Investigations of improved cooling effectiveness for ramp film cooling with compound angle film cooling jets

Purpose This paper aims to investigate the film cooling effectiveness (FCE) and mixing flow characteristics of the flat surface ramp model integrated with a compound angled film cooling jet. Design/methodology/approach Three-dimensional numerical simulation is performed on a flat surface ramp model with Reynolds Averaged Navier-Stokes approach using a finite volume solver. The tested model has a fixed ramp angle of 24 degrees and a ramp width of two times the diameter of the film cooling hole. The coolant air is injected at 30 degrees along the freestream direction. Three different film hole compound angles oriented to freestream direction at 0 degrees, 90 degrees and 180 degrees were investigated for their performance on-ramp film cooling. The tested blowing ratios (BRs) are in the range of 0.9-2.0. Findings The film hole oriented at a compound angle of 180 degrees has improved the area-averaged FCE on the ramp test surface by 86.74% at a mid-BR of 1.4% and 318.75% at higher BRs of 2.0. The 180 degrees film hole compound angle has also produced higher local and spanwise averaged FCE on the ramp test surface. Originality/value According to the authors' knowledge, this study is the first of its kind to investigate the ramp film cooling with a compound angle film cooling hole. The improved ramp model with a 180 degrees film hole compound angle can be effectively applied for the end-wall surfaces of gas turbine film cooling.