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Research Papers

Rain Ingestion in Axial Flow Compressors at Part Speed

[+] Author and Article Information
Ivor Day

Whittle Laboratory, University of Cambridge, Cambridge, CB3 0DY, United Kingdom

John Williams1

 Department of Engineering Science, University of Oxford Parks Road Oxford, OX1 3PJ, United Kingdom

Christopher Freeman

 Whittle Laboratory, University of Cambridge, Cambridge, CB3 0DY, United Kingdom

1

Formerly of the Whittle Laboratory, Cambridge.

J. Turbomach 130(1), 011024 (Feb 01, 2008) (10 pages) doi:10.1115/1.2366511 History: Received October 01, 2004; Revised February 01, 2005; Published February 01, 2008

New experimental work is reported on the effects of water ingestion on the performance of an axial flow compressor. The background to the work is the effect that heavy rain has on an aeroengine compressor when operating in a “descent idle” mode, i.e., when the compressor is operating at part speed and when the aeromechanical effects of water ingestion are more important than the thermodynamic effects. Most of our existing knowledge in this field comes from whole engine tests. The current work provides the first known results from direct measurements on a stand-alone compressor. The influence of droplet size on path trajectory is considered both computationally and experimentally to show that most rain droplets will collide with the first row of rotor blades. The water on the blades is then centrifuged toward the casing where the normal airflow patterns in the vicinity of the rotor tips are disrupted. The result of this disruption is a reduction in compressor delivery pressure and an increase in the torque required to keep the compressor speed constant. Both effects reduce the efficiency of the machine. The behavior of the water in the blade rows is examined in detail, and simple models are proposed to explain the loss of pressure rise and the increase in torque. The measurements were obtained in a low speed compressor, making it possible to study the mechanical (increase in torque) and aerodynamic (reduction in pressure rise) effects of water ingestion without the added complication of thermodynamic effects.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Droplet trajectories through rotor 1 for various droplet diameters

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Figure 2

Schematic of compressor test facility

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Figure 3

Overall pressure rise characteristics for different amounts of water ingested

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Figure 4

Loss of pressure rise at stall as a function of the amount of water ingested

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Figure 5

Characteristics showing the increase in corrected torque brought about by 11.4% water ingested

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Figure 6

Variation in corrected torque at stall point for various quantities of water ingested

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Figure 7

Static-to-static pressure rise characteristics for stage 1

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Figure 8

Water extraction measurements taken downstream of rotor 3 for 17.1% water ingested

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Figure 9

Photograph of cascade experiment showing sheets of water coming off the pressure side of the stator blades

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Figure 10

Water concentration measurements obtained from area traverse downstream of stator 3

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Figure 11

Sketch of water distribution on suction side of stator blades

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Figure 12

Local pressure recovery in compressor after sudden termination of water supply

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Figure 13

Shift in axial velocity distribution near stall due to 17.1% water ingestion

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Figure 14

Shift in rotor relative exit angle near stall due to 17.1% water ingestion

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Figure 15

Stator exit angles near stall for wet and dry operation

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Figure 16

Isentropic pressure rise compared with actual pressure rise near stall for wet and dry conditions, for stage 3

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Figure 17

Efficiency estimates for wet and dry conditions near stall, for stage 3

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Figure 18

Parallel annulus model showing the wet operating points of the inner (C) and outer (D) parts of the annulus

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Figure 19

Movement of operating points on overall total-to-static characteristic for sudden water injection

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