The study of shrouded fan vibration modes and frequencies on holograph and as a part of the engine on the test rig

The article reports about application results of holographic interferometry method for the analysis of rotating fan vibration modes. So far there are no practically the experimental works explaining behavior of turbomachinery bladed discs as a part of the engine, on the basis of knowledge about modes and frequencies of observable disc in the absence of rotation. Having initially bladed disc amplitude-frequency characteristics in the form of vibration modes pictures with the corresponding frequencies, and then strain-gauging data for this disk being a part of the engine, makes it possible to carry out the vibration modes analysis of rotating disk. Vibration modes, received on holographic installation, are identified with vibration modes of a rotating disc on coincidence of their frequencies.Vibration frequencies and modes of a fan first stage, received on holograph, and the frequencies, received using spectral analysis method for strain-gauging data, are given in the article. Close values of these frequencies allowed to connect vibration modes with rotating disc frequencies. Moreover, there is the example of turbine rotor disc research, illustrated the importance of knowledge of turbomachinery discs vibration modes, in the article. The study revealed the existence of "horizontal" connection for some vibration modes, when two different vibration modes accord with almost the same frequency. On the basis of the carriedout study it is possible to draw a conclusion that before installation of the bladed disc in the engine it is necessary to define natural frequencies and vibration modes of this disc using modern optical methods, in particular a holographic interferometry; that will allow to predict more reliably any occurrence of disc vibrations during its working as a part of the engine.