Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

Dreyer, Jochen A.H.; Slavchov, Radomir I.; Rees, Eric; Akroyd, Jethro; Salamanca, Maurin; Mosbach, Sebastian; Kraft, Markus

doi:10.1364/ao.58.002662

Cited by 43 publications

(31 citation statements)

References 47 publications

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“…The maximum soot volume fraction for nheptane is around 1.0 ppm. A similar value has been reported before [19,41]. In all the cases, the soot volume fraction increases with the addition of cyclic fuels.…”

Section: Particle Size Distribution and Soot Volume Fractionsupporting

confidence: 89%

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The impact of cyclic fuels on the formation and structure of soot

Salamanca

Botero

Martin

et al. 2020

Combustion and Flame

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This paper investigates the impact of cyclic fuels on the nanostructure, nucleation and overall production of soot in an n-heptane (C 7 H 16 ) laminar coflow diffusion flame. The fuels selected to dope the n-heptane flames are cyclopentene (C 5 H 8 ), cyclohexene (C 6 H 10 ) and methylcyclohexane (C 7 H 14 ). These fuels were chosen for their differences in their structure and sooting tendency. The flame structure was studied with Differential Mobility Spectrometry (DMS) for particle size distribution determination, two-colour ratio pyrometry to calculate the soot volume fraction and soot temperature. The soot nanostructure was investigated using Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). The addition of cyclic fuels was found to promote the formation of soot nanoparticles earlier in flames. In addition, the soot volume fraction was increased significantly by the addition of the cyclic fuels, especially by the addition of cyclopentene. The addition of 20% of cyclopentene increased the soot volume fraction by a factor of 2. HRTEM results suggest a significant influence of cyclopentene on the soot nanostructure; cyclopentene addition promotes the incorporation of five-membered rings (pentagonal rings) leading to highly curved fringes. This suggests cyclopentene could be used as a fuel to promote curvature in different carbonaceous structures to modify their properties. Highlights• Cyclic fuels promote soot formation in aliphatic flames.• The soot nanostructure changes with the addition of cyclopentene.• Cyclopentene promotes the formation of highly curved fringes and curvature integration.

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Section: Particle Size Distribution and Soot Volume Fractionsupporting

confidence: 89%

“…This methodology minimises the experimental noise when analysing the projection of axisymmetric coflow diffusion flame images for colour ratio pyrometry. A detailed description of the image processing is given in Dreyer et al [19].…”

Section: Soot Volume Fraction and Soot Temperaturementioning

confidence: 99%

The impact of cyclic fuels on the formation and structure of soot

Salamanca

Botero

Martin

et al. 2020

Combustion and Flame

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“…One challenge in colour ratio pyrometry is calculating the required flame cross section intensity R i from its line of sight projection P i recorded by the camera. For the reconstruction of R i , a recently reported Abel inversion methodology was used, called fitting the line-of-sight projection of a predefined intensity distribution (FLiPPID) [55]. Here, a suitable function for the radial intensity distribution in the flame is chosen and its forward Abel transform is fitted to the observed data.…”

Section: Colour Ratio Pyrometrymentioning

confidence: 99%

“…Here, a suitable function for the radial intensity distribution in the flame is chosen and its forward Abel transform is fitted to the observed data. A function suitable for co-flow diffusion flames was shown to be [55]:…”

Section: Colour Ratio Pyrometrymentioning

confidence: 99%

Evolution of the soot particle size distribution along the centreline of an n-heptane/toluene co-flow diffusion flame

Dreyer

Poli

Eaves

et al. 2019

Combustion and Flame

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A newly developed experimental setup for studying liquid hydrocarbon combustion in the well-established Yale burner was used to investigate the correlation between fuel composition and its sooting propensity. Soot particle size distributions (PSDs) and flame temperatures along the centreline of an n-heptane/toluene co-flow diffusion flame are reported. The results are compared to soot temperature and volume fraction profiles obtained using colour ratio pyrometry. The addition of toluene (0, 5, 10, and 15 mol%) to heptane moved soot inception to lower heights above the burner (HAB). The earlier inception extended the soot growth zone in the toluene-laden flames, leading to larger soot primary and agglomerate particles. Toluene addition had little influence on the maximum soot number density, indicating that the observed increase in soot volume fraction can mainly be attributed to the increase in particle size. The reported PSDs inside a vapour-fed diffusion flame are the first of their kind and provide a comprehensive dataset for future studies of combustion chemistry and soot particle models.

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“…The recovery of the original radial distribution from its projection is performed via a process known as Abel inversion 31 . The inverse Abel transform has been regularly used in a wide range of techniques such as color‐ratio pyrometry, 32 imaging 2D distributions of charged particles, 33 and plasma spectroscopy 34 . Due to the radial symmetry of the FLASH electron beam, Abel inversion can be used to extract the 3D dose distributions from individual projected 2D optical images of each beam pulse.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Single‐pulse beam characterization for FLASH‐RT using optical imaging in a water tank

et al. 2021

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High dose rate conditions, coupled with problems related to small field dosimetry, make dose characterization for FLASH-RT challenging. Most conventional dosimeters show significant dependence on dose rate at ultra-high dose rate conditions or fail to provide sufficiently fast temporal data for pulse to pulse dosimetry. Here fast 2D imaging of radioluminescence from a water and quinine phantom was tested for dosimetry of individual 4 μs linac pulses. Methods: A modified clinical linac delivered an electron FLASH beam of >50 Gy/s to clinical isocenter. This modification removed the x-ray target and flattening filter, leading to a beam that was symmetric and gaussian, as verified with GafChromic EBT-XD film. Lateral projected 2D dose distributions for each linac pulse were imaged in a quinine-doped water tank using a gated intensified camera, and an inverse Abel transform reconstruction provided 3D images for on-axis depth dose values. A total of 20 pulses were delivered with a 10 MeV, 1.5 cm circular beam, and beam with jaws wide open (40 × 40 cm 2 ), and a 3D dose distribution was recovered for each pulse. Beam output was analyzed on a pulse by pulse basis. Results: The R p , D max , and the R 50 measured with film and optical methods agreed to within 1 mm for the 1.5 cm circular beam and the beam with jaws wide open. Cross beam profiles for both beams agreed with film data with >95% passing rate (2%/2 mm gamma criteria). The optical central axis depth dose agreed with film data, except for near the surface. A temporal pulse analysis revealed a ramp-up period where the dose per pulse increased for the first few pulses and then stabilized. Conclusions: Optical imaging of radioluminescence was presented as a valuable tool for establishing a baseline for the recently initiated electron FLASH beam at our institution.

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Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

Cited by 43 publications

References 47 publications

The impact of cyclic fuels on the formation and structure of soot

The impact of cyclic fuels on the formation and structure of soot

Evolution of the soot particle size distribution along the centreline of an n-heptane/toluene co-flow diffusion flame

Technical Note: Single‐pulse beam characterization for FLASH‐RT using optical imaging in a water tank

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