Acoustic Noise Reduction Under Distributed Combustion

2017 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Ashwani K. Gupta
Keyword(s):  
Carbon Dioxide ◽  
Heat Release ◽  
Noise Reduction ◽  
Oxygen Concentration ◽  
Acoustic Signal ◽  
Thermal Field ◽  
Field Uniformity ◽  
Pollutants Emission ◽  
Reactive Gases ◽  
Swirl Flame

Colorless Distributed Combustion (CDC) has been shown to provide unique benefits on ultra-low pollutants emission, enhanced combustion stability, and thermal field uniformity. To achieve CDC conditions, fuel-air mixture must be properly prepared and mixed with hot reactive gases from within the combustor prior to the mixture ignition. The hot reactive gases reduce the oxygen concentration in the mixture while increasing its temperature, resulting in a reaction zone that is distributed across the reactor volume, with lower reaction rate to result in the same fuel consumption. The conditions to achieve distributed combustion were previously studied using methane and other fuels with focus on pollutants emission and thermal field uniformity. In this paper, the impact of distributed combustion on noise reduction and increased stability is investigated. Such reduced noise is critical in mitigating the coupling between flame and heat release perturbations and acoustic signal to enhance the overall flame stability and reduce the propensity of flame instabilities which can cause equipment failure. Nitrogen-carbon dioxide mixture is used to simulate the reactive entrained gases from with the combustor. Increasing the amounts of nitrogen and carbon dioxide reduced the oxygen concentration within the oxidizing mixture, fostering distributed combustion. Upon achieving distributed combustion, the overall flame noise signature decreased from 80 dB to only 63 dB, as the flame transitioned from traditional swirl flame to distributed combustion. The flow noise under these conditions was 54 dB, indicating that distributed combustion has only 9 dB increase over isothermal case as compared to 26 dB for standard swirl flame. In addition, the dominant flame frequency around 490Hz disappeared under distributed combustion. For the traditional swirl flame, both the acoustic signal and heat release fluctuations (detected through CH∗ chemiluminescence) had a peak around 150Hz, indicating coupling between the heat release fluctuations and pressure variation. However, upon transitioning to distributed combustion, this common peak disappeared, outlining the enhanced stability of distributed combustion as there is no feedback between the heat release fluctuations and the recorded acoustic signal.

Fuel Property Effects on the Fate of Volume Distributed Combustion

2016 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Ashwani K. Gupta
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Concentration ◽  
Gas Temperature ◽  
Field Uniformity ◽  
Different Temperatures ◽  
Pollutants Emission ◽  
Reactive Gases ◽  
Colorless Distributed Combustion ◽  
The Impact ◽  
No Emissions

Colorless Distributed Combustion (CDC) has been shown to provide singular benefits on ultra-low pollutants emission, enhanced stability and thermal field uniformity. To achieve CDC conditions, fuel-air mixture must be properly prepared and mixed with hot reactive gases from within the combustor prior to the mixture ignition. Hot reactive gases reduce the oxygen concentration in the mixture while increasing its temperature. In this paper, the impact of fuel type (methane, propane, and hydrogen enriched methane) on achieving distributed combustion is investigated. A mixture of nitrogen and carbon dioxide was mixed to simulate the hot recirculated gases at different temperatures using normal air upstream of the combustor. Increasing the amounts of nitrogen and carbon dioxide reduced the oxygen concentration within the combustor. Distributed combustion was identified through OH* chemiluminescence distribution across the combustor. For methane, this oxygen concentration varied between 13.8% and 11.2% (depending on the mixture temperature) with some 85% reduction in NO emissions as compared to that without entrainment. Similar behavior was demonstrated with propane and hydrogen enriched methane, albeit at a lower oxygen concentration (13.7%–11.6% and 12.2%–10.5%), to result in 94% and 92% reduction in NO emission, respectively. The inlet gas temperature was varied between 300K and 750K. Experimental data using a variety of fuels showed NO emissions of 1 PPM or less. Analysis and extrapolation of obtained data suggest that distributed combustion can be achieved at an oxygen concentration of 9.5% for hot reactive entrained gases having a temperature of 1800K. This value may be used as a guideline to achieve distributed combustion with ultra-low emission.

