Control of Thermoacoustic Chaotic Oscillations

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In thermoacoustic oscillators, a temperature gradient imposed on a gas column induces self-sustained acoustic oscillations. For the development of next generation, highly efficient thermoacoustic engines, lots of efforts are made to increase the pressure oscillations amplitude, which will lead to encounter nonlinear phenomena such as chaotic oscillations. In order to maintain these systems energy efficient, control methods are becoming necessary. On the other side, thermoacoustic oscillations can occur in gas turbine or rocket engines exposed to extreme temperatures. While threatening the stability operation and increasing NOx particles emissions of these systems, high amplitude thermoacoustic oscillations can severely damage the engines.After introducing a local contraction in simple thermoacoustic systems, we previously observed chaotic oscillations at low temperature ratios. By dissipatively coupling two of our new systems, we successfully stabilized the oscillations into a periodic motion as well as completely stopping the oscillations depending on the coupling strength and detuning parameters.We also applied a passive delay feedback on one oscillator and observed a suppression of the modes in the route to chaos by setting the delay to half of the oscillation period. Different modes were stabilized by varying the delay feedback strength and we observed an increase of the onset temperature ratio.Both the stabilization into a periodic motion and oscillation suppression find application in the development of new thermoacoustic engines and combustion engines respectively.