LES AND EXPERIMENTAL STUDY OF FLOW FEATURES IN HUMID-AIR COMBUSTION CHAMBER WITH NON-PREMIXED CIRCULAR-DISC STABILIZED FLAMES

摘要

Sydney/Sandia bluff-body flame series [1] has been world-widely studied based on a simple-geometry bluff-body. This study focuses on a turbulent piloted non-premixed methane jet flame with circular-disc which is used in a humid-air combustion chamber without a swirler. Large eddy simulation has been performed to investigate the flow features. Meanwhile, in order to validate the simulation results, an experimental study is also conducted, where the instantaneous velocity and temperature fields are measured using PIV and high temperature thermocouples, respectively. Compared to Sydney/Sandia flame series, the enlarged simulation area effectively eliminates the boundary effects on flow field. Comparisons with experimental data also show that for high resolution of grids, comparatively good agreement is obtained for the flow field. Unlike Sydney/Sandia flame series, central jet tends to break up early in this case because of the existence of the circular disc. It has also been found that the shear layer between the co-flow and the bluff-body wake is captured by LES as well as by PIV. Because of the difference in geometry between Sydney/Sandia and circular-disc bluff-bodies, it needs to be further studied how to apply the conclusions based on the former to the latter. However, current and future LESand experimental study can help to illustrate the tradeoffs among the degree of swirl and the choice of bluff-body shapes in devices such as industrial burners and gas turbines.