Excitation frequency dependent mode manipulation in radio-frequency atmospheric argon glow discharges

2009 ◽  
Vol 16 (9) ◽  
pp. 090702 ◽  
Author(s):  
Jie Zhang ◽  
Ke Ding ◽  
Kaya Wei ◽  
Jing Zhang ◽  
Jianjun Shi
Keyword(s):  
Radio Frequency ◽  
Excitation Frequency ◽  
Frequency Dependent ◽  
Glow Discharges ◽  
Atmospheric Argon

A System Identification Method for Excitation-Frequency Dependent Rotordynamic Coefficients

2012 ◽  
Author(s):  
Timothy W. Dimond ◽  
Amir A. Younan ◽  
Paul Allaire
Keyword(s):  
System Identification ◽  
Measurement Uncertainty ◽  
Excitation Frequency ◽  
Frequency Dependent ◽  
Rotordynamic Coefficients ◽  
Adjoint Systems ◽  
Dynamic Coefficients ◽  
Backward Whirl ◽  
Identification Technique ◽  
Damped Systems

Experimental identification of rotordynamic systems presents unique challenges. Gyroscopics, generally damped systems, and non-self-adjoint systems due to fluid structure interaction forces mean that symmetry cannot be used to reduce the number of parameters to be identified. Rotordynamic system experimental measurements are often noisy, which complicates comparisons with theory. When linearized, the resulting dynamic coefficients are also often a function of excitation frequency, as distinct from operating speed. In this paper, a frequency domain system identification technique is presented that addresses these issues for rigid-rotor test rigs. The method employs power spectral density functions and forward and backward whirl orbits to obtain the excitation frequency dependent effective stiffness and damping. The method is highly suited for use with experiments that employ active magnetic exciters that can perturb the rotor in the forward and backward whirl directions. Simulation examples are provided for excitation-frequency reduced tilting pad bearing dynamic coefficients. In the simulations, 20 and 50 percent Gaussian output noise was considered. Based on ensemble averages of the coefficient estimates, the 95 percent confidence intervals due to noise effects were within 1.2% of the identified value. The method is suitable for identification of linear dynamic coefficients for rotordynamic system components referenced to shaft motion. The method can be used to reduce the effect of noise on measurement uncertainty. The statistical framework can also be used to make decisions about experimental run times and acceptable levels of measurement uncertainty. The data obtained from such an experimental design can be used to verify component models and give rotordynamicists greater confidence in the design of turbomachinery.

Continuum modeling of argon radio frequency glow discharges

1987 ◽  
Vol 50 (9) ◽  
pp. 492-494 ◽  
Author(s):  
Albert D. Richards ◽  
Brian E. Thompson ◽  
Herbert H. Sawin
Keyword(s):  
Radio Frequency ◽  
Continuum Modeling ◽  
Glow Discharges

Measurements in silane radio frequency glow discharges using a tuned and heated Langmuir probe

1993 ◽  
Vol 74 (8) ◽  
pp. 4899-4902 ◽  
Author(s):  
Quixun Lin ◽  
Xuangying Lin ◽  
Yunpeng Yu ◽  
Hong Wang ◽  
Jiayi Chen
Keyword(s):  
Radio Frequency ◽  
Langmuir Probe ◽  
Glow Discharges

scholarly journals Excitation energy-dependent photocurrent switching in a single-molecule photodiode

2019 ◽  
Vol 116 (33) ◽  
pp. 16198-16203 ◽  
Author(s):  
Bing Shan ◽  
Animesh Nayak ◽  
Olivia F. Williams ◽  
Dillon C. Yost ◽  
Nicholas F. Polizzi ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Single Molecule ◽  
Indium Tin Oxide ◽  
Flash Photolysis ◽  
Theoretical Calculations ◽  
Electron Flow ◽  
Red Light ◽  
Excitation Frequency ◽  
Frequency Dependent ◽  
Oxide Electrodes

