Heat transfer characteristics induced by multiple tandem elevated inclined jets sources in cross flows

Abstract

Consideration is given in this paper to the heat transfer induced in an elevated triplet-jet-group in cross flow numerical configuration. The jets are discharged from inclined, inline and elevated cylindrical ducts. We are particularly concerned with the generated aerothermic mixing, a critical and highly affecting parameter in the protection of turbine blade surfaces subject to high temperature levels, in the optimization of air-fuel mixing, and then combustion within scramjet combustors, in the reduction of noise by means of air curtains, etc. Since the generated heat fluxes are closely related to the interacting flows' dynamics and corresponding turbulent features, we intend to bring here some clearance on the development of the aerothermic mixing of an elevated cascaded jet model within a cross flow. To reach our goal, a finite volume method is adopted to reproduce experimental data relative to three isothermal and 60°-inclined jets, placed three diameters apart, sent at a given height from the wind tunnel ground and discharged from similar elliptical cross-sections, under different injection ratios. A mesh sensibility study and different turbulence modeling tests were carried out to obtain the consistent validation of the jets’ velocities and trajectories. The first-order kωSST and the second-order RSM models gave particularly interesting results. Once a satisfactory agreement was achieved, a temperature difference between the jets and the mainstream was adopted to upgrade the model. We could then account for the induced heat transfer through the analysis of the reduced static temperature, a particularly interesting parameter for its closeness (if not similarity under some circumstances) to the film cooling efficiency.

Keywords

• Triplet jet
• Cross flow
• Jets' trajectory
• Heat transfer
• Injection height
• Static temperature ratio