On the Formation of Nitrogen Oxides During the Combustion of ...

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2 Combustion Theory 0.0004 GRI 3.0 GRI 2.11 n-Decane (Princeton) + NO x (Li) n-Decane (Princeton) + NO x (Leeds) n-Decane (Aachen) + NO x (Li) Mass fraction of NO YNO 0.0003 0.0002 0.0001 0.0000 0.000 0.004 0.008 0.012 0.016 0.020 m Spatial coordinate x Figure 2.13: Mass Fraction of Nitric Oxide over Counterflow Diffusion Flame of Methane (chosen as an example). The results were obtained from different kinetics [298]. The combination “n-Decane (Aachen) + NO x (Li)” overestimates NO formation. Since the reference mechanisms differ widely, no straightforward recommendation is possible for the optimum combination of mechanisms, based on simulations conducted for counterflow diffusion flames. However, the combination “n-Decane (Princeton) + NO x (Li)” converges best. Its results are comparable to those of the GRI 3.0 mechanism for hydrocarbon fuels. The combination “n-Decane (Princeton) + NO x (Leeds)” gives slightly lower results. Compatibility of Attached NO x Kinetics with the Main Hydrocarbon Mechanism In addition to NO x production sensitivity, the influence of the NO x kinetics attached to the main hydrocarbon mechanism was investigated simulating laminar premixed and counterflow diffusion flames. This was done by com- 52
2.3 Kinetic Modeling paring the combined mechanisms with the original C 10 H 22 mechanisms, with the latter acting as reference in terms of Equations (2.26) and (2.27). The difference (i.e. the relative error) was studied for temperature, velocity, fuel mass fraction, and product species [298]. Laminar premixed flames were calculated at an equivalence ratio of φ = 0.6 to 1.4 in steps of 0.1. Laminar flame speed S L obtained with the Princeton C 10 H 22 mechanism decreases by up to 0.4 % under near-stoichiometric conditions and up to 1% at both φ= 0.6 and 1.4 as a consequence of adding the NO x chemistry of Li and Williams [250] or the Leeds NO x kinetics [186]. Flame speeds estimated with the combination “n-Decane (Aachen) + NO x (Li)” lie 0.3% below the original Aachen mechanism. By comparison, laminar flame speed is similar for the Princeton and Aachen mechanism at φ = 0.7, but the difference goes up to almost 30% at an equivalence ratio of φ = 1.4 (cf. Fig. 2.6). Relative differences ǫ m (Eqs. (2.26) and (2.27)) were evaluated to analyze the deviation in mass fraction Y between the combined and the original C 10 H 22 mechanisms. The mass fractions Y of C 10 H 22 , H 2 O, CO 2 , and CO were studied in detail. Various calculations showed that neither fuel nor the NO x mechanism has a significant influence on the absolute values of ǫ m . The values were generally very small for ǫ m,abs and ǫ m,tot : The profile of the fuel C 10 H 22 was modified by less than 0.4 %. The H 2 O fraction decreased by around 0.15 %, while the CO 2 profile increased by 0.3 %. The formation of CO was reduced by up to 4% under lean conditions, but the difference remained negligible for stoichiometric and rich conditions. Furthermore, the mass fractions Y of OH and CH x and the relevant radical pool for NO x formation were compared for both the original and combined mechanisms. The relative differences ǫ m of these NO x precursor species were consistently below 1%. Counterflow diffusion flames performed in a similar manner to laminar premixed flames, employing the mechanisms investigated. There was a comparable agreement between the unmodified/original mechanism and combined C 10 H 22 /NO x chemistry. The maximum relative difference ǫ m was 0.5 % for the Princeton C 10 H 22 kinetics considering temperature, axial velocity, spreading rate, and mass fractions of C 10 H 22 , O 2 , H 2 O, CO 2 , and CO. The respective value for the Aachen C 10 H 22 mechanism was 0.8 %. 53
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TECHNISCHE UNIVERSITÄT MÜNCHEN In
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Vorwort Die vorliegende Arbeit ents
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Kurzfassung Die vorliegende Arbeit
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Contents List of Figures List of Ta
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CONTENTS 5 Results 155 5.1 Droplets
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LIST OF FIGURES xiv 3.3 Droplet Arr
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LIST OF FIGURES 5.19 Progression of
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LIST OF TABLES C.2 Overview of Tele
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NOMENCLATURE g Gravitational force
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NOMENCLATURE σ S Surface tension N
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NOMENCLATURE () T Thermal, temperat
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NOMENCLATURE PAL PAN PDU PFA PFC PH
Page 28 and 29: 1 Introduction In thermal engines t
Page 30 and 31: 1 Introduction 1.3 Oxides of Nitrog
Page 32 and 33: 1 Introduction residence time of th
Page 34 and 35: 1 Introduction Chapter 3 describes
Page 36 and 37: 2 Combustion Theory 2.1.1 Premixed
Page 38 and 39: 2 Combustion Theory molecules by ea
Page 40 and 41: 2 Combustion Theory four types. Out
Page 42 and 43: 2 Combustion Theory ventional combu
Page 44 and 45: 2 Combustion Theory of partial pre-
Page 46 and 47: 2 Combustion Theory Formation of Fu
Page 48 and 49: 2 Combustion Theory Moreover, exper
Page 50 and 51: 2 Combustion Theory For the gas pha
Page 52 and 53: 2 Combustion Theory combustion, ext
Page 54 and 55: 2 Combustion Theory termed “natur
Page 56 and 57: 2 Combustion Theory thin layer of u
Page 58 and 59: 2 Combustion Theory nor generally c
Page 60 and 61: 2 Combustion Theory is assumed to o
