Prediction of Fluid Inertance in Nonuniform Passageways

[+] Author and Article Information
D. Nigel Johnston

Department of Mechanical Engineering, University of Bath, United Kingdom

J. Fluids Eng 128(2), 266-275 (Jan 10, 2006) (10 pages) doi:10.1115/1.2171713 History: Received August 23, 2004; Revised January 10, 2006

The dynamic response, stability, and noise characteristics of fluid components and systems can be strongly influenced by the inertance of the fluid in passageways, which are often of complex geometry. The inertance is a parameter that has often proved to be very difficult to accurately quantify, either theoretically or experimentally. This paper presents a method of numerical calculation of the inertance in a passageway, assuming inviscid, incompressible flow and zero mean flow. The method is simple to apply and can be applied to geometries of arbitrary complexity. Two simple but unorthodox ways of calculating inertance using a computational fluid dynamics and a finite element solid-modeling package are also demonstrated. Results are presented for a simple cylindrical orifice, a simple spool valve, and a conical poppet valve. The effect of the inertance on the response of a poppet valve is demonstrated.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Simplified hydraulic circuit for “secondary source” test method

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Figure 2

Finite volume cell

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Figure 3

Cylindrical orifice model: contours of pressure amplitude (only region near orifice shown)

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Figure 4

End correction for cylindrical orifices

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Figure 5

Spool valve model: contours of pressure amplitude

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Figure 6

Effective length for spool valve orifice

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Figure 7

Poppet valve model: contours of pressure amplitude

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Figure 8

Effective length for poppet valve

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Figure 9

Pressure distribution in a square restriction obtained using CFD

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Figure 10

Simplified schematic diagram of relief valve

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Figure 11

Measured and predicted pressure ratio in relief valve

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Figure 12

Predicted impedance of a relief valve



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