ANALYSIS OF APPROACHES TO NUMERICAL MODELING OF PULVERIZED COAL FUEL COMBUSTION IN A TURBULENT FLOW

Abstract

The relevance of the research is caused by the need for accurate reproduction of experimental measurements by mathematical models, since numerical simulation is widely used both for the development of new technologies for the combustion of solid fuels and for the modernization of existing boiler units. And as it is known, the parameters of a pulverized coal flame predicted by numerical simulation directly depend on the way the combustion chemistry in a turbulent flow is modeled. The main aim of the research is to study the accuracy of reproduction of experimental measurements for four approaches to the numerical simulation of ignition and burnout of combustible components of pulverized coal fuel in a turbulent flow. Objects: temperatures, concentrations of gas components (CO2, O2, CO and NOx), axial and tangential velocity components inside the IFRF 2.4 MW furnace. Methods: comparison of experimentally measured parameters of a pulverized coal flame and those predicted by numerical simulation. Numerical simulation was performed using the ANSYS FLUENT software package. The combustion of coal dust in the furnace is modeled as a two-phase turbulent flow system consisting of gas and discrete phases. Results. Numerical modeling of the combustion of pulverized coal in a turbulent flow has been carried out using four different approaches: equilibrium chemistry models with one and two mixture fractions; model of «eddy dissipation» and its combination with the kinetic model of combustion. A comparative analysis of the simulation results with the experimentally measured parameters of a pulverized coal flame established that all the studied approaches to modeling the pulverized coal combustion in a turbulent flow demonstrate a fairly good agreement with the experimental data. The «eddy dissipation» model in combination with the combustion kinetic model has the advantage in accuracy, and the equilibrium chemistry model with one mixture fraction has the advantage in the time of solution convergence.

Keywords

• pulverized coal
• combustion
• numerical modeling
• swirl burner
• eddy dissipation model
• chemical kinetics
• chemical equilibrium model
• mixture fraction