A one-dimensional integral model of turbulent jet diffusion

Abstract

An integral model for calculating the structure of vertical turbulent jet diffusion flames is presented. The complete model includes a one-dimensional formulation of the k− ε turbulence model to calculate mean mixture fraction and mixture fraction variance, with the turbulent nonpremixed combustion process being modeled via the conserved scalar/prescribed probability density function approach. The laminar flamelet concept is used to specify the instantaneous thermochemical state of the combusting mixture. The model accounts for radial variations of the mixture fraction field, giving realistic predictions of fuel consumption rates. Previous integral models, based on top-hat profiles, have required tuning or additional empirical constants to achieve similar predictions. For nonreacting jets and natural gas jet diffusion flames, the model has been validated against laboratory scale experimental data and predictions of a fully two-dimensional model. The integral model agrees closely with the two-dimensional model, which requires significantly more computing resources, and gives adequate predictions of observed flame temperatures, velocities and species concentrations.