scholarly journals Forced Response of a Centrifugal Compressor Stage Due to the Impeller–Diffuser Interaction

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Edward J. Walton ◽  
Choon S. Tan
Keyword(s):  
Practical Implication ◽  
Forced Response ◽  
Physical Interaction ◽  
Impeller Blade ◽  
Forcing Function ◽  
Modal Coupling ◽  
Spring System ◽  
Unsteady Loading ◽  
Mass Spring ◽  
The Impact

The impact mode coupling between impeller blades and the disk backwall has on the forced response amplitude of impeller blades is assessed. The assessments focus on the forced response of two splitter blade modes to a variety of representative boundary conditions and unsteady loadings. The forcing function is the synchronous unsteady loading generated by the impeller–diffuser interaction at resonance. The results indicate that modal coupling of blade- and disk-dominant modes renders the forced response highly sensitive to small variations in airfoil and disk backwall thickness. As a complement, a reduced-order model based on the forced response of a two mass–spring system is used to elucidate the physical interaction of modal coupling. The practical implication of this finding is that a forced response issue with an impeller blade cannot be addressed adequately by stiffening the structure, such as thickening the blade or disk. Thus, appropriate measures need to be taken to avoid potential blade–disk mode couplings within the manufacturing tolerances of the part.

scholarly journals Forced Response of a Centrifugal Compressor Stage due to the Impeller-Diffuser Interaction

2015 ◽  
Author(s):  
Edward J. Walton ◽  
Choon S. Tan
Keyword(s):  
Practical Implication ◽  
Forced Response ◽  
Physical Interaction ◽  
Impeller Blade ◽  
Forcing Function ◽  
Modal Coupling ◽  
Spring System ◽  
Unsteady Loading ◽  
Mass Spring ◽  
The Impact

The impact mode coupling between impeller blades and the disk backwall has on the forced response amplitude of impeller blades is assessed. The assessments focus on the forced response of two splitter blade modes to a variety of representative boundary conditions and unsteady loadings. The forcing function is the synchronous unsteady loading generated by the impeller-diffuser interaction at resonance. The results indicate that modal coupling of blade and disk dominant modes renders the forced response highly sensitive to small variations in airfoil and disk backwall thickness. As a complement, a reduced-order model based on the forced response of a two mass-spring system is used to elucidate the physical interaction of modal coupling. The practical implication of this finding is that a forced response issue with an impeller blade cannot be addressed adequately by stiffening the structure, such as thickening the blade or disk. Thus appropriate measures need to be taken to avoid potential blade-disk mode couplings within the manufacturing tolerances of the part.

Forced Response Sensitivity of a Mistuned Rotor From an Embedded Compressor Stage

2015 ◽  
Author(s):  
Fanny M. Besem ◽  
Robert E. Kielb ◽  
Nicole L. Key
Keyword(s):  
Experimental Data ◽  
Forced Response ◽  
Symmetric System ◽  
Response Analysis ◽  
Cfd Simulations ◽  
Forcing Function ◽  
Wear And Tear ◽  
The Individual ◽  
The Impact ◽  
Interblade Phase Angle

The frequency mistuning that occurs due to manufacturing variations and wear and tear of the blades can have a significant effect on the flutter and forced response behavior of a blade row. Similarly, asymmetries in the aerodynamic or excitation forces can tremendously affect the blade responses. When conducting CFD simulations, all blades are assumed to be tuned (i.e. to have the same natural frequency) and the aerodynamic forces are assumed to be the same on each blade except for a shift in interblade phase angle. The blades are thus predicted to vibrate at the same amplitude. However, when the system is mistuned or when asymmetries are present, some blades can vibrate with a much higher amplitude than the tuned, symmetric system. In this research, we first conduct a deterministic forced response analysis of a mistuned rotor and compare the results to experimental data from a compressor rig. It is shown that tuned CFD results cannot be compared directly with experimental data because of the impact of frequency mistuning on forced response predictions. Moreover, the individual impact of frequency, aerodynamic, and forcing function perturbations on the predictions is assessed, leading to the conclusion that a mistuned system has to be studied probabilistically. Finally, all perturbations are combined and Monte-Carlo simulations are conducted to obtain the range of blade response amplitudes that a designer could expect.

