Characteristics of a novel burner for high Karlovitz number turbulent premixed flame studies

Large uncertainties exist in the description of the turbulent premixed combustion regimes and their boundaries, especially the validity regime of flamelet assumptions, due to challenges involved in experimental studies. Our understanding of the physics of turbulent premixed combustion gets nebulous as the Karlovitz number increases (exceeds 500). A novel piloted burner design capable of generating high-intensity, homogeneous, axisymmetric turbulence is presented and its flow characteristics are discussed. An impinging-jet injector is used to generate high-intensity turbulence. Axial flow measurements were made using hot-wire anemometry. Fluctuating rms velocities ranging from 1.4 m/s up to 30 m/s are reported for bulk velocities of 10 m/s to 60 m/s at the jet centerline. The measured velocity profiles were shown to be self-similar for all considered injector configurations, with flow evolving as an axisymmetric wake downstream of the nozzle. The limitations of hot-wire measurements in large turbulence and necessary corrections are discussed; the corrected length scales were compared to those obtained from scaling laws. The measured dissipation is shown to collapse with Taylor length scale and mean centerline velocity as relevant length and velocity scales. Premixed methane-air flames exceeding 60 m/s of bulk velocities and equivalence ratios ranging from 0.6 to 1.0 can be stabilized using a large laminar pilot. The tested flame conditions span over two orders of magnitude in normalized turbulence velocities and three orders of magnitude in Karlovitz number. High-fidelity measurements of premixed flames over a broad range of turbulence can be realized using the burner.