Vibration Characteristics Of Blades Research Articles

Method for Predicting Unsteady Vibration of Gas Turbine Compressor Blades Under Subsonic Near-Stall Conditions

Wind tunnel tests and numerical calculations using computational fluid dynamics (CFD) analysis and structural finite element analysis were conducted to clarify the vibration characteristics of gas turbine compressor blades under subsonic near-stall conditions. The results show that discrete low-frequency components of pressure are created by variation of the separation region and that discrete high-frequency components are created by vortex shedding when the compressor blade incidence angle is in the stall region. The natural frequency component resonated by the random fluid force is dominant in blade vibration. The numerically calculated phenomena agree well with the measured phenomena. The vibration amplitude increases with the incidence angle and the Mach number, and it increases rapidly at higher angles. A simple method for predicting the vibration stress using static calculations is reasonably accurate.

The influence of wind shear on vibration of geometrically nonlinear wind turbine blade under fluid–structure interaction

For the large-scale offshore wind turbine blades, the governing equations in fluid domain and the motion equations in structural domain with geometric nonlinearity were developed based on ALE description, and the corresponding discrete equations were obtained. Blade entity model was built up using Pro/E, and the blade vibration characteristics under fluid–structure interaction (FSI) were simulated using ANSYS. Numerical results show that wind shear effect greatly increases the peak values of response curves for displacement and stress, makes the effect of bi-directional fluid–structure interaction (BFSI) more obvious, and also accelerates the attenuation of vibration curves. The displacement of blade airfoil increases nonlinearly along the span direction, and reaches the maximum at the blade tip. The maximum Mises stress appears in the middle of the blade, and reduces gradually towards each end of the blade. Furthermore, the contribution of wind shear effect (WSE) to displacement and Mises stress is much greater than that of FSI.

Resonance Reliability Analysis of Aeroengine Compressor Rotor Blade

To describe the frequency distribution of the rotor blades and improve the optimization, resonance reliability of the rotor blades was analyzed in this paper. Considering the variety of rand-om variables, we jointly used finite element method and response surface method. The Campbell diagram was set up to describe blade resonance by analyzing the compressor rotor blade vibration characteristics. For the second-order vibration failure of the rotor blade, we considered the impact of random variables with the rotor blade material, the blade dimension and the rotor speed. The pro-bability distribution and allowable reliability of the second-order vibration frequency was calculated, and the sensitivity of the random variables influencing vibration frequency was completed. The res-ults show that the resonance reliability with the confidence level 0.95 of the rotor blade are = 0.99753 with the excited order =4 and =0.99767 with the excited order =5,and basically ag-ree with the design requirements when the rotor speed =9916.2, and the factors mainly affe-cting the distribution of the second-order vibration frequency of the blades include elastic modulus, density and the rotor speed, with the sensitivity probabilities 35.09%,34.56% and 24.15% respecti-vely.

Time-dependent vibration frequency reliability analysis of blade vibration of compressor wheel of turbocharger for vehicle application

Blade vibration failure is one of the main failure modes of compressor wheel of turbocharger for vehicle application. The existing models for evaluating the reliability of blade vibration of compressor wheel are static, and can not reflect the relationship between the reliability of compressor wheel with blade vibration failure mode and the life parameter. For the blade vibration failure mode of compressor wheel of turbocharger, the reliability evaluation method is studied. Taking a compressor wheel of turbocharger for vehicle application as an example, the blade vibration characteristics and how they change with the operating parameters of turbocharger are analyzed. The failure criterion for blade vibration mode of compressor wheel is built with the Campbell diagram, and taking the effect of the dispersity of blade natural vibration frequency and randomness of turbocharger operating speed into account, time-dependent reliability models of compressor wheel with blade vibration failure mode are derived, which embody the parameters of blade natural vibration frequency, turbocharger operating speed, the blade number of compressor wheel, life index and minimum number of resonance, etc. Finally, the rule governing the reliability and failure rate of compressor wheel and the method for determining the reliable life of compressor with blade vibration is presented. A method is proposed to evaluate the reliability of compressor wheel with blade vibration failure mode time-dependently.

