Extending the Modelling Framework for Gas-Particle Systems: Applications of Multiparameter Shape Descriptions to Non-Conventional Solid Fuels in Reacting and Non-Reacting Environments

An extended Lagrangian particle tracking and combustion model for non-conventional solid fuels such as chopped straw has been developed. Based on an extension of the existing tracking techniques, shapes are based on a superelliptic equation capable of assuming forms ranging from spheres to cylinders, through simple parameter variation. Using a concept of aerodynamical similarity, a drag coefficient accounting for orientability as well as shape variations has been defined. The model has been applied to two isothermal testcases, where different types of particles are injected into swirling flow configurations. In both cases, the model performs efficiently, and indicates a pronounced difference in terms of the aerodynamic properties of the different particle shapes. For validation purposes, terminal velocity predictions of different shapes have been carried out, and compared to experimental data, with very good results. Single particle combustion has been tested using a number of different particle combustion models applied to coal and straw particles. Comparing the results of these calculations to measurements on straw burnout, the results indicate that for straw, existing heterogeneous combustion models perform well, and may be used in high temperature ranges. Finally, the particle tracking and combustion model is applied to an existing coal and straw co- fuelled burner. The results indicate that again, the straw follows very different trajectories than the coal particles, and also that burnout occurs a different locations, as the straw is not re-entrained into the flame zone.