AN EXPERIMENTAL SETUP FOR IDEALISED STUDIES ON TRANSITION TO TURBULENCE ON A GENERIC COMPRESSOR OUTLET GUIDE VANE

摘要

The understanding of flow phenomena in turbomachinery has come far with respect to three-dimensional flow patterns and pressure distributions. Much is due to improved measurements and a continuously evolving fidelity in computational fluid dynamics (CFD). Turbulence and transition in boundary layers are two classical areas where improvements in modeling are desired and where experimental validation is required. Apart from this, fundamental improvements in efficiency can be obtained by developing experimental resources where technologies affecting transition can be studied. The reduction in friction drag can be considerable if the transition to turbulence can be delayed. An experimental setup in an idealized configuration has been designed and built with the objective to study transition on a very large-scale guide vane profile at low speed. The purpose of the rig is to enable high quality fundamental studies of technologies to delay transition, but also to see how effects of manufacturing or other constraints may affect the boundary layer. In the present paper we report the first validation of the experimental setup, by comparing the first test results to CFD calculations performed during the rig design, i.e. no post-calculations with experimental data as input to the simulations have been done yet. The pressure distribution is in line with the design intent, which is a good indicator that the tunnel design is suitable for the intended purpose. At last we report some velocity measurements performed in the wake and we calculate the total drag based on the wake velocity deficit for various Reynolds numbers and with and without turbulence tripping tape. We illustrate that a two dimensional tripping around 7% of the chord from the leading edge can increase the total drag by 50% with respect to the reference case without tripping tape.