Experimental Study on Impeller Blade Vibration During Resonance—Part II: Blade Damping

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Albert Kammerer ◽  
Reza S. Abhari
Keyword(s):  
Damping Ratio ◽  
Forced Response ◽  
Inlet Pressure ◽  
Test Facility ◽  
Blade Vibration ◽  
Impeller Blade ◽  
Dissipation Process ◽  
Curve Fit ◽  
Number Of Factors ◽  
Damping Parameter

Forming the second part of a two-part paper, the estimation of damping is presented here. Part I discusses the experimental approach and the results on blade resonant response measurements. In the study of forced response, damping is a crucial parameter, which is measured to quantify the ability of a vibrating system to dissipate vibratory energy in response to a given excitation source. The blading of turbomachinery components is particularly prone to forced response excitation, which is one of the major causes of high cycle fatigue failure during operation. In turbocharging applications, forced response cannot be avoided due to a number of factors, i.e., change in speed, inlet bends, or obstructions in the flow field. This study aims to quantify the damping parameter for the lightly damped blades of a centrifugal compressor. The impeller geometry is typical of turbocharging applications. As a first step, the nonrotating impeller was excited using piezos, and the transfer function was derived for a number of pressure settings. Both circle-fit and curve-fit procedures were used to derive material damping. In the second step, measurements were taken in the test facility where forced response conditions were generated using distortion screens upstream of the impeller. The main blade strain response was measured by sweeping through a number of resonant points. A curve-fit procedure was applied to estimate the critical damping ratio. The contributions of material and aerodynamic dampings were derived from a linear curve-fit applied to the damping data as a function of inlet pressure. Overall, it will be shown that aerodynamic damping dominates the dissipation process for applications with an inlet pressure of 1 bar. Damping was found to depend on the throttle setting of the compressor, and where applicable computational fluid dynamics results were used to point toward the possible causes of this effect.

Experimental Study on Impeller Blade Vibration During Resonance: Part 2—Blade Damping

2008 ◽  
Author(s):  
Albert Kammerer ◽  
Reza S. Abhari
Keyword(s):  
Damping Ratio ◽  
Forced Response ◽  
Inlet Pressure ◽  
Test Facility ◽  
Blade Vibration ◽  
Impeller Blade ◽  
Aerodynamic Damping ◽  
Curve Fit ◽  
Number Of Factors ◽  
Rotating Impeller

Forming the second part of a two-part paper, the estimation of damping is presented here. Part 1 discusses the experimental approach and the results on blade resonant response measurements. In the study of forced response damping is a crucial parameter which is measured to quantify the ability of a vibrating system to dissipate vibratory energy in response to a given excitation source. The blading of turbomachinery components is particularly prone to forced response excitation which is one of the major causes of high cycle fatigue failure during operation. In turbocharging applications forced response can not be avoided due to a number of factors, i.e. change in speed, inlet bends or obstructions in the flow field. This study aims to quantify the damping parameter for the lightly damped blades of a centrifugal compressor. The impeller geometry is typical of turbocharging applications. As a first step the non-rotating impeller was excited using piezos and the transfer function was derived for a number of pressure settings. Both circle-fit and a curve-fit procedure were used to derive material damping. In the second step, measurements were taken in the test facility where forced response conditions were generated using distortion screens upstream of the impeller. Main blade strain response was measured by sweeping through a number of resonant points. A curve-fit procedure was applied to estimate the critical damping ratio. The contribution of material and aerodynamic damping was derived from a linear curve fit applied to damping data as a function of inlet pressure. Overall, it will be shown that aerodynamic damping dominates the dissipation process for applications with inlet pressure of 1 bar. Damping was found to depend on the throttle setting of the compressor and where applicable CFD results were used to point towards possible causes of this effect.

