Model Validation for an Active Magnetic Bearing Based Compressor Surge Control Test Rig

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Se Young Yoon ◽  
Zongli Lin ◽  
Kin Tien Lim ◽  
Christopher Goyne ◽  
Paul E. Allaire
Keyword(s):  
Mathematical Model ◽  
Magnetic Bearing ◽  
Tip Clearance ◽  
Active Magnetic Bearing ◽  
Dynamic Responses ◽  
Compression System ◽  
Compressor Surge ◽  
Theoretical Predictions ◽  
Surge Control ◽  
The Mathematical Model

In this paper, we present experimental test data for the validation of a recently introduced mathematical model for centrifugal compression systems with variable impeller axial clearances. Employing the active magnetic bearings (AMBs) of a compressor built for the experimental study of surge, the axial clearance between the impeller and the static shroud is servo controlled, and the measured variations in the compressor output flow are compared with the mathematical model. The steady state and the dynamic responses of the compression system induced by varying the impeller tip clearance are measured and compared with the theoretical predictions, and the states of the compression system in surge condition are collected and analyzed. Parameters in the compression system model, such as the Greitzer parameter B and Helmholtz frequency ωH are experimentally identified. Also, the servo dynamics of the magnetic bearing that controls the axial impeller position is determined experimentally. To further validate the mathematical model and the feasibility of using the impeller tip clearance for controlling surge, we present a design example for an active surge controller based on the derived model, and simulate the response of the compression system. This design exercise also helps us understand the possible challenges that one could face in the design and implementation of a successful surge controller.

scholarly journals Design and Characterization of a Centrifugal Compressor Surge Test Rig

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Kin Tien Lim ◽  
Se Young Yoon ◽  
Christopher P. Goyne ◽  
Zongli Lin ◽  
Paul E. Allaire
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Fluctuations ◽  
Magnetic Bearing ◽  
Tip Clearance ◽  
Active Magnetic Bearing ◽  
Test Rig ◽  
Compressor Surge ◽  
Surge Control ◽  
Compressor Performance

A detailed description of a new centrifugal compressor surge test rig is presented. The objective of the design and development of the rig is to study the surge phenomenon in centrifugal compression systems and to investigate a novel method of surge control by active magnetic bearing servo actuation of the impeller axial tip clearance. In this paper, we focus on the design, initial setup, and testing of the rig. The latter two include the commissioning of the rig and the experimental characterization of the compressor performance. The behavior of the compressor during surge is analyzed by driving the experimental setup into surge. Two fundamental frequencies, 21 Hz and 7 Hz, connected to the surge oscillation in the test rig are identified, and the observed instability is categorized according to the intensity of pressure fluctuations. Based on the test results, the excited pressure waves are clearly the result of surge and not stall. Also, they exhibit the characteristics of mild and classic surge instead of deep surge. Finally, the change in the compressor performance due to variation in the impeller tip clearance is experimentally examined, and the results support the potential of the tip clearance modulation for the control of compressor surge. This is the first such demonstration of the feasibility of surge control of a compressor using active magnetic bearings.

scholarly journals Mathematical model of a flexible asymmetrical rotor for active magnetic bearing reaction wheel

2018 ◽  
Vol 158 ◽  
pp. 01025
Author(s):  
Miroslav Polyakov ◽  
Anatoliy Lipovtsev ◽  
Vladimir Lyanzburg
Keyword(s):  
Mathematical Model ◽  
Lagrange Equation ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Active Magnetic Bearings ◽  
Ansys Software ◽  
Mass System ◽  
Linear Elastic ◽  
Orbit Control ◽  
The Mathematical Model

The paper introduces the mathematical model of rotor for active magnetic bearing reaction/momentum wheels, used as actuator in spacecraft attitude and orbit control system. Developed model is used for estimation of critical speeds and forced oscillation magnitudes with a glance of the rotor modes. Rotor is considered as a two-mass system, consisting of a shaft and a rim, active magnetic bearings are assumed to be a linear elastic springs. The equations of the rotor motion are derived using the Lagrange equation. Developed model is verified by comparing the calculated Campbell diagrams with the results of the finite-element modal analysis, performed in the ANSYS software.

