Highly Loaded LPC Blade and Non Axisymmetric Hub Profiling Optimization for Enhanced Efficiency and Stability

Abstract

The present contribution fits into the frame of the ongoing 7th Framework European Project DREAM (valiDation of Radical Engine Architecture systeMs). One of its main themes targets the development of contra-rotating open rotors with variable pitch blades which are known to provide 10 to 15% fuel burn reduction but are noisier than high by-pass turbofans. More specifically, the present research was conducted in the frame of work package 3.4 lead by Techspace Aero, dedicated for one part to the design of a high speed booster adapted to open rotor configurations, and for the second part, from which this paper is issued, to the investigation of 3D geometries to improve LPC efficiency. A reference rotor blade has first been designed, with high loading, especially at hub. To improve its efficiency, a backward sweep has then been applied as it tends to unload midspan sections. However, this performance gain came at the price of severe stall margin degradation, the criticality of the hub region being increased. Based on 1.5 stage 3D RANS simulations, automated surrogate-assisted optimization has then been exploited to respectively evaluate the potential benefit of tailored 2D contouring and 3D hub profiling a posteriori applied to the swept rotor blade and of joint 3D hub profiling and sweep optimization of the unswept baseline rotor blade. The potential benefit of 3D profiling will be demonstrated while the joint 3D profiling and blade stacking optimization shed light on the achievable interesting 3D effects combinations.

Non-Axisymmetric Shroud Profiled Endwall Optimization of an Embedded Stator and Experimental Investigation

“…The profiled endwall mainly changes the distribution of the static pressure and controls the secondary flow by modifying the streamline curvature near the endwall.PEW is generated mainly by two means. One is control lines with two crossed directions with functional expressions [1,2], which is called function modeling method and the other one is applying perturbations to the discrete points within the profiled zone [5][6][7][8][9], which is called perturbation method. The former one often chooses trigonometric functions and B-spline curves as the control function.…”

“…The latter one can introduce more design variables and make the PEW have more degree of freedom. The optimization design method often adopts the perturbation method, as it has more freedom than the function modeling method, which could explore more probabilities of the effects of PEW on improving the flow field.However, most of the studies of PEW concentrate on the cascade or single stage [5][6][7][8][9], and fewer investigations on the multistage conditions, which are due to the complicated flow structures of the multistage turbomachinery. A troublesome problem is that the test results could not show as effective as the numerical simulation predicted, which has been reported in the previous papers [3,4].…”

Controlling Secondary Flows in Highly-Loaded Compressor Cascades

“…Secondary losses in turbine and compressor blade rows have been the topic of many investigations over the past decades. Means of secondary losses reduction via the application of endwall contouring have been the subject of several investigations, such as the ones from Hoeger et al (2002), Harvey (2008), Reising and Schiffer (2009a), Lepot et al (2011) and Hergt et al (2011) on compressor rows, and the ones from Praisner et al (2007), Knezevici (2011) and Taremi and Sjolander (2011) on turbine rows.…”

“…With the objective of reducing engine weight and cost, highly-loaded compressor blades with high diffusion factor and low solidity have been investigated by many researchers. Recent research shows diffusion factors in the range of 0.40-0.60 (Hoeger et al, 2002;Ellison, 2005;Harvey, 2008;Sonoda et al, 2008;Dickens and Day, 2009, Reising and Schiffer, 2009a, Lepot et al, 2011. For comparison purposes, the current study is done on a compressor exit guide vane with a diffusion factor of 0.52.…”

“…This approach was originally developed on axial flow turbines and its effect on endwall flow and on the blade row losses has been the subject of several investigations, such as the ones from Rose (1994), Harvey et al (2000), Hartland et al (2000) and more recently, Praisner et al (2007) and Knezevici et al (2008). The application of non-axisymmetric endwall contouring as a means of endwall flow control on compressor blade rows has only been the subject of recent studies, with the work of Harvey (2008), Schiffer (2009a, 2009b), Lu et al (2009) and Lepot et al (2011).…”