Forced Response Excitation Due to the Stator Vanes of Two and Three Compressor Stages Away

2021 ◽  
Author(s):  
Toshimasa Miura ◽  
Naoto Sakai ◽  
Naoki Kanazawa ◽  
Kentaro Nakayama
Keyword(s):  
Gas Turbines ◽  
Rotor Blade ◽  
High Efficiency ◽  
Potential Effect ◽  
Forced Response ◽  
Rotor Blades ◽  
Test Facility ◽  
Blade Vibration ◽  
Stator Vane ◽  
Aero Engines

Abstract State-of-the-art axial compressors of gas turbines employed in power generation plants and aero engines should have both high efficiency and small footprint. Thus, compressors are designed to have thin rotor blades and stator vanes with short axial distances. Recently, problems of high cycle fatigue (HCF) associated with forced response excitation have gradually increased as a result of these trends. Rotor blade fatigue can be caused not only by the wake and potential effect of the adjacent stator vane, but also by the stator vanes of two, three or four compressor stages away. Thus, accurate prediction and suppression methods are necessary in the design process. In this study, the problem of rotor blade vibration caused by the stator vanes of two and three compressor stages away is studied. In the first part of the study, one-way FSI simulation is carried out. To validate the accuracy of the simulation, experiments are also conducted using a gas turbine test facility. It is found that one-way FSI simulation can accurately predict the order of the vibration level. In the second part of the study, a method of controlling the blade vibration is investigated by optimizing the clocking of the stator vanes. It is confirmed that the vibration amplitude can be effectively suppressed without reducing the performance. Through this study, ways to evaluate and control the rotor blade vibration are validated.

Experimental Investigation of Forced Response Impeller Blade Vibration in a Centrifugal Compressor With Variable Inlet Guide Vanes: Part 2—Forcing Function and FSI Computations

2011 ◽  
Author(s):  
Armin Zemp ◽  
Reza S. Abhari ◽  
Matthias Schleer
Keyword(s):  
Experimental Investigation ◽  
Centrifugal Compressor ◽  
Guide Vane ◽  
Forced Response ◽  
Inlet Guide Vane ◽  
Compressor Stage ◽  
Blade Vibration ◽  
Impeller Blade ◽  
Inlet Guide Vanes ◽  
Vane Angle

As the second part of a two-part paper, this paper presents an experimental investigation of forced response impeller blade vibrations in a centrifugal compressor stage caused by variable inlet guide vanes. Although it is common practice to experimentally test the forced response blade vibration behavior of new impeller designs in terms of strain gauge or tip-timing measurements, the impact of the unsteady blade pressure distribution acting as an unsteady load on the blade surfaces is still not known. A centrifugal compressor impeller was therefore instrumented with dynamic strain gauges and fast-response pressure transducers to measure the forcing of the impeller blades for different compressor operating points and various inlet guide vane angle settings. The results showed a decrease in the excitation amplitudes for reduced mass flow rates of the compressor stage. The inlet guide vane angle setting affected the convection speed of the distortion pattern along the blade surface. An increase in the negative inlet guide vane angle caused higher excitation amplitudes especially in the inducer part of the blade. However, the largest negative inlet guide vane setting caused the smallest excitation amplitudes as this setup introduced the smallest amount of inlet distortion to the inlet flow field. A series of unidirectional fluid structure interaction calculations was performed to show the limitations and requirements of today’s numerical tools.

Unsteady Flow in a Turbocharger Centrifugal Compressor: 3D-CFD-Simulation and Numerical and Experimental Analysis of Impeller Blade Vibration

2005 ◽  
Author(s):  
Hans-Peter Dickmann ◽  
Thomas Secall Wimmel ◽  
Jaroslaw Szwedowicz ◽  
Dietmar Filsinger ◽  
Christian H. Roduner
Keyword(s):  
Unsteady Flow ◽  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Cfd Simulation ◽  
Forced Response ◽  
Experimental Investigations ◽  
Excitation Mechanism ◽  
Blade Vibration ◽  
Impeller Blade ◽  
Vibration Behavior

