Experiment investigation of impingement/effusion cooling on overall cooling effectiveness and temperature gradients of afterburner heat shields in a high-performance aircraft engine

Considering that the jet impingement cooling method applied to the combustion chamber and turbine blade has a beneficial effect on the cooling performance, the impingement/effusion cooling was applied in the afterburner heat shield (DCH) to improve the reliability and durability of the afterburner cylinder. Although the impingement/effusion cooling scheme has been numerously investigated on the internal heat transfer, its investigation of conjugated heat transfer characteristics is limited as applying in the afterburner heat shield. This paper aims to investigate the effects of adding array impingement and area ratio on the conjugate heat transfer of afterburner heat shield. The surface temperatures on the mainstream side of DCH in the upstream (UR), midstream (MR), and downstream (DR) regions were measured using IR thermography under a high-temperature ratio between mainstream and coolant (T_g/T_c = 2). The overall cooling effectiveness (ϕ) and temperature uniformity (RSD) were plenty compared with the single-layer effusion cooling heat shield (ECH) at three momentum flux ratios (I = 0.02,0.22,0.50). Moreover, the area ratio of film to impingement holes (A_f/A_i) was enlarged from 1 to 4 to obtain high cooling effectiveness and low-temperature gradient. The results indicate that when I is larger than 0.22, the area-averaged ϕ of DCH compared with ECH can be improved by about 16% over the whole measured regions, and 20% in the UR with the lowest ϕ. In addition, the drop coefficient of the RSD of DCH can reach 18%. In comparison with the DCH at A_f/A_i = 1, the DCH with an area ratio of 4 can achieve gains of 80% and 45% on ϕ and RSD, respectively. Therefore, adding array impingement on the coolant side of DCH and increasing A_f/A_i cannot only effectively reduce the surface temperature of the heat shield and form efficient cooling in the UR, but also increase the temperature uniformity over the entire heat shield, thereby improving the reliability and durability of the afterburner cylinder. Furthermore, the comprehensive and new database can be used to evaluate the computational fluid dynamics simulations in related coupled and decoupled research.