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The paper describes a numerical method based on a modal work approach to evaluate the forced response of bladed disks and its validation against numerical results obtained by a commercial FEM code. Forcing functions caused by rotor–stator interactions are extracted from CFD unsteady solutions properly decomposed in time and space to separate the spinning perturbation acting on the bladed disk in a cyclic environment. The method was firstly applied on a dummy test case with cyclic symmetry where the forcing function distributions were arbitrarily selected: comparisons for resonance and out of resonance conditions revealed an excellent agreement between the two numerical methods. Finally, the validation was extended to a more realistic test case representative of a low-pressure turbine bladed rotor subjected to the wakes of two upstream rows: an IGV with low blade count and a stator row. The results show a good agreement and suggest computing the forced response problem on the finer CFD blade surface grid to achieve a better accuracy. The successful validation of the method, closely linked to the CFD environment, creates the opportunity to include the tool in an integrated multi-objective procedure able to account for aeromechanical aspects. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The arrangement optimization algorithm of blades can reduce the vibration localization of mistuned bladed disk in a compressor of aero-engine, however, it will destroy the dynamic balance of bladed disk. A new arrangement optimization method of isolation zone on bladed disk system considering unbalance moment is proposed, on the basis the reduced order modeling technology. This method is based on the finite element model and can be implemented as fast and accurate vibration reduction optimization without destroying the mass balance of the bladed disk system, the method considers both mass and stiffness mistuning. Firstly, the discrete particle swarm optimization algorithm is used to sort the mass-mistuned blades according to unbalanced moment, then, the arranged bladed disk is divided into 6 isolation zones, then, in each isolation zone, the stiffness mistuned bladed disk is arranged optimally by the stiffness mistuning optimization algorithm. Under the premise of satisfying the dynamic balance of bladed disk, this algorithm optimizes the arrangement of blades with mass mistuning and stiffness mistuning, and achieves the purpose of vibration reduction optimization of mistuned bladed disk. The results show that, the maximum amplitude of the bladed disk system is reduced by 23.9 %. The vibration localization degree of the optimized blade are reduced by 46.3 %. [ABSTRACT FROM AUTHOR]

Severe blade vibrations may reduce the useful life of the high-speed blade. Nowadays, non-contact measurement using blade tip-timing (BTT) technology is becoming promising in blade vibration monitoring. However, blade tip-timing signals are typically under-sampled. How to extract characteristic features of unknown multi-mode blade vibrations by analyzing these under-sampled signals becomes a big challenge. In this paper, a novel BTT analysis method for reconstructing unknown multi-mode blade vibration signals is proposed. The method consists of two key steps. First, a sparse representation (SR) mathematical model for sparse blade tip-timing signals is built. Second, a multi-mode blade vibration reconstruction algorithm is proposed to solve this SR problem. Experiments are carried out to validate the feasibility of the proposed method. The main advantage of this method is its ability to reconstruct unknown multi-mode blade vibration signals with high accuracy. The minimal requirements of probe number are also presented to provide guidelines for BTT system design. [ABSTRACT FROM AUTHOR]

Removing some sections of the stator yoke in a permanent-magnet brushless machine can be beneficial for reducing punching waste and simplifying motor manufacture. However, in some cases, restricting the possible flux paths, in this way, will have a detrimental impact on the torque and air-gap harmonics. This paper discusses the potential implications of modular stator core arrangements and presents the air-gap flux density harmonics and winding factors for potential slot/pole combinations. Finite-element analysis (FEA) simulations are presented to support the analytical calculations. The analysis indicates that the performance reduction from using a modular stator is minimal when the number of slots and poles are similar but drops off substantially when this is not the case. A modular core stator will increase the MMF subharmonics due to the magnet field but can reduce the subharmonics due to the armature if a single-layer winding is used. The effect of slotting is very similar for a modular and conventional core machine, and FEA results match previously published analytical analyses. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents results of the complex stress and crack initiation analysis of the PZL-10W turbo-engine compressor blade subjected to high cycle fatigue (HCF). A nonlinear finite element method was utilized to determine the stress state of the blade during the first mode of transverse vibration. In this analysis, the numerical models without defects and also with V-notches were defined. The quality of the numerical solution was checked by the convergence analysis. Obtained results were next used as an input data into crack initiation (ε–N) analyzes performed for the load time history equivalent to one cycle of the transverse vibration. In the fatigue analysis the different methods such as: Neuber elastic–plastic strain correction, linear damage summation and Palmgreen–Miner rule were utilized. As a result of ε–N analysis, the number of load cycles to the first fatigue crack appearing in the compressor blades was obtained. Moreover, the influence of the blade vibration amplitude on the number of cycles to the crack initiation was analyzed. Values of the fatigue properties of the blade material according to Baumel–Seeger and Muralidharan methods were calculated. The influence of both the notch radius and values of the UTS of the blade material on the fatigue behavior of the structure was also considered. In the last part of work, the finite element results were compared with the results of an experimental vibration HCF tests performed for the compressor blades. [Copyright &y& Elsevier]