Damping and Bandgap Characteristics of a Viscoelastic Tensegrity Damper

2021 ◽  
pp. 1-47
Author(s):  
Mohamed Raafat ◽  
Amr Baz
Keyword(s):  
Mathematical Model ◽  
Material Characterization ◽  
Structural Vibrations ◽  
New Class ◽  
Structural Applications ◽  
Theoretical Predictions ◽  
Specific Frequency ◽  
The Mathematical Model ◽  
Theory And Experiments

Abstract A theoretical and experimental investigation of a new class of a tensegrity-based structural damper is presented. The damper is not only capable of attenuating undesirable structural vibrations, as all conventional dampers, but also capable of completely blocking the transmission of vibration over specific frequency bands by virtue of its periodicity. Such dual functionality distinguishes the tensegrity damper over its counterparts of existing structural dampers. Particular emphasis is placed here in presenting the concept and developing the mathematical model of the dynamics of a unit cell the damper. The model is then coupled with a Floquet-Bloch analysis in order to identify the bandgap characteristics of the damper. The predictions of the mathematical model are validated experimentally using a prototype of the damper which is built using 3D printing. A comprehensive material characterization of the damper is performed followed by a detailed extraction of the static and dynamic behavior of the damper in order to validate the theoretical predictions. Close agreement is observed between theory and experiments. The developed theoretical and experimental techniques provide invaluable means for the design of this new class of dampers particularly for critical structural applications.

Thermal Modeling of a Reversing Valve in a Refrigeration System

2003 ◽  
Author(s):  
Shirish Raichintala ◽  
Manohar Kulkarni
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Heat Pump ◽  
Pressure Losses ◽  
Heat Leakage ◽  
Theoretical Predictions ◽  
Work Input ◽  
Compressor Work ◽  
Mass Leakage ◽  
The Mathematical Model

A mathematical model of a reversing valve was developed in order to evaluate the losses and for determining the effects of a reversing valve, on the performance of a heat pump. This mathematical model of the reversing valve was tested using the experimental data of Fang and Nutter (1999). The theoretical predictions made by this model agreed with that of the experimental data. Further, the mathematical model isolated the pressure losses due to friction; pipe-fittings, mass-leakage and heat transfer from the total losses. The evaluation of constituent losses assisted in detecting a faculty reversing valve, and also determining the effect of mass leakage and heat leakage on the compressor work input and COP of the heat pump.

Dynamic responses of the rotor supported by a new type zero-clearance catcher bearing

2017 ◽  
Vol 31 (19-21) ◽  
pp. 1740014
Author(s):  
Yi-Li Zhu ◽  
Zhong-Qiao Zheng
Keyword(s):  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Dynamic Responses ◽  
Failure Event ◽  
Long Time ◽  
New Type ◽  
Amb System ◽  
Rotor Dynamic

Catcher bearings (CB) are required to support the rotor rotating for some time when a failure event of active magnetic bearing (AMB) system occurs. For this purpose, a new type zero-clearance catcher bearing (NTZCB) is proposed. The influences of different parameters of NTZCB on the rotor dynamic responses are theoretically and experimentally analyzed. The results indicate that choosing relatively soft spring and heavy moveable supporting pedestal can effectively buffer the rotor vibrations, which makes it possible for the rotor to keep rotating with the support of the CB system for a long time.

