Abstract:Highly swirled flows are commonly used in gas turbine combustors to stabilize the flame and enhance fuel-air mixing. Experiments by D. G. Lilley, 1985 have shown that swirling flow patterns (i.e. recirculation zones) are dramatically impacted by a downstream contraction. For unconstricted swirling flow, a large, central recirculation zone is formed, while for constricted swirling flows, the recirculation zone can be annular in shape and high (positive) axial velocity is seen on the centerline of the combustor.… Show more
“…Nickolaus and Smith [14] also performed RANS and LES in analysis of highly swirled and turbulent flows in a dump combustor. LES was shown to capture more accurately the flow features than RANS did.…”
a b s t r a c tLarge Eddy Simulation (LES) studies of isothermal and incompressible turbulent swirling flows in a model gas turbine combustion chamber geometry have been carried out. The focus is on the effect of outlet geometry contraction on the vortex breakdown structure and the precessing vortex core in the chamber. Nine different outlet geometries with different contraction ratio C r are considered. The results from a baseline case are compared with experimental data in the literature. The swirling flow is generated using a swirler with fifteen guide vanes similar to an existing industrial gas turbine burner. In all cases the swirler and the main chamber geometry are kept the same. The detailed swirler geometry is considered in the simulation using unstructured grids. Sensitivity tests on the influence of the grid resolution and the subgrid scale models are carried out. The mean flow field shows different vortex breakdown structures when the contraction ratio changes from 0.325 to 1.0. In particular, along the axis of the chamber the flow is shown to switch its direction when the contraction increases as a result of the change of the structure of the center recirculation zone. The underlying flow physics is analyzed by comparing the budget terms in the momentum equations, and by performing a global instability analysis.
“…Nickolaus and Smith [14] also performed RANS and LES in analysis of highly swirled and turbulent flows in a dump combustor. LES was shown to capture more accurately the flow features than RANS did.…”
a b s t r a c tLarge Eddy Simulation (LES) studies of isothermal and incompressible turbulent swirling flows in a model gas turbine combustion chamber geometry have been carried out. The focus is on the effect of outlet geometry contraction on the vortex breakdown structure and the precessing vortex core in the chamber. Nine different outlet geometries with different contraction ratio C r are considered. The results from a baseline case are compared with experimental data in the literature. The swirling flow is generated using a swirler with fifteen guide vanes similar to an existing industrial gas turbine burner. In all cases the swirler and the main chamber geometry are kept the same. The detailed swirler geometry is considered in the simulation using unstructured grids. Sensitivity tests on the influence of the grid resolution and the subgrid scale models are carried out. The mean flow field shows different vortex breakdown structures when the contraction ratio changes from 0.325 to 1.0. In particular, along the axis of the chamber the flow is shown to switch its direction when the contraction increases as a result of the change of the structure of the center recirculation zone. The underlying flow physics is analyzed by comparing the budget terms in the momentum equations, and by performing a global instability analysis.
“…Examples are provided in Refs. One of the major problems with much of the literature available on the topic is that decay functions are only defined for long axial distances. Studies on shorter distances below three times the diameter have yielded conflicting results.…”
“…Most modern gas turbines use double-concentric swirlburner because it gives the freedom to vary the distribution of axial and angular momentum of different airflow and mixing patterns can be achieved, resulting in substantial reduction in NOx emissions and lean blow off (LBO) limit in comparison to single swirler burner [20]. This technology is attractive to fit producing the required power in small size and compact combustor because several ignitions are distributed at the combustor head without any side wall among igniters.…”
The paper presents a numerical prediction of reacting flow field and temperature distribution of turbulent diffusion flame in two air blast nozzle swirling flow namely co and counter with different swirl intensities. This quantity is 0.46 for the central flow and ± 1.0 for the annular flow. Current study was focus on the rotation effect of the secondary flow. The calculated results were validated on real time through laser anemometry for both cases. The reasons behind the choice of this issue is that it is realistic in the industry but with a larger scale and our possession of the experimental values to validate the simulation. The use of two flows produced less NOx than a single flow due to its high capacity which homogenizes the temperature in the burner. The obtained results show that LES had successfully predicted the recirculation zones (CTRZ and CRZ) and the PVC with good precision.
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