University of Twente Student Theses


Oscillatory Flow in Jet Pumps: Setup Design and Experiments

Vidya, M. C. (2014) Oscillatory Flow in Jet Pumps: Setup Design and Experiments.

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Abstract:Thermoacoustic devices have been developed over the past decades for various applications, such as power generation, cryogenic cooling, refrigeration and air conditioning. Despite the advantages of the thermoacoustic devices, there are still some challenges left that need to be solved, such as an acoustic streaming namely Gedeon streaming. To suppress the Gedeon streaming, a nonuniform cross‐sectional device known as a jet pump is studied. To study the effect of a jet pump, a thermoacoustic experimental setup is used. This setup has been used previously for experiments with a standing wave. In order to perform experiments with a traveling wave, a modification of the previous setup is required. Hence, a traveling wave termination using a quarter‐wavelength resonator was designed and tested. Results show that the termination works best at 113 Hz with absorption coefficient of 99.9%. The previous experimental setup and the modified setup are used to test four jet pump samples. The jet pump samples have been designed with various geometries to investigate the applicability of both Backhaus‐Swift quasi‐steady model and the steady flow minor loss coefficient in case of an oscillatory flow. The effect of the wave phasing and the geometrical parameters, such as taper angle and number of holes, in relation to pressure drop and acoustic power dissipation are investigated. It was found that different behavior occurs for high taper angle jet pumps (15° and 18°), therefore the quasi‐steady model of Backhaus‐Swift does not hold. The higher taper angle also leads to lower pressure drop and higher energy dissipation. Thus, the steady flow minor loss coefficient also cannot be applied in the case of oscillatory flow. To get a better understanding on the behavior of the oscillatory flow, a flow visualization experiment is conducted. A new test section for flow visualization, which uses a smoke wire method, has been developed. Using this method, the gas oscillation as well as three flow patterns can be observed. The first flow pattern that was observed is a mean flow that occurs at the outer boundary of the jet pump hole, in which the smoke is sucked into the jet pump. The second flow pattern is an outburst flow which is visible only at low velocity amplitude. The last flow pattern is a vortex ring that propagates away from the jet pump opening. It can be concluded that the smoke wire method can be applied to visualize the flow pattern of a jet pump in an oscillatory flow, which represents its condition in a thermoacoustic device. The observed flow patterns can be a reference for future research using other jet pump samples.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
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