Unsteady Behavior and Control of Diffuser Leading-Edge Vortex in a Centrifugal Compressor(Fluids Engineering)

Experiments and numerical analyses were used to investigate the unsteady behavior of a vortex generated on the leading-edge of a diffuser (i.e., leading-edge vortex (LEV)) and the diffuser stall inception in a centrifugal compressor equipped with vaned diffusers. The LEV is distinct from the separation vortex of the diffuser’s leading edge and passage vortex of the diffuser; it is generated by the accumulation of vortices caused by the velocity gradient of the impeller discharge flow. The LEV increases with decreasing velocity in the diffuser passage and forms a huge flow blockage within the diffuser passage. Therefore, the LEV may help cause the diffuser stall inception in the centrifugal compressor. A diffuser vane, that was tapered only on the hub side was designed and used in the experiment. The results of the computational fluid dynamics analysis and experiments showed that the tapered diffuser vane can suppress LEV evolution during off-design operations. Therefore, the tapered diffuser vane may control the diffuser stall inception in a centrifugal compressor by suppressing LEV evolution.

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Unsteady behavior of leading-edge vortex and diffuser stall in a centrifugal compressor with vaned diffuser

Journal of Thermal Science ◽

10.1007/s11630-016-0829-z ◽

2016 ◽

Vol 25 (1) ◽

pp. 13-21 ◽

Cited By ~ 7

Author(s):

Nobumichi Fujisawa ◽

Shotaro Hara ◽

Yutaka Ohta

Keyword(s):

Centrifugal Compressor ◽

Leading Edge ◽

Vaned Diffuser ◽

Leading Edge Vortex ◽

Edge Vortex ◽

Unsteady Behavior

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Unsteady Behavior and Control of Diffuser Leading-Edge Vortex in a Centrifugal Compressor

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2010-22394 ◽

2010 ◽

Cited By ~ 4

Author(s):

Yutaka Ohta ◽

Takashi Goto ◽

Eisuke Outa

Keyword(s):

Flow Rate ◽

Noise Level ◽

Leading Edge ◽

Low Flow ◽

Leading Edge Vortex ◽

Passage Vortex ◽

Edge Vortex ◽

Compressor Performance ◽

And Control ◽

Unsteady Behavior

The unsteady behavior of a vortex generated on the diffuser leading-edge, which is called the leading-edge vortex (LEV), is discussed through experiments and numerical simulation. The LEV is different from the separating vortex of the diffuser leading-edge and passage vortex of the diffuser, develops rapidly with a decrease in the compressor mass flow rate, and forms a flow blockage in diffuser passages. Therefore, the evolution of the LEV may become a cause of diffuser stall. Additionally, in one attempt to control the LEV, two types of tapered diffuser vanes, which are shroud- or hub-side tapered diffuser vanes, were adopted. Though the shroud-side tapered diffuser vane can effectively reduce the compressor noise level, the compressor performance deteriorates remarkably. On the other hand, the hub-side tapered diffuser vane not only reduces the compressor noise level but also improves the compressor performance. According to the visualization results of the oil-film methods and numerical simulations, the hub-side tapered diffuser vane can suppress the evolution of the LEV in the compressor low-flow-rate operation.

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Stall and leading-edge vortex in a centrifugal compressor with vaned diffuser

Transactions of the JSME (in Japanese) ◽

10.1299/transjsme.15-00194 ◽

2015 ◽

Vol 81 (829) ◽

pp. 15-00194-15-00194 ◽

Cited By ~ 2

Author(s):

Nobumichi FUJISAWA ◽

Shotaro HARA ◽

Yutaka OHTA

Keyword(s):

Centrifugal Compressor ◽

Leading Edge ◽

Vaned Diffuser ◽

Leading Edge Vortex ◽

Edge Vortex

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Unsteady behavior of spiral leading-edge vortex breakdown

10.2514/6.1996-3408 ◽

1996 ◽

Cited By ~ 1

Author(s):

