Mechanism and influencing factors analysis of flowing instability of supercritical endothermic hydrocarbon fuel within a small-scale channel

Abstract

Regenerative cooling technology is widely used in advanced engines which use fuel as coolant. The occurrence of fuel flow instability during cooling process should be forbidden because it brings harm to the safe operation of the engine. The instability of supercritical endothermic hydrocarbon fuel flow during cooling is experimentally studied. Mechanism of instability is interpreted through the simulation results of a zero-dimension homogeneous model. Stability criterion is established and influencing factors are analyzed using the small deviation linearization theory and stability analysis method in the automatic control field. The experimental results indicate the instability of supercritical hydrocarbon fuel flow occurs in critical temperature region and cracking temperature region. The acute decrease in fuel density near the critical temperature region and cracking temperature region is the primary cause for instability of fuel flow. And the instability can be weakened by increasing tube heat capacity and compressible volume stiffness coefficient, reducing mass flow rate and using a fuel with density changing smoothly with temperature. The investigation on the instability mechanism and influencing factors offer guidance on inhibition methods, which can secure the stable fuel flow of cooling system.