Theoretical and experimental investigations of the excitation of high-frequency oscillations in an ion collective accelerator model based on the Doppler effect

2000 ◽  
Vol 26 (4) ◽  
pp. 344-350
Author(s):  
V. I. Butenko ◽  
D. V. Gorozhanin ◽  
A. M. Egorov ◽  
B. I. Ivanov ◽  
V. V. Ognivenko ◽  
...  
Keyword(s):  
High Frequency ◽  
Doppler Effect ◽  
Experimental Investigations ◽  
Model Based ◽  
High Frequency Oscillations ◽  
The Doppler Effect

A Driving Mechanism for High Frequency Combustion Instability in Liquid Fuel Rocket Engines

1964 ◽  
Vol 68 (645) ◽  
pp. 633-637 ◽  
Author(s):  
P. D. McCormack
Keyword(s):  
High Frequency ◽  
Liquid Fuel ◽  
Low Frequency ◽  
Pressure Oscillation ◽  
Experimental Investigations ◽  
Driving Mechanism ◽  
Rocket Engines ◽  
High Frequency Oscillations ◽  
The Subject ◽  
Motor Operation

The problem of combustion pressure oscillation in liquid-fuel rocket motor operation has long been the subject of theoretical and experimental investigations.The low frequency (less than 200 cps) type of oscillation, known as “chugging”, has been thoroughly analysed and the problem solved (see Crocco, 5th Combustion Symposium, p. 164).This Note is concerned with the more complex (and more destructive) high frequency oscillations, covering a range from about 1000 to 6000 cps. Such oscillations can resonate with the acoustical modes of the combustion chamber. Longitudinal, tangential and radial oscillating modes have been observed.

A Model for the Thermo-Acoustic Feedback of Transverse Acoustic Modes and Periodic Oscillations in Flame Position in Cylindrical Flame Tubes

2012 ◽  
Author(s):  
Joachim Schwing ◽  
Felix Grimm ◽  
Thomas Sattelmayer
Keyword(s):  
Heat Release ◽  
High Frequency ◽  
Circular Cross Section ◽  
Experimental Investigations ◽  
Constant Density ◽  
Rayleigh Criterion ◽  
Velocity Fluctuations ◽  
Acoustic Modes ◽  
High Frequency Oscillations ◽  
Transverse Acoustic

In the past decades, several feedback mechanisms for longitudinal acoustic modes in gas turbine combustors have been investigated. These mechanisms are successfully used in predictive tools like acoustic network models to analyze low-frequency instabilities in combustion systems. In contrast, little is known about high-frequency oscillations — fluctuations at several kHz. Most theories are derived from experimental investigations of afterburners in the 1950s and 1960s, indicating an interaction of vortex shedding, fluctuating vorticity and heat release. In this work a different feedback mechanism for high-frequency oscillations in cylindrical flame tubes related to transverse acoustic modes is suggested and analysed: Transverse acoustic pressure fluctuations are linked to an oscillating velocity field. A time-dependent but periodic displacement field can be derived from these velocity fluctuations. The model assumes that the zone of heat release is displaced by the velocity fluctuations. Pressure oscillations and periodically deflected heat release lead to a contribution to the Rayleigh criterion without fluctuations in the global heat release. This effect is studied in a circular cross section presuming a circular zone of heat release. Expressions for the displacement of the flame front are derived from the analytical solution of the wave equation in cylindrical geometries assuming a quiescent medium, constant density and speed of sound. The Rayleigh criterion is integrated and growth rates are evaluated whereas damping effects are neglected as they are not subject to this study. Characteristics of the model are assessed and compared to experimental observations to check the validity and the applicability of the theory.

scholarly journals Can we use intraoperative high‐frequency oscillations to guide tumor‐related epilepsy surgery?

Epilepsia ◽  
2021 ◽  
Author(s):  
Nicole E. C. Klink ◽  
Willemiek J. E. M. Zweiphenning ◽  
Cyrille H. Ferrier ◽  
Peter H. Gosselaar ◽  
Kai J. Miller ◽  
...  
Keyword(s):  
Epilepsy Surgery ◽  
High Frequency ◽  
High Frequency Oscillations

scholarly journals High-frequency oscillations recorded with surface EEG in neonates with seizures

2021 ◽  
Author(s):  
Lotte Noorlag ◽  
Maryse A. van 't Klooster ◽  
Alexander C. van Huffelen ◽  
Nicole E.C. van Klink ◽  
Manon J.N.L. Benders ◽  
...  
Keyword(s):  
High Frequency ◽  
High Frequency Oscillations ◽  
Surface Eeg
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