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Sipkens TA, Menser J, Dreier T, Schulz C, Smallwood GJ, Daun KJ. Laser-induced incandescence for non-soot nanoparticles: recent trends and current challenges. APPLIED PHYSICS. B, LASERS AND OPTICS 2022; 128:72. [PMID: 35308124 DOI: 10.1007/s00340-006-2260-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 01/24/2022] [Indexed: 05/23/2023]
Abstract
Laser-induced incandescence (LII) is a widely used combustion diagnostic for in situ measurements of soot primary particle sizes and volume fractions in flames, exhaust gases, and the atmosphere. Increasingly, however, it is applied to characterize engineered nanomaterials, driven by the increasing industrial relevance of these materials and the fundamental scientific insights that may be obtained from these measurements. This review describes the state of the art as well as open research challenges and new opportunities that arise from LII measurements on non-soot nanoparticles. An overview of the basic LII model, along with statistical techniques for inferring quantities-of-interest and associated uncertainties is provided, with a review of the application of LII to various classes of materials, including elemental particles, oxide and nitride materials, and non-soot carbonaceous materials, and core-shell particles. The paper concludes with a discussion of combined and complementary diagnostics, and an outlook of future research.
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Affiliation(s)
- Timothy A Sipkens
- Metrology Research Centre, National Research Council Canada, Ottawa, K1K 2E1 Canada
| | - Jan Menser
- IVG, Institute for Combustion and Gas Dynamics - Reactive Fluids, and CENIDE, Center for Nanointegration Duisburg Essen, University of Duisburg-Essen, 47057 Duisburg, Germany
| | - Thomas Dreier
- IVG, Institute for Combustion and Gas Dynamics - Reactive Fluids, and CENIDE, Center for Nanointegration Duisburg Essen, University of Duisburg-Essen, 47057 Duisburg, Germany
| | - Christof Schulz
- IVG, Institute for Combustion and Gas Dynamics - Reactive Fluids, and CENIDE, Center for Nanointegration Duisburg Essen, University of Duisburg-Essen, 47057 Duisburg, Germany
| | - Gregory J Smallwood
- Metrology Research Centre, National Research Council Canada, Ottawa, K1K 2E1 Canada
| | - Kyle J Daun
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, N2L 3G1 Canada
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Analysis of the Influence of the Conduction Sub-Model Formulation on the Modeling of Laser-Induced Incandescence of Diesel Soot Aggregates. ENTROPY 2019; 22:e22010021. [PMID: 33285795 PMCID: PMC7516442 DOI: 10.3390/e22010021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 12/17/2019] [Accepted: 12/19/2019] [Indexed: 11/24/2022]
Abstract
Laser-induced incandescence (LII) is a powerful diagnostic technique allowing quantifying soot emissions in flames and at the exhaust of combustion systems. It can be advantageously coupled with modeling approaches to infer information on the physical properties of combustion-generated particles (including their size), which implies formulating and solving balance equations accounting for laser-excited soot heating and cooling processes. Properly estimating soot diameter by time-resolved LII (TiRe-LII), nevertheless, requires correctly evaluating the thermal accommodation coefficient αT driving the energy transferred by heat conduction between soot aggregates and their surroundings. To analyze such an aspect, an extensive set of LII signals has been acquired in a Diesel spray flame before being simulated using a refined model built upon expressions accounting for soot heating by absorption, annealing, and oxidation as well as cooling by radiation, sublimation, conduction, and thermionic emission. Within this framework, different conduction sub-models have been tested while a corrective factor allowing the particle aggregate properties to be taken into account has also been considered to simulate the so-called shielding effect. Using a fitting procedure coupling design of experiments and a genetic algorithm-based solver, the implemented model has been parameterized so as to obtain simulated data merging on a single curve with experimentally monitored ones. Eventually, values of the thermal accommodation coefficient have been estimated with each tested conduction sub-model while the influence of the aggregate size on the so-inferred αT has been analyzed.
