The Influence of Internal Damping on the Rotordynamic Stability of a Flywheel Rotor With Flexible Hub

2005 ◽  
Author(s):  
Alfonso Moreira ◽  
George Flowers ◽  
Alex Matras ◽  
Mark Balas ◽  
Jerry Fausz
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Experimental Testing ◽  
Research Effort ◽  
Simulation Studies ◽  
Internal Damping ◽  
System Parameters ◽  
Carbon Fiber Epoxy ◽  
Testing And Evaluation ◽  
Flywheel Rotor

An investigation about the influence of internal damping on the rotordynamic stability of high-speed flywheel energy storage systems made from carbon fiber epoxy is presented. The research effort consists of simulation studies coupled with experimental testing and evaluation. Damping values obtained from composite beam samples and a composite rotor hub design are shown. The effect of vibration frequency on damping is examined and discussed. These parameters are then used in a series of simulation studies that examine the effects of internal damping on rotordynamic behavior. An experimental model has been developed to verify the conclusions made from the simulations. The experimental testing consisted of creating a prototype rig, characterizing the system parameters, applying these parameters to determine the expected critical speed and experimentally determine the actual critical speed. These results are presented and their implications for flexible hub flywheel designs discussed.

The Dynamic Analysis of High-Speed Energy Storage Flywheel Rotor System

2013 ◽  
Vol 770 ◽  
pp. 78-83
Author(s):  
Xiu Hua Zhang ◽  
Guang Xi Li ◽  
Long Nie
Keyword(s):  
Steady State ◽  
Energy Storage ◽  
High Speed ◽  
Transient Analysis ◽  
Critical Speed ◽  
Large Scale ◽  
Simulation Analysis ◽  
Rotor System ◽  
Analysis Method ◽  
Flywheel Rotor

This article aims at large-scale energy storage flywheel rotor system, obtaining the dynamic characteristics. Through theoretical analysis, and after doing a simulation analysis for a given flywheel rotor on the 0-20000 RPM, getting the flywheel rotor critical speed, the transient analysis and imbalance response. The system is in steady state at runtime according to the analysis results. Providing also certain theory basis for study of flywheel rotor system according to the analysis method .

Dynamic Instability of a High-Speed Rotor Containing a Partitioned Cavity Filled With Two Kinds of Liquids

1989 ◽  
Vol 111 (4) ◽  
pp. 450-456 ◽  
Author(s):  
Y. Jinnouchi ◽  
Y. Araki ◽  
J. Inoue ◽  
S. Kubo
Keyword(s):  
Natural Frequency ◽  
Cylindrical Cavity ◽  
High Speed ◽  
Critical Speed ◽  
Dynamic Instability ◽  
Rotor System ◽  
Rotor Speed ◽  
Unstable Region ◽  
System Parameters ◽  
Unstable Behavior

This paper is concerned with the dynamic instability of a high-speed rotor containing a partitioned cavity filled with two kinds of liquids of different density. The system considered simulates a centrifuge of two liquids type, in which the cylindrical cavity is divided into fan-shaped compartments in order to suppress asynchronous whirling motions induced by waves in the liquids traveling around the cavity. Assuming rotor vibrations to be small, liquids inviscid, and external damping negligible, perturbed motions of the liquid-rotor system are analyzed. The theory shows that the rotor containing a partitioned cavity can still exhibit unstable behavior, similar to that observed for a rotor system equipped with centrifugal pendula, in the region where the rotor speed is nearly equal to the sum of the critical speed of the system and the natural frequency of the liquids. The theory has been verified by the experiments. The dependence of the unstable region on the main system parameters is also discussed.

Formation of Standing Waves in Radial Tires

1984 ◽  
Vol 12 (1) ◽  
pp. 44-63 ◽  
Author(s):  
Y. D. Kwon ◽  
D. C. Prevorsek
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Unit Length ◽  
Standing Waves ◽  
Rolling Resistance ◽  
Damping Coefficient ◽  
Circular Membrane ◽  
Critical Speeds ◽  
Steel Cord ◽  
The Individual

Abstract Radial tires for automobiles were subjected to high speed rolling under load on a testing wheel to determine the critical speeds at which standing waves started to form. Tires of different makes had significantly different critical speeds. The damping coefficient and mass per unit length of the tire wall were measured and a correlation between these properties and the observed critical speed of standing wave formation was sought through use of a circular membrane model. As expected from the model, desirably high critical speed calls for a high damping coefficient and a low mass per unit length of the tire wall. The damping coefficient is particularly important. Surprisingly, those tire walls that were reinforced with steel cord had higher damping coefficients than did those reinforced with polymeric cord. Although the individual steel filaments are elastic, the interfilament friction is higher in the steel cords than in the polymeric cords. A steel-reinforced tire wall also has a higher density per unit length. The damping coefficient is directly related to the mechanical loss in cyclic deformation and, hence, to the rolling resistance of a tire. The study shows that, in principle, it is more difficult to design a tire that is both fuel-efficient and free from standing waves when steel cord is used than when polymeric cords are used.