Page 62 and 63: 2 Combustion Theory before it follo
Page 64 and 65: 2 Combustion Theory position, which
Page 66 and 67: 2 Combustion Theory 2.3 Kinetic Mod
Page 68 and 69: 2 Combustion Theory 1.2 m s −1 La
Page 70 and 71: 2 Combustion Theory Mole fraction o
Page 72 and 73: 2 Combustion Theory Reburn Miller a
Page 74 and 75: 2 Combustion Theory The results of
Page 76 and 77: 2 Combustion Theory Temperature T 3
Page 80 and 81: 2 Combustion Theory In conclusion,
Page 83 and 84: 3 Experiments on Droplet Array Comb
Page 85 and 86: 3.1 Droplet Combustion Facility and
Page 87 and 88: 3.1 Droplet Combustion Facility C D
Page 89 and 90: 3.1 Droplet Combustion Facility ous
Page 91 and 92: 3.1 Droplet Combustion Facility for
Page 93 and 94: 3.1 Droplet Combustion Facility par
Page 95 and 96: 3.1 Droplet Combustion Facility The
Page 97 and 98: 3.1 Droplet Combustion Facility a c
Page 99 and 100: 3.1 Droplet Combustion Facility •
Page 101 and 102: 3.1 Droplet Combustion Facility Tab
Page 103 and 104: 3.1 Droplet Combustion Facility Fig
Page 105 and 106: 3.2 Measurement Techniques and Data
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3.2 Measurement Techniques and Data
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3.3 Numerical Study of the Fluid Dy
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4 Numerical Modeling and Simulation
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4.2 Basics for Numerical Modeling 4
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4.2 Basics for Numerical Modeling 4
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4.2 Basics for Numerical Modeling n
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4.2 Basics for Numerical Modeling P
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4.2 Basics for Numerical Modeling E
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4.3 Modeling of Ignition In the end
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4.3 Modeling of Ignition 10 W Time
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4.3 Modeling of Ignition Hence, the
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4.4 Modeling of Nitrogen Oxide Form
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4.5 Simulation of Single Droplets t
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4.5 Simulation of Single Droplets e
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4.6 Model Validation with index i
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4.6 Model Validation utilized model
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4.6 Model Validation Figure 4.7 dep
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4.6 Model Validation 340 K Ambient
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4.6 Model Validation Table 4.1: Val
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4.7 Scope and Limitations of Single
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4.7 Scope and Limitations of Single
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5 Results In total, it includes 99
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5 Results atmosphere of Figure 5.1
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5 Results 32 g kg −1 2400 K Emiss
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5 Results 4.0 g kg −1 Emission in
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5 Results uses constant spatial pos
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5 Results 16 g kg −1 Emission ind
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5 Results Maximum temperature Tmax
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5 Results Even though the parameter
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5 Results Flame stand-off ratio ζ
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5 Results 5.2.3 Comparison with Mic
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5 Results 0.50 5000 ppm Emission in
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5 Results Ψ = 0.1695 (t Ψ = 5 s):
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5 Results 6.0 g kg −1 Emission in
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5 Results combustion in exhaust gas
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5 Results Flame stand-off ratio ζ
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5 Results D 0 being varied between
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5 Results 0.40 g kg −1 Initial dr
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5 Results A twofold trend was obser
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5 Results 5.6 Recommendations and F
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6 Summary and Conclusions In times
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APPENDIX
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A Chemical Mechanisms The earliest
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A Chemical Mechanisms only deduced
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A Chemical Mechanisms Another, very
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A Chemical Mechanisms the reactions
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B Investigated Conditions There are
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B Investigated Conditions Table B.1
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B Investigated Conditions high mech
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C Design Details of Experiment Equi
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D Raw Data of Microgravity Experime
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SUPERVISED THESES Student Sebastian
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References [1] J.A. Aardenne van, G
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