Experimental investigation of transient nonlinear phenomena in an annular thermoacoustic prime-mover: observation of a double-threshold effect Original Research Article

Thermoacoustic engines have been subjected to numerous studies for the past 10 years. Our current research is focused on the transient regime in an annular thermoacoustic prime-mover. It appears that several nonlinear phenomena can play a role in the amplification and saturation regimes. Indeed, acoustically induced conductivity, forced convection due to acoustic streaming, minor loss phenomenon, and saturation due to harmonic generation can be quoted among the others. The experiments presented here show for the first time a double-threshold phenomenon during the amplification regime. The first threshold, which corresponds to the setting of the thermoacoustic instability, is followed by a saturation regime. Then after a time delay, without any changes in the control parameters, a second threshold corresponding to an additional amplification has been observed.