Bladed Disk System Research Articles

Optimization analysis of vibration reduction for aeroengine multistage blade-disk system

In order to reduce the vibration localization of multistage blade-disk system of aeroengine compressor, the integral model and substructure model of multistage blade-disk system are established by using substructure modal synthesis method, and the dynamic characteristics of two models are analyzed and the accuracy of the substructure model is verified by comparison. Based on the substructure model, two optimization algorithms of the random wear mass and the snake optimization are proposed. The results show that the vibration amplitudes of the two models are in good agreement in the first 200 modes, and the substructure model meets the requirement of analysis accuracy. Both optimization algorithms can effectively reduce the degree of the vibration localization of the mistuned blade-disk system. The random wear mass algorithm can quickly reduce the amplitude of the blade. The snake optimization algorithm can find the global optimal solution with enough iterations. The results show that the maximum vibration amplitude and the vibration localization factor after optimization are reduced by 5.72 % and 12.0 % respectively by using the random wear mass algorithm, and that of 9.13 % and 16.7 % respectively by using the snake optimization algorithm. The analysis method presented in this paper takes into account the analysis efficiency and analysis precision, it can be used for dynamic analysis and vibration reduction optimization of large power machinery such as aeroengine and gas turbine, and provides a basis for further improving the reliability and service life of aircraft.

An Optimization Method for Stiffness and Damping Mistuning Identification From Blade Tip Timing Data

Abstract System identification of dynamic properties is of large interest in the turbomachinery industry to create more accurate computational models and more effective designs. Previous identification techniques were able to accurately capture the blade variability, known as mistuning, in the stiffness as well as the average damping of all the blades. Mistuning is vital to accurately identify and study because the symmetry of the system is broken and can lead to vibration localization and high amplitudes. In this work, a new method is proposed to not only capture the stiffness mistuning values, but also the blade-to-blade variability in damping. These damping mistuning values have been shown to have a significant effect on the dynamics of bladed disk systems. Incorporation of the damping mistuning into the computational model can be done utilizing an augmented component mode mistuning method with either structural or proportional damping. The mistuning values for this new identification method were compared to a well-established direct method and a previously studied optimization method. Blade responses were then found using a harmonic analysis and the newly identified mistuning values. These blade responses were then compared to experimental tip timing data from full scale rotating experiments. These comparisons show that the new model is able to better reproduce experimental data using computational models that incorporate both stiffness and damping mistuning values.

Design theory for vibration characterisation experiments on real turbine blades with underplatform damper

One of the main causes of turbine rotor blade failures is high-frequency fatigue caused by blade resonance, and the vibration of turbine blades can be effectively suppressed through the reasonable design of dry friction damping structure. In order to understand the vibration characteristics of the blade-disc system and to check whether the damping effect meets the technical specifications, it is necessary to design and carry out dry friction damping blade vibration characteristics experiment. This paper takes a certain type of underplatform damped turbine blade in production as an example, and briefly describes the design idea and design process of such blade vibration characteristic experiments under the premise of the experiment blade structure, material and other physical parameters.

Investigation on the vibration localization of mistuned bladed disk with frictional contact

The mistuning phenomenon is commonly seen in the bladed assemblies of turbomachinery, leading to an unreasonably localized energy distribution that may increase the risk of high cycle fatigue and potentially cause blade failure. The friction coupling interaction is often introduced to attenuate the effect of excessive amplification on the structural vibration. To investigate the vibration localization of damped and mistuned bladed-disk system, a typical mistuning characterization is applied to an improved four-degree-of-freedom lumped parameter model to explicit the vibratory properties with coupled frictional contact. The statistical findings of natural frequency and modal localization factor are obtained by employing the Monte Carlo simulation to explore the influence of mistuned variance and coupled stiffness on the modal localization of free and damped bladed-disk system, respectively. The forced response sensitivity featured in the mistuned variance is quantitatively analyzed from the perspective of vibration localization and energy distribution by the nonlinear solution method. The influence of excitation order and normal load are further, respectively, discussed on the response localization level of the mistuned system. The results can provide fundamental knowledge of the impact of the mistuning pattern on vibration localization for the early design of the aeroengine.

