Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the Two-Stripe Mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the ressonant frequencies lower.

Generation of the grid for blade passages with packaging using universal grid generators usually takes much time. The paper is devoted to grid generation in turbo machine blade passages with packaging in automatic mode. The main requirement to the approach is to obtain the grid with minimum engineer participant. In the developed procedure engineer must specify only general input data: number of nodes, cell size near solid bodies and geometrical data. Multiblock structured grids are considered. All grid blocks have node-to-node attachment between each other; periodicity is also specified from node to node. The grid in blade passage consists of two blocks: “O” grid around blade and “H” grid in blade passage. Additional blocks are used to describe different ZR-effects such us tip clearances, leakage seals and bleed air systems. A variational method of constructing three dimensional grids composed of hexahedral cells is applied. The combination of the energy density functional and cell size functional is used. The first functional lets us control the shapes and the second functional lets us control the sizes of grid cells. Grid untangling procedure is also developed. Developed approach was tested using the blades of axial and centrifugal compressors and axial turbines. Results of grid generation are presented.

Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the two-stripe mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the resonant frequencies lower.

The paper is pointed to the problem of numerical simulation of unsteady flow around an oscillating blade in jet engine compressor. Single compressor rotor blade row is considered. It is assumed that mode shape and frequency of blade oscillation is not influenced by airflow. The system of governing equations is transformed to a moving coordinate system to describe blade oscillations. Multi-block structured “H-O” grid is used for spatial discretization. Inner boundary of “O”-grid (representing blade airfoil surface) is moved to describe blade airfoil oscillation. To minimize discretization error, special morphing procedure was developed for “O”-grid to accommodate blade airfoil surface motion. Other grid blocks remain steady. Nonlinear harmonic method is applied to integrate Euler equations on time variable. For spatial derivation Dispersion-Relation-Preserving methodology is applied. To maintain solution accuracy nonreflecting boundary conditions are implemented on artificial boundaries (inlet and outlet). Resulting system of nonlinear algebraic equations is resolved numerically. As an alternative, time-marching method is realized in ANSYS CFX by means of user routines. Numerical and experimental cascade results are compared.