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Research Papers: Flows in Complex Systems

Instabilities of Nonreturn Valves in Low-Speed Air Systems

[+] Author and Article Information
Mark Potter, Marko Bacic

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

Phil Ligrani1

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

Matthew Plackett

Hardware Engineering-Fleet Controls, Rolls Royce PLC, P.O. Box 31, Derby DE24 8BJ, UK

1

Corresponding author.

J. Fluids Eng 130(12), 121105 (Oct 27, 2008) (8 pages) doi:10.1115/1.2969746 History: Received September 24, 2007; Revised March 25, 2008; Published October 27, 2008

Practical observations of the nonreturn valve wear in aero-engine cabin-bleed systems suggest that such valves are subject to unstable behavior. A theoretical model for the prediction of nonreturn valve instabilities in air systems is proposed and a nonlinear state-space model of the nonreturn valve and air volume interaction is derived from first principles. Experimental work is used to identify both the dynamic characteristics and the flow properties of the valve, which are used to identify the coefficients within the model. Through frequency analysis of valve oscillatory behavior, the levels of damping within the system are identified. Finally, using a local linearization of the state-space model an explicit mathematical prediction of valve stability is derived based on system parameters. These predictions are used to generate a map of the transition from stable to unstable system behavior for low-speed air flow, which is in excellent agreement with experimental data.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Spring-loaded twin flapper nonreturn valve

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Figure 2

Nonreturn valve geometry and loading

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Figure 3

Flow configuration, parameters, and arrangement

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Figure 4

Schematic of experimental setup and transducers

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Figure 5

Variation of the valve flap angle with system mass flow rate under stable operating conditions for all downstream volumes at different mass flow rates

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Figure 6

Variation of differential pressure across the valve with system mass flow rate under stable operating conditions for all downstream volumes at different mass flow rates

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Figure 7

Variation of the static discharge coefficient with the valve flap angle under stable operating conditions for all downstream volumes at different mass flow rates

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Figure 8

Variation of dynamic head with the valve flap angle (a) for a range of inlet densities (b) under stable operating conditions for all downstream volumes at different mass flow rates

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Figure 9

Variation in the valve pressure loading coefficient with the valve flap angle under stable operating conditions for all downstream volumes at different mass flow rates

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Figure 10

Example of the valve instability as mass flow rate varies with time (top) and as the valve flap angle varies with time (bottom) for a downstream volume of 0.034m3

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Figure 11

Theoretically predicted transition from stable to unstable behavior (line) along with experimentally measured stable data points (o) and unstable data points (+)

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