Experimental investigation on the onset of thermo-acoustic instability of supercritical hydrocarbon fuel flowing in a small-scale channel

• The thermo-acoustic instability is restrained with increasing mass flow rate.
• The threshold power varies non-monotonously with increasing inlet temperature.
• The threshold power varies non-monotonously with increasing operating pressure.
• The system stability is obviously promoted with increasing operating pressure.

Thermo-acoustic instability accompanied with abnormal sounds was observed for supercritical hydrocarbon fuel (RP-3) flowing in a heated small-scale channel. The instability appears when the applied heating power exceeds a threshold value. The threshold power can be affected by three operating parameters: fuel mass flow rate, channel inlet temperature and channel operating pressure. A series of experiments were designed to study the effect of these three parameters on the threshold power. It is found that the threshold power changes monotonously with fuel mass flow rate; while there is no simple linear effect of inlet temperature and operating pressure on the threshold power. Two dimensionless parameters, namely, sub-pseudo-critical number and true trans-pseudo-critical number were used to study the boundary of the thermo-acoustic instability. The result reveals that the system stability is significantly enhanced by increasing operating pressure; while the effect of mass flow rate on the system stability is strongly coupled with inlet temperature.