Development and aerothermal investigation of integrated combustor vane concept

• Main Author: Jacobi, Simon
• Other Authors: Rosic, Budimir
• Published: University of Oxford 2016
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.730243

This work focuses on the interface of combustor and high-pressure turbine of power generation gas turbines with individual can combustors. More specifically the thesis presents the development and aerothermal investigation of the integrated combustor vane concept. In this novel concept, first introduced in 2010, the conventional nozzle guide vanes (NGVs) are removed and flow turning is achieved by vanes that extend the combustor walls. The concept was developed using the inhouse CFD code TBLOCK. Aerothermal experiments were conducted using the Oxford combustor-turbine high-speed research facility. The linear cascade is comprised of two can combustor transition ducts and either four conventional vanes (CVs) or two integrated vanes (IVs). The experimental study validates the linear numerical simulations of the integrated vane development. Annular full stage simulations, used to evaluate aerodynamics and stage efficiency, confirm the trends of the linear numerical and experimental results and thus demonstrate the concept's potential for real gas turbine applications. Results show a reduction of the total pressure loss coefficient at the exit of the stator vanes by more than 25% due to a reduction in profile and endwall loss. Combined with an improved rotor performance demonstrated by unsteady stage simulations, these aerodynamic benefits result in a gain in stage efficiency of 1.5%. A distinct reduction in HTC levels on vane surfaces and endwalls on the order of 40%-50% is observed. This is attributed to the transferral of the combustor wall's boundary layer onto the integrated vane and to the removal of the horse-shoe vortex system. Furthermore it is shown that engine-realistic combustor flow with swirl leads to a slight, non-detrimental shift in the heat transfer coefficient distributions and to a less homogenous turning distribution downstream of the integrated vanes. Three-dimensional vane profiling is suitable to modify the downstream turning and thus counteract the increased losses downstream of the two-dimensional integrated vanes incurred by the combustor's swirl. The experimental and numerical investigation of the newly developed integrated vane's endwall and leading edge cooling geometries shows a superior surface coverage of cooling effectiveness, and the cooling requirements for the first vane are expected to be halved. Moreover, by halving the number of vanes, simplifying the design and eliminating the need for vane leading edge film cooling, manufacturing and development costs can be significantly reduced.