Factors Affecting Driver Injury Severity in the Wrong-Way Crash: Accounting for Potential Heterogeneity in Means and Variances of Random Parameters

2021 ◽  
pp. 036119812110098
Author(s):  
Miao Yu ◽  
Jinxing Shen ◽  
Changxi Ma
Keyword(s):  
High Speed ◽  
Injury Severity ◽  
Unobserved Heterogeneity ◽  
Research Effort ◽  
Random Parameter ◽  
Policy Implications ◽  
Contributing Factors ◽  
Severe Injuries ◽  
Data Set ◽  
Severity Levels

Because of the high percentage of fatalities and severe injuries in wrong-way driving (WWD) crashes, numerous studies have focused on identifying contributing factors to the occurrence of WWD crashes. However, a limited number of research effort has investigated the factors associated with driver injury-severity in WWD crashes. This study intends to bridge the gap using a random parameter logit model with heterogeneity in means and variances approach that can account for the unobserved heterogeneity in the data set. Police-reported crash data collected from 2014 to 2017 in North Carolina are used. Four injury-severity levels are defined: fatal injury, severe injury, possible injury, and no injury. Explanatory variables, including driver characteristics, roadway characteristics, environmental characteristics, and crash characteristics, are used. Estimation results demonstrate that factors, including the involvement of alcohol, rural area, principal arterial, high speed limit (>60 mph), dark-lighted conditions, run-off-road collision, and head-on collision, significantly increase the severity levels in WWD crashes. Several policy implications are designed and recommended based on findings.

Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions

2006 ◽  
Vol 129 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Luis San Andrés ◽  
Dario Rubio ◽  
Tae Ho Kim
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Load Capacity ◽  
Test System ◽  
Foil Bearings ◽  
Rotor Imbalance ◽  
Synchronous Motion ◽  
Damping Characteristics ◽  
Rotor Surface ◽  
Stiffness And Damping

Gas foil bearings (GFBs) satisfy the requirements for oil-free turbomachinery, i.e., simple construction and ensuring low drag friction and reliable high speed operation. However, GFBs have a limited load capacity and minimal damping, as well as frequency and amplitude dependent stiffness and damping characteristics. This paper provides experimental results of the rotordynamic performance of a small rotor supported on two bump-type GFBs of length and diameter equal to 38.10mm. Coast down rotor responses from 25krpm to rest are recorded for various imbalance conditions and increasing air feed pressures. The peak amplitudes of rotor synchronous motion at the system critical speed are not proportional to the imbalance introduced. Furthermore, for the largest imbalance, the test system shows subsynchronous motions from 20.5krpm to 15krpm with a whirl frequency at ∼50% of shaft speed. Rotor imbalance exacerbates the severity of subsynchronous motions, thus denoting a forced nonlinearity in the GFBs. The rotor dynamic analysis with calculated GFB force coefficients predicts a critical speed at 8.5krpm, as in the experiments; and importantly enough, unstable operation in the same speed range as the test results for the largest imbalance. Predicted imbalance responses do not agree with the rotor measurements while crossing the critical speed, except for the lowest imbalance case. Gas pressurization through the bearings’ side ameliorates rotor subsynchronous motions and reduces the peak amplitudes at the critical speed. Posttest inspection reveal wear spots on the top foils and rotor surface.

A Research for Angle Optimization of the SRM Used in Electric Actuator of Valves

2013 ◽  
Vol 404 ◽  
pp. 586-591
Author(s):  
Ding Hong Yang Yang ◽  
Dean Zhao ◽  
Ying Xin Jiang
Keyword(s):  
High Speed ◽  
Position Control ◽  
Experimental Testing ◽  
Optimal Switching ◽  
Switched Reluctance ◽  
Electric Actuator ◽  
Turn On ◽  
Reluctance Motor ◽  
Two Parameters ◽  
Theory Research

This paper uses TMS320F28335 DSP and MAX3032S CPLD as the controller of the 6/4 pole switched reluctance motor (SRM), and controls the motor by the method of current chopping control (CCC) in low speed and the method of angle position control (APC) in high speed. About the optimization of turn-on angle and turn-off angle when SRM is controlled by the method of APC, this paper discusses the optimal design of the two parameters by ways of theory research, simulation and experimental testing. The results show optimal switching angle can make speeded-up of the motor better and improve the performance of SRM.

Estimating Critical Speeds of Stepped Shafts with Flexible Bearings

1971 ◽  
Vol 8 (03) ◽  
pp. 327-333
Author(s):  
R. H. Salzman
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Design Stage ◽  
Normal Range ◽  
Critical Speeds ◽  
Stepped Shaft ◽  
Bearing Stiffness ◽  
Variable Support ◽  
Method Show ◽  
Good Agreement

This paper presents a semi-graphical approach for finding the first critical speed of a stepped shaft with finite bearing stiffness. The method is particularly applicable to high-speed turbine rotors with journal bearings. Using Rayleigh's Method and the exact solution for whirling of a uniform shaft with variable support stiffness, estimates of the lowest critical speed are easily obtained which are useful in the design stage. First critical speeds determined by this method show good agreement with values computed by the Prohl Method for the normal range of bearing stiffness. A criterion is also established for determining if the criticals are "bearing critical speeds" or "bending critical speeds," which is of importance in design. Discusser E. G. Baker

Study on Gyroscopic Effect of Magnetic Flywheel Rotor

2011 ◽  
Vol 130-134 ◽  
pp. 970-975
Author(s):  
Xiang Long Wen ◽  
Cao Cao
Keyword(s):  
Feedback Control ◽  
High Speed ◽  
System Stability ◽  
Rotor Speed ◽  
Gyroscopic Effect ◽  
Pd Control ◽  
The Stability ◽  
Gyroscopic Effects ◽  
Zero Points ◽  
Flywheel Rotor

In the high-speed, gyroscopic effects of the flywheel rotor greatly influence the rotor stability. The pole-zero points move to right of s-plane and the damping terms of the pole points become smaller. The stability of the system will get worse with the increasing of rotor speed when the traditional decentralized PD controller is used only. In the paper, a cross-feedback control with decentralized PD control is used for compensating gyroscopic effect. The simulation results show that the system stability is better using the cross-feedback control with decentralized PD control than using the traditional decentralized PD control.

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