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Sipkens TA, Hadwin PJ, Grauer SJ, Daun KJ. General error model for analysis of laser-induced incandescence signals. APPLIED OPTICS 2017; 56:8436-8445. [PMID: 29091624 DOI: 10.1364/ao.56.008436] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 09/17/2017] [Indexed: 06/07/2023]
Abstract
This paper presents a novel error model for TiRe-LII signals and illustrates how the model can be used to diagnose a detection system, quantify uncertainties in TiRe-LII, and characterize fluctuations in the measured process. Noise in a single TiRe-LII measurement shot obeys a Poisson-Gaussian noise model. Variation in the aerosol results in shot-to-shot fluctuations in the measured signals. These fluctuations induce a quadratic relationship between the mean and variance of a set of signals. We show how this model can elucidate aspects of the measurement system and fundamental properties of the aerosol, by comparing the noise model to four sets of experimental data.
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Fang J, Wang Y, Attoui M, Chadha TS, Ray JR, Wang WN, Jun YS, Biswas P. Measurement of Sub-2 nm Clusters of Pristine and Composite Metal Oxides during Nanomaterial Synthesis in Flame Aerosol Reactors. Anal Chem 2014; 86:7523-9. [DOI: 10.1021/ac5012816] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | - Michel Attoui
- University Paris
Est Creteil, University Paris-Diderot, LISA, UMR CNRS 7583, 94010 Créteil Cedex, France
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Sommer R, Leipertz A. Application of laser-induced incandescence to suspended carbon black particles. OPTICS LETTERS 2007; 32:1947-9. [PMID: 17603623 DOI: 10.1364/ol.32.001947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
For the first time, to the best of our knowledge, laser-induced incandescence (LII) has successfully been applied to carbon black suspensions. A linear correlation between the experimentally derived signal decay time and the mean primary particle size, determined by transmission electron microscopy, for different carbon black particles was found. Moreover, a nonlinear relation similar to that known from measurements of aerosols was observed for the peak LII signal and the laser fluence. Despite different heat transfer properties, the signal decay time was not influenced by the solvents used.
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Affiliation(s)
- Roland Sommer
- Lehrstuhl für Technische Thermodynamik, Universität Erlangen-Nürnberg, Am Weichselgarten 8, D-91058 Erlangen, Germany.
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Migliorini F, De Iuliis S, Cignoli F, Zizak G. Absorption correction of two-color laser-induced incandescence signals for soot volume fraction measurements. APPLIED OPTICS 2006. [PMID: 17068607 DOI: 10.1007/s00340-006-2210-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
A numerical iterative procedure is presented for the evaluation of the effect of signal absorption in two-color laser-induced incandescence measurements. The correction process is applied to our experimental data in an axisymmetric flame [Appl. Opt. 44, 7414 (2005)]. The influence of signal trapping on peak soot temperature and on soot volume fraction has been found to be minimal. Some numerical tests were performed to investigate the effects of soot concentration, flame size, and soot refractive index on the magnitude of the signal absorption correction.
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Affiliation(s)
- Francesca Migliorini
- Consiglio Nazionale delle Richerchee, Istituo per l'Energetica e le Interfasi, Milano, Italy
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De Iuliis S, Cignoli F, Zizak G. Two-color laser-induced incandescence (2C-LII) technique for absolute soot volume fraction measurements in flames. APPLIED OPTICS 2005; 44:7414-23. [PMID: 16353814 DOI: 10.1364/ao.44.007414] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A two-color version of the laser-induced incandescence (2C-LII) technique was implemented for measuring absolute soot volume fraction in flames. By using a calibrated tungsten ribbon lamp, soot peak temperatures were measured as a function of fluence at several locations in an ethylene diffusion flame by using a steeply edged laser beam profile. Above a certain fluence threshold, peak temperatures were tightly distributed just above 4000 K independent of the particle size and number density. Radial profiles of soot volume fraction were obtained and compared (not calibrated) with results from the laser extinction technique. Good agreement showed the validity of the 2C-LII technique at a controlled fluence.
