Observations of acoustically generated cavitation bubbles within typical fluids applied to a scroll expander lubrication system

This source preferred by Mark Hadfield

Authors: Tzanakis, I. and Hadfield, M.

Journal: Journal of Hydrodynamics

ISSN: 1001-6058

An experimental study using an ultrasonic transducer, submerged into the fluids (water-lubricant-refrigerant), is utilised to produce cavitation bubbles. Images are focused on two critical areas: the lower surface of the horn and across the boundary of the sample. The sample consists of a chromium ball mounted on a Bakelite base and implemented on the bottom of the experimental tank.

The results revealed that the lubricant bubbles have a similar behaviour to those produced in water. Refrigerant bubbles have a peculiar performance, especially across the boundary wall where they sustain a continuous oscillatory movement without regularly collapsing. The damage produced by the refrigerant bubbles is smaller than that observed within water and oil lubricant. On the contrary, lubricant bubbles exert a much higher micro-jet impact pressure. A lubrication thickness layer developed across the boundary is observed to provide a cushion, absorbing the jet impact during the implosion of a bubble. Thus the micro-jet impact pressure can significantly be decreased. A thorough investigation of the dynamic behaviour of the bubbles and their cavitation mechanisms is conducted using each of the three liquids respectively.

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Authors: Tzanakis, I., Hadfield, M. and Henshaw, I.

Journal: Experimental Thermal and Fluid Science

Volume: 35

Issue: 8

Pages: 1544-1554

ISSN: 0894-1777

DOI: 10.1016/j.expthermflusci.2011.07.005

An experimental study to evaluate the dynamic performance of three different types of cavitation bubbles is conducted. An ultrasonic transducer submerged into the working fluids of a scroll expander is utilised to produce cavitation bubbles and a high speed camera device is used to capture their behaviour. Three critical regions around the ultrasonic source, between the source and the solid boundary, and across the solid boundary were observed. Experimental results revealed that refrigerant bubbles sustain a continuous oscillatory movement, referenced as " wobbling effect" , without regularly collapsing. Analytical results indicate the influence of several factors such as surface tension/viscosity ratio, Reynolds number and Weber number which interpret that particular behaviour of the refrigerant bubbles. Within the refrigerant environment the bubbles obtain large Reynolds numbers and low Weber numbers. In contrast, within the lubricant and the water environment Weber number is significantly higher and Reynolds number substantially lower. The bubble radius and velocity alterations are accurately calculated during the cavitation process. Lubricant bubbles achieve the highest jet velocity while refrigerant bubbles having the lowest jet velocity are not considered as a destructive mean of cavitation for scroll expander systems. © 2011 Elsevier Inc.

This data was imported from Web of Science (Lite):

Authors: Tzanakis, I., Hadfield, M. and Henshaw, I.

Journal: EXPERIMENTAL THERMAL AND FLUID SCIENCE

Volume: 35

Issue: 8

Pages: 1544-1554

ISSN: 0894-1777

DOI: 10.1016/j.expthermflusci.2011.07.005

The data on this page was last updated at 05:10 on February 18, 2020.