Effect of Vane Notch and Ramp Design on the Performance of a Rectangular Inter-Turbine Burner

This research is motivated by the need to improve and optimize the performance of AFRL’s Ultra-Compact Combustor (UCC) in terms of greater combustion efficiency, reduced pressure losses and exit temperature profile requirements. The UCC operates as an Inter-turbine Burner (ITB) situated in between the high and low pressure turbine stages. The detailed understanding of the effect of the vane cavities, that are essential for the transport and mixing of the combustion products and incoming air stream in a threedimensional ITB model would be very difficult to optimize and could be experimentally and computationally prohibited. Therefore, a simple representation of somewhat similar burner is used here for optimization of the vane cavities, for improved mixing and reduced losses, using modeling and simulation. The ITB generally contains vanes to redirect the flow direction and to assist the mixing, but in this investigation we model the Trapped Vortex Combustor (TVC) ITB with a single vane with various notch designs and with ramps typically found in high speed combustion applications. In addition, the full configuration is simplified with only two fuel injection sites to get a faster turn around and to get a better understanding of the local flow development. A total of five vane configurations are studied: (1) Vane (V), (2) Vane + Notch (VN), (3) Vane + Altered Notch (VAN), (4) Vane + Extended Altered Notch (VEAN), and (5) Vane + Double Notch (VDN). Two ramp configurations are tested as well: (1) Ramp (R) and (2) Reverse Ramp (RR). FLUENT is used for modeling the three-dimensional ITB using a global eddy dissipation mechanism for C12H23-air combustion with detailed thermodynamic and transport properties. Calculations are performed using the Realizable k-e RANS turbulence model. The combustor efficiency for all ITB configurations is above 99%. Results indicate the major contributor to total drag for all ITB vane and ramp configurations investigated is the pressure drag. The side walls of the combustor do not contribute to drag. The top wall of the ITB is primarily exposed to viscous drag, whereas the bottom wall, which includes the TVC, is primarily exposed to pressure drag with small contributions from viscous drag. The vanes and ramps mainly contribute to drag due to pressure drag. The vanes contribute the most to the overall combustor drag (or pressure loss). The total drag in the combustor decreases with the addition of vane notches (or cavities). Drag decreases in descending order from V to VN, VAN, VEAN, and VDN. Whereas VN and VAN decrease pressure drag (or pressure losses) by only ~3%, VEAN and