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Affiliation(s)
- Silvana De Iuliis
- CNR-IENI, Istituto per l'Energetica e le Interfasi, Via Cozzi 53, 20125 Milano, Italy
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Murakami Y, Sugatani T, Nosaka Y. Laser-Induced Incandescence Study on the Metal Aerosol Particles as the Effect of the Surrounding Gas Medium. J Phys Chem A 2005; 109:8994-9000. [PMID: 16332003 DOI: 10.1021/jp058044n] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The fundamental heat transfer phenomena caused by the 1064 nm pulsed laser irradiations on the molybdenum aerosol particles were investigated by monitoring the time evolutions of the incandescence spectra using an ICCD detector with a multichannel spectrograph. The particle temperatures were evaluated from the incandescence spectra with the Planck function, and the cooling processes of the laser-heated particles were investigated. By measuring the decrease in the laser-heated particle temperatures with different surrounding media, the roles of the heat transfer processes such as vaporization, thermal radiation, and heat conduction to the surrounding media were discussed. The influences of the vaporization processes on the total heat transfer phenomena were investigated by monitoring the emissions of the constituent molybdenum atoms in the laser-induced incandescence spectra of the aerosol particles and also by investigating the relationships between the intensity of the incandescence and the fluence of the 1064 nm pulsed laser. The calculations using the theory of heat conduction suggested that the diameters of the particles produced by the photolysis of Mo(CO)6 depended on the nature of the surrounding gases.
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Affiliation(s)
- Yoshinori Murakami
- Department of Chemistry, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan.
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Mohr M, Lehmann U, Rütter J. Comparison of mass-based and non-mass-based particle measurement systems for ultra-low emissions from automotive sources. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2005; 39:2229-38. [PMID: 15871258 DOI: 10.1021/es049550d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Drastic reduction in particle emissions of diesel-powered vehicles and new findings on the health impact of particles raise the question of a more sensitive measurement procedure. In this paper, 16 different particle mass measurement systems are compared on a diesel heavy-duty engine equipped with a particle filter to investigate their feasibility for particle characterization for future ultra-low concentration levels. The group of instruments comprises mass-related methods (filter methods, laser-induced incandescence, photoacoustic detection, photoelectric charging, combined inertial and mobility sizing, opacity) as well as non-mass-related methods (CPC, diffusion battery, diffusion charger, ELPI, light scattering). The instruments are compared on the basis of repeatability, limit of detection, sensitivity, time resolution and correlation with the regulated gravimetric filter method, and elemental carbon fraction (EC). Several time-resolved methods show good performance and give reliable results. Opacimeters and light scattering, however, reveal shortcomings at these low concentrations. For all time-resolved advanced methods, poor correlation with the regulated filter method is observed, but most of them show good correlation with the EC fraction of the particles. This outcome demonstrates the crucial role of the sampling conditions for measurement methods that do not exclude volatile material from detection. A clear improvement in sensitivity is observed when non-mass-based instruments are applied (e.g., number or surface-related methods). The results reveal that reliable measurement methods exist for future measurement procedures. However, a change in the measurement method will lead to a discontinuity in the inventories, making it difficult to compare the particle emissions from future and past vehicle generations.
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Affiliation(s)
- Martin Mohr
- EMPA (Swiss Federal Laboratories for Materials Testing and Research), Ueberlandstrasse 129, CH-8600 Dübendorf, Switzerland.
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Sommer R, Dankers S, Leipertz A. Prozesskontrolle bei der Synthese nanoskaliger Partikel. CHEM-ING-TECH 2005. [DOI: 10.1002/cite.200500005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Seeger T, Egermann J, Dankers S, Beyrau F, Leipertz A. Comprehensive Characterization of a Sooting Laminar Methane-Diffusion Flame Using Different Laser Techniques. Chem Eng Technol 2004. [DOI: 10.1002/ceat.200407003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Egermann J, Seeger T, Leipertz A. Application of 266-nm and 355-nm Nd:YAG laser radiation for the investigation of fuel-rich sooting hydrocarbon flames by raman scattering. APPLIED OPTICS 2004; 43:5564-74. [PMID: 15508615 DOI: 10.1364/ao.43.005564] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We describe the use of linear Raman scattering for the investigation of fuel-rich sooting flames. In comparison, the frequency-tripled and -quadrupled fundamental wavelengths of a Nd:YAG laser have been used as an excitation source for study of the applicability of these laser wavelengths for analysis of sooting flames. The results obtained show that, for the investigation of strongly sooting flames, 266-nm excitation is better than 355-nm excitation. Although the entire fluorescence intensity of polycyclic aromatic hydrocarbons (PAHs) decreases with rising excitation wavelength, there is increased interference with the Raman signals by displacement of the spectral region of the Raman signals toward the fluorescence maximum of the laser-induced fluorescence emissions. Besides the broadband signals of PAHs, narrowband emissions of laser-produced C2 occur in the spectra of sooting flames and affect the Raman signals. These C2 emission bands are completely depolarized and can be separated by polarization-resolved detection. A comparison of the laser-induced fluorescence emissions of an ethylene flame with those of a methane flame shows the same spectral features, but the intensity of the emissions is larger by a factor of 5 for the ethylene fuel. Using 266-nm radiation for Raman signal excitation makes possible measurements in the ethylene flame also.
