Comparative behavior of piloted turbulent premixed jet flames of C1[sbnd]C8 hydrocarbons

Abstract

An exploratory study was performed on highly turbulent piloted premixed jet flames of straight chain (paraffin and olefin), branched, cyclo, and aromatic C1C8 hydrocarbons. The goal was to investigate fuel effects on global and local flame observables under flow conditions corresponding to the transition from the thin to the broken reaction zone regimes. The experiments were performed at atmospheric pressure, reactant temperature of 298K, jet Reynolds numbers of 12,500 and 25,000, and various equivalence ratios and fuels in order to assess the attendant effects on the flame characteristics. The effects of heat losses from the flame were considered also in order to sensitize kinetic effects. Measurements were performed using particle image velocimetry and spontaneous luminosity imaging. The averaged and fluctuating velocity components as well the average flame height were determined to scale in general with the laminar flame speed. The exception to this scaling was the height of methane flames that exhibit notable differences compared to large molecular weight fuels. Subtle differences were identified even among the large hydrocarbon flames and became evident from measurements of the instantaneous luminosity field. Finally, high-speed luminosity imaging revealed that there are apparent fuel effects on the local structure of the flame as evident by the distribution and size of luminous pockets. These results suggest that the fuel effects should be also the focus of further investigations by the community.