Calculating the statistics of forced response of a mistuned bladed disk assembly

AIAA Journal ◽  
1986 ◽  
Vol 24 (11) ◽  
pp. 1797-1801 ◽  
Author(s):  
Alok Sinha
Keyword(s):  
Forced Response ◽  
Bladed Disk ◽  
Bladed Disk Assembly

The Effect of Non-Uniform Aerodynamic Loading on the Blade Responses

2007 ◽  
Author(s):  
Abdelgadir M. Mahmoud ◽  
Mohd S. Leong
Keyword(s):  
Turbine Blades ◽  
Forced Response ◽  
Flow Section ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Bladed Disk ◽  
Aerodynamic Loading ◽  
Bladed Disk Assembly ◽  
Flow Generator ◽  
Inlet Flow Distortion

Turbine blades are always subjected to severe aerodynamic loading. The aerodynamic loading is uniform and Of harmonic nature. The harmonic nature depends on the rotor speed and number of nozzles (vanes counts). This harmonic loading is the main sources responsible for blade excitation. In some circumstances, the aerodynamic loading is not uniform and varies circumferentially. This paper discussed the effect of the non-uniform aerodynamic loading on the blade vibrational responses. The work involved the experimental study of forced response amplitude of model blades due to inlet flow distortion in the presence of airflow. This controlled inlet flow distortion therefore represents a nearly realistic environment involving rotating blades in the presence of airflow. A test rig was fabricated consisting of a rotating bladed disk assembly, an inlet flow section (where flow could be controlled or distorted in an incremental manner), flow conditioning module and an aerodynamic flow generator (air suction module with an intake fan) for investigations under laboratory conditions. Tests were undertaken for a combination of different air-flow velocities and blade rotational speeds. The experimental results showed that when the blades were subjected to unsteady aerodynamic loading, the responses of the blades increased and new frequencies were excited. The magnitude of the responses and the responses that corresponding to these new excited frequencies increased with the increase in the airflow velocity. Moreover, as the flow velocity increased the number of the newly excited frequency increased.

Modeling the Microslip in the Flange Joint and Its Effect on the Dynamics of a Multistage Bladed Disk Assembly

2017 ◽  
Vol 13 (1) ◽  
Author(s):  
Christian M. Firrone ◽  
Giuseppe Battiato ◽  
Bogdan I. Epureanu
Keyword(s):  
Element Model ◽  
Forced Response ◽  
Flange Joint ◽  
Reduced Order ◽  
Bladed Disk ◽  
Simple Geometry ◽  
Bladed Disk Assembly ◽  
Joint Contact ◽  
Turbine Disks ◽  
Complex Architecture

The complex architecture of aircraft engines requires demanding computational efforts when the dynamic coupling of their components has to be predicted. For this reason, numerically efficient reduced-order models (ROM) have been developed with the aim of performing modal analyses and forced response computations on complex multistage assemblies being computationally fast. In this paper, the flange joint connecting two turbine disks of a multistage assembly is studied as a source of nonlinearities due to friction damping occurring at the joint contact interface. An analytic contact model is proposed to calculate the local microslip based on the different deformations that the two flanges in contact take during vibration. The model is first introduced using a simple geometry representing two flanges in contact, and then, it is applied to a reduced finite element model in order to calculate the nonlinear forced response.

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

2003 ◽  
Author(s):  
Alok Sinha
Keyword(s):  
Numerical Simulations ◽  
Polynomial Chaos ◽  
Random Variable ◽  
Forced Response ◽  
Bladed Disk ◽  
Bladed Disk Assembly

The method of polynomial chaos has been used to analytically compute the statistics of 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.

Rotating Mistuned Bladed Disk Assembly Dynamic Response Prediction Using Component Mode Synthesis Methods With Interface Modes

2005 ◽  
Author(s):  
Francois Duvauchelle ◽  
Duc-Minh Tran ◽  
Roger Ohayon
Keyword(s):  
Response Prediction ◽  
Forced Response ◽  
Component Mode Synthesis ◽  
Synthesis Methods ◽  
Cyclic Symmetry ◽  
Reduced Order ◽  
Bladed Disk ◽  
Static Condensation ◽  
Bladed Disk Assembly ◽  
Reduced Order Methods

Finite element-based reduced order methods are presented with application to the prediction of rotating mistuned bladed disk forced response. These methods have already been applied to tuned non-rotating models having cyclic symmetry. The aim is to reduce significantly the number of interface co-ordinates, which can be very important in classical component mode synthesis methods. The approach is based on the use of the interface modes which result from a static condensation of the whole structure on the whole interface. A first implementation of this procedure and numerical results are presented.