Approximate symplectic approach for mistuned bladed disk dynamic problem

A blade disk system plays a crucial role in the energy conversion efficiency of turbomachinery. Generally, a bladed disk is designed as a tuned system, which implies that the dynamic behaviors of all the blades are identical. In practice, there are some differences between the blades, known as mistuning, that can result in localized vibration. Thus, in this study, an approximate symplectic method developed to reproduce the vibration localization in a mistuned bladed disk system, that can provide guidance for designing vibration control strategies for the system. Considering the morphological characteristics of the interface roughness and the dynamic/stickiness characteristics of the sliding joint surface, an improved dry friction model is established to describe the coupling effects between the blades. Considering the micro-dynamic behaviors of the multi-joint surfaces, the dynamic problem of the entire bladed disk system is formulated as a set of ordinary differential equations (ODEs). An approximate symplectic method is developed in the Hamiltonian framework to simulate the vibration of each blade in the mistuned bladed disk system. From the numerical results reported, the phenomenon of vibration localization in the mistuned bladed disk system is reproduced in the comparison with the results in the tuned bladed disk system. In addition, the influences of the initial positive pressure, contact angle, and roughness of the surfaces on the strength of the vibration localization are revealed in detail in the numerical simulations.

Dynamic characteristics of vibration localization of mistuned bladed disk due to shroud and blade damages

Dynamic behaviors of turbine blades are important for the dynamic design of whole-bladed disk systems. The bladed disk systems with shrouds are used to achieve advanced functions in operation. The shrouds are used to connect several blades as a bladed packet, and several bladed packets are assembled as a bladed disk. Previous researches mainly focus on the mistuning of the bladed disk. However, in operation, the shrouds often suffer damage and wear, and it will lead to shrouds mistuning. The shroud is a critical component for adjusting the coupling strength of the blade to the blade. The innovation of this paper is to study the coupling dynamics problem caused by blade mistuning and shroud damage. The localized vibration of the bladed disk is caused by the blade mistuning, and the shroud damage can also cause the localized vibration of the bladed disk. The coupling dynamic behaviors of bladed disk caused by blade mistuning and shroud damage are important. Therefore, the dynamic behaviors of a mistuned bladed disk with the shroud are important for the bladed disk. A numerical method is conducted to investigate the dynamic characteristics of the whole bladed disk with shroud. The coupling effect between shroud and blade mistuning on the dynamic behaviors of the bladed disk is researched. The numerical model is validated by assuming the shroud and blade mistuning is zero. The coupling effect of shroud and blade mistuning leads to the characteristics being more complicated. Bladed packet is the basic part of the bladed disk with shroud. In order to study the modal characteristics of bladed packets due to shroud, an experiment is conducted. It is worth noting that the first sub remains invariable with the increasing of stiffness ratio.

Effects of the Seal Wire on the Nonlinear Dynamics of the Aircraft Engine Turbine Blades

Abstract Complicated systems made of multiple components are known to be difficult to model, considering their solutions can change dramatically even with the slightest variations in conditions. Aircraft engines contain such complicated systems, and some components in aircraft engines' turbines can cause significant changes in the system's overall response. Hence, this study is focused on investigating the behavior of a turbine blade of an aircraft engine and the effects of the contact between the blade and the seal wire on the dynamics of the blade-disk system. The investigation is performed via various numerical simulations in time and frequency domains. One sector of the bladed disk is modeled using the finite element method with the lock plate and the seal wire imposing cyclic symmetry boundary conditions in the static, modal, and frequency domain forced response analyses. In time domain analyses, the cyclic symmetry is replaced with simplified displacement restricting boundary conditions. The time domain analysis contains steady-state forced responses of the system. The results show that contact with the seal wire is not a major source of nonlinearity and damping. The contacts with the lock plate contribute more to the vibration damping than the seal wire. However, compared to the contacts at the root of the blade, both components remain less significant with regard to frictional damping and nonlinearity.

Simulation study of crack parameters’ effects on the vibration characteristics of a bladed disk system

As a key component of the turbo machine rotor in harsh operating conditions, high cycle fatigue failure and even cracks are common in bladed disks. In this paper, modal analysis was carried out for a single cracked bladed disk system, the effects of crack depth, crack height and rotating speed on its vibration characteristics were studied by the method of both numerical simulation and orthogonal test, and the effects of crack distribution on the vibration characteristics of multi-crack bladed disk systems were also studied. Finally, some conclusions have been drawn, they provide a fundamental understanding of blade health monitoring and fault prediction, and are important to improve the reliability and safety of turbine operation.

