scholarly journals Implementation of Speed Variation in the Structural Dynamic Assessment of Turbomachinery Flow Path Components

2013 ◽  
Author(s):  
Andrew M. Brown ◽  
R. Benjamin Davis ◽  
Michael K. DeHaye
Keyword(s):  
Resonant Frequency ◽  
Dynamic Assessment ◽  
Excitation Frequency ◽  
Flow Path ◽  
Forced Response ◽  
Response Analysis ◽  
Structural Dynamic ◽  
Speed Variation ◽  
Time Histories ◽  
Life Analysis

During the design of turbomachinery flow path components, the assessment of possible structural resonant conditions is critical. Higher frequency modes of these structures are frequently found to be subject to resonance, and in these cases, design criteria require a forced response analysis of the structure with the assumption that the excitation speed exactly equals the resonant frequency. The design becomes problematic if the response analysis shows a violation of the HCF criteria. One possible solution is to perform “finite-life” analysis, where Miner’s rule is used to calculate the actual life in seconds in comparison to the required life. In this situation, it is beneficial to incorporate the fact that, for a variety of turbomachinery control reasons, the speed of the rotor does not actually dwell at a single value but instead dithers about a nominal mean speed and during the time that the excitation frequency is not equal to the resonant frequency, the damage accumulated by the structure is diminished significantly. Building on previous investigations into this process, we show that a steady-state assumption of the response is extremely accurate for this typical case, resulting in the ability to quickly account for speed variation in the finite-life analysis of a component which has previously had its peak dynamic stress at resonance calculated. A technique using Monte Carlo simulation is also presented which can be used when specific speed time histories are not available. The implementation of these techniques can prove critical for successful turbopump design, as the improvement in life when speed variation is considered is shown to be greater than a factor of two.

scholarly journals Implementation of Speed Variation in the Structural Dynamic Assessment of Turbomachinery Flow Path Components

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Andrew M. Brown ◽  
R. Benjamin Davis ◽  
Michael K. DeHaye
Keyword(s):  
Resonant Frequency ◽  
Dynamic Assessment ◽  
Excitation Frequency ◽  
Flow Path ◽  
Forced Response ◽  
Response Analysis ◽  
Structural Dynamic ◽  
Speed Variation ◽  
Time Histories ◽  
Life Analysis

During the design of turbomachinery flow path components, the assessment of possible structural resonant conditions is critical. Higher frequency modes of these structures are frequently found to be subject to resonance and, in these cases, design criteria require a forced response analysis of the structure with the assumption that the excitation speed exactly equals the resonant frequency. The design becomes problematic if the response analysis shows a violation of the high cycle fatigue (HCF) criteria. One possible solution is to perform a “finite-life” analysis, where Miner's rule is used to calculate the actual life in seconds in comparison to the required life. In this situation, it is beneficial to incorporate the fact that, for a variety of turbomachinery control reasons, the speed of the rotor does not actually dwell at a single value but instead dithers about a nominal mean speed and during the time that the excitation frequency is not equal to the resonant frequency, the damage accumulated by the structure is significantly diminished. Building on previous investigations into this process, we show that a steady-state assumption of the response is extremely accurate for this typical case, resulting in the ability to quickly account for speed variation in the finite-life analysis of a component which has previously had its peak dynamic stress at resonance calculated. A technique using a Monte Carlo simulation is also presented which can be used when specific speed time histories are not available. The implementation of these techniques can prove critical for successful turbopump design, since the improvement in life when speed variation is considered is shown to be greater than a factor of two.

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.

