Abstract
This paper presents a unied stability analysis method for thermoacoustic systems based on the Nyquist stability criterion for MIMO systems. The method consists of two procedures: (i) conventional frequency response function (transfer matrix) is transformed into the one for causal system whose input and output signals are incoming and outgoing traveling-wave pressure components; (ii) the transformed response is used to analyze the closed-loop stability by the Nyquist stability criterion for MIMO systems. It is shown that the stability analysis for both standing- and traveling-wave thermoacoustic engines can be carried out by a unied procedure. The analysis results are consistent with the actual situations of oscillation indicating reasonable stability and/or instability margins for various geometrical changes as well as the temperature ratios in engines.
