Premixed flame response to oscillatory pressure waves

2005 ◽  
Vol 30 (2) ◽  
pp. 1733-1740 ◽  
Author(s):  
O.J. Teerling ◽  
A.C. McIntosh ◽  
J. Brindley ◽  
V.H.Y. Tam
Keyword(s):  
Premixed Flame ◽  
Pressure Waves ◽  
Flame Response ◽  
Oscillatory Pressure

Premixed flame response to equivalence ratio perturbations

2010 ◽  
Vol 14 (5) ◽  
pp. 681-714 ◽  
Author(s):  
Shreekrishna ◽  
Santosh Hemchandra ◽  
Tim Lieuwen
Keyword(s):  
Equivalence Ratio ◽  
Premixed Flame ◽  
Flame Response

Effect of Nanosecond Repetitively Pulsed Discharges on the Dynamics of a Swirl-Stabilized Lean Premixed Flame

2013 ◽  
Author(s):  
D. A. Lacoste ◽  
J. P. Moeck ◽  
D. Durox ◽  
C. O. Laux ◽  
T. Schuller
Keyword(s):  
Transfer Function ◽  
Thermal Power ◽  
Premixed Flame ◽  
Plasma Discharges ◽  
Chemical Effects ◽  
Flame Dynamics ◽  
Lean Premixed ◽  
Flame Response ◽  
Order Of Magnitude ◽  
Pulsed Discharges

The effects of Nanosecond Repetitively Pulsed (NRP) plasma discharges on the dynamics of a swirl-stabilized lean premixed flame are investigated experimentally. Voltage pulses of 8-kV amplitude and 10-ns duration are applied at a repetition rate of 30 kHz. The average electric power deposited by the plasma is limited to 40 W, corresponding to less than 1 % of the thermal power of 4 kW released by the flame. The investigation is carried out with a dedicated experimental setup that allows for studies of the flame dynamics with applied plasma discharges. A loudspeaker is used to perturb the flame acoustically, and the discharges are generated between a central pin electrode and the rim of the injection tube. Velocity and CH* chemiluminescence signals are used to determine the flame transfer function assuming that plasma discharges do not affect the correlation between CH* emission and heat release rate fluctuations. Phase-locked images of the CH* emission were recorded to assess the effect of the plasma on the oscillation of the flame. The results show a strong influence of the NRP discharges on the flame response to acoustic perturbations, thus opening interesting perspectives for combustion control. An interpretation of the modifications observed in the transfer function of the flame is proposed by taking into account the thermal and chemical effects of the discharges. It is then demonstrated that by applying NRP discharges at unstable conditions, the oscillation amplitudes can be reduced by an order of magnitude, thus effectively stabilizing the system.

Oscillatory pressure wave transmission from the upper airway to the carotid artery

2007 ◽  
Vol 103 (5) ◽  
pp. 1622-1627 ◽  
Author(s):  
Lauren Howitt ◽  
Kristina Kairaitis ◽  
Jason P. Kirkness ◽  
Sarah R. Garlick ◽  
John R. Wheatley ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Common Carotid Artery ◽  
Pressure Wave ◽  
Upper Airway ◽  
Pressure Waves ◽  
Pressure Amplitude ◽  
Artery Wall ◽  
Carotid Artery Wall ◽  
The Common ◽  
Oscillatory Pressure

Snoring-associated vibration energy transmission from the upper airway to the carotid artery has been hypothesized as a potential atherosclerotic plaque initiating/rupturing event that may provide a pathogenic mechanism linking snoring and embolic stroke. We examined transmission of oscillatory pressure waves from the pharyngeal lumen to the common carotid artery wall and lumen in seven male, anesthetized, spontaneously breathing New Zealand White rabbits. Airflow was monitored via a pneumotachograph inserted in series in the intact trachea. Fifteen 20-s runs of, separately, 40-, 60-, and 90-Hz oscillatory pressure waves [pressure amplitude in the trachea (Ptramp), amplitude 2–20 cmH2O] were generated by a loudspeaker driven by a sine wave generator and amplifier and superimposed on tidal breathing via the cranial tracheal connector. Pressure transducer-tipped catheters measured pressure amplitudes in the tissues adjacent to the common carotid artery bifurcation (Pctiamp) and within the lumen (carotid sinus; Pcsamp). Data were analyzed using power spectrum analysis and linear mixed-effects statistical modeling. Both the frequency (f) and amplitude of the injected pressure wave influenced Pctiamp and Pcsamp, in that ln Pctiamp = 1.2(Ptramp) + 0.02(f) − 5.2, and ln Pcsamp = 0.6(Ptramp) + 0.02(f) − 4.9 (both P < 0.05). Across all frequencies tested, transfer of oscillatory pressure across the carotid artery wall was associated with an amplitude gain, as expressed by a Pcsamp-to-Pctiamp ratio of 1.8 ± 0.3 ( n = 6). Our findings confirm transmission of oscillatory pressure waves from the upper airway lumen to the peripharyngeal tissues and across the carotid artery wall to the lumen. Further studies are required to establish the role of this incident energy in the pathogenesis of carotid artery vascular disease.

Laminar premixed flame response to equivalence ratio oscillations

2005 ◽  
Vol 140 (1-2) ◽  
pp. 116-129 ◽  
Author(s):  
Ju Hyeong Cho ◽  
Tim Lieuwen
Keyword(s):  
Equivalence Ratio ◽  
Premixed Flame ◽  
Flame Response
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