Investigation on the Mechanism of Thermoacoustic Instability of n-Decane at Subcritical Pressure

Abstract

Thermoacoustic instability of n-decane at subcritical pressure in a small-scale channel is investigated from three aspects: the flow pattern, the fluctuations of temperature and pressure, and the dynamic model. The results show that the thermoacoustic instability is a type of dynamic instability and experiences three stages: that is, appearance, development, and disappearance. Oscillations happen for the pressure drop, fluid temperature, and wall temperature when thermoacoustic instability appears. The thermoacoustic instability is driven by a positive and a negative feedback. When the outlet oil temperature reaches saturation temperature, the positive feedback loop is on, and the thermoacoustic oscillation happens. After that, the flow pattern near the outlet recovers to annular flow and then transforms to a single-gas flow, which leads the thermoacoustic oscillation to happen again.