| Summary: | This thesis outlines a detailed study comprising the simulation, design, construction, and experimental validation of two prototypes of looped-tube travelling wave thermoacoustic electricity generators. The prototypes used air at atmospheric pressure as working gas, an audio loudspeaker as linear alternator, while most of acoustic resonator parts were made of PVC components. The hot heat exchangers were externally heated. The first prototype was a small size, single-stage generator powered by combustion from a propane gas burner. The feedback pipe includes a branched alternator and an acoustic impedance matching stub. The effect of the heat input on the generator performance has been investigated. 13W of electrical power, extracted by 12Ω electric load, was achieved at flue gas temperature of 627.4°C and regenerator temperature difference of 430K. The second prototype was a larger sized (resonator inner diameter is 128 mm) two-stage generator. Here, the heat source was an electric air heat “gun” than provides air stream at 650°C. Firstly, the single-stage engine was examined at frequencies of 48.82, 64.45 and 70.31Hz. The experiments show that the streaming can reduce acoustic power from 110.63 to 63.4W at 70.31Hz. Furthermore, the acoustic power increases from 111.45 to 153 W when the frequency is increased from 48.82 to 64.45 Hz. Subsequently, a linear alternator was attached to the engine to convert the produced acoustic power into electricity. At a load of 9Ω the single-stage generator achieved 8.52W of electricity and 1.47% efficiency. The generator was further improved by incorporating an identical second stage. The effects of matching stub length, variable load and heat input were investigated. The two-stage prototype generated 14.18W of electrical power to a load of 9Ω with a thermal-to-electrical efficiency of 2.1%. The result indicated that the generators can supply enough electricity to power LED bulbs, and charge mobile phones and batteries.
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