Impact of Syngas Addition to Methane on Laminar Burning Velocity

Exhaust gas recirculation (EGR) in spark-ignited (SI) engines is a key technique to reduce in-cylinder NOx production by decreasing the combustion temperature. The major species of the exhaust gas in rich combustion of natural gas are hydrogen and carbon monoxide, which can subsequently be recirculated to the cylinders using EGR. In this study, the effect of hydrogen and carbon monoxide addition to methane on laminar burning velocity and flame morphology is investigated. Due to the broad flammability limit and high burning velocity of hydrogen compared to methane, this addition to the gaseous mixture leads to an increase in burning velocity, less emissions production, and a boost to the thermal efficiency of internal combustion engines. Premixed CH4-H-2-CO-air flames are experimentally investigated using an optically accessible constant volume combustion chamber (CVCC) accompanied with a high-speed Z-type Schlieren imaging system. Furthermore, a numerical code is applied to quantify the laminar burning velocity based on the pressure rise during flame propagation within the CVCC. According to the empirical and numerical results, the addition of hydrogen and carbon monoxide enhances laminar burning velocity while influencing the flame structure and development.

Automated summary

The study investigates the effects of adding hydrogen and carbon monoxide to methane fuel on laminar burning velocity and flame morphology, showing that the addition leads to higher burning velocity, lower emissions, and improved thermal efficiency of internal combustion engines. The experimental research was conducted using an optically accessible combustion chamber and high-speed Schlieren imaging system, with numerical analysis confirming the enhancement of laminar burning velocity and impact on flame structure.