Experimental investigations on a single stage centrifugal compressor showed that measured blade vibration amplitudes vary considerably along a constant speed line from choke to surge. The unsteady flow has been analysed to obtain detailed insight into the excitation mechanism. Therefore, a turbocharger compressor stage impeller has been modeled and simulated by means of Computational Fluid Dynamics (CFD). Two operating points at off-design conditions were analysed. One was close to choke and the second one close to the surge line. Transient CFD was employed, since only then a meaningful prediction of the blade excitation, caused by the unsteady flow situation, can be expected. Actually, it was observed that close to surge a steady state solution could not be obtained; only transient CFD could deliver a converged solution. The CFD results show the effect of the interaction between the inducer casing bleed system and the main flow. Additionally, the effect of the non-axisymmetric components, such as the suction elbow and the discharge volute, was analysed. The volute geometry itself had not been modeled. It turned out to be sufficient to impose a circumferentially asymmetric pressure distribution at the exit of the vaned diffuser to simulate the volute. Volute and suction elbow impose a circumferentially asymmetric flow field, which induces blade excitation. To understand the excitation mechanism, which causes the measured vibration behavior of the impeller, the time dependent pressure distribution on the impeller blades was transformed into the frequency domain by Fourier decomposition. The complex modal pressure data were imposed on the structure that was modeled by Finite Element Methods (FEM). Following state-of-the-art calculations to analyze the free vibration behavior of the impeller, forced response calculations were carried out. Comparisons with the experimental results demonstrate that this employed methodology is capable of predicting the impeller’s vibration behavior under real engine conditions. Integrating the procedure into the design of centrifugal compressors will enhance the quality of the design process.

Forced Response Excitation due to the Stator Vanes of Two and Three Compressor Stages Away

2021 ◽  
Author(s):  
Toshimasa Miura ◽  
Naoto Sakai ◽  
Naoki Kanazawa ◽  
Kentaro Nakayama
Keyword(s):  
Gas Turbines ◽  
Rotor Blade ◽  
High Efficiency ◽  
Computational Cost ◽  
Forced Response ◽  
Test Facility ◽  
Vibration Level ◽  
Blade Vibration ◽  
High Rotational Speed ◽  
Axial Compressors

Abstract State-of-the-art axial compressors of gas turbines employed in power generation plants and aero engines should have both high efficiency and small footprint. Thus, in many cases, axial compressors are designed to have thin rotor blades and stator vanes with short axial distances, and are driven at high rotational speed. Recently, problems of high cycle fatigue (HCF) associated with forced response excitation have gradually increased as a result of these trends. Rotor blade fatigue can be caused not only by the wake and potential effect of the adjacent stator vane, but also by the stator vanes of two, three or four compressor stages away. Thus, accurate prediction and suppression method of them under the resonance condition are necessary in the design process. Concerning the forced response excitation associated with the adjacent stator vanes, there are many previous studies on simulating the vibration by fluid structure interaction (FSI) simulation. In these studies, the aerodynamic force acting on the blade is simulated by an efficient unsteady computational fluid dynamics (CFD) method such as the nonlinear harmonic (NLH) method. These methods can be available in commercial CFD solvers and can significantly reduce computational cost. However, there are few examples of the problems associated with the stator vanes from two and three compressor stages away and no efficient simulation method is available. In this study, the problem of rotor blade vibration caused by the stator vanes of two and three compressor stages away is studied. Ways to accurately predict and effectively control the vibration are also investigated. In the first part of the study, one-way FSI simulation is carried out using a full annulus CFD model. To validate the accuracy of the simulation, experiments are also conducted using a gas turbine test facility. The vibration level of the blade is measured using a blade tip timing (BTT) measurement system and the obtained results are compared with the simulated data. It is found that one-way FSI simulation can accurately predict the order of the vibration level. In the second part of the study, a method of controlling the forced response excitation is investigated by optimizing the clocking of the stator vanes. It is confirmed that by controlling the clocking of the stator vanes, the vibration amplitude can be effectively suppressed without reducing the compressor performance. Through this study, ways to evaluate and control the unsteady pressure force and vibration response of the rotor blade are validated. By optimizing the clocking of stator vanes, the blade vibration level can be effectively reduced.

