An Analytical Investigation Characterizing the Application of Single Frequency Acoustic Modulation for High Frequency Combustion Instability Suppression

2014 ◽  
Author(s):  
Jacob Cranford ◽  
John W. Bennewitz ◽  
Sarma L. Rani ◽  
Robert A. Frederick
Keyword(s):  
High Frequency ◽  
Combustion Instability ◽  
Analytical Investigation ◽  
Single Frequency ◽  
Acoustic Modulation

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

Influence of Tracheal Obstruction on the Efficacy of Superimposed High-frequency Jet Ventilation and Single-frequency Jet Ventilation

2015 ◽  
Vol 123 (4) ◽  
pp. 799-809 ◽  
Author(s):  
Robert Sütterlin ◽  
Antonella LoMauro ◽  
Stefano Gandolfi ◽  
Rita Priori ◽  
Andrea Aliverti ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Chest Wall ◽  
High Frequency ◽  
Blood Gases ◽  
Single Frequency ◽  
Jet Ventilation ◽  
Lung Volumes ◽  
High Frequency Jet Ventilation ◽  
Tracheal Obstruction

Abstract Background: Both superimposed high-frequency jet ventilation (SHFJV) and single-frequency (high-frequency) jet ventilation (HFJV) have been used with success for airway surgery, but SHFJV has been found to provide higher lung volumes and better gas exchange than HFJV in unobstructed airways. The authors systematically compared the ventilation efficacy of SHFJV and HFJV at different ventilation frequencies in a model of tracheal obstruction and describe the frequency and obstruction dependence of SHFJV efficacy. Methods: Ten anesthetized animals (weight 25 to 31.5 kg) were alternately ventilated with SHFJV and HFJV at a set of different fHF from 50 to 600 min−1. Obstruction was created by insertion of interchangeable stents with ID 2 to 8 mm into the trachea. Chest wall volume was measured using optoelectronic plethysmography, airway pressures were recorded, and blood gases were analyzed repeatedly. Results: SHFJV provided greater than 1.6 times higher end-expiratory chest wall volume than HFJV, and tidal volume (VT) was always greater than 200 ml with SHFJV. Increase of fHF from 50 to 600 min−1 during HFJV resulted in a more than 30-fold VT decrease from 112 ml (97 to 130 ml) to negligible values and resulted in severe hypoxia and hypercapnia. During SHFJV, stent ID reduction from 8 to 2 mm increased end-expiratory chest wall volume by up to 3 times from approximately 100 to 300 ml and decreased VT by up to 4.2 times from approximately 470 to 110 ml. Oxygenation and ventilation were acceptable for 4 mm ID or more, but hypercapnia occurred with the 2 mm stent. Conclusion: In this in vivo porcine model of variable severe tracheal stenosis, SHFJV effectively increased lung volumes and maintained gas exchange and may be advantageous in severe airway obstruction.

scholarly journals Measurements of acoustic scattering from zooplankton and oceanic microstructure using a broadband echosounder

2009 ◽  
Vol 67 (2) ◽  
pp. 379-394 ◽  
Author(s):  
Andone C. Lavery ◽  
Dezhang Chu ◽  
James N. Moum
Keyword(s):  
High Frequency ◽  
System Performance ◽  
Pulse Compression ◽  
Acoustic Scattering ◽  
Single Frequency ◽  
Frequency Range ◽  
Range Resolution ◽  
Continuous Frequency ◽  
Processing Techniques ◽  
Signal Processing Techniques

