Experimental study on flow instability of aviation kerosene under supercritical pressure in a vertical upward circular tube was conducted. The time-dependent inside-wall temperature

mass flux

outlet temperature and inlet-outlet pressure drop oscillations were investigated. The formation reason and feedback mechanism of flow instability were expounded. The expression for critical heat load prediction of flow instability was obtained. Results indicated that the abnormal fluctuations of inside-wall temperature and inlet-outlet pressure drop occurred under the flow instability conditions. The flow instability was caused by a gas-like state film

owing to the deteriorated heat transfer during the development process of boundary layer. Two types of feedback mechanism were found. On the one hand

the deteriorated and enhanced heat transfer appeared alternately due to the pseudo-film boiling and pseudo-nuclear boiling

which led to the thermal instability. On the other hand

the pressure disturbance triggered the acoustic wave

the compressed wave made a decrease in thickness of gas-like state film

and enhanced the heat transfer

while the expandsion wave made an increase in thickness of gas-like state film

and weakened the heat transfer

leading to the acoustic wave instability. The comprehensive effects of these two feedback mechanisms cause the thermo-acoustic oscillation phenomenon.