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Research Papers

Impeller-Vaned Diffuser Interaction in a Centrifugal Compressor at Off Design Conditions

[+] Author and Article Information
P. Gaetani

Laboratorio di Fluidodinamica delle Macchine, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini, 4, 20158 Milano, Italypaolo.gaetani@polimi.it

G. Persico

Laboratorio di Fluidodinamica delle Macchine, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini, 4, 20158 Milano, Italygiacomo.persico@polimi.it

A. Mora

Laboratorio di Fluidodinamica delle Macchine, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini, 4, 20158 Milano, Italyalessandro.mora@polimi.it

V. Dossena

Laboratorio di Fluidodinamica delle Macchine, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini, 4, 20158 Milano, Italyvincenzo.dossena@polimi.it

C. Osnaghi

Laboratorio di Fluidodinamica delle Macchine, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini, 4, 20158 Milano, Italycarlo.osnaghi@polimi.it

J. Turbomach 134(6), 061034 (Sep 12, 2012) (9 pages) doi:10.1115/1.4006295 History: Received July 19, 2011; Revised July 21, 2011; Published September 12, 2012; Online September 12, 2012

As centrifugal compressors find a huge number of applications in industry and in aero-engines, the detailed analysis and comprehension of the impeller-vaned diffuser interaction is of interest to improve the efficiency and the operating range. This paper presents the results of a wide experimental campaign devoted to the understanding of the impeller-diffuser interaction; in particular, the paper focuses on the features occurring when the compressor works in off design conditions. Data were taken at three operating points (near surge, best efficiency, and maximum flow rate point) in the impeller-vaned diffuser gap by a fast response probe; the single stage compressor runs at 12,500 RPM giving a peripheral Mach number of 0.77. At first, data are reduced to evidence the main impeller flow features, which are compared at different flow rates. Furthermore time mean diffuser effects on the impeller are commented and finally the impeller-diffuser interaction is discussed. Results evidence the effect of the diffuser on the impeller, mainly in terms of static pressure and flow velocity, which have a strong dependence on the flow rate.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Compressor geometry

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Figure 2

Meridional and blade to blade views. Detail of mutual impeller-diffuser position at t/T = 0.0.

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Figure 3

Time-mean TKE field in the rotating frame at traverse R1

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Figure 4

Time-mean relative Mach number field in the rotating frame at traverse R1

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Figure 5

Time-mean flow angle field in the rotating frame at traverse R1

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Figure 6

Time-mean static pressure field in the rotating frame at traverse R1

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Figure 7

Pitch-wise averaged profiles of flow angle just downstream of the impeller (R1) and just upstream of the vane (R4)

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Figure 8

Time-mean static pressure field in the stationary frame upstream of the vane at h/h2  = 38%

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Figure 9

Time-mean flow angle distribution in the stationary frame upstream of the vane at h/h2  = 38%

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Figure 10

Total pressure snapshots at two instants for maximum flow rate at h/h2  = 38%

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Figure 11

Total pressure snapshots at two instants for minimum flow rate at h/h2  = 38%

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Figure 12

Mach number snapshots at four instants for minimum flow rate at h/h2  = 38%

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Figure 13

Static pressure snapshots at four instants for minimum flow rate at h/h2  = 38%

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Figure 14

Static pressure fluctuations for all the interaction phases over an impeller pitch: minimum flow rate, h/h2  = 38%

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Figure 15

Flow angle snapshots at four instants for minimum flow rate at h/h2  = 38%

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Figure 16

Mach number snapshots at two instants for maximum flow rate h/h2  = 38%

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Figure 17

Static pressure snapshots at four instants for the maximum flow rate at h/h2  = 38%

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