Авіаційно-космічна техніка та технологія (Aug 2020)
FREE VIBRATIONS OF GAS TURBINE ENGINE AXIAL COMPRESSOR BLADES
Abstract
The required level of reliability of modern gas turbine engines cannot be achieved without ensuring the vibrational strength of the compressor blades. One of the tasks of ensuring vibrational strength is to determine the frequency spectrum of free vibrations, as well as the arising forms of vibrations. Moreover, the most reliable results are achieved by combining experimental and theoretical research methods. Experimental studies of the free vibrations of the blades were carried out by the time-dependent holographic interferometry method. A description of the experimental stand is given, the features of using optical equipment and processing units are indicated. The implemented algorithm for conducting experimental studies is described, the features of the digitization of optical signals implemented in the developed software are indicated, the mathematical equations used in the implementation of this software are presented, and some emerging experimental forms are illustrated. To verify the experimental data based on the finite element method, an updated mathematical model of the free vibrations of compressor blades has been developed. The characteristics of the finite element from which the mathematical model is formed, the basic equations used in the simulation of free vibrations are given. As an object of study, we considered a compressor blade 54 mm high and 37 mm long chord with a peripheral section twist angle of 17°, the considered blade is made of a titanium alloy. For this blade, some waveforms were obtained, the location of the nodal lines was shown, and data obtained experimentally and analytically were compared. An analysis was made of the frequency spectrum of the natural oscillations of the compressor blades, which showed that the difference between the vibration frequencies obtained by experimental and numerical methods for the same modes does not exceed 5 %.
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