Abstract
Abstract
The concept of trapped vortex combustion is emerging as a viable method of burning fuel effectively in aero-gas turbine engines. In a two-dimensional trapped vortex combustor (TVC), fuel—air mixing is characterized by using the parameter intensity of segregation (Is). When fuel and oxidizer are present (with some macro-mixing already having taken place), the parameter quantifies the extent of local micro-mixing within the domain. The regions of maximum fuel—oxidizer mixedness are identified to be the vortex edge and dump shear layer of the cavity. These two regions are observed to be zones of very good fuel—air mixing with higher levels of turbulence. Increasing aspect ratio (L/D) and the mainstream velocity (Vms) increases mainstream air entrainment into cavity, resulting in improved fuel—air distribution and mixing. However, an optimal L/D=1.2 and Vms=40 m/s results in stable vortex being trapped with better fuel distribution throughout the cavity. While non-optimal L/D and Vms may result in improved mainstream air entrainment, it is found to disrupt the trapped vortex, which is not conducive for combustion. Hence, for a given L/D, there is an optimal momentum ratio between the cavity injections and mainstream flow, which results in a single large vortex being trapped that can roll up the fuel—air injected and distribute them across the cavity, required for stable combustion in a TVC.
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