Enhanced Mixing in Trapped Vortex Combustor with Protuberances Part 2: Two-Phase Reacting Flow

The Ultra-Compact Combustor (UCC) that operates as an Inter-turbine Burner (ITB) situated in between the high and low pressure turbine stages is modeled with the Trapped Vortex Combustor (TVC) with a single vane containing a notch and with various protuberance designs and arrays, located in the vane and in the TVC. The steady threedimensional governing equations of continuity, momentum, energy, turbulence, and species in Eulerian reference frame as well as the C12H23 liquid-fuel droplet trajectory, and heat and mass exchange with the continuum phase in a Lagrangian frame were solved using FLUENT. Turbulence was modeled using the Realizable k- RANS governing equations. The density varied with pressure and the turbulence model included production of turbulent kinetic energy by mean velocity gradients and consumption also accounted for dilation dissipation. Turbulence-chemistry interaction was modeled using the eddy-dissipation model. Temperature- and species-dependent thermodynamic and transport properties were considered. This paper discusses the flow/flame structure, exit temperature profiles, and global performance parameters of the various UCC/ITB/TVC. Liquid fuel is injected in the cavity as a conical spray of droplets that evaporates and boils almost immediately after injection within the TVC cavity. A turbulent triple flame is attached to the leading edge of the TVC cavity containing a nonpremixed reaction zone (NPRZ) sandwiched by a rich premixed (RPRZ) and lean premixed reaction zone (LPRZ). When adding a vane with notch the triple flame spreads in the transverse direction attaching itself to the trailing edge of this notch. At a given streamwise location the velocity magnitude downstream of the vane is nonuniform for the vane containing notch configurations, whereas it is uniform for that configuration without vane and notch. The combustion flow field is characterized by alternating high- and low-temperature regions with intensified transverse vorticity. High temperature regions are obtained in the vane suction side and not on the vane compression side. This leads to a non-uniform averaged exit temperature distribution in the spanwise direction. Two possible solutions can be envisioned to improve the non-uniform spanwise temperature distribution. A guide vane with appropriate curvature could be used downstream of a curved vane and/or the separation distance between vanes can be reduced to allow overlapping of the high-temperature regions. At the exit plane, the temperature increases from lean to richer mixtures, it reaches a peak near stoichiometric and then it decreases again for rich mixtures. For the configuration without vane with notch, the maximum exit temperature T2500 K peaks in the rich mixture. For the other configurations containing vane with notch, the maximum temperature increases to T2700 K and shifts to a more stoichiometric mixture. Future studies of UCC/ITB/TVC could take