جستجوی مقالات مرتبط با کلیدواژه « bladed disk » در نشریات گروه « مکانیک »

Ideally, bladed disk systems are tuned and all blades are identical but, in practice there always exist small, random differences among the blades. In designing bladed disks, all the blades on each stage are generally assumed to be identical, and this is called a tuned bladed disk. However, due to manufacturing tolerances, variations in material properties and wear in service, each blade on a disk is almost always slightly different to the others. These small differences, collectively called mistuning. It is well known that even a small amount of mistuning can induce a large forced response known as mode localization. In this study a representative model for the bladed disk system is presented and equation of motion derived. Then the response of tuned system was obtained. Afterward, frequency response of mistuned system with genetic algorithm for mistuned blade in mass was studied. Also maximum frequency response of the system for mistuned blade in stiffness was calculated. The result indicated the slightly mistuning in system can increase the response of the system. The worst response of mistuned system is 5.563 times greater than the response of the tuned system. Increase in frequency response of the system is undesirable and should be considered in the initial design of these systems.

In the present study, the flutter and aeroelastic response of mistuned bladed disks to the engine order excitation are studied with the aim of determining the effects of disk structural properties and also establishing an efficient method of analysis. For modeling the solid-fluid interaction, the Whitehead’s incompressible, two dimensional cascade theory is used. The structure is also modeled, using a 4 degrees of freedom lumped mass-spring system, which accounts for the bending and torsional deformation of the blade and the disk. This model would enable us to study the effect of structural coupling of adjacent sections as well as the disk flexibility. The solution is based on expansion of the mistuned-blade response in terms of the traveling-wave modes of a tuned bladed disk. The adopted method would be appropriate for determining the aeroelastic response, since the aerodynamic loads are available only for each individual traveling-wave mode. The obtained solution is used to study the effects of disk flexibility on the aeroelastic instability, variations of natural frequencies with different numbers of nodal diameters, and the sensitivity of the vibration amplitude response to the mistuning. Furthermore, the effects of mistuning in blades torsional frequencies and the mistuning in engine order excitation is considered. Parametric studies show that for disks with a lower bending stiffness, the mistuning can significantly influence the aeroelastic behavior such that the for a certain amount of the natural frequency, the disk response could be increased more than 8 times due to the presence of mistuning.

Rotor dynamics is known as the study of vibrational behavior in axially symmetric linear rotating structures. Devices such as engines, turbines, compressors and generators are located in this category. Study of vibrational behavior of these structures in different rotational velocities yields to recognition of critical points and preventing failures, especially high cycle fatigue. The case study of the present paper is a bladed disk used in the first stage of compressor of a gas turbine engine. The material of machined integrated bladed disk is aluminum alloy. The simulations have been done by ANSYS finite element software. By using the cyclic symmetry module of ANSYS the nodal diameter mode shapes of structure have been obtained. In the next step, experimental modal analysis test has been done by measuring 58 points on the bladed disk and the nodal diameters have been obtained experimentally. Finally, experimental and simulation results have been compared to each other. The novelty of this paper is the experimental procedure of obtaining nodal diameter of a bladed disk, which is so useful in verification of numerical simulation.