Experimental Investigation of Unsteady Flow Field in the Tip Region of an Axial Compressor Rotor Passage at Near Stall Condition With Stereoscopic Particle Image Velocimetry

Abstract

Stereoscopic particle image velocimetry (SPIV) was applied to a large-scale low-speed compressor facility with the configuration of the two CCD cameras placed on each side of the light sheet to make the measurement of the vortices in the cross flow section possible and to avoid the disturbance from the light sheet containing periscope-type probe. Instantaneous velocity and vorticity distributions were successfully documented at the tip region of the rotor at near stall condition. The measurement results clearly revealed the generation and evolution of the tip leakage vortex. Comparing to design condition, the tip leakage vortex at near stall condition generates and breaks down earlier and interacts more violently with mainstream, which causes large blockage and much loss. Whether corner vortex exists or not is the primary difference between near stall and design condition. Differing from the leakage vortex, the corner vortex is composed of multiple vortices developed from the suction surface of the rotor blade. The key mechanism for the generation of the corner vortex is that the rotation of the rotor has different effect on the evolution of positive vortices and negative vortices, which makes the positive vortices dissipates faster than the negative ones, the vortices at the rotor exit therefore bear mainly negative vortices, which induces the fluids to rotate clockwise at the corner and forms the corner vortex.

Turbulence Models Assessment for Large-Scale Tip Vortices in an Axial Compressor Rotor

“…Furthermore, the TLV and the CV are the only two large-scale vortices in the tip region of the rotor. More details about the flow mechanism in the test rotor, such as the formation, development, and evolution of the TLV, as well as the CV, can be found in the previous papers [13,14].…”

“…More details about the flow in the test compressor, such as the mechanism of the formation, development, and evolution of the TLV, as well as the formation and evolution of the CV, have also been discussed in previous papers [13,14].…”

“…5 and 6 show that the occurrence of the CV at the near-stall condition is the primary difference in the rotor tip flow compared with the flows at the design condition. Unlike the TLV, the CV is a compound vortex with its vortex core composed of multiple vortices and its core fluid mainly coming from the boundary layer of the suction surface [13]. At the rotor exit, the low-speed CV occupies nearly one-half of the rotor passage and contributes primarily to the blockage and loss of the flow in the rotor tip region at the near-stall condition.…”

“…The CV predicted by all five turbulence models seems to be a single vortex, which is different from what the measurements indicate. According to the measurements, the CV is a compound vortex with its vortex core composed of multiple vortices [13].…”

“…Many efforts have been made on the tip flows by theoretical models [2,[4][5][6], experimental investigations [7][8][9][10][11][12][13][14], and numerical simulations [15][16][17][18][19] under various conditions during the last 50 years. Recently, some flow control techniques have also been tried to improve the rotor tip flow performance [20,21].…”