Influence of flow contraction at the orifice on film-cooling and the regulation mechanism of the length-to-diameter ratio

Key Points

• This research aims to understand how the length-to-diameter ratio affects film cooling efficiency and the underlying mechanisms.
• Conducted numerical studies on vertical jet film-cooling across different length-to-diameter ratios.
• Analyzed the effects of flow contraction at the orifice on the boundary layer development and cooling performance.
• Examined the relationship between supply pressure and length-to-diameter ratio.
• Cooling efficiency significantly improves as the length-to-diameter ratio increases from 0 to 0.25.
• Further increases in the ratio result in diminishing returns on cooling performance.
• Flow contraction at the orifice induces radial velocity components affecting boundary layer development.
• The supply pressure required shows a decrease followed by an increase with higher ratios, impacted by flow field decoupling and friction losses.