The transport and thermodynamic characteristics of thermally oscillating phenomena in a buoyancy-driven supercritical fuel flow

To ameliorate the thermal management of a regenerative cooling system in an advanced engine, the turbulence characteristics and entropy generation in a buoyancy-driven supercritical hydrocarbon fuel flow are numerically explored in detail. Several common buoyancy criteria (Gr/Re², Gr/Re^2.7 and Gr_q/Gr_th) are established and a three-dimensional numerical model is solved with an advanced LES model. The turbulence characteristics demonstrate that the complex and anisotropic transport properties dramatically redistribute the flow structure and thermal field and the buoyancy-induced production, P_b=−gρu_j^'‾, is strongly related to the heat transfer regime. The thermal characteristics, ρ(u_ih_s‾−u_i‾h_s‾), indicate that the laminar flow weakens the wall-normal turbulent heat flux, and the buoyancy-driven flow is responsible for the change of stream-wise turbulent heat flux. Based on the second law of thermodynamics, the two typical irreversible entropy generations are discussed, and interestingly, the existing oscillations enlarge the diffusion of local heat entropy and promote the wider heat transfer. The results provide a methodological guidance for thermal management of engines cooling systems.