Comparison of One-Dimensional and Three-Dimensional Structural Dynamics Modeling of Advanced Geometry Blades

Comparisons between one-dimensional and three-dimensional analyses are conducted systematically for advanced geometry blades, which have tip sweep, tip taper, and planform variations near the root with various materials and effects of boundary conditions in order to better understand the differences between the two approaches and the physics behind them. One-dimensional beam analysis is conducted using the rotorcraft comprehensive analysis system with variational asymptotical beam sectional analysis calculated two-dimensional cross-sectional properties. Three-dimensional finite element analysis is conducted using a commercial code MSC/Marc. Natural frequencies are calculated at various rotor rotational speeds, and the differences are quantified. There is very good agreement between the one-dimensional and three-dimensional analyses for free–free aluminum beams, even for a very short beam with beam length five times chord (). The one-dimensional analysis accurately captures the planform variation near the root for an aluminum beam. In general, the differences between the one-dimensional and three-dimensional analyses occur when there is coupling, either generated from geometry (tip sweep) or material (composite), especially for high-frequency modes. Without coupling, the one-dimensional analysis appears to capture free vibration characteristics of various advanced geometry beams and blades reasonably well for at least the six lowest frequency modes when the beam length is greater than 10 times chord.

Experimental study of coupled shaft bending - blade umbrella mode vibration of a turbine rotor model

This paper describes an experimental study on the characteristics of blade-shaft coupled bending vibration of a rotor system with a bladed disk. In a rotor with relatively long blades such as low-pressure steam turbines, the coupled vibration of shaft torsional and blade bending vibration with nodal diameter of zero (umbrella mode) must be considered in terms of reliability. The bending-torsion coupled resonance of rotor systems occurs under specific conditions, when the rotational speed is equal to the sum and/or difference of the bending natural frequency and torsional natural frequency. In this study, a test apparatus with a flexible rotor equipped with a bladed disk which simulates actual turbine blade structure was developed to study the coupled vibration characteristics of shaft bending and blade (κ=0). The rotor was excited with an active magnetic bearing for lateral direction and a servomotor for torsional direction. Resonance of a bladed disk with nodal diameter (κ) of zero, which was coupled with the rotor’s torsional vibration, occurred under the above specific condition with lateral excitation force where frequency was equal to the rotor’s bending natural frequency. In addition, resonance of rotor bending vibration was found when the rotor was excited in torsional direction of its natural frequency.

Vibration Characteristics Analysis of Wide-Chord Hollow Fan Blade

Wide-Chord Hollow Fan Blade is One of the New Technologies Used in Aircraft Engines. in this Paper, the Modal Analysis Method is Used to Analyze the Influence of the Rib Number and the Rib Thickness to Wide-Chord Hollow Fan Blade Vibration Characteristics. the Result Shows that the Wide-Chord Hollow Fan Blades Greatly Improves the First-Order Vibration Frequency Compared with the Solid Blades, and the First-Order Vibration Frequency of the Wide-Chord Hollow Fan Blades is Reduced with the Increasing Rib Number which is Not Good for Vibration Elimination. the Wide-Chord Hollow Fan Blades’ Vibration Frequency Changes a Little when the Rib Number is Larger than Three. in Addition, the Rib Thickness has Smaller Effect on Wide-Chord Hollow Fan Blade.

Dynamic Characteristic Simulation and Analysis of Blade Flutter Based on Finite Element

Blade is one of the main parts of aircraft engine. Its dynamic characteristics will produce important influence on the work efficiency and the operation reliability of the turbine engine. The paper used the theory of finite element to do modal simulation analysis on the dynamic characteristic of blade flutter, aiming at the phenomenon of serious blade vibration in the process of turbine engine running. Firstly, the paper generated a three-dimensional model by using the software UG. Then the three-dimensional model was leaded into the finite element analysis software ANSYS. Simulation analysis of the model was carried out by using the Workbench module of ANSYS software. Finally, we got the former six order natural frequencies and vibration modes of the blade. In addition, we got the blade's vibration characteristics. The results of the simulation could provide numerical basis for the blades optimization design and vibration safety inspection.

