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Your search keyword '"Ho, W."' showing total 86 results
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13. Macrophages

Author

Fehder, W.P., primary, Tuluc, F., additional, Ho, W.-Z., additional, and Douglas, S.D., additional

Published
2007
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23. Overview

Author

Ho, W. S. Winston, primary and Sirkar, Kamalesh K., additional

Published
1992
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25. Theory

Author

Ho, W. S. Winston, primary and Li, Norman N., additional

Published
1992
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42. Effect of Upstream Velocity Gradient on the Formation of Sink Vortices in a Jet Engine Test Cell.

Author

Ho, W. H., Dumbleton, H., and Jermy, M. C.

Subjects
VORTEX motion, JET engines, SPEED, COMPRESSORS, AIRPLANE motors
Abstract

Vortices can be produced and ingested into the intake of a jet engine during high power operation in the vicinity of solid surfaces causing Foreign Object Damage (FOD) or compressor stall and engine surge problems. This can occur when the engine is mounted on the wing of a plane during take-off and engine ground runs or when the engine is placed inside a test cell for testing after an engine overhaul and prior to reinstallation onto the aircraft. Procedures have been put in placed to prevent such damage from occurring on the runway. However to prevent such vortices from forming, especially in the test cells, it is necessary to be able to predict the onset of the vortex or at least to understand the factors affecting the formation of such vortices. Vortex formation in an enclosed cell is different from vortex formation over a solid plane (runway scenario). Ho and Jermy investigated vortex formation using a suction tube in a open-end box model simulating an engine in a test cell scenario and found that 3 distinct regimes of flow (regular vortex, deformed vortex and no vortex) exists as opposed to the simple vortex/no vortex flow for runway scenario. This paper extends the work by first investigating the effects changing upstream velocity gradient has on the threshold and then investigating the potential source of this upstream velocity gradient in real cells using two separate CFD simulations. The results show that an increase in upstream velocity gradient (/s) increases the range of conditions over which a vortex forms. All three regimes show signs of shifting the threshold of vortex formation to lower ratio of inlet velocity over upstream average velocity (Vi/Vo) for a given ratio of inlet height over inlet diameter (H/Di). A separate set of simulations performed showed that wind blowing across the intake stack of a U-shaped jet engine test cell produces net vorticity in the upstream plane perpendicular to the longitudinal direction of the of the suction tube. This vorticity is implicated in the formation of the vortices. [ABSTRACT FROM AUTHOR]

Published
2008

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