A Modular Modeling Method of Mistuned Blisk Based on State-Space Theory with Fitting Aerodynamic Excitation

In order to improve the solution efficiency of vibration characteristics for the mistuned blisk, a modular method combined with state-space method based on lumped-parametric model is developed for the first attempt, which provides a general modeling framework which can be employed to conveniently construct the lumped-parametric models of bladed disk systems with multiple mistuning and variable blade number. It is noteworthy that a pressure fit in the axial-span-pressure space is performed to obtain the continuous equations of aerodynamic forces according to the aerodynamic loads acting on the blade surface. The function of traveling wake excitation is established by considering the rotational velocity. Subsequently, 1N-degree-of-freedom (1N-DOF) and 2N-DOF lumped-parametirc models are respectively used to construct the mistuned blisk. A modular solution method of multiple mistuned lumped-parametirc model is derived from the controllable canonical form and minimum realisation, which reveals that the minimum dimension of the state space is two times of its DOF. The correctness of the present method is varified by several comparisions. Vibration localization is found in the transient response and steady-state response of the blisk. The effects of the mistuning on the blades and the disk are discussed, respectively.

Experimental and Computational Study of a Rotating Bladed Disk with Under-Platform Dampers

There has been an extensive amount of work developing reduced-order models (ROMs) for bladed disks using single-sector models and a cyclic analysis. Several ROMs currently exist to accurately model a bladed disk with under-platform dampers. To better predict the complex nonlinear response of a system with under-platform dampers, this work demonstrates how two linear models can determine bounds for the nonlinear response. The two cases explored are where the under-platform damper is completely stuck and also where the damper slides without friction. This work utilizes the component mode mistuning method to model small mistuning and a parametric ROM method to capture changes in properties due to rotational speed effects. Previously, these ROM methodologies have modeled freestanding bladed disk systems. To evaluate the ROM in predicting the bounds, blade tip amplitudes from the models are compared with high-speed rotating experiments conducted in a large, evacuated vacuum tank. The experimental data were collected during testing using strain gauges and laser blade tip timing probes. The blade amplitudes of the tip timing data, strain gauge data, and computational simulations are compared to determine the effectiveness of the simplified linear analysis in bounding the nonlinear response of the physical system.

A novel mathematical model for the design of the resonance mechanism of an intentional mistuning bladed disk system

Abstract. Bladed disk systems with advanced functions are widely used in turbo-machineries. However, there are always deviations in physical dynamic properties between blades and blades due to the tolerance and wear in operation. The deviations will lead to vibration localization, which will result in high cycle fatigue and accelerate the damage of the bladed disk system. Therefore, many intentional mistuning patterns are proposed to overcome this larger local vibration. Previous studies show that intentional mistuning patterns can be used to reduce the vibration localization of the bladed disk. However, the determination of the resonance mechanism of the intentional mistuning bladed disk system is still an unsolved issue. In this paper, a novel mathematical model of resonance of an intentional mistuning bladed disk system is established. Mistuning of blades and energy resonance are included in this theoretical model. The method of the mechanical power of the rotating blade for one cycle is applied to obtain the resonance condition. By using this theoretical model, the resonance mechanism of an intentional mistuning bladed disk is demonstrated. The results suggest that the ideal results can be obtained by adjusting the intentional mistuning parameter. This paper will guide the design of the dynamic characteristics of the intentional mistuning bladed disk.

Vibration characteristics of mistuned multistage bladed disks of the aero-engine compressor

In order to analyze the vibration characteristics of mistuned multistage bladed disks of an aero-engine compressor, a finite element reduction model of mistuned multistage bladed disks is established based on substructure modal synthesis method. The accuracy of the substructure model was verified by comparing calculation accuracy of the substructure model and the integral model. The influence of different modal truncation numbers on the calculation results are discussed. The vibration modes of each stage of the bladed disks are obtained, the forced response is analyzed from the perspective of strain energy. The result shows that modal truncation number, rotation softening effect, and speed have significant effects on the dynamic frequency calculation results of the multistage bladed disks. The typical mode shapes of the first 200 orders of multistage bladed disks are obtained. With the increase of mistuning standard deviation, the strain energy of multistage bladed disk system decreases gradually.

