Streamwise evolution and mechanism of film cooling over a longitudinal corrugated heat shield in an aero-engine afterburner

Reliable film cooling is essential for protecting afterburner heat shields subjected to extremely high thermal loads in modern aero-engines. However, most previous studies have focused on short corrugated configurations or limited corrugation segments, while the film cooling behavior along long-axial corrugated heat shields, which are commonly used in practical afterburners, remains poorly understood. In this study, the film cooling characteristics of a longitudinal corrugated heat shield with multiple corrugation waves were investigated using pressure-sensitive paint measurements combined with numerical simulations, and the effects of momentum ratio (I), mainstream Reynolds number (Re_g), amplitude ratio (A/L), and open ratio (φ) were systematically examined. The results reveal a pronounced streamwise evolution of the cooling behavior, with vortex-dominated cooling upstream and film-accumulation-dominated behavior downstream. Increasing I stabilizes the coolant film and transforms the streamwise distribution from persistent oscillations to upstream fluctuations followed by downstream stabilization. Increasing Re_g from 1.8 × 10⁴ to 8.8 × 10⁴ accelerates coolant dissipation and weakens downstream cooling. Increasing A/L from 0.045 to 0.065 reduces the film cooling effectiveness (η) by 16.1% upstream and 24.4% downstream. In addition, η shows a non-monotonic dependence on φ, with downstream improvement reaching 44.9% at φ = 2.62%, higher than the 37.0% increase upstream. These results reveal the underlying evolution mechanism of film cooling in long corrugated channels and provide guidance for the design of high-efficiency afterburner heat shields.