Experimental Forced Response Analysis of Two-Degree-of-Freedom Piecewise-Linear Systems With a Gap

2020 ◽  
Author(s):  
Akira Saito ◽  
Junta Umemoto ◽  
Kohei Noguchi ◽  
Meng-Hsuan Tien ◽  
Kiran D’Souza
Keyword(s):  
Piecewise Linear ◽  
Excitation Frequency ◽  
Forced Response ◽  
Degree Of Freedom ◽  
Linear Oscillator ◽  
Phase Portraits ◽  
Response Analysis ◽  
Experimental Setup ◽  
The Masses ◽  
Two Degree Of Freedom

Abstract In this paper, an experimental forced response analysis for a two degree of freedom piecewise-linear oscillator is discussed. First, a mathematical model of the piecewise linear oscillator is presented. Second, the experimental setup developed for the forced response study is presented. The experimental setup is capable of investigating a two degree of freedom piecewise linear oscillator model. The piecewise linearity is achieved by attaching mechanical stops between two masses that move along common shafts. Forced response tests have been conducted, and the results are presented. Discussion of characteristics of the oscillators are provided based on frequency response, spectrogram, time histories, phase portraits, and Poincaré sections. Period doubling bifurcation has been observed when the excitation frequency changes from a frequency with multiple contacts between the masses to a frequency with single contact between the masses occurs.

Advanced Modelling of Underplatform Friction Dampers for Analysis of Bladed Disc Vibration

2006 ◽  
Author(s):  
E. P. Petrov ◽  
D. J. Ewins
Keyword(s):  
Large Scale ◽  
Dynamic Models ◽  
Normal Load ◽  
Forced Response ◽  
Response Analysis ◽  
Finite Element Models ◽  
Structural Dynamic ◽  
Stick Slip ◽  
Friction Dampers ◽  
Inertia Forces

Advanced structural dynamic models for both wedge and split underplatform dampers have been developed. The new damper models take into account inertia forces and the effects of normal load variation on stick-slip transitions at the contact interfaces. The damper models are formulated for the general case of multiharmonic forced response analysis. An approach for using the new damper models in the dynamic analysis of large-scale finite element models of bladed discs is proposed and realised. Numerical investigations of bladed discs are performed to demonstrate the capabilities of the new models and an analysis of the influence of the damper parameters on the forced response of bladed discs is made.

Compressor Upgrade on Existing Platform: A Study on Vibration from Structural Perspective

2021 ◽  
Author(s):  
See Yee Teh ◽  
Ahmad Rizal A Rahman ◽  
Raja Sharifuddin Ahmad Raja Badrol ◽  
Mohd Hafis Muhammad Daud
Keyword(s):  
Dynamic Analysis ◽  
Structural Engineering ◽  
Dynamic Effect ◽  
Forced Response ◽  
Project Team ◽  
Response Analysis ◽  
Element Analysis ◽  
Structural Dynamic ◽  
Processing Platform ◽  
Gas Lift

Abstract Due to an increase in gas lift demand on an existing field in Sarawak, an existing Gas Lift Compressor (GLC) on the processing platform requires to be upgraded to meet incremental oil production requirement. These sets of compressors consist of 2x100% reciprocating compressors that were designed for 1.5 MMscfd each, with discharge pressure of 55.1 barg (800psig). The gas from these compressors is used mainly for gas lift at the processing platform as well as gas lift, instrument gas and utility gas at adjacent wellhead platforms. From the Conceptual Study, the existing compressors are not able to be retrofit for upgrade and is to be replaced with 2 × 100 % new gas engine driven compressor that capable of delivery 3.0 MMscfd of compressed gas each. During the engineering stage of GLC package, Skid Dynamic Analysis has been carried out to evaluate the GLC skid structural design due to the operating dynamic load cases. The study recommended that the skid to be welded to the platform where the compressor is located to prevent the risk of high vibration. With the recommendation from Contractor's study, project team proceeded to carry out Structural Dynamic Analysis to assess the dynamic effect of the GLC skids to the platform deck. The Finite Element Analysis (FEA) results revealed that there are several modal modes mainly at the drilling deck and extension deck non-compliance to PTS guideline. Structural Dynamic Modification (SDM) and optimization was performed to dynamically stiffens the structures to shift the modal modes away from the operating range to fulfil PTS criteria. However, the SDM results was still unable to comply thus the need of Anti-Vibration Mounts (AVMs) is considered. Prior to application of AVMs, Structural Forced Response Analysis needs to be carried out to evaluate the risk of the system and confirm the requirement of the AVMs. Without the forced response analysis, the effect of AVMs, locations and numbers of AVMs cannot be addressed during the design study. This paper will discuss the issues concerning vibration from reciprocating compressors upgrade on an existing platform, changes in the existing operating and design philosophy, challenges in addressing compressor installation and utilization of AVM from the perspective of Project Team. The paper will also provide key lessons learn and recommendation for future considerations in Compressor upgrades on existing facilities from a Structural Engineering point of view. The project is currently at its detail design finalization and installation is expected to be completed by November 2021.

