| 1. |
- Li, Bo, et al.
(author)
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A review of femtosecond laser-induced emission techniques for combustion and flow field diagnostics
- 2019
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In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 9:9
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Research review (peer-reviewed)abstract
- The applications of femtosecond lasers to the diagnostics of combustion and flow field have recently attracted increasing interest. Many novel spectroscopic methods have been developed in obtaining non-intrusive measurements of temperature, velocity, and species concentrations with unprecedented possibilities. In this paper, several applications of femtosecond-laser-based incoherent techniques in the field of combustion diagnostics were reviewed, including two-photon femtosecond laser-induced fluorescence (fs-TPLIF), femtosecond laser-induced breakdown spectroscopy (fs-LIBS), filament-induced nonlinear spectroscopy (FINS), femtosecond laser-induced plasma spectroscopy (FLIPS), femtosecond laser electronic excitation tagging velocimetry (FLEET), femtosecond laser-induced cyano chemiluminescence (FLICC), and filamentary anemometry using femtosecond laser-extended electric discharge (FALED). Furthermore, prospects of the femtosecond-laser-based combustion diagnostic techniques in the future were analyzed and discussed to provide a reference for the relevant researchers.
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| 2. |
- Li, Xiaofeng, et al.
(author)
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Enhancement of femtosecond laser-induced plasma fluorescence using a nanosecond laser
- 2019
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In: Optics Express. - 1094-4087. ; 27:4, s. 5755-5763
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Journal article (peer-reviewed)abstract
- We demonstrate the enhancement of femtosecond (fs) laser-induced filaments in air and nitrogen flow fields using a nanosecond (ns) laser. With the ns laser being imposed on the filaments, the length and the emission intensity of the filaments were largely increased. Temporally resolved spectra of the enhanced filaments were obtained. The results show that the ns laser enhanced the short-lifetime fluorescence of nitrogen, which comes from the transition processes of N 2 + (B 2 Σ u + - X 2 Σ g + ), N 2 (B 3 Π g - A 3 Σ u + ) and N 2 (C 3 Π u - B 3 Π g ). However, it had little effect on the long-lifetime chemiluminescence, which mainly comes from reactions such as N 2 (A 3 Σ u + ) + N 2 (A 3 Σ u + ) → N 2 (X 1 Σ g + , v = 0) + N 2 (B 3 Π g ). A possible explanation of this phenomenon is given, and this phenomenon might have potential applications in instantaneous one-dimensional measurements of various species in gas flow fields.
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| 3. |
- Liu, Jixu, et al.
(author)
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Ammonia Measurements with Femtosecond Two-Photon Laser-Induced Fluorescence in Premixed NH3/Air Flames
- 2020
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In: Energy and Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 34:2, s. 1177-1183
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Journal article (peer-reviewed)abstract
- Ammonia (NH3), which can be a hydrogen carrier, is a promising alternative to fossil fuels in the future carbon-free economy. In situ techniques feasible for the remote and non-intrusive detection of NH3 will provide strong support for developing clean NH3 combustion. Here, we demonstrated a femtosecond two-photon laser-induced fluorescence (fs-TPLIF) technique for interference-free in situ NH3 measurements in laminar premixed NH3/air flames. The two-head band of NH3 at ∼565 nm was observed, which verifies the feasibility of fs-TPLIF for NH3 measurements in a combustion environment. The single-shot NH3 fs-TPLIF images with efficient signal-to-noise ratios were obtained. The variation of the thickness of the reaction zone with the equivalence ratio of NH3 flames was also obtained. As a result of the broad line width of the femtosecond laser, the OH fluorescence was also observed together with the NH3 fluorescence. The potential of fs-TPLIF for simultaneous measurements of NH3 and OH with only one laser was analyzed. The laser power dependence of NH3 and NH emissions was investigated. The radial distributions of NH3, NH, and OH in the flame were also discussed. This work is the first attempt of fs-TPLIF for NH3 measurements in a combustion environment, and the results indicate that fs-TPLIF is a feasible tool for NH3 measurements in combustion diagnostics.
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| 4. |
- Zhang, Dayuan, et al.
(author)
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Ammonia measurements with femtosecond laser-induced plasma spectroscopy
- 2019
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In: Applied Optics. - 1559-128X. ; 58:5, s. 1210-1214
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Journal article (peer-reviewed)abstract
- Femtosecond laser-induced plasma spectroscopy for in situ ammonia (NH 3 ) measurements was demonstrated in NH 3 ∕N 2 mixtures. When a femtosecond laser at 800 nm was focused at the flow field, the parent NH 3 molecules would be photolyzed to generate electronics excited NH fragments, and then indirect measurements of NH 3 could be realized by detecting the NH fluorescence (A 3 Π − X 3 Σ − ) at 336 nm. A detection limit of 205 ppm was achieved. This work is the first attempt, to the best of our knowledge, for ammonia measurements with a femtosecond laser, and the results are useful for the development of ammonia diagnostics.
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| 5. |
- Zhang, Dayuan, et al.
(author)
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Femtosecond laser-induced plasma spectroscopy for combustion diagnostics in premixed ammonia/air flames
- 2019
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In: Applied Optics. - 1559-128X. ; 58:28, s. 7810-7816
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Journal article (peer-reviewed)abstract
- Ammonia (NH3) is a sustainable fuel with excellent emission characteristics. Hence, it is important to develop diagnostic techniques for NH3 combustion. In this paper, femtosecond laser-induced plasma spectroscopy (FLIPS) was performed in premixed NH3∕air flames. The plasma emission spectra induced by the femtosecond laser in the flame and the chemiluminescence spectra of the flame itself were both measured. Through calibration, we found that the spectral intensity ratio of NH (336 nm)∕N2 (337 nm) could be used for equivalence ratio measurements in NH3 combustion flow fields. This work is the first attempt at using a femtosecond laser-based technique for NH3 combustion diagnostics.
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| 6. |
- Zhang, Dayuan, et al.
(author)
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Instantaneous one-dimensional ammonia measurements with femtosecond two-photon laser-induced fluorescence (fs-TPLIF)
- 2019
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In: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 44:47, s. 25740-25745
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Journal article (peer-reviewed)abstract
- Ammonia (NH3) has been identified as a potential hydrogen-carrier fuel with no carbon emissions. Non-intrusive in-situ NH3 diagnostic technique is of great interest. In this work, femtosecond two-photon laser-induced fluorescence (fs-TPLIF) was demonstrated in NH3/N2 mixtures to achieve NH3 measurements. A femtosecond laser at 305 nm was used for two-photon excitation of NH3 to its excited state (X–C′), and the subsequent fluorescence at ~565 nm from transition C′-A was detected. In addition, a detection limit of 730 ppm was achieved in NH3/N2 mixtures. Furthermore, one-dimensional single-shot images of NH3 were obtained in both laminar and turbulent flow fields. This work is the first attempt of fs-TPLIF for polyatomic molecular gases measurements, and the obtained results indicate that fs-TPLIF could be a promising tool for NH3 measurements.
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