A Numerical Study of Reacting Flows Using Finite Rate Chemistry

Doctoral thesis, 2012

Fossil fuels will remain the main source of energy for mankind in the foreseeable future. Heat released in combustion of fossil fuels is always accompanied by emission of undesired pollutants. Environmental concerns have led to stringent emission rules for combustion industry specially for reducing the amount of NOx production. Lean premixed combustion has increasingly gained interest in recent years as an approach toward reduced NOx emissions by reducing the operating temperature. However, lean blow off limit and the tendency of the dynamic flame to become unstable present technical challenges. The low swirl burner concept is a rather new and promising design to stabilize lean premixed flames close to their flammability limit. Large Eddy Simulation together with a finite rate chemistry combustion model have been used here for numerical studies of a laboratory low swirl stabilized flame. The importance of the inlet boundary condition is investigated and an optimized approach is suggested. The flame stabilization mechanism is discussed and it is shown that the choice of the inlet boundary condition can significantly affect this mechanism. Air transport is becoming more common and aviation contribution to anthropogenic CO2 production will soon become prominent. Turbomachinery efficiency in modern aircraft engines is close to perfection and innovative core designs are needed for significant efficiency improvements. Unsteady phenomena in the working cycle of a conceptual Pulse Detonation Engine is studied here using URANS and a finite rate chemistry combustion model. The limitations imposed by the unsteady flow at compressor side are compared for two alternative engine configurations