13th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
In this paper we demonstrate non-monotonic behaviour for loss coefficient in a compressor cascade as incident turbulence intensity varies. An experimental investigation of a linear cascade reveals that the interaction of free-stream turbulence with the suction side bound-ary layer interacts with laminar separation bubbles (LSBs) to set the dominant component of the loss. Turbulence intensity changes were considered as the main parameter to control the size of the LSB. Turbulence grids produced intensities of 1.27%, 2.63% and 4.05% at the blade row inlet. The entropy-based loss coefficient for the suction side boundary layer is determined from the trailing edge momentum thickness and deviation using Denton’s correlation. It is found that, up to a critical value, increased turbulence intensity increases the momentum thickness which gives rise to higher overall loss. Further increase in tur-bulence intensity to values that enable transition before suction surface separation lead to reduced overall losses.