Addressing heat transfer deterioration of supercritical aviation hydrocarbon fuel under systematically operational conditions

Heat transfer degradation (HTD) in supercritical RP-3 aviation kerosene is critical for thermal safety design of hypersonic engine regenerative cooling systems. Current research have two main limitations: 1) Most HTD studies focus on water and CO₂, while RP-3 has unique multi-component thermophysical properties; 2) It lacks wide range multi-parameter coupled analysis, and critical HTD boundaries are poorly quantified, thus limiting direct support for engine thermal safety design. To address these issues, this study utilizes k-ω SST turbulence model to numerically study supercritical RP-3 flow and heat transfer, accounting for its temperature and pressure dependent thermophysical properties. The investigation covers broad operating ranges of 523–773 K inlet temperature, 1.5–2.75 g/s mass flow, 3.0–5.5 MPa systematic pressure and 500–700 kW/m2 heat flux. The simulation results obtained are validated against the experimental data achieved from a valuable test rig (specifically designed for extreme high-temperature and high-pressure circumstances). The novelty of this work is reflected in four aspects: a) The inhibitory effect of inlet temperature increment on HTD is clarified, with the wall-temperature peak reduced by about 29%. At low inlet temperatures of 523–623 K, abrupt property variations triggers heat transfer deterioration; whereas at high inlet temperatures of 673–773 K, smoother property changes alleviate local heat accumulation. b) The coupled regulation of mass flow and heat flux is revealed, with the wall-temperature peak suppressed by 21.4% under high flow. At low mass flow rates of 1.5–2.0 g/s, higher heat absorption per unit mass intensifies thermal expansion; while at high flow rates of 2.25–2.75 g/s, stronger flow inertia suppresses expansion-induced HTD. c) The interactive suppression mechanism of system pressure and heat flux is resolved, with the peak wall temperature reduced by 31% under high pressure. At low pressures of 3.0–4.0 MPa, density fluctuations promote near-wall low-density-layer formation; whereas at high pressures of 4.5–5.5 MPa, weakened density fluctuation mitigates HTD. d) Within the broad operating ranges coupled, three HTD critical boundaries are quantitatively identified. Their engineering value lies in keeping systematically operational conditions above the boundaries through preheating, increased mass flow and sufficient pressure.