Study of NO  emission characteristics in pressurized staged combustor concepts

Meisl, Jürgen; Koch, Rainer; Kneer, Reinhold; Wittig, Sigmar

doi:10.1016/s0082-0784(06)80742-3

Cited by 9 publications

(7 citation statements)

References 5 publications

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“…In one study, NO x emissionswere measuredfrom a model RQL combustoroperatingat variouspressuresand inlet temperatures,but only for a 20 roundhole quick-mixing section. 10 However, the results from this RQL study did emphasize that the optimization of the quick-mixing section was integral in lowering the total NO x emissions from the RQL combustor.…”

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confidence: 78%

Optimization of Jet Mixing into a Rich, Reacting Crossflow

Leong

Samuelsen

Holdeman

2000

Journal of Propulsion and Power

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Radial jet mixing of pure air into a fuel-rich, reacting cross ow con ned to a cylindrical geometry is addressed with a focus on establishing an optimal number of jet ori ces. Note that the optimum would not be expected to be universal. That is, the optimum mixer that one would identify will depend on both the momentum-ux ratio and an axial distance appropriate to the application.The number of round holes that most ef ciently mixes the jets with the mainstream ow, and thereby minimizes the residence time of near-stoichiometric and unreacted packets, was determined. Such a condition might reduce pollutant formation in axially staged, gas turbine combustor systems. Five different con gurations consisting of 8, 10, 12, 14, and 18 round holes are reported. An optimum number of jet ori ces is found for a jet to mainstream momentum-ux ratio J of 57 and a mass-ow ratio (MR) of 2.5. For this condition, the 14-ori ce case produces the lowest spatial unmixedness and the most uniformly distributed species concentration and temperature pro les at a plane located an axial distance equal to one duct diameter from the jet ori ce inlet. Note that this is the same con guration that would be identi ed from non-reacting experiments. Nomenclature d= ori ce axial length, or round hole diameter J = jet to mainstream momentum-ux ratio, (qV 2 ) jets / (qV 2 ) main MR = jet to mainstream mass-ow ratio, (qVA) jets / (qVA) main n = number of round holes in quick-mix module R = radius of the quick-mix module r = radial distance from the module center T = ow eld temperature T jet = average temperature of the jets T main = average mainstream temperature at a plane one duct radius upstream of the jets U s = spatial unmixedness V = velocity V ref = reference velocity de ned at nonreacting inlet conditions x = axial distance from the leading edge of the ori ces q = density u = equivalence ratio, (fuel/air) local /(fuel/air) stoichiometric Introduction VARIOUS systems, such as fuel injection and exhaust temperature control processes, rely on a rapid and thorough jet mixing with a cross ow of gas to mix streams of uid. Jet mixing in a cross ow, in fact, may play a fundamentalrole in the next generation of low-pollutant-emittingengines such as the rich-burn/quick-mix/ lean-burn (RQL) combustion concept. The success of this combustor over conventional gas turbine combustors in lowering pollutant production depends on the mixing section between the fuel-rich (u > 1) and fuel-lean (u < 1) stages of combustion. In this combustor design, the jets of air introduced through the quick-mixing section mix with the rich reacting cross ow as quickly as possible to bring the reaction to an overall lean equivalenceratio. The formation of various pollutants is driven by high temperaturesattained in near- stoichiometric reactions. Therefore, the strategy in this combustor design lies in minimizing the lifetime of, as well as preventing the formation of, near-stoichiometric uid packets. As passing through stoichiometric regions is inevitable, rapid mixing reduces ...

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confidence: 78%

Optimization of Jet Mixing into a Rich, Reacting Crossflow

Leong

Samuelsen

Holdeman

2000

Journal of Propulsion and Power

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“…The second source is the formation of thermal NO x that may occur in the Quick-mix section which increases significantly with pressure. The study by Meisl et al [33] also concluded that NO x emissions are minimized by optimal mixing.…”

Section: Reacting Jic Mixingmentioning

confidence: 96%

“…Experimental measurements under reacting conditions at elevated pressure were provided by Meisl et al [33]. The inlet air was preheated but the temperature was not varied, nor were the number of orifices in the mixing section varied.…”

Section: Reacting Jic Mixingmentioning

confidence: 99%

“…The authors of [33] noted the two wellknown sources for the emissions of NO x , namely promptand thermal-NO x . The first of these is the formation of NO in the fuel-rich primary zone [34], a contribution that Meisl et al [33] found was relatively insensitive to pressure. The second source is the formation of thermal NO x that may occur in the Quick-mix section which increases significantly with pressure.…”