Experimental Study on Impeller Blade Vibration During Resonance: Part 1—Blade Vibration Due to Inlet Flow Distortion

2008 ◽  
Author(s):  
Albert Kammerer ◽  
Reza S. Abhari
Keyword(s):  
Experimental Study ◽  
Speckle Pattern ◽  
Pressure Fluctuations ◽  
Forced Response ◽  
Dynamic Strain ◽  
Flow Distortion ◽  
Blade Vibration ◽  
Impeller Blade ◽  
Inlet Flow ◽  
Forcing Function

Forming the first part of a two-part paper, the experimental approach to acquire resonant vibration data is presented here. Part 2 deals with the estimation of damping. During the design process of turbomachinery components, mechanical integrity has to be guaranteed with respect to high cycle fatigue of blades subject to forced response or flutter. This requires the determination of stress levels within the blade which in turn depend on the forcing function and damping. The vast majority of experimental research in this field has been performed on axial configurations for both compressors and turbines. This experimental study aims to gain insight into forced response vibration at resonance for a radial compressor. For this purpose a research impeller was instrumented with dynamic strain gauges and operated under resonant conditions. Modal properties were analysed using FEM and verified using an optical method termed Electronic-Speckle-Pattern-Correlation-Interferometry (ESPI). During the experiment, unsteady forces acting on the blades were generated by grid installations upstream of the impeller which created a distorted inlet flow pattern. The associated flow properties were measured using an aerodynamic probe. The resultant pressure fluctuations on the blade surface and the corresponding frequency content were assessed using unsteady CFD. The response of the blades was measured for three resonant crossings which could be distinguished by the excitation order and the natural frequency of the blades. Measurements were undertaken for a number of inlet pressure settings starting at near vacuum and then increasing. The overall results showed that the installed distortion screens generated harmonics in addition to the fundamental frequency. The resonant response of the first and second blade mode showed that the underlying dynamics support a single-degree-of-freedom model.

Experimental Study on Impeller Blade Vibration During Resonance—Part I: Blade Vibration Due to Inlet Flow Distortion

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Albert Kammerer ◽  
Reza S. Abhari
Keyword(s):  
Experimental Study ◽  
Speckle Pattern ◽  
Pressure Fluctuations ◽  
Forced Response ◽  
Dynamic Strain ◽  
Flow Distortion ◽  
Blade Vibration ◽  
Impeller Blade ◽  
Inlet Flow ◽  
Forcing Function

Forming the first part of a two-part paper, the experimental approach to acquire resonant vibration data is presented here. Part II deals with the estimation of damping. During the design process of turbomachinery components, mechanical integrity has to be guaranteed with respect to high cycle fatigue of blades subject to forced response or flutter. This requires the determination of stress levels within the blade, which in turn depend on the forcing function and damping. The vast majority of experimental research in this field has been performed on axial configurations for both compressors and turbines. This experimental study aims to gain insight into forced response vibration at resonance for a radial compressor. For this purpose, a research impeller was instrumented with dynamic strain gauges and operated under resonant conditions. Modal properties were analyzed using finite element method and verified using an optical method termed electronic-speckle-pattern-correlation-interferometry. During the experiment, unsteady forces acting on the blades were generated by grid installations upstream of the impeller, which created a distorted inlet flow pattern. The associated flow properties were measured using an aerodynamic probe. The resultant pressure fluctuations on the blade surface and the corresponding frequency content were assessed using unsteady computational fluid dynamics. The response of the blades was measured for three resonant crossings, which could be distinguished by the excitation order and the natural frequency of the blades. Measurements were undertaken for a number of inlet pressure settings starting at near vacuum and then increasing. The overall results showed that the installed distortion screens generated harmonics in addition to the fundamental frequency. The resonant response of the first and the second blade mode showed that the underlying dynamics support a single-degree-of-freedom model.

