Modeling Flame Propagation of Coal Char Particles in Heterogeneous Media

In the present research, combustion of a quiescent coal char particle cloud has been studied in the media with spatially discrete sources by means of numerical approach. A thermal model based on diffusion-controlled regime of coal char particles has been generated in order to estimate the characteristics of flame propagation in heterogeneous media. The model uses discrete heat sources to analyze dust combustion of particles with the diameter of 50 μm. Oxygen and Nitrogen have been considered as the main oxidizer and the inert gas, respectively. Flame propagation speed in various dust and oxygen concentrations has been studied. Flame speed as a function of particle size has been investigated and comparison between cases with and without consideration of radiation effect has been made. Furthermore, minimum ignition energy as a function of dust concentration for different particle sizes has been studied. Results show a reasonable compatibility with the existing experimental data

Large eddy simulation of turbulent diffusion jet flames based on novel modifications of flamelet generated manifolds

A novel mathematical definition is introduced to achieve the inherently monotonic progress, namely Absolute Cumulative Variation (ACV). The classical progress variable is defined as a weighted summation of species mass fraction while weight factors are determined in the ad-hoc procedure. The ACV definition presents the systematic method to generate a fully bijective look-up table appropriate for the vast combustion applications. This method utilizing the preferential diffusion effects and has the potential to predict the autoignition delay time as well as pollutants, like YCO and YNO. The flamelet-generated manifold is coupled with ACV to make the ACV-FGM method. Furthermore, the Variable Ignition Mixing Layer (VIML) is presented as a modified method to generate a 2-D look-up table for the multi-inflow streams as well as varying composition reactants at the domain boundaries. This model helps to reduce the size of the look-up table for complex inflow boundary conditions and computational cost as well. The validation process for the ACV-FGM and VIML methods includes a one-dimensional laminar flame along with large eddy simulation (LES) of the Sandia piloted flames D, E, and F, and Delft Jet-Hot Coflow (DJHC) burner as lifted turbulent jet flame. The results indicate the ACV-FGM method successfully predicts the autoignition delay time, lift-off height, temperature rise as well as spices mass fractions and pollutants. Moreover, The VIML method appropriately reproduces the variation of chemical compositions and temperature at the domain boundary using the 2-D look-up table

Large eddy simulation of turbulent diffusion jet flames based on novel modifications of flamelet generated manifolds

\u3cp\u3eA novel mathematical definition is introduced to achieve the inherently monotonic progress, namely Absolute Cumulative Variation (ACV). The classical progress variable is defined as a weighted summation of species mass fraction while weight factors are determined in the ad-hoc procedure. The ACV definition presents the systematic method to generate a fully bijective look-up table appropriate for the vast combustion applications. This method utilizing the preferential diffusion effects and has the potential to predict the autoignition delay time as well as pollutants, like Y\u3csub\u3eCO\u3c/sub\u3e and Y\u3csub\u3eNO\u3c/sub\u3e. The flamelet-generated manifold is coupled with ACV to make the ACV-FGM method. Furthermore, the Variable Ignition Mixing Layer (VIML) is presented as a modified method to generate a 2-D look-up table for the multi-inflow streams as well as varying composition reactants at the domain boundaries. This model helps to reduce the size of the look-up table for complex inflow boundary conditions and computational cost as well. The validation process for the ACV-FGM and VIML methods includes a one-dimensional laminar flame along with large eddy simulation (LES) of the Sandia piloted flames D, E, and F, and Delft Jet-Hot Coflow (DJHC) burner as lifted turbulent jet flame. The results indicate the ACV-FGM method successfully predicts the autoignition delay time, lift-off height, temperature rise as well as spices mass fractions and pollutants. Moreover, The VIML method appropriately reproduces the variation of chemical compositions and temperature at the domain boundary using the 2-D look-up table.\u3c/p\u3