Section: Reacting Jic Mixingmentioning

confidence: 99%

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Experimental and modeling investigation of the effect of air preheat on the formation of NOx in an RQL combustor

et al. 2012

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The Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept has been proposed to minimize the formation of oxides of nitrogen (NO x ) in gas turbine systems. The success of this low-NO x combustor strategy is dependent upon the links between the formation of NO x , inlet air preheat temperature, and the mixing of the jet air and fuel-rich streams. Chemical equilibrium and kinetics modeling calculations and experiments were performed to further understand NO x emissions in an RQL combustor. The results indicate that as the temperature at the inlet to the mixing zone increases (due to preheating and/or operating conditions) the fuel-rich zone equivalence ratio must be increased to achieve minimum NO x formation in the primary zone of the combustor. The chemical kinetics model illustrates that there is sufficient residence time to produce NO x at concentrations that agree well with the NO x measurements. Air preheat was found to have very little effect on mixing, but preheating the air did increase NO x emissions significantly. By understanding the mechanisms governing NO x formation and the temperature dependence of key reactions in the RQL combustor, a strategy can be devised to further reduce NO x emissions using the RQL concept. List of symbolsNumber of round holes in quick-mix module R Radius of the quick-mix module r Radial distance from the module center S Orifice spacing U Axial velocity U M Unmixed mainstream velocity V J Jet exit velocity x Downstream distance; x = 0 at orifice leading edge q J Density of jet flow q M Density of mainstream flow / Equivalence ratio = (fuel/air) actual /(fuel/air) stoichiometric

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“…The effect has been demonstrated with conventional hydrocarbon fuels by many researchers [1][2]. The authors have applied rich-lean combustion to a hydrogen gas turbine and shown its effect of NOx reduction in previous research [3][4].…”

Section: Introductionmentioning

confidence: 99%

NO reduction and NO2 emission characteristics in rich-lean combustion of hydrogen

Shudo

Omori²,

Hiyama

2008

International Journal of Hydrogen Energy

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Hydrogen is a clean alternative to conventional hydrocarbon fuels, but it is very important to reduce the nitrogen oxides (NOx) emissions generated by hydrogen combustion. The rich-lean combustion or staged combustion is known to reduce NOx emissions from continuous combustion burners such as gas turbines and boilers, and NOx reduction effects have been demonstrated for hydrocarbon fuels. The authors applied rich-lean combustion to a hydrogen gas turbine and showed its NOx reduction effect in previous research. The present study focused on experimental measurements of NO and NO 2 emissions from a co-axial rich-lean burner fueled with hydrogen. The results were compared with diffusion combustion and methane rich-lean combustion. Significant reductions in NO and NO 2 were achieved with rich-lean combustion. The NO and NO 2 reduction effects by rich-lean combustion relative to conventional diffusion combustion were higher with hydrogen than with methane.Keywords: Hydrogen, Rich-Lean Combustion, Staged Combustion, Nitrogen Oxides, Zel'dovich NO, Fenimore NO, prompt NO, NO 2 INTRODUCTIONHydrogen is considered an ideal alternative to conventional hydrocarbon fuels, because hydrogen can be produced from any kind of energy source and as it burns without emitting soot or carbon dioxide. Nitrogen oxides (NOx) are the only potential pollutants from hydrogen combustion, and it is crucial to reduce NOx emissions from hydrogen combustion.Rich-lean combustion or staged combustion is known as a technique to reduce NOx formation in continuous combustion burners such as gas turbines and boilers. The effect has been demonstrated with conventional hydrocarbon fuels by many researchers [1][2]. The authors have applied rich-lean combustion to a hydrogen gas turbine and shown its effect of NOx reduction in previous research [3][4]. The rich-lean combustion reduces the thermal NO, the Zel'dovich NO [5][6], which is the main part of combustion-generated NOx. At the same time, the prompt NO, Fenimore NO [7], is formed in hydrocarbon combustion especially under fuel-rich conditions. Though the amount of prompt NO is quite small for conventional premixed or diffusion combustion, it could become a significant portion of the total NO emissions from rich-lean combustion due to the largely decreased thermal NO and the existence of fuel-rich mixture. Also, the NOx emissions from combustion include NO 2 which is more harmful to human health than NO and also has a strong green house effect. The current paper analyzes the emission characteristics of NO and NO 2 from a coaxial rich-lean burner fueled with hydrogen. The results are compared with rich-lean combustion with methane.

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Study of NO emission characteristics in pressurized staged combustor concepts

Cited by 9 publications

References 5 publications

Optimization of Jet Mixing into a Rich, Reacting Crossflow

Optimization of Jet Mixing into a Rich, Reacting Crossflow

Experimental and modeling investigation of the effect of air preheat on the formation of NOx in an RQL combustor

NO reduction and NO2 emission characteristics in rich-lean combustion of hydrogen

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