Laser-induced grating spectroscopy in non-uniform temperature fields and flames
<p>The application of Laser-Induced Grating Spectroscopy (LIGS) to thermometry of temperature-controlled ethylene flows and an ethylene-air flame from a Gülder burner is studied. A model for simulating the effect of contributions from regions of different temperature within the LIGS probe volu...
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| Format: | Thesis |
| Language: | English |
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2014
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| _version_ | 1797109669809881088 |
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| author | Wijeyasinghe, NC |
| author2 | Ewart, P |
| author_facet | Ewart, P Wijeyasinghe, NC |
| author_sort | Wijeyasinghe, NC |
| collection | OXFORD |
| description | <p>The application of Laser-Induced Grating Spectroscopy (LIGS) to thermometry of temperature-controlled ethylene flows and an ethylene-air flame from a Gülder burner is studied. A model for simulating the effect of contributions from regions of different temperature within the LIGS probe volume is developed for comparison with experimental data. The model includes a weighted sum of contributions from regions at a single temperature to the total signal intensity. An appropriate experimental set-up is constructed for this study, with careful consideration given to the dimensions of the probe volume. Temperature measurements are made in a dual flow of ethylene, where the probe volume contains two distinct temperature regions: one from an unheated flow and the second from a temperature-controlled hot flow. The model is shown to correspond well with experimental data; the presence of two discrete contributions, 293 ± 2 K and 310 ± 2K (0.6 – 0.7% precision), is identified in the LIGS signal from the cooler region.</p> <p>LIGS signals are recorded at several spatial positions in the lower region of a flame with fixed stoichiometry. Signals measured in the 0.0 – 5.0 mm height above burner (HAB) range and the 0.0 – 3.5 mm radial position range are analysed using MATLAB; temperature information is extracted with precisions of 0.9 – 4.4%. The OH* distribution in the flame is recorded during a chemiluminescence experiment to identify the location of the reaction zone. The model is used to demonstrate that derived temperatures are the spatial average of a continuous temperature gradient within the probe volume. The suitability of LIGS for thermometry in environments with unknown temperature gradients is thus verified. Comparisons are made between the flame measurements and ethylene flow data; simple changes to improve the model are proposed. Strong non-oscillatory decay features in the LIGS signal, indicative of the laser heating of soot, are reported at HAB 20.0 – 50.0 mm; relevant implications are discussed.</p> |
| first_indexed | 2024-03-07T07:44:45Z |
| format | Thesis |
| id | oxford-uuid:fa338a46-62f8-41cb-978b-45bf831ac9de |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T07:44:45Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:fa338a46-62f8-41cb-978b-45bf831ac9de2023-05-16T14:39:12ZLaser-induced grating spectroscopy in non-uniform temperature fields and flamesThesishttp://purl.org/coar/resource_type/c_bdccuuid:fa338a46-62f8-41cb-978b-45bf831ac9deAtomic and laser physicsEnglishOxford University Research Archive - Valet2014Wijeyasinghe, NCEwart, P<p>The application of Laser-Induced Grating Spectroscopy (LIGS) to thermometry of temperature-controlled ethylene flows and an ethylene-air flame from a Gülder burner is studied. A model for simulating the effect of contributions from regions of different temperature within the LIGS probe volume is developed for comparison with experimental data. The model includes a weighted sum of contributions from regions at a single temperature to the total signal intensity. An appropriate experimental set-up is constructed for this study, with careful consideration given to the dimensions of the probe volume. Temperature measurements are made in a dual flow of ethylene, where the probe volume contains two distinct temperature regions: one from an unheated flow and the second from a temperature-controlled hot flow. The model is shown to correspond well with experimental data; the presence of two discrete contributions, 293 ± 2 K and 310 ± 2K (0.6 – 0.7% precision), is identified in the LIGS signal from the cooler region.</p> <p>LIGS signals are recorded at several spatial positions in the lower region of a flame with fixed stoichiometry. Signals measured in the 0.0 – 5.0 mm height above burner (HAB) range and the 0.0 – 3.5 mm radial position range are analysed using MATLAB; temperature information is extracted with precisions of 0.9 – 4.4%. The OH* distribution in the flame is recorded during a chemiluminescence experiment to identify the location of the reaction zone. The model is used to demonstrate that derived temperatures are the spatial average of a continuous temperature gradient within the probe volume. The suitability of LIGS for thermometry in environments with unknown temperature gradients is thus verified. Comparisons are made between the flame measurements and ethylene flow data; simple changes to improve the model are proposed. Strong non-oscillatory decay features in the LIGS signal, indicative of the laser heating of soot, are reported at HAB 20.0 – 50.0 mm; relevant implications are discussed.</p> |
| spellingShingle | Atomic and laser physics Wijeyasinghe, NC Laser-induced grating spectroscopy in non-uniform temperature fields and flames |
| title | Laser-induced grating spectroscopy in non-uniform temperature fields and flames |
| title_full | Laser-induced grating spectroscopy in non-uniform temperature fields and flames |
| title_fullStr | Laser-induced grating spectroscopy in non-uniform temperature fields and flames |
| title_full_unstemmed | Laser-induced grating spectroscopy in non-uniform temperature fields and flames |
| title_short | Laser-induced grating spectroscopy in non-uniform temperature fields and flames |
| title_sort | laser induced grating spectroscopy in non uniform temperature fields and flames |
| topic | Atomic and laser physics |
| work_keys_str_mv | AT wijeyasinghenc laserinducedgratingspectroscopyinnonuniformtemperaturefieldsandflames |