Modelling, Analysis and Identification of the Parallel and Angular Misalignments in a Coupled Rotor-Bearing-AMB System

2020 ◽  
Author(s):  
Siva Srinivas R ◽  
Rajiv Tiwari ◽  
Ch. Kanna Babu
Keyword(s):  
Mathematical Model ◽  
Vibration Suppression ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Identification Algorithm ◽  
Rotor Systems ◽  
Force Moment ◽  
Coupling Force ◽  
Auxiliary Bearing ◽  
Amb System

Abstract The standard techniques used to detect the misalignment in rotor systems are loopy orbits, multiple harmonics with predominant 2X component, and high axial vibration. This paper develops a new approach for the identification of misalignment in coupled rotor systems modelled using 2-node Timoshenko beam finite elements. The coupling connecting the turbine and generator rotor systems is modelled by a stiffness matrix, which has both static and additive components. While the magnitude of static stiffness component is fixed during operation, the time varying additive stiffness component displays a multi-harmonic behaviour and exists only in the presence of misalignment. To numerically simulate the multi-harmonic nature coupling force/moment as observed in experiments, a pulse wave is used as the steering function in the mathematical model of the additive coupling stiffness (ACS). The representative TG system has two-rotor systems, each having two discs and supported on two flexible bearings - connected by coupling. An active magnetic bearing (AMB) is used as an auxiliary bearing on each rotor for the purposes of vibration suppression and fault identification. The formulation of mathematical model is followed by the development of an identification algorithm based on the model developed, which is an inverse problem. Least-squares linear regression technique is used to identify the unbalances, bearing dynamic parameters, AMB constants and importantly the coupling static and additive stiffness coefficients. The sensitivity of the identification algorithm to signal noise and bias errors in modelling parameters have been tested. The novelty of paper is the representation and identification of misalignment using the ACS matrix coefficients, which are direct indicators of both type and severity of the misalignment.

Simulation and Model Validation of a Multi-Concentration Points Concentrated Photovoltaic Thermal System

2018 ◽  
Vol 13 (10) ◽  
pp. 1552-1556
Author(s):  
M. Imtiaz Hussain ◽  
Gwi Hyun Lee ◽  
Jun-Tae Kim
Keyword(s):  
Mathematical Model ◽  
Model Validation ◽  
Transient Behavior ◽  
Dynamic Responses ◽  
Thermo Electric ◽  
One Dimensional ◽  
Photovoltaic Thermal System ◽  
The Mathematical Model ◽  
The Heat Balance ◽  
T System

In this study, the transient behavior of a concentrated photovoltaic thermal (CPV/T) system is assessed using one-dimensional mathematical model. The model is based on the heat balance of the concentrated photovoltaic (CPV) solar cells, receiver pipe, thermal fluid, insulation, and the storage tank attached to PV/T system via insulated pipes. The mathematical model was developed and solved using ordinary differential equation solvers in MATLAB® computer program. The interdependence thermo-electric dynamic responses of the CPV/T system were modeled and analyzed by considering two cases such as with and without glass enclosure around the receiver. The electrical and thermal efficiencies are evaluated as the function of enclosure effect, beam solar radiation, and circulating fluid flow rate. For the purpose of model validation, experimental measurements of the CPV/T system were performed. Satisfactory agreements were found between the experimental data and the predicted results. The developed dynamic model is most suitable to predict and evaluate the performance of a point-focused CPV/T system.

The Differential Passive Magnetic Bearing for High-Speed Flexible Rotor

2008 ◽  
Vol 144 ◽  
pp. 273-278 ◽  
Author(s):  
Zdzisław Gosiewski ◽  
Krzysztof Falkowski
Keyword(s):  
Mathematical Model ◽  
High Speed ◽  
Magnetic Bearing ◽  
Laboratory Model ◽  
Magnetic Flux Density ◽  
Flexible Rotor ◽  
Neodymium Magnet ◽  
The One ◽  
Neodymium Magnets ◽  
The Mathematical Model

Lab stand of a differential passive magnetic bearing is presented in the paper. The passive bearing will be used in high-speed flexible rotor. The one neodymium magnet MP 41x15x10 – N38 and two neodymium magnets MP 40x22x10 – N38 were used to design the passive magnetic bearing. The mathematical model of differential bearing, laboratory model and distribution of magnetic flux density are presented and analyzed.

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