Coupled Fluidic Vibration Isolators for Rotorcraft Pitch Link Loads Reduction

2012 ◽  
Author(s):  
Nicolas A. Kurczewski ◽  
Lloyd H. Scarborough ◽  
Christopher D. Rahn ◽  
Edward C. Smith
Keyword(s):  
Harmonic Excitation ◽  
Wide Frequency Range ◽  
Rotor Speed ◽  
Frequency Range ◽  
Vibration Isolators ◽  
Transmitted Force ◽  
Fluidic Devices ◽  
Fluidic Device ◽  
Multiple Frequencies ◽  
Blade Loads

Replacing rigid pitch links on rotorcraft with coupled fluidic devices has the potential to reduce the aerodynamic blade loads transmitted from the blade root to the swashplate. An analytical model of two coupled fluidic isolators is derived and experimentally validated for even and odd harmonic pitch link loads. The system consists of two elastomeric pumpers with fluid chambers that are coupled by an inertia track. This passive fluidic device can be tuned to reduce the transmitted force at a particular odd harmonic of the rotor speed by tailoring the fluid inertance in the inertia track. Benchtop experimental results agree with theory, demonstrating a reduction in odd harmonic pitch link loads of up to 90% compared to the system without fluid. The coupled fluidic isolators also significantly reduce transmitted loads relative to a rigid pitch link over a wide frequency range. Simulation of a UH-60 Blackhawk retrofit example shows potential for targeted odd harmonic excitation loads reduction up to 94% for multiple frequencies without affecting the even harmonic excitation response.

Fluidic Composite Tunable Vibration Isolators

2010 ◽  
Author(s):  
Lloyd H. Scarborough ◽  
Christopher D. Rahn ◽  
Edward C. Smith
Keyword(s):  
Material Properties ◽  
Unique Feature ◽  
Vibration Reduction ◽  
Vibration Isolator ◽  
Frequency Range ◽  
Vibration Isolators ◽  
New Class ◽  
Isolation Frequency ◽  
Transmitted Force ◽  
Flexible Matrix Composite

Coupling a Fluidic Flexible Matrix Composite (F2MC) to an air-pressurized fluid port produces a fundamentally new class of tunable vibration isolator. This device provides significant vibration reduction at an isolation frequency that can be tuned over a broad frequency range. The material properties and geometry of the F2MC element, as well as the port inertance, determine the isolation frequency. A unique feature of this device is that the port inertance depends on pressure so the isolation frequency can be adjusted by changing the air pressure. For constant port inertance, the isolation frequency is largely independent of the isolated mass so the device is robust to changes in load. A nonlinear model is developed to predict isolator length and port inertance. The model is linearized and the frequency response calculated. Experiments agree with theory, demonstrating a tunable isolation range from 9 Hz to 36 Hz and minimum transmitted force reductions of 90% at the isolation frequency.

Fluidic Composite Tunable Vibration Isolators

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Lloyd H. Scarborough ◽  
Christopher D. Rahn ◽  
Edward C. Smith
Keyword(s):  
Nonlinear Model ◽  
Material Properties ◽  
Unique Feature ◽  
Vibration Reduction ◽  
Frequency Range ◽  
Vibration Isolators ◽  
New Class ◽  
Isolation Frequency ◽  
Transmitted Force ◽  
Flexible Matrix Composite

Coupling a fluidic flexible matrix composite (F2MC) to an air-pressurized fluid port produces a fundamentally new class of tunable vibration isolators. This Fluidlastic device provides significant vibration reduction at an isolation frequency that can be tuned over a broad frequency range. The material properties and geometry of the F2MC element, as well as the port inertance, determine the isolation frequency. A unique feature of this device is that the port inertance depends on pressure so the isolation frequency can be adjusted by changing the air pressure. For constant port inertance, the isolation frequency is largely independent of the isolated mass so the device is robust to changes in load. A nonlinear model is developed to predict isolator length and port inertance. The model is linearized and the frequency response calculated. Experiments agree with theory, demonstrating a tunable isolation range from 9 Hz to 36 Hz and transmitted force reductions of up to 60 dB at the isolation frequency.

