Method for Dynamic Stress Design in a Variable Section Blade of a Turbo Machine

The problem of assessing the dynamic stresses arising from vibrations of the blades of turbo machines is an urgent and significant problem affecting the overall reliability of the turbo machine. Its solution requires a mathematical study and a physical experiment to determine the intensity of the gas flow impact and the blade reaction.However, there is relatively little information in the scientific publications on this issue. The article considers a semi-empirical method for calculating dynamic stresses at the base of a variable cross-section blade at the first tone resonant vibrations. These vibrations can be considered as the most dangerous because of the maximum amplitude. To perform the calculation a real blade was replaced with a calculated one, composed of separate portions with a constant profile, and the contribution of each part to the stress in the base section was determined. An example of calculating the dynamic stress by the proposed method with a resonant vibration of the first tone of a constant-section blade is given. The calculation showed that the solution to a complex problem can be represented as a sum of solutions to simpler problems. The calculation method can be used in the design of turbine and compressor blades.

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