Time evolution of a buoyant jet diffusion flame

Predictions of the time and spatial evolutions of a buoyant jet diffusion flame by a direct numerical simulation are experimentally evaluated. The simulation involves the solution of the full time-dependent Navier-Stokes equations in conjunction with a flame sheet model. The experiments involve a vertical, buoyant diffusion flame in a coflowing air environment. The fuel is a propane and nitrogen mixture (50% by mass) and the burner is a long tube (22.94 mm inside diameter) with a sharpo lip at the exit. Planar visualizations and thin-filament-pyrometry temperature measurements are phase-locked to the naturally periodic oscillation of the flame. A comparison of experimental and theoretical results for seven phase angles shows that the model gives an adequate representation of the time evolution of the flame. Temperature profiles obtained at ten axial locations show reasonable agreement when a 20% reduction in heat release is used to approximate the radiative heat loss from the flame. Time-averaged velocity, measurements in the near-nozzle region also compare favorably with the prediction.