Measured steady and unsteady aerodynamic performance of a family of three highly-loaded low-pressure turbine cascades

Midspan measurements were made in a low-speed wind tunnel for three low-pressure turbine (LPT) cascades at design and off-design incidence. The baseline profile was the midspan section of an LPT vane of a Pratt & Whitney Aircraft (PWA) engine, and is regarded as moderately highly-loaded blade. To examine the influence of increased loading two additional airfoils were designed by PWA, each providing 25% higher loading than the baseline version. All three airfoils have the same axial chord, and inlet and outlet design flow angles. The main difference between the airfoils with higher loading was in the pressure distribution: one airfoil was front-loaded, while the other was aft-loaded.;It was found that an increase of 25% in loading was possible only with a small increase in the losses. The front loaded airfoil performed much better at both low Reynolds numbers and at off-design incidence than the aft loaded one due to milder pressure gradients on the suction surface of the airfoil. The effects of the wakes generated by a simulated upstream blade row were beneficial for the stalled case, resulting in flow reattachment and a consequent reduction in losses. The upstream wakes resulted in a slight loss increase for the other case where the flow was attached.;The aerodynamic performance was investigated for wide range of Reynolds numbers at design incidence and for two values of freestream turbulence intensity. In addition, the performance at +5° and -5° relative to the design incidence was examined at the same two turbulence intensities for a fixed value of Reynolds number. Measurements were made using a three-hole pressure probe, surface pressure taps and single hotwire probe. For one of the low Reynolds number cases, the unsteady flow effects were examined by using a moving-bar wake generator.