In order to achieve an environmental-friendly engine ie with more efficiency and less noise emission, a geared ultra-high bypass ratio fan test rig has been designed within the EU-funded project SILENCE® Engine cycle requirements were untypical in terms of mass flow rate, pressure ratio and BPR In order to reach the desired mass flow rate and simultaneously to avoid a strong interaction of the shocks with the boundary layer an S-shape leading edged rotor with forward sweep close to casing has been designed Specific blade numbers for rotor and stator has been used to minimize the rotor-stator interaction noise For the same purpose a backward swept bypass stator has been designed There are two stators in the core duct in order to bring the flow to zero swirl which is a necessity for test rig measurements The main design loop includes blade shape and the flow path optimization as well as the computation of stress distribution in all blades and the rotor disc The fan is being manufactured from titanium because of its specific aeroelastic properties and stators are made of steel The rig is scheduled to be tested in 2006 for its aerodynamic and aeroacoustic performanceCopyright © 2006 by ASME

Design of a Highly Efficient Low-Noise Fan for Ultra-High Bypass Engines

The exit flow field of the fan root of large turbofan engines defines the inlet conditions to the core compressor. This in turn could have significant impact to the performance of the core compressor. This study is aimed to resolve two related issues concerning the impact of the fan root flow on the core compressor performance: to establish the effect of an increased loss at the inlet on the engine specific fuel consumption (SFC) and to assess the effect of the radial distribution of the fan root flow on the engine performance. With understanding of these issues, the geometric parameters and design details which can produce a more uniform core flow at the exit of the fan stage module can be identified. The fan root flow is analysed with methods of different complexity and fidelity. A simple cycle analysis is used to assess the impact on engine SFC of a stagnation pressure deficit at the fan root; a throughflow code is used for the preliminary study of the curvature effect of the root flow path and 3D RANS CFD calculations are then used to simulate the flow path from the inlet of the fan to the first stage of the core compressor. The adequacy of the application of the numerical code in this case has been assessed and confirmed by the comparison with the experimental data for two rig configurations. The results of this study show that the flow at the fan hub region is very complex and dominated by 3D effects. The interaction of the secondary flow with real geometries, such as leakage flows, is found to have a strong detrimental effect on the core performance. The curvature of the hub end-wall is a key parameter controlling the fan root flow topology; it influences the strength of the secondary flow, the spanwise distribution of the flow and its sensitivity to leakage flow. With this understanding it is possible to redesign of the fan hub flow path to reduce the loss generation by a significant amount.© 2009 ASME

Fan Root Aerodynamics for Large Bypass Gas Turbine Engines: Influence on the Engine Performance and 3D Design

Recent development of high speed computers and use of optimization techniques have given a big momentum of turbomachinery design replacing expensive experimental cost as well as trial and error approaches. The surrogate based optimization techniques being used for aerodynamic turbomachinery designs coupled with Reynolds-averaged Navier-Stokes equations analysis involve single- and multi-objective optimization methods. The objectives commonly tried to improve were adiabatic efficiency, pressure ratio, weight etc. Presently coupling the fluid flow and structural analysis is being tried to find better design in terms of weight, flutter and vibration, and turbine life. The present article reviews the surrogate based optimization techniques used recently in turbomachinery shape optimizations.

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Surrogate Based Optimization Techniques for Aerodynamic Design of Turbomachinery

An experimental and numerical study of the transonic flow through a linear compressor cascade with endwalls was conducted. The cascade with a low aspect ratio of 1.34 was tested at an inlet Mach number of 1.09 and a Reynolds number of 1.9 310 6 . Detailed flow visualizations on the surfaces and five-hole probe measurements inside the blading and in the wake region showed clearly a three-dimensional boundary layer separation on the blade surface and the sidewall, and a severe corner stall induced by a strong 3-D shock system at blade passage entrance. The experimental data have been used to validate and improve the 3-D Navier-Stokes code TRACE. Results showed an excellent resolution of the complex flow field. Surface pressure distributions on the entire blade surface and the endwalls, flow angle and total pressure contours within the blade passage and the wake are compared with the experimental results. An analysis of the secondary flow of this highly staggered cascade did not show the classical corner vortex. Instead, a severe flow deviation and partly reverse flow near the walls is seen. The flow solver helped to identify a weak ring vortex that originates from the passage sidewall. Surface oil flow pictures on the blade contour and the sidewall are in qualitatively good agreement to numerical surface streaklines. A considerable improvement of the numerical results could be achieved by a gradual grid refinement, especially in the corner region and by successive code development.@DOI: 10.1115/1.1460913#

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3-D Transonic Flow in a Compressor Cascade With Shock-Induced Corner Stall

Aerodynamic shape optimization of a transonic fan by an adjoint-response surface method

The paper describes an advanced three-dimensional blading concept for highly loaded transonic compressor stators. The concept takes advantage of the aerodynamic effects of sweep and dihedral. To the knowledge of the authors this is the first approach reported in the open literature that combines those two basic types of lean in an engine-worthy aerofoil design. The paper makes a contribution to the understanding of the endwall effect of both features with special emphasis put on sweep. The advanced three-dimensional blading concept was applied to an Engine Section Stator (ESS) of an aero-engine fan. In order to demonstrate how three-dimensional flow can be controlled, numerical analysis of the flow structure in a conventional and an advanced stator configuration was performed using a three-dimensional Navier-Stokes solver. The numerical analysis showed the advanced blade improving both radial loading distribution and the three-dimensional endwall boundary layer development. In particular, a strong hub corner stall could be largely alleviated. High-speed rig testing of the advanced ESS confirmed the concept and showed good qualitative agreement between measurement and prediction. The work presented was closely linked to the development of the BR710 engine on which the advanced ESS is in service today.

H.-P. Kau

Papers

Using Sweep and Dihedral to Control Three-Dimensional Flow in Transonic Stators of Axial Compressors