PERFORMANCE EVALUATION OF STANDING WAVE THERMOACOUSTIC ENGINES REGARDING HARMONIC SUPPRESSION

Abstract

This work consists of a comparative study between two standing wave thermoacoustic engines that differ in the geometry of their resonant chambers, but hold the same internal elements and operate at the same fundamental frequency and boundary conditions. One of the engines consists of a straight tube of circular cross-section as its main part that defines a resonant acoustic waveguide, while the other one consists of, in addition to a similar straight tube, also a conical bulb connected to one of its ends acting as a coupled Helmholtz resonator. According to the literature, the Helmholtz cavity causes a higher pitch quality in the first harmonic mode, which is of greatest interest from the energetic point of view. The main objective of this work is to verify and evaluate such an effect on the engine performance so that to explore its optimization by means of frequency and geometric. Both engines are simulated in the DeltaEC software. DeltaEC, however, does not include harmonics other than the fundamental one. Understanding of the influence of higher acoustic modes may lead to a better management of the thermoacoustic engine configuration towards higher thermal efficiencies.