Turbulent Flow, Heat Transfer Deterioration, and Thermal Oxidation of Jet Fuel

Computational fluid dynamics simulations can be used to simulate the flow, heat transfer, and fuel chemistry within fuel system cooling passageways. The standard k-epsilon turbulence model with the standard wall function, renormalization group k-epsilon model with an enhanced wall function, and the shear stress transport k-omega model were evaluated for their ability to represent turbulent fuel flow and heat transfer under high heat flux and flow rate conditions. The renormalization group k-epsilon model with an enhanced wall function provided the greatest fidelity in representation of turbulent thermal and flow behavior studied in heated tube experiments conducted at supercritical pressure. Moreover, the renormalization group k-epsilon model with an enhanced wall function allowed reasonable simulation of heat transfer deterioration, which was more likely for flow conditions involving a large heat flux with low mass flux rate. As the fuel was heated from the liquid to the supercritical phase, the viscosity temperature dependence was the primary transport property leading to heat transfer deterioration. A pseudodetailed chemical kinetic mechanism was used to study the effect of high heat flux and flow rate on dissolved O-2 consumption together with a global submechanism for the simulation of thermal-oxidative surface deposition. The deposition submechanism developed previously for low heat flux conditions provided reasonable agreement between normalized, measured, and simulated deposit profiles.