Operating The Tour Split-Cycle Engine on Hydrogen/Methane Fuel Blends to Achieve High Efficiency and Reduction of Both GHG and NOx Emissions

Decarbonized or low carbon fuels, such as hydrogen/methane blends, can be used in internal combustion engines to support ambitious greenhouse gas (GHG) emission reduction goals worldwide, including potentially carbon neutrality by 2045. However, as the volumetric concentration of hydrogen in these fuel blends surpasses 30%, the in-cylinder flame propagation and combustion rates increase significantly, causing an unacceptable increase in nitrogen oxides (NOx) emissions, which is known to have substantial negative effects on human health and the environment. This rise in engine-out NOx emissions is a major concern, limiting the use of hydrogen fuels as a means to reduce GHG emissions from both mobile and stationary power generation engines. In this study, an experimental investigation of the combustion performance and emissions characteristics of a fourth generation Tour split-cycle engine was undertaken while operating on 100% methane and various hydrogen/methane fuel blends (30%, 40%, and 50% by volume of hydrogen). Taking advantage of the Tour engine’s superior operating flexibility and its inherent capability to manipulate combustion phasing, the results demonstrate that the Tour split-cycle engine operating on hydrogen/methane fuel blends is capable of high brake thermal efficiency and reduced GHG emissions, while at the same time exhibiting reduced engine-out NOx emissions.