Protrusion-enhanced flow and heat transfer in jet impingement cooling: a combined study

Impingement cooling in the mid-chord region of turbine vanes is constrained by reduced jet penetration resulting from strong crossflow accumulation, which significantly limits cooling effectiveness under engine-relevant conditions. This configuration differs from previous studies by explicitly tailoring the protrusion geometry and orientation to enhance jet–flow interaction control. Combined numerical simulations and experiments were performed to evaluate smooth, spherical, ellipsoidal, and teardrop protrusion plates, and to quantify the effects of jet Reynolds number (Re_j), protrusion height ( e/H ), and streamwise spacing ( s/H ). Results indicate that ellipsoidal protrusions provide the most favorable enhancement, increasing the area-averaged Nusselt number by 15 % at identical Re_j relative to a smooth plate. Increasing the ellipsoidal protrusion height from e/H = 0.25 to 0.75 yields a further 22 % improvement for Re_j ≥ 10,000, without incurring additional flow-resistance penalties. Reducing the streamwise spacing strengthens heat-transfer performance for all structured plates while keeping pressure-loss variations within 5 % across the investigated Reynolds numbers. These findings demonstrate that the proposed inclined-protrusion design offers an effective and low-penalty strategy for enhancing impingement cooling in turbine vane applications.