Experimental characterization of non-premixed turbulent jet propane flames

This paper reports an experimental study conducted on turbulent jet propane flames aiming at further understanding of turbulent structure in non-premi xed slow-chemistry combustion systems. Measurements of mean and fluctuating velocity and temperature fields, mean concentration of major chemical spec ies, correlation between velocity and temperature fluctuations, and dissipa tion of temperature fluctuations are reported in a turbulent round jet non- premixed propane flame, Re = 20 400 and 37 600, issuing vertically in still air. The experimental conditions were designed to provide a complete defin ition of the upstream boundary conditions in the measurement domain for the purpose of validating computational models. The measured data depicts usef ul flow field information for describing turbulent non-premixed slow-chemis try flames. Velocity-temperature correlation measurements show turbulent he at fluxes tended to be restricted to the mixing layer where large temperatu re gradients occurred. Observations of nongradient diffusion of heat at x/D = 10 were verified. Temperature fluctuation dissipation, ii, showed the hi ghest values in the shear layer, where the variance of temperature fluctuat ions was maximum and combustion occurred. The isotropy between the temperat ure dissipation in the radial and tangential directions was confirmed. By c ontrast, the observed anisotropy between axial and radial directions of dis sipation suggests the influence of large structures in the entrainment shea r layer on the production of temperature fluctuations in the flame region. The value of the normalized scalar dissipation at the stoichiometric mixtur e fraction surface, chi (st), was calculated, and ranges between 2 and 4 s( -1). The measured data were used to estimate the budgets in the balance equ ations for turbulent kinetic energy, Reynolds shear stresses, turbulent hea t flux and temperature variance, quantifying the mechanisms involved in the generation of turbulence as well as in the transport of the temperature. ( C) 2000 Elsevier Science Inc. All rights reserved.