The MIT Blowdown Turbine Facility

1984 ◽  
Author(s):  
A. H. Epstein ◽  
G. R. Guenette ◽  
R. J. G. Norton
Keyword(s):  
Heat Transfer ◽  
Fluid Mechanics ◽  
Short Duration ◽  
Three Dimensional ◽  
Inlet Pressure ◽  
Test Facility ◽  
Turbine Inlet ◽  
High Work

A short duration (0.4 sec) test facility, capable of testing 0.5-meter diameter, film-cooled, high work aircraft turbine stages at rigorously simulated engine conditions has been designed, constructed, and tested. The simulation capability of the facility extends up to 40 atm inlet pressure at 2500°K (4000°F) turbine inlet temperatures. The facility is intended primarily for the exploration of unsteady, three-dimensional fluid mechanics and heat transfer in modern turbine stages.

Experimental determination of IGV preswirl effect on impeller blade vibration in an unshrouded centrifugal compressor

2021 ◽  
pp. 095765092110247
Author(s):  
Xinwei Zhao ◽  
Hongkun Li ◽  
Shuhua Yang ◽  
Zhenfang Fan ◽  
Yang Wang
Keyword(s):  
Dynamic Stress ◽  
Operating Conditions ◽  
Large Shift ◽  
Blade Vibration ◽  
Impeller Blade ◽  
Inlet Flow ◽  
Vibration Data ◽  
Aerodynamic Loading ◽  
High Dynamic

The unshrouded impeller is widely used in industrial centrifugal compressors and normally operates at high tip speed and large volume flow. However, this type of impeller can be very sensitive to flow excitations such as IGV wake, and hence encounters the challenge of high dynamic stress. Due to the lack of experimental vibration data, this paper aims to enhance the understanding of the IGV preswirl effect. The real operating representative data from strain gauges is acquired during the experiment. The blade transient and quasi-steady response due to upstream IGV wake under different configurations are investigated and quantified. Results show that the blade response increases with larger positive regulation. And under specific operating conditions, the vibration of the blade is quite large, which is comparable with synchronize resonance. This increment is attributed to the aerodynamic loading change due to enhanced distortion of the inlet flow. Based on the current findings, accurate numerical prediction of the blade forced vibration for a large shift of inlet flow condition is also needed for more reliable operating of the impeller.

Measured Torsional Vibration Characteristics of a 100 Megawatt Wind Tunnel Drive Line

1999 ◽  
Author(s):  
James M. Corliss ◽  
H. Sprysl
Keyword(s):  
Steady State ◽  
Damping Ratio ◽  
Forced Response ◽  
Operating Conditions ◽  
Pulse Load ◽  
Torsional Vibrations ◽  
Variable Frequency Drive ◽  
Steady State Operation ◽  
Torque Measurements ◽  
Torsional Analysis

Abstract A new 100 MW (135,000 Hp) adjustable speed drive system has recently been installed in the NASA Langley National Transonic Facility. The 100 MW system is the largest of its kind in the world and consists of a salient pole synchronous motor powered by a 12-pulse Load Commutated Inverter variable frequency drive. During system commissioning the drive line torsional vibrations were measured with strain gages and a telemetry-based data acquisition system. The torque measurements included drive start-up and steady-state operation at speeds where the drive motor’s pulsating torques match the drive line’s torsional natural frequency. Rapid drive acceleration rates with short dwell times were effective in reducing torsional vibrations during drive starts. Measured peak torsional vibrations during steady-state operation were comparable to predicted values and large enough to produce noticeable lateral vibrations in the drive line shafting. Cyclic shaft stresses for all operating conditions were well within the fatigue limits of the drive line components. A comparison of the torque measurements to an analytical forced response model concluded that a 0.5% critical damping ratio was appropriately applied in the drive line’s torsional analysis.

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