Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane Droplets
In this study, we examined the impact of droplet size and laser energy on droplet fragmentation and the resulting species composition due to laser irradiation of an acoustically levitated heptane droplet. Using shadowgraphy and spatially resolved laser-induced breakdown spectroscopy (LIBS), we obser...
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MDPI AG
2024-11-01
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| author | Parneeth Lokini Ciprian Dumitrache Bret C. Windom Azer P. Yalin |
| author_facet | Parneeth Lokini Ciprian Dumitrache Bret C. Windom Azer P. Yalin |
| author_sort | Parneeth Lokini |
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| description | In this study, we examined the impact of droplet size and laser energy on droplet fragmentation and the resulting species composition due to laser irradiation of an acoustically levitated heptane droplet. Using shadowgraphy and spatially resolved laser-induced breakdown spectroscopy (LIBS), we observed two different fragmentation regimes for the conditions studied. The experiments demonstrated that low laser energy densities (<~70 mJ/mm<sup>3</sup>), designated as regime 1, resulted in a single plasma breakdown event accompanied by broadband emission and C<sub>2</sub> Swan bands, suggesting weak plasma formation. Conversely, high energy densities (>~70 mJ/mm<sup>3</sup>), designated as regime 2, resulted in multiple plasma breakdowns that resulted in the emission of H<sub>α</sub>, O, and N, implying a full laser breakdown in the gaseous reactive mixture. Additionally, in regime 2, we calculated the electron density using Stark broadening of the H<sub>α</sub> line and temperature using Boltzmann analysis of O lines at 715 nm and 777 nm. We found that the electron densities and temperatures within the air spark and heptane droplets are quite similar. The findings from this research could impact the design of spray ignition systems and may also aid in validating the modeling efforts of aerosols, droplet breakdown, and ignition. |
| format | Article |
| id | doaj-art-52603c026e894cc9a2787e8be4b411e4 |
| institution | Kabale University |
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| publishDate | 2024-11-01 |
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| spelling | doaj-art-52603c026e894cc9a2787e8be4b411e42024-11-26T18:18:23ZengMDPI AGPhotonics2304-67322024-11-011111104410.3390/photonics11111044Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane DropletsParneeth Lokini0Ciprian Dumitrache1Bret C. Windom2Azer P. Yalin3Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80524, USADepartment of Mechanical Engineering, Colorado State University, Fort Collins, CO 80524, USADepartment of Mechanical Engineering, Colorado State University, Fort Collins, CO 80524, USADepartment of Mechanical Engineering, Colorado State University, Fort Collins, CO 80524, USAIn this study, we examined the impact of droplet size and laser energy on droplet fragmentation and the resulting species composition due to laser irradiation of an acoustically levitated heptane droplet. Using shadowgraphy and spatially resolved laser-induced breakdown spectroscopy (LIBS), we observed two different fragmentation regimes for the conditions studied. The experiments demonstrated that low laser energy densities (<~70 mJ/mm<sup>3</sup>), designated as regime 1, resulted in a single plasma breakdown event accompanied by broadband emission and C<sub>2</sub> Swan bands, suggesting weak plasma formation. Conversely, high energy densities (>~70 mJ/mm<sup>3</sup>), designated as regime 2, resulted in multiple plasma breakdowns that resulted in the emission of H<sub>α</sub>, O, and N, implying a full laser breakdown in the gaseous reactive mixture. Additionally, in regime 2, we calculated the electron density using Stark broadening of the H<sub>α</sub> line and temperature using Boltzmann analysis of O lines at 715 nm and 777 nm. We found that the electron densities and temperatures within the air spark and heptane droplets are quite similar. The findings from this research could impact the design of spray ignition systems and may also aid in validating the modeling efforts of aerosols, droplet breakdown, and ignition.https://www.mdpi.com/2304-6732/11/11/1044laser-induced breakdown spectroscopy (LIBS)shadowgraphydroplet fragmentationelectron densitytemperaturecombustion |
| spellingShingle | Parneeth Lokini Ciprian Dumitrache Bret C. Windom Azer P. Yalin Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane Droplets Photonics laser-induced breakdown spectroscopy (LIBS) shadowgraphy droplet fragmentation electron density temperature combustion |
| title | Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane Droplets |
| title_full | Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane Droplets |
| title_fullStr | Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane Droplets |
| title_full_unstemmed | Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane Droplets |
| title_short | Laser-Induced Breakdown Spectroscopy and Shadowgraphy of Acoustically Levitated Heptane Droplets |
| title_sort | laser induced breakdown spectroscopy and shadowgraphy of acoustically levitated heptane droplets |
| topic | laser-induced breakdown spectroscopy (LIBS) shadowgraphy droplet fragmentation electron density temperature combustion |
| url | https://www.mdpi.com/2304-6732/11/11/1044 |
| work_keys_str_mv | AT parneethlokini laserinducedbreakdownspectroscopyandshadowgraphyofacousticallylevitatedheptanedroplets AT cipriandumitrache laserinducedbreakdownspectroscopyandshadowgraphyofacousticallylevitatedheptanedroplets AT bretcwindom laserinducedbreakdownspectroscopyandshadowgraphyofacousticallylevitatedheptanedroplets AT azerpyalin laserinducedbreakdownspectroscopyandshadowgraphyofacousticallylevitatedheptanedroplets |