Numerical investigation on the control of cryogenic fluid oscillations by applying an external sound source

Abstract

Self-excited oscillations that occur in the cryogenic helium tube system are seen as thermoacoustic instabilities. To increase the operation stability of the system and suppress the conversion of thermal energy into acoustic waves, one solution where an external sound source driven by a piston is applied to control oscillations in a helium tube system. In this work, a numerical study of minimizing self-excited oscillations is conducted. Oscillation frequency and amplitude of the coupling system of the helium tube system and the external sound source are acquired as functions of the piston speed and frequency. It is found that the suppression of pressure oscillations can be achieved when the driving frequency is far from the self-excited oscillation frequency of the cryogenic helium tube. Increasing the driving speed of the piston gives rise to the coupling oscillation amplitude, and the control strategy leads to 99.2% oscillation amplitude reduction. Moreover, the nonlinear dynamics behavior caused by the coupling of self-excited oscillations and the external sound source is revealed. Synchronization of frequency occurs when the system is coupled to the external sound source oscillating with different frequencies. Our findings could provide a guideline in minimizing self-excited oscillations in the cryogenic helium system.