The Vibration Characteristics of Steam Turbine Blades with New Friction Damping Structures

The hysteresis curves that show the relationship between the tangential friction force and relative displacement of the contact surface were measured. The equivalent stiffness and damping of the friction contact surface under different normal loads were computed by harmonic balance method (HBM). The finite element model of steam turbine blades with new friction damping structures was established. The effects of friction between the contact surfaces were considered by using spring damping elements to connect the friction damper and the blade. The equivalent stiffness and damping which were calculated by the experiment results were applied to the spring damping elements under different rotational speeds. Based on the natural frequencies which were computed by finite element analysis, the Campbell diagram of the whole blades was obtained. The results showed that there were no 3-coincide points in the working speed range.

Influence of Radial Slots on the Vibration Characteristics of Circular Saw Blade

In order to improve thin circular saw blade’s cutting stability, it’s nonlinear dynamic incremental equilibrium equation was obtained according to nonlinear vibration theory and D’Alembert principle. It could be concluded from the above equation that cutting several radial slots on the circumference of the saw blade will cause significant change of dynamic characteristics of the saw blade. This thesis, employing the finite element method and matrix perturbation principle, calculated and studied respectively the effect of number, length and width of the radial slots on natural frequencies of the saw blade. Results show that number and length have distinct influence on natural frequencies but hardly does width have. So proper choice of number, length and width of the radial slots can improve effectively the dynamic characteristics of the saw blade.

Vibration Analysis of an Ocean Current Turbine Blade

Vibration characteristics of an ocean current turbine blade have been analyzed using Design foil, BET tool, Pro/Engineer and Finite Element Package ANSYS. Natural frequencies and mode shapes of a turbine blade can be evaluated by Vibration Analysis. It can also serve as a starting base for another, dynamic analysis, such as a transient dynamic analysis, or a spectrum analysis. The natural frequencies and mode shapes are important parameter in the design and analysis of an ocean current turbine blade. Modal analysis can also be performed on a pre-stressed spinning turbine blade. It has been investigated that the blade would not fail in an ocean current of 2.3 to 2.5 m/s that can produce power production up to 151 KW. The blade is of Composite structure with carbon fibers and foam core. It is also facilitated with two webs of carbon fibers to add shear rigidity. Eight design cases of blade were analyzed involving the differences in geometry, material properties and internal structures. Results from the vibration analysis revealed that the recommended blade design have adequate frequency difference than the frequency of other components of turbine like rotor, assembly to produce proposed power of 151 KW without any resonance or structural failure. Deflection analysis and Principal stress analysis have been conducted that showed the proposed blade design have adequate strength.

Vibration Characteristics Analysis of Aeroengine Composite Blade

In order to validate the dynamic response and the dynamic stress distribution of the blade, EMA and FEM were performed to study the vibration characteristics. A non-contact laser scanning viberometer was used to measure the blade modal response. After the signal process of the response, the natural frequencies, mode shapes and their nodal lines can be obtained by the modal parameter identification method. And the blade modal damping ratio can be calculated from its frequency response function (FRF), which was obtained during the test, by the half-power method. Based on the test results, a simplified computational model was established by layup method, and after modification, the error of FEM results and EMA results was less than 5%. So the blade vibration characteristics and its finite element prediction model were obtained by the two methods combined, which would laid a foundation for the dynamic test and the vibration fatigue life prediction of the blade.

Analysis of 3D Dynamic Response for TC4 Blades by the FEM

TC4 blades are one of the major parts of the aero engine, and the examples of engine invalid and even wrecked are common. In this paper, a 3D analysis system of the vibration behaviors of the TC4 blades is given. The 3D analysis model of blade was described using 20 nodes elements. The finite element procedure was worked out using the blade vibration behaviors analysis of the aero engine. At last, the modal shapes and stress nephograms of the first six frequencies are gotten which influenced the blade vibration characteristics. Results show that the program has offered an effective, flexible research means for analyzing dynamic response of TC4 blades.

