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| Title: | Size and morphology of soot particulates sampled from a turbulent nonpremixed acetylene flame |
| Author (s): | Hu, B. Koylu, Umit |
| Department/Lab Affiliations: | Mechanical & Aerospace Engineering Space Systems Engineering |
| Keywords: | Acetylene turbulent flame Electron microscope Soot particulates Soot processes |
| Issue Date: | 2004 |
| Publisher: | Taylor and Francis Group |
| Citation: | Hu, Bing and Koylu, Umit, “Size and Morphology of Soot Particulates Sampled from a Turbulent Nonpremixed Acetylene Flame, Aerosol Science and Technology 38: 1009-1018 (2004). |
| Abstract: | Soot processes within a turbulent nonpremixed flame burning acetylene/air were investigated by conducting thermophoretic sampling experiments at various axial and radial locations. Analyses of transmission electron microscope images yielded the mean soot spherule diameter, number of spherules per aggregate, and fractal morphology within this highly luminous turbulent flame. Specifically, translucent particles were observed at low-to-intermediate heights above the flame with the formation and evolution of young soot precursors. The soot spherule diameter peaked at 34 nm halfway along the centerline, identifying the flame regions of surface growth and oxidation processes. In the meantime, the aggregation was continuous along the flame axis with the mean number of spherules per aggregate reaching 150 at the highest sampling location. Size ranges of spherules and aggregates were narrow and broad, respectively, while the relative widths of both size distributions remained similar throughout the flame. In contrast to the observed axial variations, the radial changes of the mean spherule and aggregate sizes appeared to be small. Aggregate morphologies were universally characterized by a fractal dimension of 1.82 and a fractal prefactor of 1.9 for all the flame positions. In comparison to a lightly sooting ethylene flame, these measurements in the acetylene turbulent flame revealed that the fuel type mainly affected the axial evolution of spherule diameters but not their range, and enhanced the aggregate sizes but not their morphology. The effective decoupling of spherule and aggregate sizes permitted the separation of soot surface growth and oxidation from aggregation. This key aspect provided a stringent test for the existing particulate diagnostics and predictive models in their ability to quantify the actual particle surface area, particularly in optically thick conditions that are encountered in many practical combustion environments. |
| Type: | Article - Journal text |
| In Title: | Aerosol Science and Technology |
| Copyright Notice: | This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. FULL COPYRIGHT INFORMATION: |
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| title | Size and morphology of soot particulates sampled from a turbulent nonpremixed acetylene flame |
| contributor.author | Hu, B. |
| contributor.author | Koylu, Umit |
| contributor.deptlab | Mechanical & Aerospace Engineering |
| contributor.deptlab | Space Systems Engineering |
| contributor.sponsor | National Science Foundation |
| contributor.sponsor | University of Missouri Research Board |
| subject | Acetylene turbulent flame |
| subject | Electron microscope |
| subject | Soot particulates |
| subject | Soot processes |
| date.issued | 2004 |
| publisher | Taylor and Francis Group |
| identifier.citation | Hu, Bing and Koylu, Umit, “Size and Morphology of Soot Particulates Sampled from a Turbulent Nonpremixed Acetylene Flame, Aerosol Science and Technology 38: 1009-1018 (2004). |
| identifier.pub.URI | |
| description.abstract | Soot processes within a turbulent nonpremixed flame burning acetylene/air were investigated by conducting thermophoretic sampling experiments at various axial and radial locations. Analyses of transmission electron microscope images yielded the mean soot spherule diameter, number of spherules per aggregate, and fractal morphology within this highly luminous turbulent flame. Specifically, translucent particles were observed at low-to-intermediate heights above the flame with the formation and evolution of young soot precursors. The soot spherule diameter peaked at 34 nm halfway along the centerline, identifying the flame regions of surface growth and oxidation processes. In the meantime, the aggregation was continuous along the flame axis with the mean number of spherules per aggregate reaching 150 at the highest sampling location. Size ranges of spherules and aggregates were narrow and broad, respectively, while the relative widths of both size distributions remained similar throughout the flame. In contrast to the observed axial variations, the radial changes of the mean spherule and aggregate sizes appeared to be small. Aggregate morphologies were universally characterized by a fractal dimension of 1.82 and a fractal prefactor of 1.9 for all the flame positions. In comparison to a lightly sooting ethylene flame, these measurements in the acetylene turbulent flame revealed that the fuel type mainly affected the axial evolution of spherule diameters but not their range, and enhanced the aggregate sizes but not their morphology. The effective decoupling of spherule and aggregate sizes permitted the separation of soot surface growth and oxidation from aggregation. This key aspect provided a stringent test for the existing particulate diagnostics and predictive models in their ability to quantify the actual particle surface area, particularly in optically thick conditions that are encountered in many practical combustion environments. |
| type | Article - Journal |
| type.DCMIType | text |
| type.status | Postprint |
| rights | This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. |
| rights.URI | |
| relation.isPartOf | Aerosol Science and Technology |
| date.accessioned | 2007-04-11T17:00:48Z |
| date.available | 2008-05-12T21:22:04Z |
| identifier.persist.URI |