Numerical investigation on flow and heat transfer mechanisms of supercritical pressure hydrocarbon fuel in lattice structures

The viability of using lightweight lattice structures instead of rectangular active cooling channels in thermal protection of high-temperature walls of a high Mach number air-breathing engine was explored in this study. The flow and heat transfer characteristics of supercritical pressure RP-3 inside three types of lattice active cooling structures were numerically investigated. The operating pressure， wall heat flux， and inlet Reynolds number were 5 MPa， 2 MW·m-2， and 6 804， respectively. The results indicated that the lattice core， which was an enhancing element， significantly improved the heat transfer performance on the heated wall. Complex vortex structures were formed as the fuel flowed around the rods， and the shear stress was strengthened. The developed flow and thermal boundary layers were disturbed， and the mixing between fluids in the near-wall region and flow core was also enhanced. Based on the NACA airfoil profiles， a new modified 3D-Kagome lattice active cooling structure was proposed. The heat transfer factor γ of the modified 3D-Kagome lattice structure increased by 8.6% compared with the rectangular cooling channel. The maximum temperature， average temperature， and standard deviation of the temperature on the heating wall are reduced by 6.74%， 5.92%， and 77.08%， respectively. Meanwhile， the structural weight was reduced by 14.8%. The ratio of heat flux across the heated surface of the fluid domain to the total heat flux was 72.16%~81.38%. Future research on enhancing the heat transfer rate on the heated surface and reducing the thermal resistance inside the lattice core rods might find significance in the optimization of lattice active cooling structures.