Internal Entrainment Effects on Distributed Combustion

2015 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Ashwani K. Gupta
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Concentration ◽  
High Intensity ◽  
Flame Structure ◽  
Low Oxygen ◽  
Air Stream ◽  
Pollutants Emission ◽  
Reactive Gases ◽  
Colorless Distributed Combustion ◽  
The Impact

Colorless Distributed Combustion (CDC) has been shown to provide ultra-low emissions and enhanced combustion performance of high intensity gas turbine combustors in terms of efficiency and stability. To achieve distributed combustion, the flowfield needs to be carefully tailored for adequate mixing between reactants and hot reactive species from within the combustor to result in high temperature low oxygen concentration environment prior to ignition. Such distributed reactions result in uniform thermal field and also eliminates any hot spots for mitigating NOx emission. Though Distributed Combustion have been extensively studied using a variety of geometries, injection velocities, heat release intensities, and fuels, the role of hot reactive internally recirculated gases requires further examination. In this paper, the impact of internal entrainment of reactive gases on flame structure and behavior is investigated with focus on fostering distributed combustion and providing guidelines for designing high intensity combustors operating in distributed combustion mode. A mixture of nitrogen and carbon dioxide, used to simulate the recirculated gases, is introduced to the air stream prior to mixing with the fuel and subsequent combustion. Increase in the amounts of nitrogen and carbon dioxide (simulating increased entrainment), led to volume distributed reaction over a larger volume in the combustor with enhanced and uniform distribution of the OH* chemiluminescence intensity. At the same time, the bluish flame stabilized by the swirler is replaced with a more uniform almost invisible bluish flame. The increased recirculation also reflected on the pollutants emission, where NO emissions were significantly decreased for the same amount of fuel burned. Lowering oxygen concentration from 21% to 15% (due to increased entrainment) resulted in 80∼90% reduction in NO with no impact on CO emission with sub PPM NO emission achieved at an equivalence ratio of 0.7. The same trend was seen at higher diluents injection temperature as well, with significant pollutants emission reduction down to an oxygen concentration of 10%.

Impact of Internal Entrainment on High Intensity Distributed Combustion

2015 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Ashwani K. Gupta
Keyword(s):  
Carbon Dioxide ◽  
Gas Turbine ◽  
Oxygen Concentration ◽  
High Intensity ◽  
Flame Structure ◽  
Flame Stabilization ◽  
Low Oxygen ◽  
Gas Turbine Combustors ◽  
Reactive Gases ◽  
The Impact

Colorless Distributed Combustion (also referred to as CDC) has been shown to provide ultra-low emissions and enhanced performance of high intensity gas turbine combustors. To achieve distributed combustion, the flowfield needs to be tailored for adequate mixing between reactants and hot reactive species from within the combustor to result in high temperature low oxygen concentration environment prior to ignition. Such reaction distribution results in uniform thermal field and also eliminates any hot spots for mitigating NOx emission. Though CDC have been extensively studied using a variety of geometries, heat release intensities, and fuels, the role of internally recirculated hot reactive gases needs to be further investigated and quantified. In this paper, the impact of internal entrainment of reactive gases on flame structure and behavior is investigated with focus on fostering distributed combustion and providing guidelines for designing future gas turbine combustors operating in distributed combustion mode. To simulate the recirculated gases from within the combustor, a mixture of nitrogen and carbon dioxide is introduced to the air stream prior to mixing with fuel and subsequent combustion. Increase in the amounts of nitrogen and carbon dioxide (simulating increased entrainment), led to volume distributed reaction over a larger volume in the combustor with enhanced and uniform distribution of the OH* chemiluminescence intensity. At the same time, the bluish flame stabilized by the swirler is replaced with a more uniform almost invisible bluish flame. The increased recirculation also reflected on the pollutants emission, where NO emissions were significantly decreased for the same amount of fuel burned. Lowering oxygen concentration from 21% to 15% (due to increased recirculation) resulted in 80∼90% reduction in NO with no impact on CO emission with sub PPM NO emission achieved at an equivalence ratio of 0.7. Flame stabilization at excess recirculation can be achieved using preheated nitrogen and carbon dioxide, achieving true distributed conditions with oxygen concentration below 13%.