The present paper describes the use of Monet wavelet transform in understanding the stall inception mechanism in a single stage axial flow fan. Unsteady pressure data from wall mounted sensors were used in the wavelet transforms. This paper was carried out under undistorted and distorted inflow conditions as well as for slow throttle closure and throttle ramping. It was observed from the wavelet transforms that the stall inception under clean inflow (undistorted) and counter-rotating inflow distortions (in the direction opposing the rotor rotation) incur through short length-scale disturbances and through long length-scale disturbances under static and co-rotating inflow distortions (in the same direction of rotor rotation). Modal activity was observed to be insignificant under clean inflow while under static inflow distortion, long length-scale disturbances evolved due to interaction between rotor blades and the distorted sector especially near the trailing edge of the distortion screen. The presence of a strong mode was observed under both co- and counter-rotating inflow distortions. With throttle ramping, stall inception occurs through long and short length-scale disturbances under co- and counter-rotating inflow distortions, respectively. Some preliminary flow characteristics were studied using a seven hole probe. A significant increase in flow angle and decrease in axial flow coefficient close to the rotor tip were observed under co-rotating inflow distortion as compared with counter-rotating inflow distortion. [ABSTRACT FROM AUTHOR]

This paper presents a method to calculate the harmonic content of stator vibrations and acoustic noise resulting from radial force excitations in switched reluctance machines (SRM). The method is based on a thin cylinder approximation of the stator. The eigen modes are represented by their transmission impedance. The spectral composition of the vibrations can be calculated using superposition of the eigen modes and vibrations caused by all phases of the SRM. [ABSTRACT FROM AUTHOR]

Probabilistic failure assessments for integrally bladed disks are system reliability problems where a failure in at least one blade constitutes a rotor system failure. Turbine engine fan and compressor blade life is dominated by High Cycle Fatigue (HCF) initiated either by pure HCF or Foreign Object Damage (FOD). To date performing an HCF life assessment for the entire rotor system has been too costly in analysis time to be practical. Although the substantial run-time has previously precluded a full-rotor probabilistic analysis, reduced order models make this process tractable as demonstrated in this work. The system model includes frequency prediction, modal stress variation, mistuning amplification, FOD effect, and random material capability. The model has many random variables which are most easily handled through simple random sampling. [ABSTRACT FROM AUTHOR]

Diagnosis of rub-impact faults is the challenging topic because features of many rotor vibration rub-impact faults are the same as the other faults such as imbalance. In this paper, stator vibration is used as diagnosis information source. Firstly, the phenomena of stator vibration under the condition of impact rub are analyzed. The pulse force from rub-impact may lead to stator resonance, so the demodulate resonance technique can be brought out to diagnose rub-impact faults. To overcome the disadvantages of band-pass filter, the IFFT method is brought out to demodulate stator resonance signal. Secondly, the envelope signal is obtained through Hibert transformation of the stator resonance signal and amplitude spectrum through the FFT analysis. Lastly, experiments with one-point rub-impact and local rub-impact are carried out respectively. The actual measurement stator vibration signals are analyzed, results reveal that the stator resonance envelope signals can indicate rub-impact faults, and the fault position can be determined well coupling with angle displacement signal. The results demonstrate that analysis of stator vibration signals of impact-rubbing faults will provide a new diagnostic approach. [ABSTRACT FROM AUTHOR]

The linear aeroelastic stability of a simplified mass-spring model representing the basic dynamics of a packet of Na airfoils has been used to uncover a new type of coupled mode flutter. This simple model retains an essential dynamical feature of the vane packet the presence of a duster of Na -1 nearly identical purely structural natural frequencies due to the much larger stiffness of the lower platform as compared to that of the airfoil. Using this model it may be seen that this degeneracy makes the Na - 1 associated mode shapes extremely sensible to the addition of small perturbations such as the aerodynamic forces. Since the determination of the aerodynamic vibrational correction (damping and frequency) requires knowing the mode shape, the aerodynamic corrections of the Na -1 cluster modes are now unavoidably coupled together Moreover the computation of the aerodynamic correction independently for each structural mode shape leads typically to dangerously overpredicting the stabilizing effect of vane packing. it is shown that the expected stabilizing effect due to the packets may be negligible, depending on the relative frequency split associated with the strength of the aerodynamic forces and realistic structural effects such as the finite stiffness of the lower platform. it is also shown that in these cases, the most unstable mode may be, in a first approximation, very similar to that obtained modeling the stator as a continuous ring. [ABSTRACT FROM AUTHOR]

The article offers information on the stabilization of the flutter of turbocompressor rotor blades and flow modes. It states that synchronization of vibrations of rotor blades passes through an air flow, in which acoustic modes of pressure pulsations appear during flutter. It mentions that fluttering of the blades of a turbocompressor rotor is directed by the circular modes of synchronous vibrations.

Presents a synthesis method for determining the adaptive law's gain matrix such that the adaptation's stability and steady-state performance of rotor vibrations are robust with respect. Examples of the method used; Conclusions reached.

The article reports on the study regarding the advantages of using multiple surrogates for approximation and reduction of helicopter rotor blade vibration.

The article focuses on the findings of a study concerning the significance of pendulum absorbers for the reduction of the vibration of the rotor blades in helicopters. It mentions that the dimension of the pendulum absorbers was determined by the anti-resonance concept based on linear theory. Moreover, it notes that the authors of the study propose a two-degree-of-freedom model of the rotor blades.