Performance of an Inter-Turbine Burner (ITB) Concept with Three-Different Vane Cavity Shapes

Abstract

Three-dimensional CFD simulations were conducted in this study to determine the performance of an UltraCompact-Combustor (UCC) for use as an Inter-Turbine Burning (ITB) in aero gas turbine engines. The study considered the AFRL novel UCC/ITB concept and its performance associated with three different Radial Vane Cavity (RVC) shapes, namely rectangular (or angled), backward and forward facing step cavities, was numerically obtained. The CFD results demonstrated that the performance of UCC/ITB is profoundly dependent upon the shape of the RVC utilized for radial transport of combustion products and continual lean burning. In particular, the radial transport of the combustion products from the Circumferential Cavity (CC) into the main airflow was predicted to be substantially lower for the backward facing step RVC than that for the rectangular (angled) and forward facing step cavities. Intense burning in the ITB circumferential cavity was predicted by the CFD simulations, suggesting strong flame stability characteristics, improved lean blowout performance, and high combustion efficiency of the AFRL UCC/ITB concept. The results further showed that the shape of the RVC plays an important role in determining the migration mechanism and shedding rate of the combustion products from the high g-loaded swirling circumferential cavity into the main airflow and as a result variant burning patterns were obtained downstream of the trailing edges of the cavities. These burning patterns, however, were found to produce somewhat unconventional radial temperature and fuel-air ratio profiles at the ITB exit plane and these radial profiles were attributed to the inadequate mixing of the combustion products and main airflow. This study, therefore, warrants further design, CFD, and experimental efforts to improve main air stream and combustion products mixing performance.