An Experimental Investigation of the Steady-State Response of a Noncontacting Flexibly Mounted Rotor Mechanical Face Seal

1995 ◽  
Vol 117 (1) ◽  
pp. 153-159 ◽  
Author(s):  
An Sung Lee ◽  
Itzhak Green
Keyword(s):  
Experimental Investigation ◽  
Steady State ◽  
Dynamic Behavior ◽  
Amplitude Ratio ◽  
Theoretical Work ◽  
Operating Conditions ◽  
Superior Performance ◽  
Steady State Response ◽  
State Response ◽  
Operation Conditions

Recent theoretical work on the dynamics of the noncontacting flexibly mounted rotor (FMR) seal has shown that it is superior in every aspect of dynamic behavior compared to the flexibly mounted stator (FMS) seal. The FMR seal is inherently stable regardless of the operating speed, the maximum relative misalignment response is smaller, and the critical stator misalignment is larger. All these are measures of superior performance. This work undertakes the experimental investigation of the dynamic behavior of a noncontacting FMR seal. The steady-state response of the FMR seal was measured at various operating conditions. The results are given in terms of dynamic and static transmissibilities, i.e., amplitude ratio of responses to two forcing inputs: the initial rotor and fixed stator misalignments. These are then compared to the analytical predictions. Further, operation maps are drawn for each set of operation conditions. The maps indicate how safely (away from contact) the seal operates. It is shown that the combination of the seal parameters that maximize the fluid film stiffness is optimal for safe noncontacting operation.

Steady-State Analysis of Mechanical Seals With Two Flexibly Mounted Rotors

1997 ◽  
Vol 119 (1) ◽  
pp. 200-204 ◽  
Author(s):  
J. Wileman ◽  
I. Green
Keyword(s):  
Steady State ◽  
Dynamic Behavior ◽  
Reference Frames ◽  
Rapid Determination ◽  
Equations Of Motion ◽  
Steady State Response ◽  
Mechanical Seals ◽  
State Response ◽  
Forcing Functions ◽  
Flexible Supports

The dynamic behavior of a mechanical face seal with two flexibly mounted rotors is investigated. The equations of motion are derived using linearized rotor dynamic coefficients to model the dynamic behavior of the fluid film. The equations are shown to be linear in the inertial reference with harmonic forcing functions which result from the initial misalignment of the flexible supports. A method for obtaining the steady-state response in the system is derived by transforming the equations of motion into reference frames which rotate with the shafts. The resulting equations contain constant forcing functions and can be readily solved for the magnitude of the steady-state response. The method presented allows a rapid determination of the steady-state misalignment of a seal without resorting to numerical modeling.

Steady-State Response of a Piping System Under Harmonic Excitations Considering Pipe-Support Friction With Variable Normal Loads

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
José Argüelles ◽  
Euro Casanova
Keyword(s):  
Steady State ◽  
Operating Conditions ◽  
Dynamic Loads ◽  
Computational Time ◽  
Piping System ◽  
Steady State Response ◽  
State Response ◽  
Harmonic Excitations ◽  
Piping Systems ◽  
Support Surfaces

Dynamic loads in piping systems are mainly caused by transient phenomena generated by operating conditions or installed equipment. In most cases, these dynamic loads may be modeled as harmonic excitations, e.g., pulsating flow. On the other hand, when designing piping systems under dynamic loads, it is a common practice to neglect strong nonlinearities such as shocks and friction between pipe and support surfaces, mainly because of the excessive cost in terms of computational time and the complexity associated with the integration of the nonlinear equations of motion. However, disregarding these nonlinearities for some systems may result in overestimated dynamic amplitudes leading to incorrect analysis and designs. This paper presents a numerical approach to calculate the steady-state response amplitudes of a piping system subjected to harmonic excitations and considering dry friction between the pipe and the support surfaces, without performing a numerical integration. The proposed approach permits the analysis of three dimensional piping systems, where the normal forces may vary in time and is based in the hybrid frequency–time domain method (HFT). Results of the proposed approach are compared and discussed with those of a full integration scheme, confirming that HFT is a valid and computationally feasible option.

