In order to increase the performance of a modern gas turbine, compressors are required to provide higher pressure ratio and avoid incurring higher losses. The tandem aerofoil has the potential to achieve a higher blade loading in combination with lower losses compared to single vanes. The main reason for this is due to the fact that a new boundary layer is generated on the second blade surface and the turning can be achieved with smaller separation occurring. The lift split between the two vanes with respect to the overall turning is an important design choice. In this paper an automated three-dimensional optimisation of a highly loaded compressor stator is presented. For optimisation a novel methodology based on the Multipoint Approximation Method (MAM) is used. MAM makes use of an automatic design of experiments, response surface modelling and a trust region to represent the design space. The CFD solutions are obtained with the high-fidelity 3D Navier-Stokes solver HYDRA. In order to increase the stage performance the 3D shape of the tandem vane is modified changing both the front and rear aerofoils. Moreover the relative location of the two aerofoils is controlled modifying the axial and tangential relative positions. It is shown that the novel optimisation methodology is able to cope with a large number of design parameters and produce designs which performs better than its single vane counterpart in terms of efficiency and numerical stall margin. One of the key challenges in producing an automatic optimisation process has been the automatic generation of high-fidelity computational meshes. The multi block-structured, high-fidelity meshing tool PADRAM is enhanced to cope with the tandem blade topologies. The wakes of each aerofoil is properly resolved and the interaction and the mixing of the front aerofoil wake and the second tandem vane are adequately resolved.
At present, it is a common practice to expose engine components to main annulus air temperatures exceeding the thermal material limit in order to increase the overall engine performance and to minimize the engine specific fuel consumption. To prevent overheating of the materials and thus the reduction of component life, an internal flow system is required to cool and protect the critical engine parts. Previous studies have shown that the insertion of a deflector plate in turbine cavities leads to a more effective use of reduced cooling air, since the coolant is fed more effectively into the disk boundary layer. This paper describes a flexible design parameterization of an engine representative turbine stator well geometry with stationary deflector plate and its implementation within an automated design optimization process using automatic meshing and steady-state computational fluid dynamics (CFD). Special attention and effort is turned to the flexibility of the parameterization method in order to reduce the number of design variables to a minimum on the one hand, but increasing the design space flexibility and generality on the other. Finally, the optimized design is evaluated using a previously validated conjugate heat transfer method (by coupling a finite element analysis (FEA) to CFD) and compared against both the nonoptimized deflector design and a reference baseline design without a deflector plate.
Compressors of gas turbine engines are multi-disciplinary systems whereas the different disciplines are largely considered separately. In order to produce feasible designs, the components need to be re-designed several times which is time consuming. A multi-disciplinary design process enabling an integrated approach for all discipline is described in this paper. The main disciplines considered are aerodynamics and ice impact-worthiness for the front stage intermediate pressure compressor (IPC) rotor of a modern three-spool jet-engine. Due to long lead times, ice impact analyses are usually not carried out until the aerodynamic design is reasonably mature. Only small changes to the rotor are usually allowed in order to satisfy the impact requirements that may lead to sub-optimal designs. Therefore, the introduction of ice impact analysis in the earlier design stages provides higher flexibility for the designers and leads to an overall better compressor performance. A fast thick-shell approach has been developed to model the transient dynamics of the compressor rotor impacted by crystalline ice cuboids released from upstream stators. The disciplines are linked using surrogate models which are based on the Kriging method. An adaptive multi-objective, multi-disciplinary optimisation approach has been used in order to increase the accuracy of the surrogate model iteratively in the areas of interest. It allows to optimise the performance of each discipline individually. The obtained Pareto front shows design trends in order to improve each discipline individually or both together. NOMENCLATURENumber of baldes/vanesNon-dimensional wall distance 1Copyright 2017 c by Rolls-Royce plc INTRODUCTIONAircraft fly through cold and moist air during take-off and landing where the liquid water droplets are super-cooled which means that the water temperature is below −15• C. The super-cooled water droplets are entering the core engine and are freezing instantaneously when hitting cold engine surfaces such as stators and casings. The ice accretes to thick crystalline ice shells and eventually shed in presence of vibrations and warmed-up components. The ice cuboids will then travel downstream impacting the compressor rotor. Due to the high rotor speeds, the ice impact cause severe mechanical damage. Hence, it is important to consider the impact-worthiness during the design process. Only the front stages of the compressor are typically affected by the ice impact threat as the rear stages are warmer. However, recent incidents shows that also melting ice particles can accrete on rear stages (Saxena et al. (2015)). In addition, the ice ingestion can affect the compressor aerodynamics causing a shift of the working line and stall margin when the ice melts and evaporates as shown by Saxena et al. (2015).Numerical impact analysis is common for many aircraft structures such as wings and windscreens and also fan blades. Most commonly, two kinds of foreign object damage (FOD), bird strike (softbody) and impact from foreign object debr...
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