A New Oxygen Mask: Comparison with Other Clinical Methods of Giving Oxygen

1974 ◽  
Vol 2 (3) ◽  
pp. 214-219 ◽  
Author(s):  
W A Crosbie ◽  
J P Warren ◽  
L A Smith
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Concentration ◽  
Cor Pulmonale ◽  
Blood Levels ◽  
Supplementary Oxygen ◽  
Arterial Blood ◽  
Oxygen Mask ◽  
Clinical Methods ◽  
Expired Air

The performance of a new mask (Mix-O-Mask) for giving supplementary oxygen in clinical situations was compared with three other methods in a patient with cor pulmonale. Measurements were made of the intra-tracheal gas concentrations and arterial blood levels of oxygen and carbon dioxide. The new mask was as reliable as Ventimasks in delivering a claimed oxygen concentration and did not cause rebreathing of expired air. The mask proved durable when worn for sixteen hours in a day and was preferred for comfort by the patient.

scholarly journals Effect of Urban Heat Island and Global Warming Countermeasures on Heat Release and Carbon Dioxide Emissions from a Detached House

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 572
Author(s):  
Daisuke Narumi ◽  
Ronnen Levinson ◽  
Yoshiyuki Shimoda
Keyword(s):  
Carbon Dioxide ◽  
Global Warming ◽  
Heat Release ◽  
Urban Heat Island ◽  
Co2 Emissions ◽  
Heat Island ◽  
Sensible Heat ◽  
Heating Season ◽  
Urban Heat ◽  
Cooling Effects

Urban air temperature rises induced by the urban heat island (UHIE) effect or by global warming (GW) can be beneficial in winter but detrimental in summer. The SCIENCE-Outdoor model was used to simulate changes to sensible heat release and CO2 emissions from buildings yielded by four UHIE countermeasures and five GW countermeasures. This model can evaluate the thermal condition of building envelope surfaces, both inside and outside. The results showed that water-consuming UHIE countermeasures such as evaporative space cooling and roof water showering provided positive effects (decreasing sensible heat release and CO2 emissions related to space conditioning) in summer. Additionally, they had no negative (unwanted cooling) effects in winter since they can be turned off in the heating season. Roof greening can provide the greatest space- conditioning CO2 emissions reductions among four UHIE countermeasures, and it reduces the amount of heat release slightly in the heating season. Since the effect on reducing carbon dioxide (CO2) emissions by UHIE countermeasures is not very significant, it is desirable to introduce GW countermeasures in order to reduce CO2 emissions. The significance of this study is that it constructed the new simulation model SCIENCE-Outdoor and applied it to show the influence of countermeasures upon both heat release and CO2 emissions.

Laser Ignition of Surgical Drape Materials in Air, 50% Oxygen, and 95% Oxygen

2004 ◽  
Vol 100 (5) ◽  
pp. 1167-1171 ◽  
Author(s):  
Gerald L. Wolf ◽  
George W. Sidebotham ◽  
Jackson L. P. Lazard ◽  
Jean G. Charchaflieh
Keyword(s):  
Carbon Dioxide ◽  
Operating Room ◽  
Oxygen Concentration ◽  
High Energy ◽  
Ignition Source ◽  
Laser Ignition ◽  
Surgical Tools ◽  
Time To Ignition ◽  
Room Fires ◽  
Surgical Laser

Background Operating room fires fueled by surgical drapes and ignited by high-energy surgical tools in air and oxygen-enriched atmospheres continue to occur. Methods The authors examined the time to ignition of huck towels and three commonly used surgical drape materials in air, 50% oxygen, and 95% oxygen using a carbon dioxide surgical laser as an ignition source. In addition, a phenol-polymer fabric was tested. Results In air, polypropylene and phenol polymer do not ignite. For polypropylene, the laser instantly vaporized a hole, and therefore, interaction between the laser and material ceased. When tested in combination with another material, the polypropylene time to ignition assumed the behavior of the material with which it was combined. For phenol polymer, the laser did not penetrate the material. Huck towels, cotton-polyester, and non-woven cellulose-polyester ignited in air with decreasing times to ignition. All tested materials ignited in 50% and 95% oxygen. Conclusion The results of this study reveal that with increasing oxygen concentration, the time to ignition becomes shorter, and the consequences become more severe. The possibility exists for manufacturers to develop drape materials that are safer than existing materials.