Abstract Lavery, A. C., Chu, D., and Moum, J. N. 2010. Measurements of acoustic scattering from zooplankton and oceanic microstructure using a broadband echosounder. – ICES Journal of Marine Science, 67: 379–394. In principle, measurements of high-frequency acoustic scattering from oceanic microstructure and zooplankton across a broad range of frequencies can reduce the ambiguities typically associated with the interpretation of acoustic scattering at a single frequency or a limited number of discrete narrowband frequencies. With this motivation, a high-frequency broadband scattering system has been developed for investigating zooplankton and microstructure, involving custom modifications of a commercially available system, with almost complete acoustic coverage spanning the frequency range 150–600 kHz. This frequency range spans the Rayleigh-to-geometric scattering transition for some zooplankton, as well as the diffusive roll-off in the spectrum for scattering from turbulent temperature microstructure. The system has been used to measure scattering from zooplankton and microstructure in regions of non-linear internal waves. The broadband capabilities of the system provide a continuous frequency response of the scattering over a wide frequency band, and improved range resolution and signal-to-noise ratios through pulse-compression signal-processing techniques. System specifications and calibration procedures are outlined and the system performance is assessed. The results point to the utility of high-frequency broadband scattering techniques in the detection, classification, and under certain circumstances, quantification of zooplankton and microstructure.

A Study of the Response of a Small Porous Chamber to Forced Oscillation

1966 ◽  
Vol 88 (1) ◽  
pp. 25-32
Author(s):  
R. L. Peskin ◽  
E. Martinez
Keyword(s):  
Phase Angle ◽  
High Frequency ◽  
Gas Flow ◽  
Low Frequency ◽  
Pressure Change ◽  
Analytical Investigation ◽  
Frequency Curve ◽  
Cylindrical Chamber ◽  
Gas Damping ◽  
Vibrating Systems

An analytical investigation of the pressure response to forced volume oscillations of a shallow cylindrical chamber with a porous end is undertaken. Investigation is in the frequency domain. Both infinite and finite-length chambers are considered. The irreversible gas flow introduces a frequency-dependent phase angle between volume and pressure change. Pressure leads volume at low frequency, and the phase angle becomes zero at high frequency. Curve characteristics suggest applications such as gas damping of vibrating systems.

Combustion Instability Control Through Acoustic Modulation at the Inlet Boundary: Experiments

2015 ◽  
Vol 31 (6) ◽  
pp. 1672-1688 ◽  
Author(s):  
John W. Bennewitz ◽  
Robert A. Frederick ◽  
Jacob T. Cranford ◽  
David M. Lineberry
Keyword(s):  
Combustion Instability ◽  
Instability Control ◽  
Acoustic Modulation

Effects of Source Position and Frequency on Geoacoustic Inversion

1998 ◽  
Vol 06 (01n02) ◽  
pp. 245-255 ◽  
Author(s):  
Renhe Zhang ◽  
Fenghua Li ◽  
Wenyu Luo
Keyword(s):  
Simulated Annealing ◽  
Theoretical Analysis ◽  
High Frequency ◽  
Low Frequency ◽  
Sound Field ◽  
Propagation Model ◽  
Single Frequency ◽  
Test Cases ◽  
Source Position ◽  
Geoacoustic Inversion

In this paper, geoacoustic inversion based on simulated annealing and the BDRM propagation model is applied to the test cases from the 1997 Geoacoustic Inversion Workshop. The effects of the bottom parameters on the sound field are discussed theoretically and two characteristic angles dependent upon geoacoustic parameters are defined. Based on the theoretical analysis of the characteristic angles, a multi-frequency inversion scheme is given as follows: High frequency and farfield data are used to invert the upper bottom parameters first, and then low frequency and nearfield data are used to invert the lower bottom parameters. Simulated tests show that the results of multi-frequency inversion are more accurate and reliable than single frequency inversion.

Combustion Instability Control Through Acoustic Modulation at the Inlet Boundary: Analysis

2015 ◽  
Vol 31 (6) ◽  
pp. 1689-1695
Author(s):  
John W. Bennewitz ◽  
Sarma L. Rani ◽  
Jacob T. Cranford ◽  
Robert A. Frederick
Keyword(s):  
Combustion Instability ◽  
Boundary Analysis ◽  
Instability Control ◽  
Acoustic Modulation
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