The direction of electron flow in molecular optoelectronic devices is dictated by charge transfer between a molecular excited state and an underlying conductor or semiconductor. For those devices, controlling the direction and reversibility of electron flow is a major challenge. We describe here a single-molecule photodiode. It is based on an internally conjugated, bichromophoric dyad with chemically linked (porphyrinato)zinc(II) and bis(terpyridyl)ruthenium(II) groups. On nanocrystalline, degenerately doped indium tin oxide electrodes, the dyad exhibits distinct frequency-dependent, charge-transfer characters. Variations in the light source between red-light (∼1.9 eV) and blue-light (∼2.7 eV) excitation for the integrated photodiode result in switching of photocurrents between cathodic and anodic. The origin of the excitation frequency-dependent photocurrents lies in the electronic structure of the chromophore excited states, as shown by the results of theoretical calculations, laser flash photolysis, and steady-state spectrophotometric measurements.

Discharge ignition characteristics of pulsed radio-frequency glow discharges in atmospheric helium

2009 ◽  
Vol 16 (7) ◽  
pp. 070702 ◽  
Author(s):  
Jianjun Shi ◽  
Yeqing Cai ◽  
Jie Zhang ◽  
Ke Ding ◽  
Jing Zhang
Keyword(s):  
Radio Frequency ◽  
Glow Discharges ◽  
Discharge Ignition ◽  
Ignition Characteristics

A Study on the Leakage and Rotordynamic Performance of a Long Labyrinth Seal Under Mainly Air Conditions

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Silicone Oil ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Labyrinth Seal ◽  
System Stability ◽  
Test Fluid ◽  
Liquid Volume ◽  
Frequency Dependent ◽  
Frequency Independent ◽  
The Impact

Abstract This paper investigates the impact of liquid presence in air on the leakage and rotordynamic coefficients of a long (length-to-diameter ratio L/D = 0.747) teeth-on-stator labyrinth seal. The test fluid is a mixture of air and silicone oil (PSF-5cSt). Tests are carried out at inlet pressure Pi = 62.1 bars, three pressure ratios from 0.21 to 0.46, three speeds from 10 to 20 krpm, and six inlet liquid volume fractions (LVFs) from 0% to 15%. Complex dynamic-stiffness coefficients Hij are measured. The real parts of Hij are too frequency dependent to be fitted by frequency-independent stiffness and virtual-mass coefficients. Therefore, this paper presents frequency-dependent direct stiffness KΩ and cross-coupled stiffness kΩ. The imaginary parts of Hij produce frequency-independent direct damping C. Test results show that, under both pure- and mainly air conditions, the leakage mass flowrate m˙ of the test seal steadily increases as inlet LVF increases. KΩ is negative under all test conditions, and the magnitude of KΩ increases as inlet LVF increases, leading to a larger negative centering force on the associated compressor rotor. Under pure-air conditions, kΩ is a small negative value. Injecting oil into the air increases kΩ slightly and make the magnitude of kΩ closer to zero. Under mainly air conditions, increasing inlet LVF from 2% to 15% has little impact on kΩ. C normally increases as inlet LVF increases. The value of the effective damping Ceff = C − kΩ/Ω near 0.5ω is of significant interest to the system stability since an unstable centrifugal compressor may precess at approximately 0.5ω. Ω denotes the excitation frequency. The oil presence in the air has little impact on the value of Ceff near 0.5ω. Also, the liquid presence does not change the insensitiveness of m˙, KΩ, kΩ, C, and Ceff to change in ω; i.e., under both pure- and mainly air conditions, changes in ω has little impact on m˙, KΩ, kΩ, C, and Ceff.

scholarly journals Electron trapping in radio-frequency atmospheric-pressure glow discharges

2007 ◽  
Vol 90 (4) ◽  
pp. 041502 ◽  
Author(s):  
D. W. Liu ◽  
J. J. Shi ◽  
M. G. Kong
Keyword(s):  
Radio Frequency ◽  
Atmospheric Pressure ◽  
Electron Trapping ◽  
Glow Discharges

Deposition of Super-Hydrophobic and Oleophobic Fluorocarbon Films in Radio Frequency Glow Discharges

2007 ◽  
Vol 247 (1) ◽  
pp. 295-302 ◽  
Author(s):  
L. Laguardia ◽  
D. Ricci ◽  
E. Vassallo ◽  
A. Cremona ◽  
E. Mesto ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Fluorocarbon Films ◽  
Glow Discharges
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