Print Email Facebook Twitter The Effect of Variable Air–Fuel Ratio on Thermal NOx Emissions and Numerical Flow Stability in Rotary Kilns Using Non-Premixed Combustion Title The Effect of Variable Air–Fuel Ratio on Thermal NOx Emissions and Numerical Flow Stability in Rotary Kilns Using Non-Premixed Combustion Author El Abbassi, M. (TU Delft Numerical Analysis) Lahaye, D.J.P. (TU Delft Mathematical Physics) Vuik, Cornelis (TU Delft Numerical Analysis) Date 2021 Abstract One of the quickest ways to influence both the wall temperature and thermal NOx emissions in rotary kilns is to change the air–fuel ratio (AFR). The normalized counterpart of the AFR, the equivalence ratio, is usually associated with premixed flames and studies of its influence on diffusion flames are inconsistent, depending on the application. In this paper, the influence of the AFR is investigated numerically for rotary kilns by conducting steady-state simulations. We first conduct three-dimensional simulations where we encounter statistically unstable flow at high inflow conditions, which may be caused by vortex stretching. As vortex stretching vanishes in two-dimensional flow, the 2D simulations no longer encounter convergence problems. The impact of this simplification is shown to be acceptable for the thermal behaviour. It is shown that both the wall temperature and thermal NOx emissions peak at the fuel-rich and fuel-lean side of the stoichiometric AFR, respectively. If the AFR continues to increase, the wall temperature decreases significantly and thermal NOx emissions drop dramatically. The NOx validation, however, shows different results and indicates that the simulation model is simplified too much, as the measured NOx formation peaks at significantly fuel-lean conditions. Subject Conjugate heat transferDiffusion flameNon-premixed combustionOpenFOAMRadiative heat transferRotary kilnThermal NOxTurbulence To reference this document use: http://resolver.tudelft.nl/uuid:4b0eebb1-bd5d-40f1-84ea-191652c90203 DOI https://doi.org/10.3390/pr9101723 ISSN 2227-9717 Source Processes, 9 (10), 1-19 Part of collection Institutional Repository Document type journal article Rights © 2021 M. El Abbassi, D.J.P. Lahaye, Cornelis Vuik Files PDF processes_09_01723.pdf 2.35 MB Close viewer /islandora/object/uuid:4b0eebb1-bd5d-40f1-84ea-191652c90203/datastream/OBJ/view