Laminar flame speed and Markstein length of syngas at normal and elevated pressures and temperatures

• Measured laminar flame speeds and Markstein lengths of syngas.
• Compared experimental data with predictions from various kinetic models for syngas.
• Assessed the effects of Lewis number and flame temperature using various oxidizers.
• Examined the effects of pressure and initial temperature.

Synthetic gas, or syngas, is a popular alternative fuel for gas turbine industry. However, the composition of syngas is complex which complicates the combustor design. In this study, a dual-chambered pressure-release type combustion apparatus was developed and used for measurements of laminar flame speed which could be operated at high pressures and temperatures. The laminar flame speeds of syngas were measured at normal and elevated pressures and temperatures. The effects of Lewis number, flame temperature, pressure and initial temperature on the laminar flame speed and Markstein length of typical syngas mixtures were investigated. The results showed that the unstretched laminar flame speed increased with the increase of Lewis number and flame temperature, and that it decreased with the increase of pressure. The Markstein length decreased with the increase of pressure and initial temperature. It was found that the Markstein length was less sensitive to change of initial temperature than that of pressure. Furthermore, the performance on theoretical model for Markstein length using different Lewis numbers was examined. It was found that for syngas, the diffusion-based effective Lewis number rather than the volume or heat release-based Lewis number should be used to evaluate the Markstein length from the theoretical model.