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Affiliation(s)
- Jan Egermann
- Lehrstuhl für Technische Thermodynamik, Universität Erlangen-Nürnberg, Am Weichselgarten 8, 91058 Erlangen, Germany.
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Michelsen HA, Witze PO, Kayes D, Hochgreb S. Time-resolved laser-induced incandescence of soot: the influence of experimental factors and microphysical mechanisms. APPLIED OPTICS 2003; 42:5577-5590. [PMID: 14526849 DOI: 10.1364/ao.42.005577] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present a data set for testing models of time-resolved laser-induced incandescence of soot. Measurements were made in a laminar ethene diffusion flame over a wide range of laser fluences at 532 nm. The laser was seeded to provide a smooth temporal profile, and the beam was spatially filtered and imaged into the flame to provide a homogeneous spatial profile. The particle incandescence was imaged onto a fast photodiode. The measurements are compared with the standard Melton model [Appl. Opt. 23,2201 (1984)] and with a new model that incorporates physical mechanisms not included in the Melton model.
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Affiliation(s)
- Hope A Michelsen
- Combustion Research Facility, Sandia National Laboratories, MS 9055, P.O. Box 969, Livermore, California 94551, USA.
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Stephens M, Turner N, Sandberg J. Particle identification by laser-induced incandescence in a solid-state laser cavity. APPLIED OPTICS 2003; 42:3726-36. [PMID: 12868806 DOI: 10.1364/ao.42.003726] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The laser-induced incandescence of a particle of unknown size and composition can be detected simultaneously with the light elastically scattered by the particle, providing information on both the size and composition of the particle. The technique relies on vaporization of the particle; detection of the incandescence signal at the time of vaporization allows determination of the boiling point of the particle, which can in turn be related to the composition of the particle. The elastically scattered signal provides information about the size of the particle and confirmation that it was vaporized. The technique is demonstrated by directing particles through a Nd:YAG laser cavity with approximately 10(6) W/cm2 of circulating intensity. Elements such as tungsten, silicon, and graphite, as well as common aerosols such as soot, can be detected and identifed.
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Affiliation(s)
- Michelle Stephens
- Research Electro-Optics, 5505 Airport Boulevard, Boulder, Colorado 80301, USA.
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Lehre T, Jungfleisch B, Suntz R, Bockhorn H. Size distributions of nanoscaled particles and gas temperatures from time-resolved laser-induced-incandescence measurements. APPLIED OPTICS 2003; 42:2021-30. [PMID: 12716142 DOI: 10.1364/ao.42.002021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Laser-induced-incandescence (LII) signal decays are measured in sooting premixed atmospheric and low-pressure flames. Soot particle temperatures are obtained from LII signals measured at two wavelengths. Soot particle size distributions P(r) and flame temperatures T are measured spatially resolved by independent techniques. Heat and mass transfer kinetics of the LII process are determined from measured soot particle temperatures, flame temperatures, and particle sizes. Uncertainties of current LII models are attributed to processes during the absorption of the laser pulse. Implications for LII experiments are made in order to obtain primary soot particle sizes. Soot particle size distributions and flame temperatures are assessed from measured particle temperature decays by use of multi-D nonlinear regression.
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Affiliation(s)
- Thilo Lehre
- Institut für Chemische Technik and Engler-Bunte-Institut/Verbrennungstechnik, TH Karlsruhe, Kaiserstrasse 12, 76131 Karlsruhe, Germany.