Noise Reduction During Acoustic Monitoring of Laser Welding of High-Strength Steels

2009 ◽  
Author(s):  
Wei Huang ◽  
Radovan Kovacevic
Keyword(s):  
Laser Welding ◽  
Noise Reduction ◽  
Acoustic Signal ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Weld Penetration ◽  
Acoustic Signatures ◽  
Reduction Methods ◽  
Laser Welding Process

During the laser welding process of high-strength steels, different defects, such as a partial weld penetration, spatters, and blow-through holes could be present. In order to detect the presence of defects and achieve a quality control, acoustic monitoring based on microphones is applied to the welding process. As an effective sensor to monitor the laser welding process, however, the microphone is greatly limited by intensive noise existing in the complex industrial environment. In this paper, in order to acquire a clean acoustic signal from the laser welding process, two noise reduction methods are proposed: one is the spectral subtraction method based on one microphone and the other one is the beamforming based on a microphone array. By applying these two noise reduction methods, the quality of the acoustic signal is enhanced, and the acoustic signatures are extracted both in the time domain and frequency domain. The analysis results show that the extracted acoustic signatures can well indicate the different weld penetration states and they can also be used to study the internal mechanisms of the laser-material interaction.

scholarly journals Intra-Cage Air Change Rate on Forced-Air-Ventilated Micro-Isolation System-Environment within Cages: Carbon Dioxide and Oxygen Concentration.

1997 ◽  
Vol 46 (4) ◽  
pp. 251-257 ◽  
Author(s):  
Masakazu HASEGAWA ◽  
Yuzuru KURABAYASHI ◽  
Toshinori ISHII ◽  
Kazuya YOSHIDA ◽  
Nobukazu UEBAYASHI ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Concentration ◽  
Isolation System ◽  
Change Rate ◽  
System Environment ◽  
Air Change Rate ◽  
Forced Air

Effects of Ambient Temperature and Oxygen Concentration on Soot Evolution in Diesel Spray Combustion

Volume 4 ◽  
2004 ◽  
Author(s):  
Yi Xu ◽  
Chia-Fon F. Lee
Keyword(s):  
Ambient Temperature ◽  
Heat Release ◽  
Oxygen Concentration ◽  
Heat Release Rate ◽  
Release Rate ◽  
Soot Formation ◽  
Premixed Combustion ◽  
Ambient Oxygen ◽  
Lower Heat ◽  
Soot Measurement

A newly developed Forward Illumination Light Extinction (FILE) soot measurement technique was applied in a constant volume spray chamber to study the effects of ambient temperature and oxygen concentration on soot evolution in diesel combustion. The FILE technique with the capability of two-dimensional time-resolved quantitative soot measurement provides the much-needed information to investigate the soot formation mechanism. The ambient temperatures of 1200K, 1000K and 800K were tested to study the temperature effects on soot formation. A decrease of ambient temperature results in a longer ignition delay, which promotes a larger premixed combustion zone combining with higher heat release rates. The change of ambient temperature from 1200K to 800K increases the fuel portion burnt in the premixed combustion period. At 800K, combustion is dominated by the premixed combustion and much less soot is formed. Diesel combustion with 21% and 15% ambient oxygen concentration was also studied. With lower ambient oxygen concentration, the combustion process is basically not changed, but expands into a longer time span with a lower heat release rate. The lower heat release rate results in a lower flame temperature, which benefits the NOx emission control. However, with about the same amount of soot within the flame, and much longer soot life, soot has more chance to escape to the exhaust.

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