Mistuned Bladed Disk Assembly Research Articles

Response of large mistuned bladed disk assembly subjected to random excitations

In this study, the effects of large geometric mistuning on blade response are investigated considering the change of mistuning properties and excitation characteristics. The response variations because of large mistuning are negligible under white noise excitations and are highly significant under narrow band excitations. For the different excitation correlations, the responses are represented using non-dimensional variables in order for the results to be comparable to each other. It is shown that the ratio of the modal frequency between the tuned and large mistuned blades determines the propagation direction of the natural frequencies of the mistuned system, therefore, the responses of large mistuned blades depend primarily on their level of modal frequency.

Performance of friction dampersin geometric mistuned bladed disk assembly subjected to random excitations

In this study, the performance of friction dampers of a geometric mistuned bladed disk assembly is examined under random excitations. The results are represented by non-dimensional variables. It is shown that the performance of the blade-to-blade damper can deteriorate when the correlated narrow band excitations have a dominant frequency near the 1st natural frequency of the bladed disk assembly. Based on a simple model of a geometric mistuned bladed disk assembly, the analytical technique shows an efficient way to design friction dampers.

Application of Improved Hybrid Interface Substructural Component Modal Synthesis Method in Dynamic Characteristics Analysis of Mistuned Bladed Disk Assemblies

Application of Improved Hybrid Interface Substructural Component Modal Synthesis Method in Dynamic Characteristics Analysis of Mistuned Bladed Disk Assemblies

Vibratory characteristic analysis of integral mistuned bladed disk assemblies for aeroengine

An improved hybrid interface substructural component modal synthesis method (IHISCMSM) is proposed to increase the computational efficiency of mistuned bladed disk assemblies (BDA) under the condition of meeting the computational accuracy for a large amount of calculation via the classical hybrid interface substructural component modal synthesis method (CHISCMSM). The parametric models of the blades and the disk are built to investigate each substructural finite element model. They are synthesized by the double coordinating conditions of the displacement and the force to obtain natural frequency and vibratory output response which will ensure the computational accuracy. Compared with the high fidelity integral structure finite element method (HFISFEM), the computational time is shortened by 23.86–31.56% and the modal deviation is 0.002–0.157% via IHISCMSM. It is faster by 4.46–10.57% than the CHISCMSM. Meanwhile, the factors which impact the frequency are researched by IHISCMSM, including rotational speed, gas temperature, and geometry size. It is shown that the rotational speed makes the frequency increased, the gas temperature makes it declined, the rotational speed has greater influence on the low-order modal, but the temperature has greater influence on the high-order modal. The frequency of the BDA does not change much when the rotational speed and temperature are both considered. However, the geometric dimensioning almost has no influence on the frequency. The vibratory output response is enlarged with the mistuned level increasing and multiple peaks are observed. The reason is that the combined action of the mistuning and the resonance. When the mistuned level is 0–3%, the incremental saltation of the output response is obvious. When the mistuned level is continuing increasing, the localization phenomenon of the output response does not much different from the mistuned level 3%. The above research lays a solid foundation for the further study on the probabilistic analysis of the mistuned BDA.

Computation of the Optimal Normal Load for a Mistuned and Frictionally Damped Bladed Disk Assembly Under Different Types of Excitation

Using nondimensional variables, the performances of friction dampers of a mistuned bladed disk assembly are examined for different types of excitation: white noise excitation, independent narrow band random excitation, and sinusoidal excitation with unknown amplitudes. Based on the harmonic balance method, an analytical technique is developed to compute the statistics of response for sinusoidal excitation with unknown amplitudes. The performances of blade-to-blade and blade-to-ground dampers are compared under different types of excitation. It is found that the nondimensional optimal normal loads of friction dampers are almost independent of the nature of excitation. Therefore, optimal normal loads of friction dampers can be chosen without any knowledge of the nature of excitation.

