DETERMINING THE VIBRATION CHARACTERISTICS OF BLADING WITH DAMPER CONNECTIONS (OPREDELENIE VIBRATSIONNYKH KHARAKTERISTIK OBLOPACHIVANIYA S DEMPFERNYMI SVYAZYAMI)

Several modifications of the damper connections were tested by a single method in conditions completely analogous to those in an operating turbine under a load. The blading in the final stage of an experimental stream turbine with a diameter of 787 mm was tested at a maximum speed of 9000 rpm. The unit was loaded by a multidisc hydraulic brake. Frequencies and stresses in the blades were measured by strain gages protected from mechanical damage by steel foil. Particular attention was given to exact duplication of experimental conditions since the final goal of the tests was a comparative analysis of all blading modifications. It was found that the use of damper wires closed into a circle sharply reduces the amplitude of vibrational stresses in the blades for the case of tangential bending oscillations on the fundamental frequency. These stresses were reduced by a factor of approximately 10 when a single row of damper wire was used. There is an additional reduction in vibration stresses when a second wire is added. Stress measurements should not be restricted to no-load conditions when determining vibrational stresses in turbine blades since there may be a considerable difference between these stresses and those measured under a load. (Author) Unedited rough draft trans. of Energomashinostroenie (USSR) v11 n11 p5-7 1965, by F. Dion.