NOx Sensitivities for Gas Turbine Engines Operated on Lean-Premixed Combustion and Conventional Diffusion Flames

Nicol, David G.; Malte, Philip C.; Lai, Jenkin; Marinov, Nick N.; Pratt, David T.; Corr, Robert A.

doi:10.1115/92-gt-115

Cited by 17 publications

(16 citation statements)

References 13 publications

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“…(Leonard and Correa also conducted experiments for lower pressures and mixture inlet temperatures. Those results were modeled previously by the present authors [4].) The length of the burner, i.e., the distance from the porous-plate to the sampling point, is 11.4cm, and the burner diameter is 5cm.…”

Section: Experimental Conditionssupporting

confidence: 69%

“…Combustion stabilization is then accomplished by including one or more recycle zones, by which hot, burnt gases are brought forward to the initial plug-flow reactor stage. In a previous study of leanpremixed combustion for gas turbine engines [4], this variation was found to cause little change in the NOx compared to that predicted by the baseline model, and thus, is not reconsidered herein.…”

Section: Chemical Reactor Modelmentioning

confidence: 98%

“…Reaction (9), with rate data as estimated in [2], has been added to the DB mechanism; and the pressure sensitivities of reaction (4) and the CH4 dissociation reaction have been extended from 20 to 35atm. The rate data selected for reaction (12) are from [4], since these have been found to give the best overall agreement between the model results and the jet-stirred reactor and porous-plate datasets considered. The DB kinetic mechanism, which was developed from verification of laminar, premixed flame data taken at the burner surface, shows an enhanced importance of the prompt NOx pathway [1].…”

Section: The Chemical Kinetic Mechanismsmentioning

confidence: 99%

“…These cases have been selected for modeling because of the extensive database of [8] at 1.8ms (and the use of [8] for kinetic mechanism development [5]), and the accurate temperatures of [9]. (In [4], comparison of the all of measurements shown in Figure 2 to the model with the DB mechanism was conducted. )…”

Section: Nox Pathwaysmentioning

confidence: 99%

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The Importance of the Nitrous Oxide Pathway to NOx in Lean-Premixed Combustion

et al. 1993

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This study addresses the importance of the different chemical pathways responsible for NOx formation in lean-premixed combustion, and especially the role of the nitrous oxide pathway relative to the traditional Zeldovich pathway. NOx formation is modeled and computed over a range of operating conditions for the lean-premixed primary zone of gas turbine engine combustors. The primary zone, of uniform fuel-air ratio, is modeled as a micro-mixed well-stirred reactor, representing the flame zone, followed by a series of plug flow reactors, representing the post-flame zone. The fuel is methane. The fuel-air equivalence ratio is varied from 0.5 to 0.7. The chemical reactor model permits study of the three pathways by which NOx forms, which are the Zeldovich, nitrous oxide, and prompt pathways. Modeling is also performed for the well-stirred reactor alone. Three recently published, complete chemical kinetic mechanisms for the C1-C2 hydrocarbon oxidation and the NOx formation are applied and compared. Verification of the model is based on the comparison of its NOx output to experimental results published for atmospheric pressure jet-stirred reactors and for a ten atmosphere porous-plate burner. Good agreement between the modeled results and the measurements is obtained for most of the jet-stirred reactor operating range. For the porous-plate burner, the model shows agreement to the NOx measurements within a factor of two, with close agreement occurring at the leanest and coolest cases examined. For lean-premixed combustion at gas turbine engine conditions, the nitrous oxide pathway is found to be important, though the Zeldovich pathway cannot be neglected. The prompt pathway, however, contributes small-to-negligible NOx. Whenever the NOx emission is in the 15 to 30ppmv (15% O2, dry) range, the nitrous oxide pathway is predicted to contribute 40 to 45% of the NOx for high pressure engines (30atm), and 20 to 35% of the NOx for intermediate pressure engines (10atm). For conditions producing NOx of less than 10ppmv (15% O2, dry), the nitrous oxide contribution increases steeply and approaches 100%. For lean-premixed combustion in the atmospheric pressure jet-stirred reactors, different behavior is found. All three pathways contribute; none can be dismissed. No universal behavior is found for the pressure dependence of the NOx. It does appear, however, that lean-premixed combustors operated in the vicinity of 10atm have a relatively weak pressure dependence, whereas combustors operated in the vicinity of 30atm have an approximately square root pressure dependence of the NOx.

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Section: Experimental Conditionssupporting

confidence: 69%

Section: Chemical Reactor Modelmentioning

confidence: 98%

Section: The Chemical Kinetic Mechanismsmentioning

confidence: 99%

Section: Nox Pathwaysmentioning

confidence: 99%

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The Importance of the Nitrous Oxide Pathway to NOx in Lean-Premixed Combustion

et al. 1993

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“…6) the slightly lower calculated NO level results rather from too low formation rates worked out by the Miller-Bowman reaction mechanism than from a non-ideal PFR flow. A similar observation was made by Nicol et al (1992), who noticed an underprediction of NO for temperatures below 1800 IC by actual kinetic mechanisms.…”

Section: Nitrogen Free Fuelssupporting

confidence: 83%

NOx Emission Characteristics of a Catalytic Combustor Under High-Temperature Conditions

Valk

Vortmeyer

Kappler

1995

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

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A catalytic combustor concept with short catalyst segments and a thermal reactor is investigated with regard to NO, production of this concept under high-temperature conditions. The maximum combustor exit temperature was more than 1800 K with catalyst temperatures below 1300 K. For combustion of iso-octane, NO emissions of 4 ppm (day. 15% 02) at a flame temperature of 1800 K were measured. No significant influence of catalyst length, reference velocity and overall residence time on NO" emissions was observed.Additionally, the test combustor was fuelled with commercial diesel and kerosene (Jet-A). In this case, NO emissions were noticeable higher due to fuel-bound nitrogen. The emissions measured were for diesel, 12 ppm, and for kerosene, 7 ppm, (each dry, 15% 02), again at a flame temperature of 1800 K. To evaluate the conversion ratio of fuel-bound nitrogen to NO,, isooctane was doped with various amounts of ammonia and metyhlamine. The conversion rates were 70 to 90%, with a slight tendency to lower values (50%) for nitrogen mass fractions above 0.1%.Considering the NO emission level of actual premix burners, the lower emission value of the presented catalytic combustor results from a perfect premixed plug-flow combustion system incorporating a catalyst herein and not from a specific advantage of the principle of catalytic combustion itself. Again similar to a premix-combustor are the NO emission characteristics in the case of lean combustion of nitrogen bound fuels, which yield very high conversion rates.

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