In-cylinder thermochemical fuel reforming (TFR) in a spark-ignition natural gas engine

This experimental study demonstrates the potential to apply the thermochemical fuel reforming (TFR) concept to simultaneously reduce emissions and improve brake specific fuel consumption in a spark-ignition natural gas engine. CH4, H2 and CO are the major components of TFR exhaust gas over a range of rich equivalence ratios. A numerical analysis is conducted to illustrate the chemical reaction pathways for H2 and CO formation, which occurs in the cylinder during the TFR process. The main reaction pathways for H2 and CO formation under 3 modeling conditions (20%, 50% and 80% fuel consumed) are different from each other. According to the experimental analysis, thermochemical fuel reforming gas improves combustion performance and accelerates the burn rate in every phase of the natural gas engine. Combustion stability, brake thermal efficiency, brake specific fuel consumption (BSFC), brake specific hydrocarbon (BSHC) and brake specific carbon monoxide (BSCO) emissions can also be improved by TFR. The brake specific oxides of nitrogen (BSNOx) emissions for natural gas engines, combined with a TFR system, are still lower than those of an original natural gas engine in the same operation mode. Thermochemical fuel reforming has been shown to be effective in simultaneously reducing emissions and improving thermal efficiency for a spark-ignition natural gas engine. Furthermore, a 1.2 equivalence ratio for cylinder 4 (TFR cylinder) can be recommended in future research on TFR optimization, based on BSFC and combustion stability.