The Auditory Steady-State Response: Full-Term and Premature Neonates

2002 ◽  
Vol 13 (05) ◽  
pp. 260-269 ◽  
Author(s):  
Barbara Cone-Wesson ◽  
John Parker ◽  
Nina Swiderski ◽  
Field Rickards
Keyword(s):  
Steady State ◽  
Premature Infants ◽  
Modulation Frequency ◽  
Otoacoustic Emission ◽  
Full Term ◽  
Steady State Response ◽  
Pass Rates ◽  
Term Infants ◽  
State Response ◽  
Auditory Steady State Response

Two studies were aimed at developing the auditory steady-state response (ASSR) for universal newborn hearing screening. First, neonates who had passed auditory brainstem response, transient evoked otoacoustic emission, and distortion-product otoacoustic emission tests were also tested with ASSRs using modulated tones that varied in frequency and level. Pass rates were highest (> 90%) for amplitude-modulated tones presented at levels ≥ 69 dB SPL. The effect of modulation frequency on ASSR for 500- and 2000-Hz tones was evaluated in full-term and premature infants in the second study. Full-term infants had higher pass rates for 2000-Hz tones amplitude modulated at 74 to 106 Hz compared with pass rates for a 500-Hz tone modulated at 58 to 90 Hz. Premature infants had lower pass rates than full-term infants for both carrier frequencies. Systematic investigation of ASSR threshold and the effect of modulation frequency in neonates is needed to adapt the technique for screening.

scholarly journals Steady State Response of Linear Time Invariant Systems Modeledby Multibond Graphs

2021 ◽  
Vol 11 (4) ◽  
pp. 1717
Author(s):  
Gilberto Gonzalez Avalos ◽  
Noe Barrera Gallegos ◽  
Gerardo Ayala-Jaimes ◽  
Aaron Padilla Garcia
Keyword(s):  
Steady State ◽  
Linear Time ◽  
Direct Determination ◽  
The State ◽  
Steady State Response ◽  
State Variables ◽  
Linear Time Invariant ◽  
State Response ◽  
Time Invariant

The direct determination of the steady state response for linear time invariant (LTI) systems modeled by multibond graphs is presented. Firstly, a multiport junction structure of a multibond graph in an integral causality assignment (MBGI) to get the state space of the system is introduced. By assigning a derivative causality to the multiport storage elements, the multibond graph in a derivative causality (MBGD) is proposed. Based on this MBGD, a theorem to obtain the steady state response is presented. Two case studies to get the steady state of the state variables are applied. Both cases are modeled by multibond graphs, and the symbolic determination of the steady state is obtained. The simulation results using the 20-SIM software are numerically verified.

Decreased Gamma Auditory Steady-State Response Is Associated With Impaired Real-World Functioning in Unmedicated Patients at Clinical High Risk for Psychosis

2020 ◽  
pp. 155005942098270
Author(s):  
Sarah Ahmed ◽  
Jennifer R. Lepock ◽  
Romina Mizrahi ◽  
R. Michael Bagby ◽  
Cory J. Gerritsen ◽  
...  
Keyword(s):  
Steady State ◽  
High Risk ◽  
Functional Impairment ◽  
Real World ◽  
Steady State Response ◽  
Clinical High Risk ◽  
State Response ◽  
Auditory Steady State Response ◽  
Gamma Synchrony ◽  
40 Hz

Aim Deficits in synchronous, gamma-frequency neural oscillations may contribute to schizophrenia patients’ real-world functional impairment and can be measured electroencephalographically using the auditory steady-state response (ASSR). Gamma ASSR deficits have been reported in schizophrenia patients and individuals at clinical high risk (CHR) for developing psychosis. We hypothesized that, in CHR patients, gamma ASSR would correlate with real-world functioning, consistent with a role for gamma synchrony deficits in functional impairment. Methods A total of 35 CHR patients rated on Global Functioning: Social and Role scales had EEG recorded while listening to 1-ms, 93-dB clicks presented at 40 Hz in 500-ms trains, in response to which 40-Hz evoked power and intertrial phase-locking factor (PLF) were measured. Results In CHR patients, lower 40-Hz PLF correlated with lower social functioning. Conclusions Gamma synchrony deficits may be a biomarker of real-world impairment at early stages of the schizophrenia disease trajectory.

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