Effect of taper angle on the performance of jet pumps for a loop-structured thermoacoustic engine

Abstract

Gedeon streaming, which circulates throughout the loop configuration with a time-averaged manner in the oscillating flow, can considerably deteriorate the efficiency of traveling-wave thermoacoustic engine. A jet pump is characterized by a tapered channel with different opening areas, which can produce a time-averaged pressure drop to suppress Gedeon streaming. Three jet pumps with different taper angles, i.e., 5°, 9°, 15°, are studied. Following Iguchi's hypothesis, the turbulent oscillating flow can be considered as a steady flow. The flow structures though the jet pumps are numerically simulated. Meanwhile, an experimental apparatus has been built to measure the performance of jet pump operating in the turbulent oscillating flow. The results show that the simulation is in a good agreement with the experiment data for the jet pumps with small taper angles. For the jet pump with 15° taper angle, the simulation results match well with the experiment data when the velocity at small opening of jet pump is higher than 50 m/s. However, when the velocity is lower, the simulation results deviate from the experiment data considerably, which can be attributed to the flow separation in the diverging direction operated differently in the steady flow and oscillating flow at lower velocity.