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- Flame,
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chapter 5 turbulent diffusion flames - FedOA

The energy expended in vaporization of carbon is written in terms of heat of vaporization of carbon, ΔHv, molecular weight of solid carbon, M = 12 g/mol and rate of mass vaporization, dm/dt, obtained solving mass balance: dm dt 2 da 2 = 4πρs a = −4πa ρνU dt where ρs and ρv are the density of soot in vapor and solid phase respectively, Uv is the velocity with which the vapor leaves particles normally given by the relation of Langmuir: U v ⎛ RT = ⎜ ⎝ 2M in which Ts is the surface temperature of the particle, that for the simplification done is equal to that inner T, R is the universal gas constant and Mv is the molecular weight of carbon in vapor phase. The energy loss by blackbody radiation, the radiative transfer expression, is simply given by the Stefan-Boltzmann law: 40 s v ⎞ ⎟ ⎟ ⎠ 1 2 2 4 4 ( 4π a ) ( T − T ) Qb = εσ SB where σSB is the Stefan Boltzmann constant and ε is the soot emissivity that can be taken equal to the absorption coefficient Kabs. 0 ν

Solving the mass and energy balances we obtain the time dependant particle size, a(t) and temperature, T(t), for a particular choice of the excitation wavelength, λexc, flame temperature T0 and initial particle diameter, a0. Finally the LII signal must be calculated taking into consideration the density of primary particles, Np = N np, and the spectral bandwidth of detection, Δλ, around a central wavelength λ0: C1 ⎡ C2 ⎤ 2 ( λ0, t) = ⎢exp( − −1⎥ N 4πa ( t) ε ( t) Δλ λ0 ⎣ λ0T ( t) ⎦ 41 −1 LII p where C1 and C2 are the first and second Planck constant. By integrating the above equations Melton showed that the LII signal at the maximum temperature (dT/dt), also called “prompt LII”, is proportional to: x Pr omptLII ∝ Npdp where dp is the particle diameter and the exponent x is x= 3 + 154 nm/ λdet This simple finding and the easiness of the experimental set-up promoted the development of the LII technique as the major diagnostic tool for soot detection in practical combustion systems. Based on the Melton interpretations of the LII signal a great number of models have been developed to describe the heating and the cooling of the particles by solving the energy and mass balance equations for temperature and primary particle size. Differences and comparisons from the models are well reported in the review work of Schulz et al. [50], where a briefly description of the major models, nine in the work of Schulz, and their reference are given.

- Page 1 and 2: Università degli studi di Napoli
- Page 3 and 4: CONTENTS ABBREVIATIONS _5 INTRODUCT
- Page 5 and 6: ABBREVIATIONS LIF Laser Induced Flu
- Page 7 and 8: INTRODUCTION In the last thirty yea
- Page 9 and 10: Two fuels are prevalently tested an
- Page 11 and 12: the relative contribution of the di
- Page 13 and 14: 1.1 POLYCYCLIC AROMATIC HYDROCARBON
- Page 15 and 16: [8] and point out that these author
- Page 17 and 18: In particular the results obtained
- Page 19 and 20: ultraviolet could be considered soo
- Page 21 and 22: the first formed particles have a d
- Page 23 and 24: 1.3 SOOT FORMATION, GROWTH AND OXID
- Page 25 and 26: Gas Phase The gas-phase formation a
- Page 27 and 28: In summary the complete scheme is m
- Page 29 and 30: CHAPTER 2 COMBUSTION SYSTEMS AND EX
- Page 31 and 32: 2.2 LABORATORY COMBUSTION REACTORS
- Page 33 and 34: During the thesis an experimental i
- Page 35 and 36: small-scale structures are modeled.
- Page 37 and 38: 2.3 OPTICAL MEASUREMENTS In this pa
- Page 39: where the five terms represent in t
- Page 43 and 44: LII signals by integrating over the
- Page 45 and 46: signals strongly dependent on the v
- Page 47 and 48: Moreover, as reported by Brockhinke
- Page 49 and 50: 6π E( m) Kext = Kabs = λ Where is
- Page 51 and 52: With reference to the Fig. 2.9, whe
- Page 53 and 54: Finally, by combining these equatio
- Page 55 and 56: ange of electrical mobility exit wi
- Page 57 and 58: techniques and subsequently by Rola
- Page 59 and 60: CHAPTER 3 LAMINAR PREMIXED FLAMES T
- Page 61 and 62: LIF, cm -1 sr -1 LIF, cm -1 sr -1 1
- Page 63 and 64: LII, cm -1 sr -1 1.2E-07 1.0E-07 8.
- Page 65 and 66: The different temporal decay of the
- Page 67 and 68: 3.2 LAMINAR PREMIXED METHANE FLAMES
- Page 69 and 70: fv soot, ppm fv, ppm 0.25 0.2 0.15
- Page 71 and 72: Scattering coefficient, cm -1 sr -1
- Page 73 and 74: 30°C and the first stage is 3°C h
- Page 75 and 76: fluorescence peak in the near UV-vi
- Page 77 and 78: scattering coefficients measured in
- Page 79 and 80: According to the experimental resul
- Page 81 and 82: fluorescence signal, cm -1 sr -1 fl
- Page 83 and 84: incandescence signal, cm -1 sr -1 i
- Page 85 and 86: Therefore, as obtained in premixed
- Page 87 and 88: carbon particles decreases at incre
- Page 89 and 90: Size, nm 14 12 10 8 6 4 2 0 0 1 2 3
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CHAPTER 5 TURBULENT DIFFUSION FLAME

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Quite the same behavior is shown by

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particles over the fluorescence of

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NOC volume fraction, cm -3 /cm -3 4

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Size, nm 10 9 8 7 6 5 4 3 2 1 0 10

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CHAPTER 6 BURNERS FOR HOME APPLIACE

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which have more affinity with water

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techniques (estimated to be about 1

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OC, mg/Nm 3 OC, mg/Nm 3 OC, mg/Nm 3

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The experimental evidences allow us

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REFERENCES 1. H. Richter, J.B. Howa

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19. Bittner JD, Howard JB. Composit

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36. Sardar SB, Fine PM, Sioutas C,

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56. Bengtsson PE, Alden M, Soot-vis

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75. Cecere D, Sgro LA, Basile G, D'

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PUBBLICATIONS APPENDICIES 1) M. Com