Tip-timing measurements of transient vibrations in mistuned bladed disks

Bladed disks are usually characterized by a rich dynamic response during service due to the occurrence of several mode shapes that vibrate at resonance within the operative range. In particular, during start-ups and shutdowns, the variable speed causes a temporary crossing of resonance that cannot be neglected to determine stress envelope and safety margins of the system during its whole mission. In fact, fluid flow induces fluctuating loads with variable frequencies (non-stationary regime) on the blades being responsible of a dynamic response which does not follow the so-called steady-state (stationary) response. This paper proposes a novel post-processing method for Blade Tip-Timing (BTT) measurements for the identification of the resonance parameters of mistuned bladed disks working in non-stationary operative conditions. The method is based on a two degrees of freedom model (2DOF) and focuses on transient resonances in which two mistuned modes with close resonance frequencies are involved in the dynamic response. In such circumstances, the identification method based on the single degree of freedom (1DOF) model usually fails.To verify the effectiveness of the method, numerical and experimental investigations have been performed. First, a mathematical simulator based on a lumped parameter model of a bladed disk system is used to generate the BTT simulated data. Experimental signals are measured using a commercial BTT system through a set of optical probes mounted circumferentially around a rotating dummy blisk. It is shown that the method produces accurate predictions for the numerical simulation, even in the presence of considerable noise levels. Moreover, experimental results confirm a successful implementation of the method on the actual BTT measurements.

Mobile Interface CMS Method for Vibration Characteristics Prediction of Mistuned Bladed Disk with Different Coupling Degrees

The prediction of vibration characteristics was studied in the mistuned bladed disk by the mobile interface prestressed component mode synthesis (CMS) superelement method. When the strongly, generally, and weakly coupling in the mistuned bladed disk, according to the results of the direct FEM method, the prediction accuracy of this method was verified and compared with the fixed-interface CMS method by using the relative error of dynamic frequency, vibration mode matching function, and dimensionless root mean square error of vibration amplitudes. It is pointed that for mistuned bladed disk in the strong coupling, the prediction accuracy of dynamic frequency and vibration amplitudes are higher by the mobile interface CMS method and the vibration modes are matched with the direct method. In weak coupling, the results of dynamic frequency and vibration modes predicted by the mobile interface CMS method and the fixed-interface CMS method are consistent with the direct method, but the vibration amplitudes’ prediction error of the mobile interface CMS method is lower than that of the fixed-interface CMS method. In general coupling, the mobile interface CMS method has higher dynamic frequency prediction accuracy at low order, and the two methods have comparable dynamic frequency prediction accuracy at high order. The vibration modes predicted by the two methods are matched with the direct FEM method, and the prediction accuracy of vibration amplitude by the mobile interface CMS method is better than that of the fixed-interface CMS method. The results indicate that the mobile interface CMS method could more accurately predict vibration characteristics of the mistuned bladed disk with different coupling degrees and could be an effective measurement for studying the vibration characteristics of the mistuned bladed disk system.

Nonlinear response analysis of aero-engine rotor bearing rub-impact system caused by horizontal yawing maneuver load

Based on the simplified aero-engine rotor system, a new nonlinear response prediction model of rotor bearing rub-impact system is established. Different from the traditional rotor system rub-impact model, based on the detailed characteristics of the blade–disc system, this paper considers the influence of the number of blades and the dynamic to static clearance on the rub-impact force. In addition, the influence of additional load on the established rotor-bearing system due to the change in the flight motion state of the horizontal yawing maneuver is also considered The Newmark-β numerical method is used to solve the system, and the effects of maneuver load and rub-impact stiffness on the nonlinear dynamics of the system are studied The results show that the system produces a kind of sub harmonic resonance rub-impact phenomenon, that is, the system will produce 1/2 sub harmonic resonance under the action of maneuver load near the double critical speed, which will increase the vibration response amplitude of the system. With the increase of maneuver load, the system always has complex nonlinear phenomenon; with the increase of rub-impact stiffness, the system produces a large number of frequency division and frequency multiplication components, which can be used as the characteristic frequency of rub-impact faults.

Tabu Genetic Cat Swarm Algorithm Analysis of Optimization Arrangement on Mistuned Blades Based on CUDA

Tabu genetic cat swarm optimization algorithm is proposed for optimization arrangement on mistuned blades. Furthermore, it is improved to be an innovative parallel algorithm based on Compute Unified Device Architecture (CUDA), whose performance is analyzed both in continuous and discrete solution space. The lumped parameter model and finite element model of the bladed-disk system are established for dynamics analysis and optimization verification. The complete mistuned parameter identification method and the improved mixed-interface prestressed substructure modal synthesis method are two other highlights. The results indicate that the algorithm in this paper has the advantages of low cost and high efficiency. The vibration localization and amplitude of the mistuned bladed-disk system are both reduced significantly. The optimization analysis method is proved to be applicable to the mistuned bladed-disk system of the aeroengine in engineering practice.

