scholarly journals A Prediction Method for the Damping Effect of Ring Dampers Applied to Thin-Walled Gears Based on Energy Method

Symmetry ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 677 ◽  
Author(s):  
Yanrong Wang ◽  
Hang Ye ◽  
Xianghua Jiang ◽  
Aimei Tian
Keyword(s):  
Numerical Method ◽  
Prediction Method ◽  
Normal Pressure ◽  
Nonlinear Damping ◽  
Forced Response ◽  
Design Parameters ◽  
Response Analysis ◽  
Friction Damping ◽  
Resonance Amplitude ◽  
Thin Walled

In turbomachinery applications, thin-walled gears are cyclic symmetric structures and often subject to dynamic meshing loading which may result in high cycle fatigue (HCF) of the thin-walled gear. To avoid HCF failure, ring dampers are designed for gears to increase damping and reduce resonance amplitude. Ring dampers are installed in the groove. They are held in contact with the groove by normal pressure generated by interference or centrifugal force. Vibration energy is attenuated (converted to heat) by frictional force on the contact interface when the relative motion between ring dampers and gears takes place. In this article, a numerical method for the prediction of friction damping in thin-walled gears with ring dampers is proposed. The nonlinear damping due to the friction is expressed as equivalent mechanical damping in the form of vibration stress dependence. This method avoids the forced response analysis of nonlinear structures, thereby significantly reducing the time required for calculation. The validity of this numerical method is examined by a comparison with literature data. The method is applied to a thin-walled gear with a ring damper and the effect of design parameters on friction damping is studied. It is shown that the rotating speed, geometric size of ring dampers and friction coefficient significantly influence the damping performance.

scholarly journals An Equivalent Damping Numerical Prediction Method for the Ring Damper Used in Gears under Axial Vibration

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1469 ◽  
Author(s):  
Shuai Wang ◽  
Xiaolei Wang ◽  
Yanrong Wang ◽  
Hang Ye
Keyword(s):  
Structural Parameters ◽  
Great Influence ◽  
Prediction Method ◽  
Forced Response ◽  
Numerical Prediction ◽  
Axial Stiffness ◽  
Response Analysis ◽  
Axial Vibration ◽  
Equivalent Damping ◽  
Vibration Loads

In aircraft gas turbine engines, gears in the transmission system are typically cyclic in structure and inevitably encounter large dynamic loads, such as meshing excitation, resulting in high vibration loads in resonance. To prevent gear resonance failure, a ring damper is employed to reduce the resonance response. As relative motion between the gear and the ring damper occurs, vibration loads can be reduced by friction energy dissipation. Moreover, the gears in the aircraft engine are thin-walled and their axial stiffness is much smaller than radial stiffness; thus, it is easier for axial vibration to cause resonance failure. This paper proposes an equivalent damping numerical prediction method for a ring damper under axial vibration, which greatly shortens the calculation time and prevents the forced response analysis of nonlinear structures. Via this method, the influence of ring damper structural parameters on friction damping in gears under axial vibration is investigated. The results indicate that the friction coefficient and mass of the ring damper have a great influence on damping performance.

Nonlinear Dynamics Analysis of Mistuned Turbine Bladed Disks With Damped Shrouds

2017 ◽  
Author(s):  
Wei Zhao ◽  
Di Zhang ◽  
Lei Sun ◽  
Yonghui Xie
Keyword(s):  
Dry Friction ◽  
Normal Load ◽  
Forced Response ◽  
Vibration Response ◽  
Amplification Coefficient ◽  
Response Analysis ◽  
Friction Damping ◽  
Friction Forces ◽  
Bladed Disk ◽  
The Impact

This paper deals with the real dynamics characteristics of a mistuned steam turbine bladed disk subjected to dry friction forces to better understand the nonlinear mistuning phenomenon. Normal load, which directly affects contact stiffness between interfaces, is chosen as the mistuning parameter. Based on Mindlin model, a forced response analysis of the finite element model of mistuned bladed disk with damped shrouds is performed in ANSYS. Compared with results of other simplified models, a real and complicated nonlinear behavior are observed here. A mass of qualitative analysis is also performed to assess the impact of the mistuning magnitude and excitation level on the vibration. The result shows that, vibration response of bladed disk is affected by excitation and mistuning level significantly. Local amplification coefficient of vibration response in the cases of different mistuning levels is obtained by introducing 10 random mistuned patterns. In addition, frequency splitting phenomena even appears at one of the blades by the contribution of high mistuning levels. According to the calculated results for different excitation levels, the curve of modal damping varying with response amplitude is gained. Lastly, rigidity mistuning is introduced and a combined analysis is performed to investigate the influence of friction damping mistuning on rigidity mistuning in the same 10 random mistuning patterns. The arrangement of dry friction damping mistuning also could be controlled to reduce the local vibration amplification originating from structure mistuning. However, further statistical investigations should be made to gain more information. (CSPE)

