| The purpose of this research is to branch out from thermoacoustics in the plane wave geometry to study radial wave thermoacoustic engines. Two possible advantages of radial systems are proposed: a reduction in harmonic generation due to the natural anharmonicity of the resonator, and the possibility of improved engine performance using naturally sloped stacks.; The radial wave prime mover is described. Experimental results for the temperature at which oscillations begin are compared with theoretical predictions. Accounting for a pore distribution in the stack and temperature discontinuities between the stack and heat exchangers, theory and experiment are shown to be in agreement. In addition, spectral measurements in the radial prime mover show that the anharmonicity of the resonator significantly reduces non-linear harmonic generation.; To gain a better understanding of naturally sloped stacks in the radial engine, the physics of sloped stacks is extended to the plane geometry, where fewer constraints exist. A theoretical treatment of thermoacoustic engines with varying stack pore cross-section and/or varying resonator cross-section in the temperature gradient supporting stack region is presented along with numerical results for plane and radial wave prime movers and refrigerators. Results show significant improvements in refrigerator COP in plane wave systems. |
