Oscillatory flow in jet pumps. Setup design and experiments
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 resolved, such as an acoustic streaming namely Gedeon streaming. To suppress the Gedeon streaming, a non-uniform cross-sectional device known as a jet pump is studied.
A thermoacoustic experimental setup is used to study the effect of a jet pump. This setup has been used before for experiments with a standing wave. In order to perform experiments with a traveling wave, a modification of this thermoacoustic setup is required. Thus, a traveling wave termination using a quarter-wavelength resonator was designed and tested. This termination works best at 113 Hz with absorption coefficient of 99.8%.
Four jet pump samples have been designed with various geometries. Series of experiments were performed for these samples using both standing wave and traveling wave setup. The effects of taper angle, number of holes and wave phasing to the pressure drop and acoustic power dissipation are investigated. It was found that different behavior occurs for high taper angle jet pumps (15° and 18°). The quasi-steady model of Backhaus and Swift does not hold for both cases. The higher taper angle also leads to lower pressure drop and higher energy dissipation.
A new test section for flow visualization using a smoke wire has been developed. Using this method, the gas oscillation can be observed, as well as a mean flow. A mean flow occurs at the outer boundary of the jet pump hole, where the smoke is sucked into the jet pump. Another flow pattern is visible in the form of a vortex ring that propagates from the jet pump opening. It can be concluded that the experimental results can give a better understanding of the flow pattern and jet pump behavior in an oscillating flow, which represents its condition in a thermoacoustic device.