Optimization of thermoacoustic stacks for maximum generation of acoustic energy

The stack of a thermoacoustic engine is optimized by the variation of pore geometry, operating pressure, working fluid, mean temperature gradient and the acoustic conditions at the stack. The goal of the optimization is to identify conditions that assure maximum generation of acoustic energy at the stack. For this purpose, the stack is described as an acoustic multi-port, represented mathematically by its scattering matrix. From the scattering matrix, an acoustic power balance matrix is deduced. The eigenvectors of the latter are acoustic states, which correspond to maximum generation or annihilation of acoustic energy at the multi-port ("instability potentiality"). Design parameters, operating conditions and frequencies are identified, which give maximum generation of acoustic energy. The maximum gain eigenvector is interpreted physically.