X. Huang ◽

E. Hanff

Keyword(s):

Vortex Breakdown ◽

Leading Edge ◽

Leading Edge Vortex ◽

Edge Vortex ◽

Unsteady Behavior

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G0501-6-4 Behavior of Leading-edge Vortex at Diffuser Vane of a Centrifugal Compressor

The proceedings of the JSME annual meeting ◽

10.1299/jsmemecjo.2009.2.0_59 ◽

2009 ◽

Vol 2009.2 (0) ◽

pp. 59-60

Author(s):

Takashi GOTO ◽

Eri OHMOTO ◽

Yutaka OHTA ◽

Eisuke OUTA

Keyword(s):

Centrifugal Compressor ◽

Leading Edge ◽

Leading Edge Vortex ◽

Edge Vortex

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Unsteady Behavior of Diffuser Stall in a Centrifugal Compressor With Vaned Diffuser

Volume 2D: Turbomachinery ◽

10.1115/gt2017-63400 ◽

2017 ◽

Cited By ~ 1

Author(s):

Nobumichi Fujisawa ◽

Daiki Ema ◽

Yutaka Ohta

Keyword(s):

Centrifugal Compressor ◽

Vortical Structure ◽

Leading Edge ◽

Rotating Stall ◽

Longitudinal Vortex ◽

Suction Surface ◽

Vaned Diffuser ◽

Edge Vortex ◽

Flow Blockage ◽

Unsteady Behavior

In this study, the unsteady behavior of a diffuser rotating stall in a centrifugal compressor with a vaned diffuser was investigated through experiments and numerical analyses. From the casing static pressure measurements, it was determined that the diffuser stall propagated at 25% of impeller rotational speed in the vaneless space. The numerical results revealed the presence of a typical vortical structure on the diffuser’s leading edge. Under partial flow condition, a tornado-type vortex was generated on the diffuser’s leading edge. Furthermore, a longitudinal vortex at the shroud/suction surface corner (i.e., leading edge vortex (LEV)) was induced by the rolling-up flow on the diffuser suction surface. As the velocity was decreased, the development of the tornado-type vortex and LEV forms a substantial flow blockage within the diffuser passages. Furthermore, the diffuser stall cell was caused by the systematic vortical structure which consisted of the tornado-type vortex, LEV, and vortex in the throat area of diffuser passages. In addition to this, the developed LEV interacted with the next diffuser leading edge and formed the throat area blockage with the passage of time. Then, the tornado-type vortex and LEV developed by the throat area blockage and diffuser stall cell, which was caused by the systematic vortical structure, propagated to the succeeding diffuser vane. Therefore, the diffuser stall in the centrifugal compressor was caused by the evolution of the tornado-type vortex and LEV.

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Flight

10.1093/oso/9780199674923.003.0032 ◽

2018 ◽

Author(s):

Anders Hedenström

Keyword(s):

Bird Species ◽

Leading Edge ◽

Micro Air Vehicles ◽

Leading Edge Vortex ◽

Confined Spaces ◽

Unsteady Aerodynamic ◽

Maneuvering Flight ◽

Edge Vortex ◽

Lifting Surfaces ◽

Animal Flight

Animal flight represents a great challenge and model for biomimetic design efforts. Powered flight at low speeds requires not only appropriate lifting surfaces (wings) and actuator (engine), but also an advanced sensory control system to allow maneuvering in confined spaces, and take-off and landing. Millions of years of evolutionary tinkering has resulted in modern birds and bats, which are achieve controlled maneuvering flight as well as hovering and cruising flight with trans-continental non-stop migratory flights enduring several days in some bird species. Unsteady aerodynamic mechanisms allows for hovering and slow flight in insects, birds and bats, such as for example the delayed stall with a leading edge vortex used to enhance lift at slows speeds. By studying animal flight with the aim of mimicking key adaptations allowing flight as found in animals, engineers will be able to design micro air vehicles of similar capacities.

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