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Combustion of normal and low calorific fuels in high temperature and oxygen deficient environment
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2006 (English)In: Combustion Science and Technology, ISSN 0010-2202, E-ISSN 1563-521X, Vol. 178, no 7, 1345-1372 p.Article in journal (Refereed) Published
Abstract [en]

Combustion characteristics of two different gaseous fuels (a low calorific value fuel and methane fuel) have been examined using high temperature and low oxygen concentration combustion air. The momentum flux ratio between the fuel jet and the combustion airflow was kept constant to provide similarity in mixing between the different experimental cases to understand the role of fuel jet property on combustion. Direct flame photography, 2-D Particle image velocimetry (PIV), Light Emission Spectroscopy and chemiluminescent NOX analyzer was used as the diagnostics. These diagnostics allowed information on global flame features, mean and rms components of axial and radial velocity, axial strain rates and vorticity, the spatial distribution of combustion intermediate species, such as, OH and CH, and overall NOX emission levels. The results indicate a slower mixing during high temperature air combustion with low calorific value fuel as compared to methane fuel. The results showed higher turbulence levels and higher axial strain rates for low calorific fuel jets as compared to methane fuel jet during the high temperature air combustion condition. This results in less intense (or mild) combustion conditions with the result of increased flame length and volume and lower NOX emissions. Even for the normal methane fuel high temperature and oxygen deficient combustion conditions provided lower NOX emission. Furthermore, the high temperatures obtained for methane combustion provided lower vorticity and axial strain rates than the low calorific value fuel due to the suppression of vortical structure formation from the stronger heat release. In the case of low calorific value fuel, higher fuel jet velocity into low-density high temperature air leads to longer jet length. This jet causes a local stagnation to the upstream cross-flow to create local higher value of turbulence levels immediately upstream of the jet. The spatial distribution of the flame generated radicals (OH and CH) revealed significant ignition delay of the LCV fuel jet and a far more uniform distribution of the intermediate species. The methane fuel jet showed a prolonged reaction zone and faster ignition at high temperature and oxygen deficient conditions when compared to normal temperature air combustion of methane.

Place, publisher, year, edition, pages
2006. Vol. 178, no 7, 1345-1372 p.
Keyword [en]
flow field; high temperature air combustion; combustion; low calorific value fuel; NOX emission
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5117DOI: 10.1080/00102200500325280ISI: 000237425300008Scopus ID: 2-s2.0-33646758546OAI: oai:DiVA.org:kth-5117DiVA: diva2:7896
Note
QC 20100610Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Study of gas fuel jet burning in low oxygen content and high temperature oxidizer
Open this publication in new window or tab >>Study of gas fuel jet burning in low oxygen content and high temperature oxidizer
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

During the past decade, new advanced combustion systems that share the same basic concept of using a substantially diluted and high-temperature oxidizer in the reaction volume have gained a great deal of interest regarding their application in industrial and power systems. These novel combustion technologies have proved to offer significant benefits compared to traditional combustion techniques. These benefits include reductions in pollutant emissions and energy consumption, as well as a higher and more uniformly distributed heat flux. This entails the potential to, for example, reduce the size of equipment in industrial units or increase production rates while fuel consumption and the subsequent CO2 emissions are decreased or maintained at the same level.

Although the development of these new combustion technologies has occurred fairly recently, it has gained worldwide recognition. During the past few years the technique has been used commercially with several different types of burners. Despite its widespread use, the basic understanding of the chemical-physical phenomena involved is limited, and a better understanding of the combustion phenomena is required for more effective utilization of the technology.

The objectives of this work have been to obtain fuel-jet characteristics in combustion under high-temperature, low-oxygen conditions and to develop some theoretical considerations of the phenomena. The effect of the preheat temperature of the combustion air, combustion stoichiometry and the fuel-jet calorific value on flame behavior was investigated. Temperature and heat-flux distribution were also studied using a semi-industrial test furnace to see if similar flame features would be found for the small- and large-scale experiments.

Particle Image Velocimetry (PIV) was used for the first time to obtain information on the flow dynamics of a fuel jet injected into a crossflow of oxidizer at either a normal temperature or a very high temperature. Light emission spectroscopy was used to collect information on time-averaged radical distributions in the combustion jet.

Jet turbulence, time-averaged velocity distribution, fuel-jet mixing, the distribution of radicals such as CH, OH and C2, and flame photographs were investigated. The results showed delayed mixing and combustion under high-temperature low-oxygen-concentration conditions. The combustion air preheat temperature and oxygen concentration were found to have a significant effect on the burning fuel-jet behavior. The results of the semi-industrial-scale tests also showed the features of even flame temperature and heat flux.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xx, 94 p.
Keyword
Materials science, combustion, entrainment, jet in crossflow, PIV, ICCD, Materialvetenskap
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-204 (URN)91-7178-043-2 (ISBN)
Public defence
2005-05-27, D3, KTH, Lindstedtsvägen 5, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100610Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2011-11-10Bibliographically approved

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