Super-aggressive intermediate turbine duct integrated counter-rotating low-pressure turbine vane: an aerodynamic performance optimization study considering sealing flow

As advanced aeroengines become increasingly critical to energy-efficient propulsion and sustainable aviation, the integrated design of guide vanes within a super-aggressive intermediate turbine duct (SAITD) is a key strategy for enhancing engine performance, effectively reducing axial length and improving the thrust-to-weight ratio of aeroengines. However, the highly diffusive flow within the SAITD makes vane surfaces prone to separation, and the associated flow complexity renders conventional low-pressure turbine aerodynamic design methods ineffective for integrated vane design. Therefore, this study proposes a systematic approach to improving the aerodynamic performance of SAITD-integrated counter-rotating low-pressure turbine vanes using intelligent optimization techniques. Initially, a database of 3,000 parameterized blade geometries was constructed using an in-house parametric modeling framework integrated with numerical simulations. Subsequently, a Transformer-based neural network surrogate model was trained to predict aerodynamic performance and incorporated into a Bayesian optimization framework to determine the optimal blade configuration. Finally, the optimized design was assessed through detailed analysis of the flow field topology. The optimization results obtained using the proposed design methodology demonstrate a 15.24 % reduction in the outlet total pressure loss coefficient compared to the initial integrated guide vane design. This improvement is primarily attributed to geometric modifications at the leading and trailing edges, which effectively suppressed the unstable leading-edge spanwise vortex and improved the sealing flow characteristics at the trailing-edge. The findings provide an effective strategy for reducing aerodynamic losses in SAITD and offer new insights into the aerodynamic design of integrated guide vanes.