Advanced Modeling of Underplatform Friction Dampers for Analysis of Bladed Disk Vibration

2006 ◽  
Vol 129 (1) ◽  
pp. 143-150 ◽  
Author(s):  
E. P. Petrov ◽  
D. J. Ewins
Keyword(s):  
Large Scale ◽  
Dynamic Models ◽  
Normal Load ◽  
Forced Response ◽  
Response Analysis ◽  
Bladed Disks ◽  
Structural Dynamic ◽  
Stick Slip ◽  
Bladed Disk ◽  
Inertia Forces

Advanced structural dynamic models for both wedge and split underplatform dampers have been developed. The new damper models take into account inertia forces and the effects of normal load variation on stick-slip transitions at the contact interfaces. The damper models are formulated for the general case of multiharmonic forced response analysis. An approach for using the new damper models in the dynamic analysis of large-scale finite element models of bladed disks is proposed and realized. Numerical investigations of bladed disks are performed to demonstrate the capabilities of the new models and an analysis of the influence of the damper parameters on the forced response of bladed disks is made.

scholarly journals Stereo-DIC Measurements of a Vibrating Bladed Disk: In-Depth Analysis of Full-Field Deformed Shapes

2021 ◽  
Vol 11 (12) ◽  
pp. 5430
Author(s):  
Paolo Neri ◽  
Alessandro Paoli ◽  
Ciro Santus
Keyword(s):  
Single Point ◽  
Excitation Frequency ◽  
Phase Variation ◽  
Operating Conditions ◽  
Image Correlation ◽  
Response Analysis ◽  
Full Field ◽  
Low Speed ◽  
Bladed Disk ◽  
Depth Analysis

Vibration measurements of turbomachinery components are of utmost importance to characterize the dynamic behavior of rotating machines, thus preventing undesired operating conditions. Local techniques such as strain gauges or laser Doppler vibrometers are usually adopted to collect vibration data. However, these approaches provide single-point and generally 1D measurements. The present work proposes an optical technique, which uses two low-speed cameras, a multimedia projector, and three-dimensional digital image correlation (3D-DIC) to provide full-field measurements of a bladed disk undergoing harmonic response analysis (i.e., pure sinusoidal excitation) in the kHz range. The proposed approach exploits a downsampling strategy to overcome the limitations introduced by low-speed cameras. The developed experimental setup was used to measure the response of a bladed disk subjected to an excitation frequency above 6 kHz, providing a deep insight in the deformed shapes, in terms of amplitude and phase distributions, which could not be feasible with single-point sensors. Results demonstrated the system’s effectiveness in measuring amplitudes of few microns, also evidencing blade mistuning effects. A deeper insight into the deformed shape analysis was provided by considering the phase maps on the entire blisk geometry, and phase variation lines were observed on the blades for high excitation frequency.

scholarly journals Complex response analysis of a non-smooth oscillator under harmonic and random excitations