Vibration Characteristics of Steam Turbine Blades with Straddle Mount (Effect of Contact Condition on Vibration Characteristics)

There are several kinds of blade root structures to support centrifugal forces acting on steam turbine blades such as straddle mount type root, T-root, axial or side entry root and fork type root. Steam turbine blades are surrounded by contact surfaces at a cover and the above blade root. It is known that contact conditions affect vibration characteristics of turbine blades. In this paper, the effects of contact surfaces on vibration characteristics of steam turbine blades with straddle mount type root were investigated. For that purpose, developed analysis method was applied, and natural frequencies and non-linear frequency responses of a steam turbine blade with contact surfaces at the cover and straddle mount type root were obtained using this method. From these results, it was concluded as follows. (1) Natural frequencies of the blade gradually decrease with increasing rotation speed due to the variation of contact area of the blade root. (2) The effect of friction damping at the cover was dominant and the effects at others were small. To verify these results, natural frequencies and dynamic responses of the blades during rotation were obtained in a spin pit test. Calculated results showed good agreement with experiment results and the analysis method was verified.

Nonlinear Vibration Characteristics of a Flexible Blade with Friction Damping due to Tip-Rub

An approximate approach is proposed in this paper for analyzing the two-dimensional friction contact problem so as to compute the dynamic response of a structure constrained by friction interfaces due to tip-rub. The dynamical equation of motion for a rotational cantilever blade in a centrifugal force field is established. Flow-induced distributed periodic forces and the internal material damping in the blade are accounted for in the governing equation of motion. The Galerkin method is employed to obtain a three-degree-of-freedom oscillator with friction damping due to tip-rub. The combined motion of impact and friction due to tip-rub produced a piecewise linear vibration which is actually nonlinear. Thus, a complete vibration cycle is divided into successive intervals. The system possesses linear vibration characteristic during each of these intervals, which can be determined using analytical solution forms. Numerical simulation shows that the parameters such as gap of the tip and the rotational speed of the blades have significant effects on the dynamical responses of the system. Finally, the nonlinear vibration characteristics of the blade are investigated in terms of the Poincare graph, and the frequency spectrum of the responses and the amplitude-frequency curves.

536 鞍型翼根部を有する蒸気タービン動翼の振動特性 : 接触条件が振動特性に及ぼす影響

536 鞍型翼根部を有する蒸気タービン動翼の振動特性 : 接触条件が振動特性に及ぼす影響

全周1リング翼構造と群翼構造が混在したタービン翼の不規則振動特性(機械力学,計測,自動制御)

全周1リング翼構造と群翼構造が混在したタービン翼の不規則振動特性(機械力学,計測,自動制御)

Determination of vibration characteristics of blades of gas turbine engines contactless method

Non-contact method simulation for blade real-time dynamic behavior determination is presented. This method uses eddy-current, capacitance or optical probes for blade tip deflections measurements which are related with time of blade tip passing trough the probe.

프로펠러 날개의 진동특성에 대한 실험적 연구

An experiment method has been developed to analyse the vibration characteristics of marine propeller blades, and vibration tests have been carried out on the model scale propeller in air and in water. The driving point transfer function(acceleration/excitation force) has been measured and modified by compensating the attachment effect of the impedance head. The measured natural frequencies in air have been compared with the theoretical results by an in-house FEM code PROSTEC. The added masses have been derived by comparing the measured natural frequencies in air and in water, and the results have been compared to the results using existing formula based on experience.

Simulation of Rotating Vibration Test of Bladed Disk System

Recently, the blade with friction damper has been used in the steam turbine and gas turbine to improve the blade reliability. In designing the damper blade, the vibration characteristics can be predicted by the analysis and the optimal damper shape is determined. As for the verification test of the damper blades, sometimes rainbow test, in which several kinds of damper blades are installed on the desk, is carried out to reduce the cost of test. It is probable that the vibration characteristics of each damper blade cannot be identified from the rainbow test because of the coupling effect through the disk and mistuning. In this paper, the bladed-disk systems of damper blades are represented by the equivalent spring mass system and the simulation of the rainbow test is carried out to clarify the condition from which the vibration characteristics of each blade is identified.