Burning Velocities of Alternative Gaseous Fuels at Elevated Temperature and Pressure

Abstract

This study has been undertaken to investigate turbulent burning velocities of alternative gaseous fuels at elevated temperature and pressure using the established Bunsen burner method. The experiments were conducted in the industrial scale high-pressure optical chamber at the Gas Turbine Research Centre of Cardiff University. Five different gaseous fuels, methane, two methane―carbon dioxide mixtures, and two methane―hydrogen mixtures were studied. Experiments were conducted at two different temperatures (473 K and 673 K) and two different pressures (3 bara and 7 bara). Analysis of measurements made using 100% methane showed anticipated burning velocity trends with variation in temperature and pressure. The results reported here showed reasonable agreement with the available turbulent burning velocity correlations, although the burning velocities recorded by the other researchers were somewhat higher. The stoichiometric flames considered were all purposely contained within one flame regime on the Borghi―Peters diagram, namely the corrugated flamelet regime, through appropriate choice of operating conditions. Hydrogen enrichment and carbon dioxide dilution of methane show some expected trends. As expected, dilution of methane with carbon dioxide reduces the measured burning velocity. However, increasing pressure and temperature in this case have competing effects, with temperature raising the burning velocity and pressure reducing it. Comparison of the methane―carbon dioxide mixture results presented here are consistent with the qualitative trends recently reported by the group of researchers, but exhibit quantitative differences thought to be due to experimental and data analysis differences. Hydrogen enrichment of the methane leads to a significant increase in the measured burning velocity compared with methane, as anticipated. Comparison of the methane―hydrogen mixture results reported here show reasonable agreement with the measurements of other researchers. Our measurements show that increases in temperature and pressure independently lead to increased turbulent burning velocity, with a more pronounced effect of pressure for lean flames.