A Method for the Optimal Design of Split Ring Dampers for Aviation Gears

2017 ◽  
Author(s):  
Hang Ye ◽  
Yanrong Wang ◽  
Xianghua Jiang
Keyword(s):  
Damping Ratio ◽  
Equations Of Motion ◽  
Nonlinear Damping ◽  
Forced Response ◽  
Design Parameters ◽  
Dissipated Energy ◽  
Vibration Energy ◽  
Equivalent Damping ◽  
Important Approach ◽  
Energy Dissipated

In order to reduce the resonance of aviation bevel gears, designing frictional interfaces for gear systems is an important approach through dissipate vibration energy. One emerging technology uses ring dampers, which are ring-like substructures constrained to move inside a groove at the rim of the gear. Ring dampers are in contact with the rim of the gear due to centrifugal force, and they create nonlinear dissipation by relative motion between the ring and the gear. The analysis of the dynamic response of nonlinear structures is commonly done by numerical integration of the equations of motion, which is computationally inefficient, especially for steady-state responses. In this paper an efficient methodology to predict the effect of the ring damper based on energy method, predicting the dissipated energy by friction force, converting into equivalent damping and to identify the main design parameters affecting the damper performance is proposed. The approach is based on expressing the vibration energy dissipated by nonlinear forces per vibration cycle as equivalent nonlinear damping ratio. This method avoids computing the forced response of the gear with ring damper in the frequency domain, that can increase the efficiency of the ring damper design. The methodology is applied to an aviation bevel gear. The effect of the principal design parameters of the ring damper is identified.

Regeneration-Induced Forced Response in Axial Turbines

2013 ◽  
Author(s):  
Jens Aschenbruck ◽  
Christopher E. Meinzer ◽  
Linus Pohle ◽  
Lars Panning-von Scheidt ◽  
Joerg R. Seume
Keyword(s):  
Turbine Blades ◽  
Forced Response ◽  
Response Analysis ◽  
Geometrical Parameters ◽  
Turbine Stage ◽  
Structural Dynamic ◽  
Air Turbine ◽  
Axial Turbines ◽  
Interaction Approach ◽  
Stagger Angle

The regeneration of highly loaded turbine blades causes small variations of their geometrical parameters. To determine the influence of such regeneration-induced variances of turbine blades on the nozzle excitation, an existing air turbine is extended by a newly designed stage. The aerodynamic and the structural dynamic behavior of the new turbine stage are analyzed. The calculated eigenfrequencies are verified by an experimental modal analysis and are found to be in good agreement. Typical geometric variances of overhauled turbine blades are then applied to stator vanes of the newly designed turbine stage. A forced response analysis of these vanes is conducted using a uni-directional fluid-structure interaction approach. The effects of geometric variances on the forced response of the rotor blade are evaluated. It is shown that the vibration amplitudes of the response are significantly higher for some modes due to the additional wake excitation that is introduced by the geometrical variances e.g. 56 times higher for typical MRO-induced variations in stagger-angle.

Chatter Prediction Based on NC Physical Simulation in Machining Ti6Al4V Thin-Walled Components

2013 ◽  
Vol 395-396 ◽  
pp. 1008-1014
Author(s):  
Yu Li ◽  
Chao Sun
Keyword(s):  
Tool Path ◽  
Physical Simulation ◽  
Prediction Method ◽  
Cutting Parameters ◽  
Simulation Software ◽  
Cnc Machining ◽  
Machining Process ◽  
Chatter Stability ◽  
Chatter Prediction ◽  
Thin Walled

Chatter has been a problem in CNC machining process especially during machining thin-walled components with low stiffness. For accurately predicting chatter stability in machining Ti6Al4V thin-walled components, this paper establishes a chatter prediction method considering of cutting parameters and tool path. The fast chatter prediction method for thin-walled components is based on physical simulation software. Cutting parameters and tool path is achieved through the chatter stability lobes test and finite element simulation. Machining process is simulated by the physical simulation software using generated NC code. This proposed method transforms the NC physical simulation toward the practical methodology for the stability prediction over the multi-pocket structure milling.

scholarly journals Vibration and Instability of Rotating Composite Thin-Walled Shafts with Internal Damping

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ren Yongsheng ◽  
Zhang Xingqi ◽  
Liu Yanghang ◽  
Chen Xiulong
Keyword(s):  
Virtual Work ◽  
Numerical Study ◽  
Equations Of Motion ◽  
Beam Theory ◽  
Dynamical Analysis ◽  
Design Parameters ◽  
Internal Damping ◽  
Analysis Method ◽  
Governing Equations ◽  
Thin Walled

The dynamical analysis of a rotating thin-walled composite shaft with internal damping is carried out analytically. The equations of motion are derived using the thin-walled composite beam theory and the principle of virtual work. The internal damping of shafts is introduced by adopting the multiscale damping analysis method. Galerkin’s method is used to discretize and solve the governing equations. Numerical study shows the effect of design parameters on the natural frequencies, critical rotating speeds, and instability thresholds of shafts.

