SUBSONIC STALL FLUTTER OF A LINEAR TURBINE BLADE CASCADE USING EXPERIMENTAL AND CFD ANALYSIS

Stall flutter of long blades influences the operation safety of the large steam turbines in off-design conditions. As angles of attack are typically high, a partial or complete separation of the flow from the blade surface occurs. The prediction of stall flutter of turbine blades is a crucial task in the design and development of modern turbomachinery units and reliable design tools are necessary. In this work, aerodynamic stability of a linear turbine blade cascade is tested experimentally at high angle of attack +15 degrees, Ma = 0.2 and the reduced frequency of 0.38. Controlled flutter testing has been performed in a travelling wave mode approach for the torsion with the motion amplitude of 0.5 degrees. In addition, ANSYS CFX with SST k-omega turbulent model is used for URANS simulations of a full-scale computational domain. A separation bubble formed on suction surface near the leading edge has been found in CFD results for each blade. Excellent agreement between the experimental and numerical results in stability maps has been achieved for this case under investigation. This is encouraging and both experimental and numerical techniques will be tested further.