Nitric Oxide Formation Analysis Using Chemical Reactor Modelling and Laser Induced Fluorescence Measurements on Industrial Swirl Flames PDF Download
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Author: Syed Mashruk
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Languages : en
Pages :
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Author: Syed Mashruk
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721932672
Category :
Languages : en
Pages : 286
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Laser-induced fluorescence (LIF) measurements of NO concentration in a variety of CH4/O2/N2 flames are used to evaluate the chemical kinetics of NO formation. The analysis begins with previous measurements in flat, laminar, premixed CH4/O2/N2 flames stabilized on a water-cooled McKenna burner at pressures ranging from 1 to 14.6 atm, equivalence ratios from 0.5 to 1.6, and volumetric nitrogen/oxygen dilution ratios of 2.2, 3.1 and 3.76. These measured results are compared to predictions to determine the capabilities and limitations of the comprehensive kinetic mechanism developed by the Gas Research Institute (GRI), version 2.11. The model is shown to predict well the qualitative trends of NO formation in lean-premixed flames, while quantitatively underpredicting NO concentration by 30-50%. For rich flames, the model is unable to even qualitatively match the experimental results. These flames were found to be limited by low temperatures and an inability to separate the flame from the burner surface. In response to these limitations, a counterflow burner was designed for use in opposed premixed flame studies. A new LIF calibration technique was developed and applied to obtain quantitative measurements of NO concentration in laminar, counterflow premixed, CH4/O2/N2 flames at pressures ranging from 1 to 5.1 atm, equivalence ratios of 0.6 to 1.5, and an N2/O2 dilution ratio of 3.76. The counterflow premixed flame measurements are combined with measurements in burner-stabilized premixed flames and counterflow diffusion flames to build a comprehensive database for analysis of the GRI kinetic mechanism. Pathways, quantitative reaction path and sensitivity analyses are applied to the GRI mechanism for these flame conditions. The prompt NO mechanism is found to severely underpredict the amount of NO formed in rich premixed and nitrogen-diluted diffusion flames. This underprediction is traced to uncertainties in the CH kinetics as well as in the nitrogen oxidation chemistry. S
Author:
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Category :
Languages : en
Pages : 290
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Author:
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Category :
Languages : en
Pages : 5
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In this paper we study the formation of NO in laminar, nitrogen diluted methane diffusion flames that are seeded with ammonia in the fuel stream. We have performed numerical simulations with detailed chemistry as well as laser-induced fluorescence imaging measurements for a range of ammonia injection rates. For comparison with the experimental data, synthetic LIF images are calculated based on the numerical data accounting for temperature and fluorescence quenching effects. We demonstrate good agreement between measurements and computations. The LIF corrections inferred from the simulation are then used to calculate absolute NO mole fractions from the measured signal. The NO formation in both doped and undoped flames occurs in the flame sheet. In the undoped flame, four different mechanisms including thermal and prompt NO appear to contribute to NO formation. As the NH3 seeding level increases, fuel-NO becomes the dominant mechanism and N2 shifts from being a net reactant to being a net product. Nitric oxide in the undoped flame as well as in the core region of the doped flames are underpredicted by the model; we attribute this mainly to inaccuracies in the NO recycling chemistry on the fuel-rich side of the flame sheet.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721936540
Category :
Languages : en
Pages : 216
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Lean direct-injection (LDI) spray flames offer the possibility of reducing NO(sub x) emissions from gas turbines by rapid mixing of the liquid fuel and air so as to drive the flame structure toward partially-premixed conditions. We consider the technical approaches required to utilize laser-induced fluorescence methods for quantitatively measuring NO concentrations in high-pressure LDI spray flames. In the progression from atmospheric to high-pressure measurements, the LIF method requires a shift from the saturated to the linear regime of fluorescence measurements. As such, we discuss quantitative, spatially resolved laser-saturated fluorescence (LSF), linear laser-induced fluorescence (LIF), and planar laser-induced fluorescence (PLIF) measurements of NO concentration in LDI spray flames. Spatially-resolved LIF measurements of NO concentration (ppm) are reported for preheated, LDI spray flames at pressures of two to five atmospheres. The spray is produced by a hollow-cone, pressure-atomized nozzle supplied with liquid heptane. NO is excited via the Q(sub 2)(26.5) transition of the gamma(0,0) band. Detection is performed in a two nanometer region centered on the gamma(0,1) band. A complete scheme is developed by which quantitative NO concentrations in high-pressure LDI spray flames can be measured by applying linear LIF. NO is doped into the reactants and convected through the flame with no apparent destruction, thus allowing a NO fluorescence calibration to be taken inside the flame environment. The in-situ calibration scheme is validated by comparisons to a reference flame. Quantitative NO profiles are presented and analyzed so as to better understand the operation of lean-direct injectors for gas turbine combustors. Moreover, parametric studies are provided for variations in pressure, air-preheat temperature, and equivalence ratio. Similar parametric studies are performed for lean, premixed-prevaporized flames to permit comparisons to those for LDI flames. Finall
Author:
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ISBN:
Category :
Languages : en
Pages : 218
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Author: Antonio Lipardi
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Category :
Languages : en
Pages :
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"Nitrogen oxides (NOx) are pollutants emitted by various combustion processes that are subject to increasingly-stringent regulations due to their impact on human health and the environment. Exhaust gas recirculation (EGR) has been shown to reduce NOx emissions by decreasing the oxygen concentration and, for a given heat release, reducing peak flame temperatures. Previous simulated combustion results (at a constant burning temperature) have demonstrated that EGR dilution may generate an NO minimization range governed by an increase in the prompt NO formation and a decrease in the thermal NO rate. However, this range is not predicted by all combustion models, thereby necessitating its experimental validation.This thesis conveys the constant burning temperature effects of EGR on NOx formation and the modelling performance of three thermochemical mechanisms (Gri-Mech 3.0, San-Diego 2005, and Combustion Science and Engineering). Using NO planar laser-induced fluorescence (NO-PLIF) and particle tracking velocimetry (PTV), constant burning temperature (1850K and 2000K) measurements of nitric oxide (NO-PLIF), temperature (NO-PLIF), and flame reactivity (PTV) were performed on methane-air flames with (and without) EGR dilution using a counterflow apparatus. These results confirmed the existence of the EGR-induced NO minimization range. However, this interesting engine design constraint was obscured by the high level of variability (factor of approx. 4) and uncertainty (up to 99%) found in the simulated NO profiles. A reduced set of reactions that may serve as a basis for the optimization process of the investigated NO submodels is also presented." --
Author:
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Category : Mechanics, Applied
Languages : en
Pages : 400
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Author:
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Category : Aeronautics
Languages : en
Pages : 492
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Author: James Joshua Driscoll
Publisher:
ISBN:
Category :
Languages : en
Pages : 266
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