Experimental and numerical investigation on the film cooling and aerodynamic performance of a fully shielded strut featuring complex vortices

The fully shielded strut is an important component of aero-engines for achieving infrared stealth capability. Film cooling is applied on the strut surface to reduce the wall temperature and consequently suppress the infrared radiation intensity. Unlike turbine blades and other hot-section components, the flow within the strut passage is diffusive, leading to the formation of complex secondary vortices. This paper investigates the film cooling performance and aerodynamic characteristics of a fully shielded strut, with particular emphasis on the influence of secondary vortices. The film cooling effectiveness (FCE) was experimentally measured using the pressure-sensitive paint technique. Experiments were conducted under different blowing ratios (M = 0.75, 1.00, 1.25, and 1.50) and mainstream attack angles (δ = −10°, −5°, 0°, 5°, and 10°). Numerical simulations were further performed to elucidate the mechanisms in how vortex structures affect the coolant distribution. In addition, the aerodynamic performance of the film-cooled strut was numerically evaluated. The results show that the coolant exhibits lateral divergence and convergence in different regions under the combined influence of passage vortices and wall vortices. The FCE is positively correlated with the blowing ratio, the area-averaged FCE in the case of M = 1.50 increases by 29.9% in compared with the case of M = 0.75. While the FCE is negatively correlated with attack angle at positive attack angles, and the area-averaged FCE at δ = 10° decreases to 95.2% of the δ = 0° case. As for pressure loss, the introduction of film cooling results in an increase in total pressure loss of up to 15.7%. This work provides valuable insights for the film cooling design of aero-engine struts.