Flame structure changes resulting from hydrogen-enrichment and pressurization for low-swirl premixed methane–air flames

Emadi, Majid; Karkow, Douglas; Salameh, T.; Gohil, Ameet; Ratner, Albert

doi:10.1016/j.ijhydene.2012.04.017

Cited by 72 publications

(18 citation statements)

References 22 publications

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“…Same trend was found for hydrogen enriched natural gas flames at atmospheric pressure by Schefer et al [6J. Also at elevated pres sures, the lean blowout limit is shifted toward leaner equivalence ratios [12,13], Hydrogen addition will also affect the flame struc ture. The higher reactivity and higher flame speed associated with flames having hydrogen components in the fuel makes the flame front thinner and makes also the flame to move more upstream compared to flames without hydrogen in the fuel.…”

Section: Introductionsupporting

confidence: 54%

Investigation of Hydrogen Enriched Natural Gas Flames in a SGT-700/800 Burner Using OH PLIF and Chemiluminescence Imaging

Lantz

Collin

Aldén

et al. 2014

Journal of Engineering for Gas Turbines and Power

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The effect o f hydrogen enrichment to natural gas flames was experimentally investigated at atmospheric pressure conditions using flame chemiluminescence imaging, planar laser-induced fluorescence of hydroxyl radicals (OH PLIF), and dynamic pressure moni toring. The experiments were petformed using a third generation dry low emission (DLE) burner used in both SGT-700 and SGT-800 industrial gas turbines from Siemens. The burner was mounted in an atmospheric combustion test rig at Siemens with optical access in the flame region. Four different hydrogen enriched natural gas flames were investi gated; 0 vol. %, 30 vol. %, 60 vol. %, and 80 vol. % of hydrogen. The results from flame chemiluminescence imaging and OH PLIF show that the size and shape of the flame was clearly affected by hydrogen addition. The flame becomes shorter and narrower when the amount of hydrogen is increased. For the 60 vol. % and 80 vol. % hydrogen flames the flame has moved upstream and the central recirculation zone that anchors the flame has moved upstream the burner exit. Furthermore, the position of the flame front fluctuated more for the full premixed flame with only natural gas as fuel than for the hydrogen enriched flames. Measurements of pressure drop over the burner show an increase with increased hydrogen in the natural gas despite same airflow thus confirming the observa tion that the flame front moves upstream toward the burner exit and thereby increasing the blockage of the exit. Dynamic pressure measurements in the combustion chamber wall confirms that small amounts of hydrogen in natural gas changes the amplitude of the dynamic pressure fluctuations and initially dampens the axial mode but at higher levels of hydrogen an enhancement of a transversal mode in the combustion chamber at higher frequencies could occur.

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Section: Introductionsupporting

confidence: 54%

Investigation of Hydrogen Enriched Natural Gas Flames in a SGT-700/800 Burner Using OH PLIF and Chemiluminescence Imaging

Lantz

Collin

Aldén

et al. 2014

Journal of Engineering for Gas Turbines and Power

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“…This is attrib uted to its high ignition temperature and low flame propagation speed with ensuing poor lean burning [1]. Consequently, addition of fuel such as hydrogen with low ignition energy, high burning velocity and high diffusivity [2,3] with a wider flammability range will improve the flame stability of methane under lean condition [4], In furtherance of the aforementioned, Emadi et al [5] has shown that the addition of 20% and 40% H2 to CH4 improves its blow off limit by about 7% and 35%, respectively, and stabilizes the flame in a wider range of equivalence ratio. Ilbas et al [6] reported that increasing the H2 percentage in H2-C H 4 mixture widened the flammability limits.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Effect of Hydrogen Enrichment of Methane on the Stability and Emission of Nonpremixed Swirl Stabilized Combustor