scholarly journals Neural Network Control of a Robot Interacting With an Uncertain Hunt-Crossley Viscoelastic Environment

2008 ◽  
Author(s):  
S. Bhasin ◽  
K. Dupree ◽  
P. M. Patre ◽  
W. E. Dixon
Keyword(s):  
Neural Network ◽  
Network Control ◽  
Contact Dynamics ◽  
Neural Network Control ◽  
Contact Conditions ◽  
Real Behavior ◽  
Spring System ◽  
Mass Spring ◽  
The Impact ◽  
Viscoelastic Contact

The objective in this paper is to control a robot as it transitions from a non-contact to a contact state with an unactuated viscoelastic mass-spring system such that the mass-spring is regulated to a desired final position. A nonlinear Hunt-Crossley model, which is physically consistent with the real behavior of the system at contact, is used to represent the viscoelastic contact dynamics. A Neural Network feedforward term is used in the controller to estimate the environment uncertainties, which are not linear-in-parameters. The NN Lyapunov based controller is shown to guarantee uniformly ultimately bounded regulation of the system despite parametric and nonparametric uncertainties in the robot and the viscoelastic environment respectively. The proposed controller only depends on the position and velocity terms, and hence, obviates the need for measuring the impact force and acceleration. Further, the controller is continuous, and can be used for both non-contact and contact conditions.

scholarly journals DETERMINATION OF THE WAVE ATTACK ANTICIPATED UPON A STRUCTURE FROM LABORATORY AND FIELD OBSERVATIONS

2011 ◽  
Vol 1 (7) ◽  
pp. 37
Author(s):  
W.A. Venis
Keyword(s):  
Comparative Study ◽  
Model Tests ◽  
Water Levels ◽  
Field Observations ◽  
Wave Impact ◽  
Spring System ◽  
Mass Spring ◽  
The Comparative Study ◽  
The Impact

Model tests have been carried out to obtain an insight into the magnitude of the wave-pressures in various situations. These tests showed, that sharp high pressure peaks occur in addition to the pressures caused by the reflecting of the waves, which pressures are quasi-static. As the structure can be compared with a multiple mass-spring system these pressure-peaks may cause the whole construction to vibrate. Wave-attack therefore can be expressed in terms of impact. Moreover, calculations revealed that the impact pressures were critical factors in determining the strength of the structure. So many model tests were carried out to determine the design and location of the sluices. These tests involved numerous water-levels discharges and waves. Regarding the pressure-peaks a comparative study was made in the model, which led to the structure being designed in such a way that the occurrence of critical impacts was reduced to an acceptable minimum. As it was impossible to avoid the occurrence of impact pressures entirely it remained necessary to determine a basic load for the structure that takes care of the impact pressures. As it has not yet appeared possible physically to determine a theoretical maximum for the impact pressures, it has to be borne in mind that there is a probability that each pressure measured will be exceeded. So this paper describes, how the cumulative frequency curve of the impacts for the case mentioned in 1.1 sub a, which served as a basis for determining the basic load was arrived at by a certain combination of laboratory and field observations. The data used for this purpose were a. Results of wave-impact measurements on a model of the sluices. This model, built in accordance with the results of the comparative study, was situated in the wind-flume of the "de Voorst" hydraulic laboratory. b. Wave height measurements in the Haringvliet during 1957 and 1958. c. Wind-speed measurements on board the lightship Qoeree, likewise during 1957 and 1958. d. Tidal registrations at Hellevoetsluis from 1920 to 1960. e. Wind-force data from the Hook of Holland, likewise from 1920 to 1960.

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.

