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Energies 2017, 10(2), 232; doi:10.3390/en10020232

Exploring Soot Particle Concentration and Emissivity by Transient Thermocouples Measurements in Laminar Partially Premixed Coflow Flames

1
Istituto di Ricerche sulla Combustione, CNR, P.le Tecchio 80, 80125 Napoli, Italy
2
Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale—Università degli Studi di Napoli Federico II, P.le Tecchio 80, 80125 Napoli, Italy
*
Author to whom correspondence should be addressed.
Received: 15 December 2016 / Accepted: 8 February 2017 / Published: 15 February 2017
(This article belongs to the Special Issue Combustion and Propulsion)
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Abstract

Soot formation in combustion represents a complex phenomenon that strongly depends on several factors such as pressure, temperature, fuel chemical composition, and the extent of premixing. The effect of partial premixing on soot formation is of relevance also for real combustion devices and still needs to be fully understood. An improved version of the thermophoretic particle densitometry (TPD) method has been used in this work with the aim to obtain both quantitative and qualitative information of soot particles generated in a set of laminar partially-premixed coflow flames characterized by different equivalence ratios. To this aim, the transient thermocouple temperature response has been analyzed to infer particle concentration and emissivity. A variety of thermal emissivity values have been measured for flame-formed carbonaceous particles, ranging from 0.4 to 0.5 for the early nucleated soot particles up to the value of 0.95, representing the typical value commonly attributed to mature soot particles, indicating that the correct determination of the thermal emissivity is necessary to accurately evaluate the particle volume fraction. This is particularly true at the early stage of the soot formation, when particle concentration measurement is indeed particularly challenging as in the central region of the diffusion flames. With increasing premixing, an initial increase of particles is detected both in the maximum radial soot volume fraction region and in the central region of the flame, while the further addition of primary air determines the particle volume fraction drop. Finally, a modeling analysis based on a sectional approach has been performed to corroborate the experimental findings. View Full-Text
Keywords: soot; thermal emissivity; carbonization; partially premixed; coflow flames; thermocouple; thermophoresis soot; thermal emissivity; carbonization; partially premixed; coflow flames; thermocouple; thermophoresis
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

De Falco, G.; Moggia, G.; Sirignano, M.; Commodo, M.; Minutolo, P.; D’Anna, A. Exploring Soot Particle Concentration and Emissivity by Transient Thermocouples Measurements in Laminar Partially Premixed Coflow Flames. Energies 2017, 10, 232.

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