Study on Influence of Multi-Parameter Variation of Bladed Disk System on Vibration Characteristics

As the main components of the rotor system of aero-engines and other rotating machinery equipment, the bladed disk system has high requirements on its structure design, safety and stability. Taking the rotor disk system of aero-engines as the research object, modal calculation of the rotor disk system was based on the group theory algorithm, and using the fine sand movement on the experimental disk to express the disk vibration shape. The experimental vibration mode is used to compare with the finite element calculation results to verify the reliability of the finite element analysis. Study on the effect of dissonance parameter changes on the bladed disk system vibration characteristics concluded that the vibration mode trends of the blisk system and the disc are, basically, consistent. As the mass of the blade increases, the modal frequencies of the entire blisk system gradually decrease, and the amplitude slightly increases. When the mass increases at different parts of the blade, the effect on the modal frequencies of the bladed disk system are not obvious. When the bladed disk system vibrates at low frequency, the disc will not vibrate and each blade will vibrate irregularly. The bladed disk should be avoided to work in this working area for a long time, so as not to cause fatigue damage or even fracture of some blades.

A New Method of Reducing the Vibration Localization of the Multi-packet Whole Mistuned Bladed Disk System Using Bladed Packets

Multi-packet whole bladed disks are found in some turbo engines. At the same time, mistuning of blades is inevitable and it will lead to the vibration localization in which vibration energy mainly locates in some blades in the bladed disk system. It can accelerate the high cycle fatigue of the bladed disk. It is critical to search for an efficient way to control the level of vibration localization of the mistuned bladed disk system. Therefore, in this paper, a new method of reducing the vibration localization of the mistuned bladed disk system using bladed packets is studied. A mathematical model is developed in which a coupling stiffness is introduced to describe the coupling relationship due to bladed packets. The effect of bladed packets on the vibration localization of the whole mistuned bladed disk is discussed. The results indicate that the bladed packet can really reduce the degree of the vibration localization of bladed disk. The relationship between the coupling strength of blade to blade and the vibration localization is researched. Moreover, different number of bladed packets of the mistuned bladed disk on the vibration localization of the mistuned bladed disk is investigated for researching the optimal multi-packet structures.

Investigation on the parameter sensitivity of bladed assemblies undergoing mistuning features

The present study's objectives are primarily to reveal the mistuning effects on the coupling system's nonlinear vibration performance with a mechanical model of the flexible bladed disk system. And the sensitivities of the coupling system to different mistuning cases are also compared and estimated. Firstly, the tuned system's nonlinear characteristics are presented for providing a reference to interpret the nonlinear dynamics of the mistuning case. Then present analysis exploits the nonlinear response spectrum of the coupling system undergoing a series of parameter mistuning conditions. The numerical simulation reveals that the response characteristics of cycle blades exhibit perfect identity in the tuned system. When the parameter mistuning condition occurs, the identity characteristics are destroyed, especially the blade length mistuning case. The mistuning feature can also lead to new resonances at the modal frequency of flexible disk, which exhibits distinctive sensitivity to the different mistuning case. Besides, the vibration localization phenomenon occurs due to the broken cyclic periodicity of the bladed disk structure. Furthermore, enough attention should be paid to the coupling effects in the bladed disk system undergoing parameter mistuning in engineering practice.

Effect of mistuning parameters on dynamic characteristics of mistuned bladed disk

The aim of this paper is to study the nonlinear dynamics of the tenon and mortise of aero-engine compressor blades, based on lumped parameter model of tenon and mortise of blade disk system, considering the influence of gap and friction, The nonlinear vibration characteristics of mistuned bladed disk with different mistuning parameters are studied. The effects of tenon and mortise gap, dry friction, blade damping mistuning and tenon damping mistuning on the vibration characteristics of the mistuned bladed disk under strong coupling and weak coupling are obtained respectively. The results show that the gap and friction has little effect on the vibration response of the weakly coupled bladed disk, but the gap and friction has a great influence on the strongly coupled bladed disk, the larger the gap, the more complex the nonlinear dynamic characteristics of tenon. Under the same gap and coupling strength, the mistuning parameters have a certain influence on the vibration amplitude of the bladed disk.