Min-Max Solutions for the Linear Mass-Spring System

1957 ◽  
Vol 24 (1) ◽  
pp. 131-136
Author(s):  
Eugene Sevin
Keyword(s):  
Upper And Lower Bounds ◽  
Constant Force ◽  
Linear Mass ◽  
Maximum Displacement ◽  
Natural Period ◽  
Load Duration ◽  
Forcing Function ◽  
Total Impulse ◽  
Spring System ◽  
Mass Spring

Abstract Absolute upper and lower bounds have been determined for the maximum displacement of an undamped linear mass-spring system acted on by a non-negative forcing function characterized only by total impulse and duration. The upper bound is shown to result from applying the total impulse to the mass as an initial blow. The lower bound is shown to depend upon the ratio of load duration to natural period of the system, and this response results from a forcing function consisting of an initial and final impulse and an intermediate constant force. In the latter case, for sufficiently short durations, the forcing function reduces simply to equal initial and final impulses.

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 impact of applying the Common Customs Tariff on the armenian export of Cut and Polished Gems to Russia

2019 ◽  
pp. 33-41
Author(s):  
V. L. Harutyunyan ◽  
S. V. Dokholyan ◽  
A. R. Makaryan
Keyword(s):  
Manufacturing Sector ◽  
Practical Implication ◽  
Dominant Role ◽  
New Technology ◽  
Manufacturing Companies ◽  
Medium Term ◽  
Diamond Cutting ◽  
Global Trends ◽  
The Common ◽  
The Impact

The presented study discusses the issues of applying the Common Customs Tariff (CCT) rates of the Eurasian Economic Union (EAEU) on rough diamonds and the impact thereof on the exports of stones cut and polished inArmeniaand then exported toRussia.Aim. The study aims to identify the possible strategies Armenian diamond cutting and polishing companies could adopt as a response to the application of the CCT rates on rough diamonds and how it would affect exports to various destinations, namely to Russia.Tasks. The authors analyze the current state of the gems and jewelry sector and substantiate the need to either integrate it into the jewelry manufacturing sector or to apply various strategies to facilitate exports to either Russia or other destinations in the medium term in response to the application of the CCT rates.Methods. This study uses general scientific methods of cognition, including analytical and methodological approaches and elements of forecasting. Possible strategies the Armenian diamond cutting and polishing companies could adopt in the medium term in response to the application of the EAEU CCT rates are determined using the analytical research method, forecasts in the context of the developments in the Armenian gem processing and jewelry market and global trends, statistical data on the imports and exports of cut and polished gems and jewelry for 2014–2018 published by the UN Comtrade Statistics.Results. Statistics on the exports of processed diamonds from 2014 to 2018 highlights the issue associated with the loss of competitiveness suffered by Armenian companies (mainly in comparison with Indian diamond cutters). The major global trends in the diamond cutting and polishing business indicate that it could be virtually impossible for Armenian cutters and polishers to compete with Indian companies in the medium term if they do not comes to investing in new technology to achieve operational efficiency. For these companies, it is important not to lose the Russian market due to an increase in the tariff rate and concentrate on the processing of gems that are larger than 1 carat. Another strategy to avoid an increase in the customs tariff rates would depend on the Armenian government’s ability to negotiate with Russia in respect of direct imports of diamond stones from Russian manufactures. Two other options for Armenian cutters involve focusing on cutting and polishing of rubies, sapphires, emeralds, etc. or integrating into the jewelry sector either by being the primary supplier or by considering this business as a channel to sell processed diamond stones by setting up their own jewelry manufacturing companies.Conclusions. With CCT going into effect in January 2021 and India’s dominant role in the diamond cutting and polishing business, Armenia needs to carefully consider all of the strategies the Armenian companies could adopt, as discussed above. As a member state of the EAEU, Armenia freely exports to Russia, however, further exports to Russia would depend on Armenia’s ability to ensure that cost-effective operations are in place, or to concentrate on the processing of precious gems rather than diamonds, or to switch to the manufacturing of jewelry items as a major export item.Practical Implication. The findings of this study could be of interest to the Ministry of Economy of the Republic of Armenia and Business Armenia that could be used in elaborating the strategy for the development of Armenian gems and jewelry sector of the economy.

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