scholarly journals A Novel Dynamic Absorber Using Enhanced Magnetorheological Elastomers for Powertrain Vibration Control

2008 ◽  
Vol 47-50 ◽  
pp. 117-120 ◽  
Author(s):  
Nong Zhang ◽  
Nga Hoang ◽  
Hai Ping Du
Keyword(s):  
Vibration Control ◽  
Harmonic Excitation ◽  
Wide Frequency Range ◽  
Shear Mode ◽  
Frequency Range ◽  
Magnetorheological Elastomers ◽  
Powertrain System ◽  
Narrow Bandwidth ◽  
Dynamic Absorber ◽  
Mr Effect

This paper presents a novel Adaptive Tuned Vibration Absorber (ATVA) using the enhanced magnetorheological elastomers (MREs) for powertrain vibration reduction. The MRE material used in this application includes micro-sized iron particles enhanced by adding nano-sized magnetic powders. With the enhancement, MRE’s elastic modulus significantly increases due to the MR effect. In the new ATVA, the MRE plays a role as a torsional spring whose stiffness coefficient can be varied with an external magnetic field. Additionally, this ATVA could operate in shearsqueeze mode rather than shear mode. Thus, the frequency range is much wider than that of general MREs. Such property of the enhanced MRE is an advantage for constructing a smart ATVA for powertrain vibration control because the ATVA can work effectively in a wide frequency range instead of a narrow bandwidth as a conventional dynamic absorber does. Numerical simulations of a powertrain system for the second and third gear fitted with the ATVA are used to validate its effectiveness. The obtained results show that the powertrain vibration can be greatly suppressed. Particularly, the ATVA is effective in reducing the powertrain vibration not only in case of the single harmonic excitation but also for the case of the multi-harmonic excitation. Furthermore, the simulation results can be used to optimize the ATVA’s design, which will be our next work.

scholarly journals Stability Analysis of Different Regulation Modes of Hydropower Units

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1933
Author(s):  
Xinran Guo ◽  
Yuanchu Cheng ◽  
Jiada Wei ◽  
Yitian Luo
Keyword(s):  
Stable Operation ◽  
Rotor Speed ◽  
Frequency Range ◽  
Power Regulation ◽  
Normal Frequency ◽  
Dynamic Performances ◽  
Negative Damping ◽  
The Stability ◽  
Regulation Mode ◽  
Water Inertia

The dynamic characteristics of hydropower unit governing systems considerably influence the stability of hydropower units and the connected power system. The dynamic performances of hydropower units with power regulation mode (PRM) and opening regulation mode (ORM) are different. This paper establishes a detailed linear model of a hydropower unit based on the Phillips–Heffron model. The damping characteristic and stability of two regulation modes with different water inertia time constants TW were analyzed. ORM tended to provide negative damping, while PRM often provided positive damping in the major parts of the frequency range within the normal frequency oscillations when TW was large. Eigenvalue analysis illustrated that PRM has better stability than ORM. To validate the analysis, a simulation under two typical faults WAS conducted based on a nonlinear model of a hydropower unit. The simulation results illustrated that the responses of units with PRM are more stable in terms of important operating parameters, such as output power, rotor speed, and power angles. For hydropower units facing challenges in stable operation, PRM is recommended to obtain good dynamic stability.

Installation for testing electronic voltmeters over a wide frequency range

1976 ◽  
Vol 19 (10) ◽  
pp. 1525-1526
Author(s):  
A. M. Fedorov ◽  
V. V. Krestovskii ◽  
V. S. Kiselev ◽  
S. A. Razumovskii ◽  
V. A. Shcheglov
Keyword(s):  
Wide Frequency Range ◽  
Frequency Range
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