Sanusi

Habib

Mokheimer

2014

Journal of Energy Resources Technology

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An ultra lean mixture (0< O .5 ) o f methane-hydrogen-air was experimentally investi gated to explore the effect o f fuel flexibility on the flame stability and emission o f a non premixed swirl stabilized combustor. In order to isolate the effect o f hydrogen addition to methane, experiments were carried out at fixed fuel energy input to the combustor while increasing the hydrogen content from 0% up to 50% in the methane-hydrogen mixture on volume basis. The combustor fuel energy was then increased up to the range o f typical gas turbine combustors. Equivalence ratio sweep was carried out to determine the lean stability limit o f the combustor. Results show that the hydrogen c ontent in the fuel mixture and fuel energy input have a coupled effect on the combustor lean blow o ff velocity (LBV), temperature and emissions. The LBV increases by ~103% with the addition o f 30% H2. On the other hand, the LBV increases by ~20% as the fuel energy increases from 1.83MWIm3 to 2.75 MWIni3. Burning under ultra lean condition sen>es two pur poses. (I) The excess air supplied reduces the overall combustor temperature with its ensuing effect on low NOx formation. (2) It increases the overall combustor volume flow rate which reduces the residence time fo r NO, formation. The axial temperature profile presented along with the emission data can serve as basis fo r the validation o f numerical models. This would give more insight onto the effect o f hydrogen on the turbulence level and how it would improve the localized extinction o f methane in a cost-effective way.

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“…One of these candidate additive fuels is hydrogen. Hydrogen enrichment of fuel helps to broaden the flammability range and enables operation at lower equivalence ratios (Emadi et al, 2012). Since hydrogen increases the global reactivity and the mixture's resistance to the flow oscillations, it can improve combustion stability.…”

Section: Figure 12 Feedback Mechanism Responsible or Combustion Instmentioning

confidence: 99%

Flame structure and thermo-acoustic coupling for the low swirl burner for elevated pressure and syngas conditions

Emadi¹

Self Cite

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Reduction of the pollutant emissions is a challenge for the gas turbine industry. A solution to this problem is to employ the low swirl burner which can operate at lower equivalence ratios than a conventional swirl burner. However, flames in the lean regime of combustion are susceptible to flow perturbations and combustion instability. Combustion instability is the coupling between unsteady heat release and combustor acoustic modes where one amplifies the other in a feedback loop. The other method for significantly reducing NO x and CO 2 is increasing fuel reactivity, typically done through the addition of hydrogen. This helps to improve the flammability limit and also reduces the pollutants in products by decreasing thermal NO x and reducing CO 2 by displacing carbon. In this work, the flammability limits of a low swirl burner at various operating conditions, is studied and the effect of pressure, bulk velocity, burner shape and percent of hydrogen (added to the fuel) is investigated. Also, the flame structure for these test conditions is measured using OH planar laser induced fluorescence and assessed. Also, the OH PLIF data is used to calculate Rayleigh index maps and to construct averaged OH PLIF intensity fields at different acoustic excitation frequencies (45-155, and 195Hz). Based on the Rayleigh index maps, two different modes of coupling between the heat release and the pressure fluctuation were observed: the first mode, which occurs at 44Hz and 55Hz, shows coupling to the flame base (due to the bulk velocity) while the second mode shows coupling to the sides of the flame. In the first mode, the flame becomes wider and the flame base moves with the acoustic frequency. In the second mode, imposed pressure oscillations induce vortex shedding in the flame shear layer. These vortices distort the flame front and generate locally compact and sparse flame areas. The local flame structure resulting from these two distinct modes was markedly different.

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Flame structure changes resulting from hydrogen-enrichment and pressurization for low-swirl premixed methane–air flames

Cited by 72 publications

References 22 publications

Investigation of Hydrogen Enriched Natural Gas Flames in a SGT-700/800 Burner Using OH PLIF and Chemiluminescence Imaging

Investigation of Hydrogen Enriched Natural Gas Flames in a SGT-700/800 Burner Using OH PLIF and Chemiluminescence Imaging

Experimental Study on the Effect of Hydrogen Enrichment of Methane on the Stability and Emission of Nonpremixed Swirl Stabilized Combustor

Flame structure and thermo-acoustic coupling for the low swirl burner for elevated pressure and syngas conditions

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