Computation of the Statistics of Forced Response of a Mistuned Bladed Disk Assembly via Polynomial Chaos

The method of polynomial chaos has been used to analytically compute the statistics of the forced response of a mistuned bladed disk assembly. The model of the bladed disk assembly considers only one mode of vibration of each blade. Mistuning phenomenon has been simulated by treating the modal stiffness of each blade as a random variable. The validity of the polynomial chaos method has been corroborated by comparison with the results from numerical simulations.

Effects of the Nature of Excitation on the Response of a Mistuned Bladed Disk Assembly

In this paper, responses of a mistuned bladed disk assembly are examined and compared for three types of excitations: uncorrelated narrow band random excitations, correlated narrow band random excitations and sinusoidal excitations with unknown (time-invariant and random) amplitudes. Analytical techniques are also developed to compute the statistics of responses for these types of excitations. Effects of correlations of narrow band excitations are investigated in details. It has been found that the response statistics for correlated narrow band random excitations can be viewed in terms of the concepts related to the response to a deterministic engine order excitation.

Statistics of Response of a Mistuned Bladed Disk Assembly Subjected to White Noise and Narrow Band Excitation

This paper deals with the statistics of the response of a mistuned bladed disk assembly subjected to random excitation. Analytical techniques are developed to compute this statistics for two types of random excitation: white noise and narrow band. The validity of the analytical methods has been established by comparison with the results from numerical simulations. The sensitivities of the response to mistuning have been examined as a function of the width of the frequency band of the random excitation, the dominant frequency of the random excitation and the structural coupling between adjacent blades.

Reduced Order Modeling and Vibration Analysis of Mistuned Bladed Disk Assemblies With Shrouds

This paper presents important improvements and extensions to a computationally efficient reduced order modeling technique for the vibration analysis of mistuned bladed disks. In particular, this work shows how the existing modeling technique is readily extended to turbomachinery rotors with shrouded blades. The modeling technique employs a component mode synthesis approach to systematically generate a reduced order model (ROM) using component modes calculated from a finite element model (FEM) of the rotor. Based on the total number of degrees of freedom, the ROM is typically two or three orders of magnitude smaller than the FEM. This makes it feasible to predict the forced response statistics of mistuned bladed disks using Monte Carlo simulations. In this work, particular attention is devoted to the introduction of mistuning into the ROM of a shrouded assembly. Mistuning is modeled by projecting the mistuned natural frequencies of a single, cantilever blade with free shrouds onto the harmonic modes of the shrouded blade assembly. Thus, the necessary mistuning information may be measured by testing individual blades.

Vibration of a mistuned bladed-disk assembly using structurally damped beams

Vibration of a mistuned bladed-disk assembly using structurally damped beams

A Reduced Order Approach for the Vibration of Mistuned Bladed Disk Assemblies

A reduced order approach is introduced in this paper that can be used to predict the steady-state response of mistuned bladed disks. This approach takes results directly from a finite element analysis of a tuned system and, based on the assumption of rigid blade base motion, constructs a computationally efficient mistuned model with a reduced number of degrees of freedom. Based on a comparison of results predicted by different approaches, it is concluded that: The reduced order model displays structural fidelity comparable to that of a finite element model of the entire bladed disk system with significantly improved computational efficiency; and under certain circumstances both the finite element model and the reduced order model predict quite different response from simple spring-mass models.

Probabilistic Method to Compute the Optimal Slip Load for a Mistuned Bladed Disk Assembly With Friction Dampers

In this paper, an analytical technique has been developed to compute the statistics of forced response of a mistuned bladed disk assembly with friction dampers (blade-to-blade or blade-to-ground). The method is based on the statistical linearization approach and predicts the probability distribution function of a blade’s amplitude. The validity of this technique has been corroborated by comparison with the results from numerical simulations. Using this technique, the optimal value of the slip load at the friction joint has been computed to minimize the probability that a blade’s amplitude will exceed a critical value.