Velocity Field Response of a Forced Swirl Stabilized Premixed Flame

2017 ◽  
Author(s):  
Kiran Manoharan ◽  
Travis Smith ◽  
Benjamin Emerson ◽  
Christopher M. Douglas ◽  
Tim Lieuwen ◽  
...  
Keyword(s):  
Heat Release ◽  
Shear Layer ◽  
Recirculation Zone ◽  
Stokes Equations ◽  
Quantitative Agreement ◽  
Forced Response ◽  
Response Analysis ◽  
Annular Jet ◽  
Experimental Response ◽  
Prediction Approach

This study is motivated by the necessity to develop a low order prediction approach for unsteady heat release response characteristics in lean premixed gas turbine combustors. This in turn requires an accurate description of the coherent hydrodynamic oscillations induced in the combustor flow by acoustic forcing. Time resolved velocity and flame position fields are obtained using sPIV and OH-PLIF measurements on a single nozzle, swirl-stabilized, premixed, methane-air flame in a model “unwrapped” annular combustor rig. A natural acoustic oscillation in the rig at 115 Hz results in a coherent flow oscillation that is concentrated primarily within the shear layer between the annular jet flow and the central recirculation zone. A linear stability analysis performed about time averaged base flow fields shows that the flow does not have any self-excited hydrodynamic modes. We then compare predictions from a forced response analysis at a forcing frequency of 115 Hz, based on the linearized Navier-Stokes equations for this coherent response. Good qualitative agreement between linear forced response analysis predictions and experimental response results, is seen for the spatial variation of velocity oscillation amplitude fields, away from the burner centerline. Further, good quantitative agreement between predictions and the experimental response is seen for the phase speed of velocity oscillations along the shear layer between the annular jet and the central recirculation zone. This phase velocity is an important flow field characteristic that has a significant impact on the heat release response that results from these coherent velocity oscillations. Present methods for forced response analysis assume uniform forcing amplitude along the radial direction at the forcing location, as well as, open flows along the streamwise direction. Both these assumptions are not strictly true for the present burner which has a center body on its axis. This maybe the reason for somewhat poor qualitative and quantitative agreement between experiments and predictions at the centerline.

Influence of Detailing on Aerodynamic Forcing of a Transonic Axial Turbine Stage and Forced-Response Prediction for Low-Engine-Order (LEO) Excitation

2017 ◽  
Author(s):  
Tobias R. Müller ◽  
Damian M. Vogt ◽  
Klemens Vogel ◽  
Bent A. Phillipsen ◽  
Peter Hönisch
Keyword(s):  
Numerical Study ◽  
Response Prediction ◽  
Forced Response ◽  
Resonance Excitation ◽  
Response Analysis ◽  
Turbine Stage ◽  
Flow Induced Vibration ◽  
Axial Turbine ◽  
Timing Data ◽  
Generalized Force

The effects of detailing on the prediction of forced-response in a transonic axial turbine stage, featuring a parted stator design, asymmetric inlet and outlet casings as well as rotor cavities, is investigated. Ensuring the mechanical integrity of components is of paramount importance for the safe and reliable operation of turbomachines. Among others, flow induced resonance excitation can lead to high-cycle fatigue (HCF) and potentially to damage of components unless properly damped. This numerical study is assessing the necessary degree of detailing in terms of spatial and temporal discretization, boundary conditions of the pre-stressed rotor geometry as well as geometrical detailing for the reliable prediction of the aerodynamic excitation of the structure. In this context, the sensitivity of the aerodynamic forcing is analyzed by means of the generalized force criterion, showing a significant influence for some of the investigated variations of the numerical model. Moreover, the origin and further progression of several low-engine-orders (LEO) within the flow field, as well as their interaction with different geometric details has been analyzed based on the numerical results obtained from a full 360° CFD-calculation of the investigated turbine stage. The predicted flow induced vibration of the structure has been validated by means of a full forced-response analysis, where a good agreement with tip-timing data has been found.

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