Newsletter  2017.2  Index

Theme : "The Conference of Fluid Engineering Division"  Preface M.MOTOZAWA, T.HASHIMOTO, S.MATSUDA The Study of Turbulence in the 21st Century Shinichiro YANASE (Okayama University) Research on amorphous actuators utilizing liquid crystal flows Rinko MATSUDA, Tomohiro TSUJI, Shigeomi CHONO (Kochi University of Technology) Flow Structure of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor Seishiro SAITO（Kyushu University） A levitating droplet over a moving surface Erina SAWAGUCHI, Kai HAMA, Yoshiyuki TAGAWA (Tokyo University of Agriculture and Technology) Innovative Cellulose Material Synthesis by Electrostatic Fibril Alignment Yusuke Takeda (Tohoku University), Christophe Brouzet, Nitesh Mittal, Fredrik Lundell (KTH Royal Institute of Technology, Sweden), Hidemasa Takana (Tohoku University) Developing “Dream Strider”, a machine for the removal of floating materials on the water surface Kota TSUBONE, Yo MUNETA (Hiroshima Kokutaiji Senior High School) The Dreams of Flow Contest Haruka YAMAUCHI (Meisei University)

 

Flow Structure of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor

Seishiro SAITO Kyushu University

Abstract

In this study, the hub corner separation in a multi-stage transonic axial compressor has been investigated using a large-scale detached eddy simulation (DES) with about 4.5 hundred million computational cells. The complicated flow field near the hub wall in a stator with partial tip clearances was analyzed by data mining techniques extracting important flow phenomena from the DES results. The data mining techniques applied in the present study include vortex identification based on the critical point theory and topology data analysis of the limiting streamline pattern visualized by the line integral convolution (LIC) method. The analysis result shows that hub-corner separation occurs in the first stator. Because of the rotor-stator interaction, the hub corner separation vortex violently fluctuates with time. It is found from the time-averaged flow field in the first stator that the hub-corner separation vortex formed near the solid part of the stator tip interacts with the tip leakage and secondary flows on the hub wall, resulting in a complicated vertical flow field. Near the leading edge of the stator, the leakage flow from the front partial clearance generates the tip leakage vortex, which produces loss from the leading edge to 10 percent chord position. At the mid-chord, the hub-corner separation vortex suffers a breakdown, resulting in the widespread huge loss production. It is shown from limiting streamlines on the suction surface of the stator that a reverse flow region expands radially from the solid part of the stator tip toward the downstream. From mid-chord position to the trailing edge of the stator, the leakage flow through the rear partial clearance interacts with the secondary flow on the hub wall. The leakage vortex generated along the rear partial clearance becomes major loss factor there.

 

Key words

Transonic Axial Compressor, DES, Visual Data Mining, Blade Tip Clearance, Hub Corner Separation

 

Figures

Fig. 1  Computational grid

Fig. 2  Magnitude of density gradient at 10%span

Fig. 3  Entropy at 10%span

(a) Instantaneous flow structures	(b) Time-averaged flow structures
Fig. 4  Limiting streamlines on suction surface and vortex cores in the 1st stator

Fig. 5  Limiting streamlines on hub surface (in time-averaged case)