Flow Disturbance by Intrusive Instrumentation: Part 2 – Protrusions on the Suction Side of HP Compressor Vanes

In this study, we investigate the aerodynamic impact of spanwise pressure tubes located on the suction side of a high-pressure compressor stator vane. For our experiments in a linear cascade wind tunnel, we modeled the pressure tubes as simplified protrusions. The experiments were conducted at a Mach number of ∼0.5 and a Reynolds number of 790,000. By testing six configurations with protrusion widths between 8% to 24% of the chord lengths and heights of 33% and 66% of the maximum vane thickness, we find that increasing the protrusion height as well as reducing the protrusion width leads to an increase of the total pressure loss. Consequently, the narrowest and highest protrusion with a width of 8% and a height of 66% represents the worst case with a total pressure loss increase of factor 5.7 compared to a nominal vane. In the best case, the protrusion with a width of 24% and a height of 33% leads to an increase in the total pressure loss of factor 2.1 compared to a nominal vane. Oil flow visualization and CFD simulations reveal complete flow separation downstream of higher protrusions, creating large recirculation zones. For lower protrusions the flow mostly reattaches at the top of the protrusions. The study offers insights for engineers designing intrusive instrumentation on compressor vanes, enabling them to minimize additional total pressure loss.