INFLUENCE OF SHROUD PLATFORM DISPLACEMENT ANGLES ON THE DAMP-ING CAPACITY OF A TURBINE BLADE RING

Purpose. Investigation of the influence of the ratio between the displacement angles of the Z-shaped shroud shelf and the inclination angle of the working contact surface on the vibration stress of turbine rotor blades under resonant oscillations in high-frequency mode. Research methods. Experimental investigations were carried out on a cantilever-mounted first-stage fan turbine blade using a laboratory setup comprising a signal generator, amplifier, piezovibrator, microscope, and piezoprobe. Two high-frequency vibration modes (2810 Hz and 3550/3620 Hz) were examined. The angular displacements of eight control points on the shroud platform were measured using a microscope. Results. It was established that the damping efficiency depends on the relationship between the displacement direction of the shroud platform and the angle of the contact surface. When these directions are closely aligned, stable contact and effective damping are maintained even during out-of-phase blade vibrations. Modification of the airfoil geometry reduced the intensity of vibrations in the second vibration mode and improved contact conditions. Scientific novelty. For the first time, it has been demonstrated that the direction of shroud platform displacement significantly affects the damping performance of the blade ring, regardless of the contact pressure. The feasibility of optimizing the blade geometry to stabilize contact interaction is substantiated. Practical value. The findings can be applied in the tuning of aircraft turbines, especially when the use of dampers or axial dimension adjustments is not possible. The proposed recommendations contribute to increased service life of the shroud connection without altering the contact force.