This report intends to shed an insight into the effect of large relative tip clearances on the onset of instability in a highly loaded centrifugal compressor. Time-resolved pressure measurements have been performed along the casing of a scaled-up model of a small compressor for two clearances at a wide range of operating conditions. Based on these time-resolved measurements, the pressure distribution along the meridional length and the blade loading distribution are calculated for each operating condition. In addition, the phase locked pressure fluctuation and its deviation are computed. The results show the behavior of each subcomponent of the compressor at different flow conditions and explain the role of the relative tip clearance on the onset of instability. For high mass-flow rates, the steady pressure distribution along the casing reveals that the inducer acts as an accelerating nozzle. Pressure is only built up in the radial part due to the centrifugal forces and in the subsequent diffuser due to area change. For off-design conditions, incidence effects are seen in the blade loading distribution at the leading edge while the inducer is unloaded. A region of high pressure deviation originates at the leading edge of the main blade and convects downstream. This feature is interpreted as the trajectory of the leakage vortex. The trajectory of these vortices is strongly affected by the mass-flow coefficient. If the mass-flow rate is sufficiently small, the trajectory of the leakage vortex becomes perpendicular to the axis of rotation, the leakage vortex interacts with the adjacent blade, and inlet tip recirculation is triggered. If the flow rate is further reduced, the leakage vortex vanishes and rotating stall is initiated in the diffuser. For larger clearances, stronger vortices are formed, stall is triggered at higher flow rates, and the overall compressor performance deteriorates.
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July 2008
Research Papers
Clearance Effects on the Onset of Instability in a Centrifugal Compressor
Matthias Schleer,
Matthias Schleer
Turbomachinery Laboratory,
Swiss Federal Institute of Technology Zurich
, 8092 Zurich, Switzerland
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Seung Jin Song,
Seung Jin Song
School of Mechanical and Aerospace Engineering,
Seoul National University
, 151-742 Seoul, Korea
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Reza S. Abhari
Reza S. Abhari
Turbomachinery Laboratory,
Swiss Federal Institute of Technology Zurich
, 8092 Zurich, Switzerland
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Matthias Schleer
Turbomachinery Laboratory,
Swiss Federal Institute of Technology Zurich
, 8092 Zurich, Switzerland
Seung Jin Song
School of Mechanical and Aerospace Engineering,
Seoul National University
, 151-742 Seoul, Korea
Reza S. Abhari
Turbomachinery Laboratory,
Swiss Federal Institute of Technology Zurich
, 8092 Zurich, SwitzerlandJ. Turbomach. Jul 2008, 130(3): 031002 (11 pages)
Published Online: April 1, 2008
Article history
Received:
November 23, 2006
Revised:
December 10, 2006
Published:
April 1, 2008
Citation
Schleer, M., Song, S. J., and Abhari, R. S. (April 1, 2008). "Clearance Effects on the Onset of Instability in a Centrifugal Compressor." ASME. J. Turbomach. July 2008; 130(3): 031002. https://doi.org/10.1115/1.2776956
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