The variable inlet guide vane (VIGV) is a common device for industrial centrifugal compressors to control the mass flow by a customized pre-swirl in the inlet plane of the impeller. However, due to open flow separation occurring at a critical stagger angle of the VIGV blades, the efficient working range of the VIGV is restricted. In order to overcome the limitations of current blade geometries and to enhance the operation range of the entire compressor system, split blade geometries consisting of a separate front and tail blade segment proved to be particularly promising. This blade concept was profoundly investigated by Stark and Böhle [1] and further improved by Händel et al. [2] introducing the pivoted front blade segment. The front and the tail blade segment are thereby individually staggered, which enables a gradual flow deflection along the chord length. Compared to a state-of-the-art reference in industrial applications, a significant extension of the efficient deflection range by a factor of almost two was demonstrated by Händel et al. [2]. Due to the sole focus on profile losses in 2D-cascades, however, the referred measurements are not fully conclusive. The significant proportion of secondary flow losses induced by the open blade tips and wall-blade interactions in a real, annular VIGV could not be considered in the investigated two-dimensional case.In order to gain a more conclusive understanding of the overall loss characteristics, complementary investigations were therefore conducted at the VIGV test facility of the Bundeswehr University Munich allowing highly resolved five-hole probe measurements in the wake field of actual, annular VIGV geometries. Besides the previously investigated profile losses, secondary flow induced losses are thus considered. In total, four configurations were investigated; the state-of-the-art reference case and three variations of the split blade configuration with either full, partial or missing sealing in the gap between the front and the tail segment. A broad investigation of the full operation range of the VIGV was ensured by stagger angle variations from 90 to 40° in steps of 10°. The results of this comparative, experimental study will be presented in-depth in the full-length paper.&nbsp;Literature[1] U. Stark und M. Böhle, „Theoretische und experimenteile Untersuchungen an ungestaffelten Gittern aus Profilen mit mechanischen Klappen,“ Forschung im Ingenieurwesen, Bd. 56, Nr. 6, 1990.[2] D. Händel, R. Niehuis und J. Klausmann, „Aerdoynamic Invesitgations of an Advanced VIGV Design of Adjustable Geometry for Very High Flow Turning,“ Proceedings of ASME Turbo Expo, Nr. GT2015-42166, June 2015.&nbsp;

Loss Characterization of Advanced Vigv Configurations With Adjustable Blade Geometry

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

Turbo Expo 2021

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