Graduation Year

2015

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Mechanical Engineering

Major Professor

Jose L. Porteiro, Ph.D.

Co-Major Professor

Steven T. Weber, Ph.D.

Committee Member

Rajiv Dubey, Ph.D.

Committee Member

Richard Gilbert, Ph.D.

Committee Member

Craig Lusk, Ph.D.

Committee Member

Kandethody Ramachandran, Ph.D.

Keywords

Fluid Flow, High Pressure, Low Pressure, Mass Flow Rate, Steady State Analysis, Unsteady State Analysis

Abstract

The main objective of this study is to explore the complex fluid flow phenomena that result in the generation of a high frequency noise in counterbalance valves through an experimental and numerical investigation of the flow. Once the influence of the different components involved in noise generation is established, a secondary objective is the introduction of design modifications that eliminate the undesired effect without altering the operation envelope or the performance of the valve.

A hydraulic test bench was used to carry out an experimental investigation of the noise generation process. A computer based data acquisition system was used to record pressure fluctuations, flowrates and hydraulic oil temperatures in a production valve under a variety of operational conditions. Extensive experimental measurements and numerical modeling lead to the hypothesis that noise generation is the result of an acoustic resonance triggered by shear layer instability at the valve inlet. The pressure gradients developed when the shear layer entrains the stagnant fluid in the valve main cavity cause the layer to become unstable and oscillate. The oscillation frequency will depend on a great number of factors such as valve geometry, pressure and velocity gradients and the density and viscosity of the fluid. It is postulated that the observed noise is generated when this frequency matches one of the resonant frequencies of the valve cavity.

The proposed mechanism is theoretically poorly understood and well beyond simplified analysis, its accurate numerical simulation is computational very intensive requiring sophisticated CFD codes. The numerical investigation was carried out using STAR–CCM+, a commercially available CFD code featuring 3-D capabilities and sophisticated turbulence modeling. Streamline, pressure, velocity-vector and velocity-scalar plots were obtained for several valve configurations using steady and unsteady state flow simulations.

An experimental and numerical analysis of an alternative valve geometry was carried out. Experimental results demonstrated a greatly reduced instability range. The numerical analysis of the unsteady behavior of the shear-layer streamlines for both valves yielded results that were compatible with the experimental work.

The results of this investigation promise a great positive impact on the design of this type of hydraulic valves.

Steady state movie for A mid gap.avi (15439 kB)
Steady state movie for A-small-gap

Steady state movie for A-large gap.avi (15436 kB)
Steady state movie for A mid gap

Steady state movie for A-small-gap.avi (15436 kB)
Steady state movie for A-large gap

Steady state movie for B-large gap.avi (15425 kB)
Steady state movie for B-small gap

Steady state movie for B-mid gapn.avi (15439 kB)
Steady state movie for B-mid gap

Steady state movie for B-small gap.avi (14567 kB)
Steady state movie for B-large gap

Unsteady state movie for A-large gap.avi (76885 kB)
Unsteady state movie for A-large gap

Unsteady state movie for A-mid gap.avi (15438 kB)
Unsteady state movie for A-mid gap

Unsteady state movie for A-small gap.avi (30789 kB)
Unsteady state movie for A-small gap

Unsteady state movie for B-large gap.avi (30789 kB)
Unsteady state movie for B-large gap

Unsteady state movie for B-mid gap.avi (15434 kB)
Unsteady state movie for B-mid gap

Unsteady state movie for B-small gap.avi (30806 kB)
Unsteady state movie for B-small gap

Additional Files

Steady state movie for A mid gap.avi (15439 kB)
Steady state movie for A-small-gap

Steady state movie for A-large gap.avi (15436 kB)
Steady state movie for A mid gap

Steady state movie for A-small-gap.avi (15436 kB)
Steady state movie for A-large gap

Steady state movie for B-large gap.avi (15425 kB)
Steady state movie for B-small gap

Steady state movie for B-mid gapn.avi (15439 kB)
Steady state movie for B-mid gap

Steady state movie for B-small gap.avi (14567 kB)
Steady state movie for B-large gap

Unsteady state movie for A-large gap.avi (76885 kB)
Unsteady state movie for A-large gap

Unsteady state movie for A-mid gap.avi (15438 kB)
Unsteady state movie for A-mid gap

Unsteady state movie for A-small gap.avi (30789 kB)
Unsteady state movie for A-small gap

Unsteady state movie for B-large gap.avi (30789 kB)
Unsteady state movie for B-large gap

Unsteady state movie for B-mid gap.avi (15434 kB)
Unsteady state movie for B-mid gap

Unsteady state movie for B-small gap.avi (30806 kB)
Unsteady state movie for B-small gap

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