Response Statistics and Reliability Analysis of a Mistuned and Frictionally Damped Bladed Disk Assembly Subjected to White Noise Excitation

2010 ◽  
Author(s):  
Pankaj Kumar ◽  
S. Narayanan
Keyword(s):  
White Noise ◽  
Probability Density ◽  
Gaussian White Noise ◽  
Random Excitation ◽  
Forced Response ◽  
Computationally Efficient ◽  
Bladed Disk ◽  
White Noise Excitation ◽  
Bladed Disk Assembly ◽  
Mean Square Response

In the design of gas turbine engines, the analysis of nonlinear vibrations of mistuned and frictionally damped blade-disk assembly subjected to random excitation is highly complex. The transitional probability density function (PDF) for the random response of nonlinear systems under white or coloured noise excitation (delta-correlated) is governed by both the forward Fokker-Planck (FP) and backward Kolmogorov equations. This paper presents important improvement and extensions to a computationally efficient higher order, finite difference (FD) technique for the solution of higher dimensional FP equation corresponding to a two degree of freedom nonlinear system representative of vibration of tip shrouded frictionally damped bladed disk assembly subjected to Gaussian white noise excitation. Effects of friction damping on the mean square response of a blade are investigated. The friction coefficient of the damper is assumed to be a function of the sliding velocity of the contact surface. The effects of stiffness and damping mistuning on the forced response of frictionally damped bladed disk are investigated. Numerical studies are presented for a pair of mistuned blades of cyclic assemblies. The response and reliability of a blade subjected to random excitation is also obtained. With time averaged probability density as an invariant measure, the probability of large excursion in case of damping mistuning is also presented. The results of the FD method are validated by comparing with Monte Carlo Simulation (MCS) results.

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

2005 ◽  
Vol 128 (4) ◽  
pp. 449-457 ◽  
Author(s):  
Alok Sinha
Keyword(s):  
Numerical Simulations ◽  
Polynomial Chaos ◽  
Random Variable ◽  
Forced Response ◽  
Bladed Disk ◽  
Bladed Disk Assembly

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.

Investigation of Alternate Mistuned Turbine Blades Non-Linear Coupled by Underplatform Dampers

2013 ◽  
Author(s):  
S. Tatzko ◽  
L. Panning-von Scheidt ◽  
J. Wallaschek ◽  
A. Kayser ◽  
G. Walz
Keyword(s):  
Turbine Blades ◽  
Forced Response ◽  
Mode Shapes ◽  
Nodal Diameter ◽  
Frictional Contacts ◽  
Bladed Disk ◽  
Engine Order ◽  
Bladed Disk Assembly ◽  
Last Stage ◽  
Software Code

Freestanding turbine blades have typically low structural damping and thus require additional friction damping devices, such as underplatform dampers. The friction coupling between neighboring blades reduces response amplitude and increases resonance frequency. Along with forced response excitation large blades, especially of last stage, could be excited by fluid structural interaction (flutter). To prevent such excitation alternate mistuned blade patterns are beneficial disturbing traveling waves in the stage. In this paper the influence of alternate mistuning is investigated with a simplified oscillator chain as well as a bladed disk assembly coupled by frictional contacts. It is pointed out that the performance of friction coupling can be improved by alternate mistuning as long as the engine order of the excitation is below quarter of the number of blades. Alternate mistuning causes a mode coupling between two nodal diameter vibration mode shapes allowing for energy transfer. The in-house developed software code DATAR is enhanced and alternate mistuning can be applied to the blades as well as to the damping elements. For validation the DATAR code was applied to an alternate mistuned last stage blade of a Siemens gas turbine and compared with available field engine measurement.

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

1990 ◽  
Vol 112 (2) ◽  
pp. 214-221 ◽  
Author(s):  
S. Chen ◽  
A. Sinha
Keyword(s):  
Probabilistic Method ◽  
Critical Value ◽  
Forced Response ◽  
Statistical Linearization ◽  
Friction Dampers ◽  
Analytical Technique ◽  
Bladed Disk ◽  
Optimal Value ◽  
Bladed Disk Assembly ◽  
Friction Joint

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.

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