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Hofmann M, Bessler WG, Schulz C, Jander H. Laser-induced incandescence for soot diagnostics at high pressures. APPLIED OPTICS 2003; 42:2052-2062. [PMID: 12716145 DOI: 10.1364/ao.42.002052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The influence of pressure on laser-induced incandescence (LII) is investigated systematically in premixed, laminar sooting ethylene/air flames at 1-15 bar with wavelength-, laser fluence-, and time-resolved detection. In the investigated pressure range the LII signal decay rate is proportional to pressure. This observation is consistent with the prediction of heat-transfer models in the free-molecular regime. Pressure does not systematically affect the relationship between LII signal and laser fluence. With appropriate detection timing the pressure influence on LII signal's proportionality to soot volume faction obtained by extinction measurements is only minor compared with the variation observed in different flames at fixed pressures. The implications for particle sizing and soot volume fraction measurements using LII techniques at elevated pressures are discussed.
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Affiliation(s)
- Max Hofmann
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany.
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Michelsen HA. Understanding and predicting the temporal response of laser-induced incandescence from carbonaceous particles. J Chem Phys 2003. [DOI: 10.1063/1.1559483] [Citation(s) in RCA: 199] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Vander Wal RL, Berger GM, Ticich TM, Patel PD. Application of laser-induced incandescence to the detection of carbon nanotubes and carbon nanofibers. APPLIED OPTICS 2002; 41:5678-5690. [PMID: 12269569 DOI: 10.1364/ao.41.005678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Laser-induced incandescence applied to a heterogeneous, multielement reacting flow is characterized by temporally resolved emission spectra, time-resolved emission at selected detection wavelengths, and fluence dependence. Two-pulse laser measurements are used to further probe the effects of laser-induced changes on the optical signal. Laser fluences above 0.6 J/cm2 at 1064 nm initiate laser-induced vaporization, yielding a lower incandescence intensity, as found through fluence-dependence measurements. Spectrally derived temperatures show that values of excitation laser fluence greater than this value lead to superheated plasmas with temperatures well above the vaporization point of carbon. The temporal evolution of the emission signal at these fluences is consistent with plasma dissipation processes, not incandescence from solidlike structures. Two-pulse laser experiments reveal that other material changes are produced at fluences below the apparent vaporization threshold, leading to nanostructures with different optical and thermal properties.
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Affiliation(s)
- Randy L Vander Wal
- National Center for Microgravity Research on Fluids and Combustion, NASA Glenn Research Center, Cleveland, Ohio 44135-3191, USA.
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Bryce DJ, Ladommatos N, Zhao H. Quantitative investigation of soot distribution by laser-induced incandescence. APPLIED OPTICS 2000; 39:5012-5022. [PMID: 18350100 DOI: 10.1364/ao.39.005012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Strategies employed for quantitative measurement by laser-induced incandescence are detailed. Data are obtained for several laminar diffusion flames formed from blended Diesel fuels of known composition. A tomographic procedure is developed to scale the two-dimensional data to soot volume fraction and to correct for the trapping of signal by the soot field. Scaling is achieved by use of laser extinction along the measurement plane. The findings are used in discussions of measurement issues within turbulent environments. Data are augmented with elastic scattering measurements, allowing particle-size and number-density distributions to be inferred. A degree of axial and radial similarity among various flames suggests that the processes of soot formation and oxidation occur over similar time scales for each fuel.
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Axelsson B, Collin R, Bengtsson PE. Laser-induced incandescence for soot particle size measurements in premixed flat flames. APPLIED OPTICS 2000; 39:3683-3690. [PMID: 18349943 DOI: 10.1364/ao.39.003683] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Measurements of soot properties by means of laser-induced incandescence (LII) and combined scattering-extinction were performed in well-characterized premixed ethylene-air flames. In particular, the possibility of using LII as a tool for quantitative particle sizing was investigated. Particle sizes were evaluated from the temporal decay of the LII signal combined with heat balance modeling of laser-heated particles, and these sizes were compared with the particle sizes deduced from scattering-extinction measurements based on isotropic sphere theory. The correspondence was good early in the soot-formation process but less good at later stages, possibly because aggregation to clusters began to occur. A critical analysis has been made of how uncertainties in different parameters, both experimental and in the model, affect the evaluated particle sizes for LII. A sensitivity analysis of the LII model identified the ambient-flame temperature as a major source of uncertainty in the evaluated particle size, a conclusion that was supported by an analysis based on temporal LII profiles.
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