ASME Turbo Expo 
Virtual Conference, 7-11 June 2021Authors: J. Eckel, V. Gümmer, Institute of Turbomachinery and Flight PropulsionTitle: Numerical Investigation of the Aerodynamic Performance of Hybrid Aerofoils in a 1.5-Stage Low-Speed Compressor&nbsp;AbstractIn advanced highly loaded compressors compressor aerodynamic design tandem vanes have been used as an option to further increase the working range of the machine and maintaining good design point efficiency. Tandems have demonstrated the capability of significantly increasing the achievable level of flow turning across most of the span due to an advanced lift distribution of the front and rear vane, and the inherent formation of a fresh boundary layer on the rear vane. However, near both endwalls the tandem vanes produce higher secondary flow losses than conventional aerofoils. Introducing the tandem concept to the rotor of a compressor stage two tip leakage vortices occur and give rise to a major source of loss production. In order to overcome these endwall loss penalties a hybrid aerofoil concept has been introduced to the blading of a 1.5-stage low-speed compressor. The hybrid aerofoil concept combines tandem aerofoil geometries applied in the main flow path region with single aerofoil geometries introduced in the endwall regions.This paper describes the numerical investigation of hybrid aerofoil geometries in a 1.5-stage low-speed compressor, which in its baseline configuration features a conventional rotor and a tandem. Both of these are eventually replaced by hybrid aerofoils, using the initial tandem stator blade profile geometry at mid span. In this course of design investigations also a pure tandem rotor was generated and analysed as the initial geometry of the hybrid rotor. The aerodynamic design and performance of the tandem rotor and the hybrid aerofoils will be discussed in this paper.The numerical analysis is aimed at understanding the secondary flow phenomena and limiting factors of the working range of the reference stage. Based on this knowledge the advantages of the hybrid aerofoil design will be discussed. On one hand, the origin and development of three-dimensional flow structures near the endwall regions of the rear vane of the tandem stator are investigated in detail, as they appear to play a major role at de-throttled operating conditions. On the other hand, the tip vortex leakage of the single rotor and the pure tandem rotor are considered, showing the tip vortex taking a major role in loss generation and stall inception at throttled operating conditions, and strongly interacting with the tandem stator secondary flow phenomena at the casing. Both these performance-limiting factors can be addressed by implementing hybrid aerofoils.The paper will present and discuss the improvement of secondary flow loses and aerodynamic performance based on steady state RANS simulations.

Numerical Investigation of the Aerodynamic Performance of Hybrid Aerofoils in a 1.5-Stage Low-Speed Compressor

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

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