparison with gasoline and ethanol decomposition is performed. Engine feeding with methanol steam reforming products shows an 18%-39% increase in the indicated efficiency and a reduction of 73-94%, 90-96%, 85-97%, and 10-25% in NOx, CO, HC and CO2 emissions, respectively, compared to gasoline within a wide power range. Efficiency improvement and emissions reductions are obtained compared to ethanol decomposition products as well. The possibility of an unthrottled engine operating with a substantially lower cycle-to-cycle variation compared to both gasoline and ethanol decomposition is demonstrated. At high loads, the injector flow area was insufficient for a low injection pressure of 40 bar, leading to late injection and reduced engine efficiency for methanol steam reforming products. In the case of ethanol decomposition, the problem was less severe due to the higher energy content of ethanol decomposition products per mole. The concept of a direct-injection internal combustion engine with high-pressure methanol steam reforming shows good potential, while additional research on injection strategies and gaseous reformate combustion is required.