Vibration Characteristics Analysis Of Hollow Turbine Blades

Turbine blade is the main component of aero-engine which converts thehigh-temperature gas energy into mechanical energy, its structural strength directlyaffects the engine’s efficiency and service life. The working environment of turbineblade is very terrible, so it’s easy to get faults. Turbine blade with high-temperaturealloy material can work reliably in the terrible environment and it always cast intocomplex hollow structure for cooling. In this paper, we use the high-temperaturehollow blades as the object to study their vibration characteristics, which providethe evidence for optimization design of the hollow blades and to avoid resonance.In this paper, it started with the vibration theory analysis of the blade, thehollow blade was simplified as a cantilever beam based on the structure shape tostudy the free vibration of lateral bending, and it was simplified as a thin-walledstructure with closed cross section to study the free torsional vibration of theconstraint situation. Then the free differential equation of vibration were established,the relationship between the frequency of system and the elastic properties ofmaterial, also the geometric parameters of the simplified model was obtained.The APDL program was run by using the finite element software ANSYS toestablish the model of hollow blades and then the modal analysis was conducted.Considering the effects of boundary conditions, the temperature fields and the vanecrown on the hollow blade modal, some valuable conclusions were obtained.The software ANSYS was used to conduct the modal analysis of the rotatingblades in working by considering the factors of the stress stiffening and the spinsoftening and both cases respectively. And thus an empirical formula utilized tocalculate the dynamic frequency approximately was obtained. The paper worked onthe research of effects on dynamic frequency of the turning diameter and installationangle of the hollow blade and obtained the relationship equation between thedynamic frequency and the turning diameter. Also the paper got the approximaterelationship between the dynamic frequency of blade and the temperature of thesimplified temperature field, and obtained the calculate formula for dynamicalfrequency combine with the factors of rotation speed, turning diameter andtemperature. Based on the modal analysis of the hollow blade by using ANSYS, theCampbell diagram was drawn to conduct the resonance analysis, which resulted toprovide a theoretical basis for the optimization design and avoiding resonance of theblades we studied.At last, a test platform for the experimental modal analysis of the hollow blades was designed and built, which the hammer modal test module of LMS wasused to carry out the experimental modal analysis of the blades, Furthermore, thetest results were compared with the modal analysis results of finite element methodto verify the validity of the finite element models which were established.