2021 ◽  
Vol 42 (5) ◽  
pp. 641-648
Author(s):  
Shichao Ma ◽  
Xin Ning ◽  
Liang Wang ◽  
Wantao Jia ◽  
Wei Xu
Keyword(s):  
Excitation Frequency ◽  
System Stability ◽  
Response Analysis ◽  
External Excitation ◽  
Stochastic Response ◽  
Impact Oscillator ◽  
Nonlinear Parameters ◽  
Bifurcation Phenomena ◽  
Mc Simulation ◽  
Smooth System

AbstractIt is well-known that practical vibro-impact systems are often influenced by random perturbations and external excitation forces, making it challenging to carry out the research of this category of complex systems with non-smooth characteristics. To address this problem, by adequately utilizing the stochastic response analysis approach and performing the stochastic response for the considered non-smooth system with the external excitation force and white noise excitation, a modified conducting process has proposed. Taking the multiple nonlinear parameters, the non-smooth parameters, and the external excitation frequency into consideration, the steady-state stochastic P-bifurcation phenomena of an elastic impact oscillator are discussed. It can be found that the system parameters can make the system stability topology change. The effectiveness of the proposed method is verified and demonstrated by the Monte Carlo (MC) simulation. Consequently, the conclusions show that the process can be applied to stochastic non-autonomous and non-smooth systems.

Vibration behavior of an overhead conductor under updraft winds

2021 ◽  
pp. 107754632110058
Author(s):  
Qi Zhou ◽  
Liangtao Zhao ◽  
Chong Zheng ◽  
Feng Tu
Keyword(s):  
Induced Response ◽  
Response Analysis ◽  
Response Factor ◽  
Structural Dynamic ◽  
Resonance Response ◽  
Structural Dynamic Characteristics ◽  
Strong Winds ◽  
American Society ◽  
Gust Response Factor ◽  
Gust Response

At present, the wind-induced response analysis of an overhead conductor is mainly based on the action of horizontal normal wind. However, for crossing hillsides or extremely strong winds, such a conductor will bear the action of updraft wind, which will change the geometry of the conductor and make its structural dynamic characteristics nonlinear to some extent. In this work, the in-plane and out-of-plane two-dimensional nonlinear equations were established under the action of self-weight and updraft wind. Furthermore, the improved equations of conductor tension and sag were obtained, and the wind-induced vibration response was further investigated. The results showed that the updraft wind caused the nonlinearity of the tension and sag of the overhead conductor, and the nonlinear geometric change significantly affected its resonance response, which exceeded 25% if the wind speed was 50 m/s. In addition, because the proportion of the resonance response in the total wind-induced response was different, the influence of the wind attack angle calculated using the gust response factor method on the gust response factor was slightly larger than that calculated using the the American society of civil engineers method.

scholarly journals Analysis of a Cantilevered Piezoelectric Energy Harvester in Different Orientations for Rotational Motion

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1206 ◽  
Author(s):  
Wei-Jiun Su ◽  
Jia-Han Lin ◽  
Wei-Chang Li
Keyword(s):  
Theoretical Model ◽  
Resonant Frequency ◽  
Rotational Motion ◽  
Axial Load ◽  
Energy Harvester ◽  
Excitation Frequency ◽  
Experimental Studies ◽  
Piezoelectric Energy ◽  
Piezoelectric Cantilever ◽  
Tip Mass

This paper investigates a piezoelectric energy harvester that consists of a piezoelectric cantilever and a tip mass for horizontal rotational motion. Rotational motion results in centrifugal force, which causes the axial load on the beam and alters the resonant frequency of the system. The piezoelectric energy harvester is installed on a rotational hub in three orientations—inward, outward, and tilted configurations—to examine their influence on the performance of the harvester. The theoretical model of the piezoelectric energy harvester is developed to explain the dynamics of the system and experiments are conducted to validate the model. Theoretical and experimental studies are presented with various tilt angles and distances between the harvester and the rotating center. The results show that the installation distance and the tilt angle can be used to adjust the resonant frequency of the system to match the excitation frequency.

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