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Webb AM, Crabtree CQ, Athmanathan V, Meyer TR, Kearney SP, Slipchenko MN. High-efficiency narrow-bandwidth KTP optical parametric oscillator for kHz-MHz planar laser-induced fluorescence. OPTICS LETTERS 2024; 49:1473-1476. [PMID: 38489428 DOI: 10.1364/ol.510334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 01/23/2024] [Indexed: 03/17/2024]
Abstract
The electronic excitation of key combustion species or flow tagging of chemical species requires a narrowband tunable UV source. In this work, a potassium titanyl phosphate (KTP) burst-mode optical parametric oscillator (OPO) pumped by a 532 nm laser is developed to generate a spectrally narrow signal and an idler output with 1.48 ± 0.19 cm-1 bandwidth without the need for injection seeding. The idler (1410-1550 nm range) is further mixed with 355 or 266 nm to generate 284 or 226 nm for OH or NO planar laser-induced fluorescence (PLIF), respectively, with up to 1.9% conversion efficiency from 1064 nm to the UV. MHz-rate burst profiles are reported, and OH and NO PLIF are demonstrated in a rotating detonation combustor at rates up to 200 kHz.
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Ruchkina M, Raveesh M, Dominguez A, Bood J, Brackmann C. Simultaneous single-shot imaging of H and O atoms in premixed turbulent flames using femtosecond two-photon laser-induced fluorescence. OPTICS EXPRESS 2023; 31:12932-12943. [PMID: 37157442 DOI: 10.1364/oe.479562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A method based on femtosecond two-photon excitation has been developed for simultaneous visualization of interference-free fluorescence of H and O atoms in turbulent flames. This work shows pioneering results on single-shot simultaneous imaging of these radicals under non-stationary flame conditions. The fluorescence signal, showing the distribution of H and O radicals in premixed CH4/O2 flames was investigated for equivalence ratios ranging from ϕ = 0.8 to ϕ = 1.3. The images have been quantified through calibration measurements and indicate single-shot detection limits on the order of a few percent. Experimental profiles have also been compared with profiles from flame simulations, showing similar trends.
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Compressed fluorescence lifetime imaging via combined TV-based and deep priors. PLoS One 2022; 17:e0271441. [PMID: 35960754 PMCID: PMC9374265 DOI: 10.1371/journal.pone.0271441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 06/30/2022] [Indexed: 11/19/2022] Open
Abstract
Compressed fluorescence lifetime imaging (Compressed-FLIM) is a novel Snapshot compressive imaging (SCI) method for single-shot widefield FLIM. This approach has the advantages of high temporal resolution and deep frame sequences, allowing for the analysis of FLIM signals that follow complex decay models. However, the precision of Compressed-FLIM is limited by reconstruction algorithms. To improve the reconstruction accuracy of Compressed-FLIM in dealing with large-scale FLIM problem, we developed a more effective combined prior model 3DTGp V_net, based on the Plug and Play (PnP) framework. Extensive numerical simulations indicate the proposed method eliminates reconstruction artifacts caused by the Deep denoiser networks. Moreover, it improves the reconstructed accuracy by around 4dB (peak signal-to-noise ratio; PSNR) over the state-of-the-art TV+FFDNet in test data sets. We conducted the single-shot FLIM experiment with different Rhodamine reagents and the results show that in practice, the proposed algorithm has promising reconstruction performance and more negligible lifetime bias.
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Zhang W, Dong X, Sun Z, Zhou B, Wang Z, Richter M. 100 kHz CH 2O imaging realized by lower speed planar laser-induced fluorescence and deep learning. OPTICS EXPRESS 2021; 29:30857-30877. [PMID: 34614804 DOI: 10.1364/oe.433785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 08/20/2021] [Indexed: 06/13/2023]
Abstract
This paper reports an approach to interpolate planar laser-induced fluorescence (PLIF) images of CH2O between consecutive experimental data by means of computational imaging realized with convolutional neural network (CNN). Such a deep learning based method can achieve higher temporal resolution for 2D visualization of intermediate species in combustion based on high-speed experimental images. The capability of the model was tested for generating 100 kHz PLIF images by interpolating single and multiple PLIF frames into the sequences of experimental images of lower frequencies (50, 33, 25 and 20 kHz). Results show that the prediction indices, including intersection over union (IoU), peak signal to noise ratio (PSNR), structural similarity index (SSIM), and time averaged correlation coefficient at various axial positions could achieve acceptable accuracy. This work sheds light on the utilization of CNN-based models to achieve optical flow computation and image sequence interpolation, also providing an efficient off-line model as an alternative pathway to overcome the experimental challenges of the state-of-the-art ultra-high speed PLIF techniques, e.g., to further increase repetition rate and save data transfer time.
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Lauriola DK, Rahman KA, Stauffer HU, Slipchenko MN, Meyer TR, Roy S. Concentration and pressure scaling of CH 2O electronic-resonance-enhanced coherent anti-Stokes Raman scattering signals. APPLIED OPTICS 2021; 60:1051-1058. [PMID: 33690411 DOI: 10.1364/ao.415496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 12/30/2020] [Indexed: 06/12/2023]
Abstract
Nanosecond electronic-resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) is evaluated for the measurement of formaldehyde (CH2O) concentrations in reacting and nonreacting conditions. The three-color scheme utilizes a 532 nm pump beam and a scanned Stokes beam near 624 nm for Raman excitation of the C-H symmetric stretch (ν1) vibrational mode; further, a 342 nm resonant probe is tuned to produce the outgoing CARS signal via the 101403 vibronic transition between the ground (X~1A1) and first excited (A~1A2) electronic states. This allows detection of CH2O at concentrations as low as 9×1014molecules/cm3 (55 parts per million) in a calibration cell with CH2O and N2 at 1 bar and 450 K with 3% uncertainty. The measurements show a quadratic dependence of the signal with CH2O number density. Pressure scaling experiments up to 11 bar in the calibration cell show an increase in signal up to 8 bar. We study pressure dependence up to 11 bar and further apply the technique to characterize the CH2O concentration in an atmospheric premixed dimethyl ether/air McKenna burner flame, with a maximum concentration uncertainty of 11%. This approach demonstrates the feasibility for spatially resolved measurements of minor species such as CH2O in reactive environments and shows promise for application in high-pressure combustors.
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Grib SW, Hsu PS, Jiang N, Felver JJ, Schumaker SA, Carter CD, Roy S. 100 kHz krypton planar laser-induced fluorescence imaging. OPTICS LETTERS 2020; 45:3832-3835. [PMID: 32667296 DOI: 10.1364/ol.395389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
Krypton planar laser-induced fluorescence (Kr PLIF) was demonstrated at a repetition rate of 100 kHz. To achieve this increased rate, a custom injection-seeded optical parametric oscillator was built to efficiently convert the 355 nm output of a high-energy, high-repetition-rate nanosecond burst-mode laser to 212.56 nm to excite Kr from the ground to the 5p[1/2]0 electronic state. Successful tracking of flow structures and mixture fraction was demonstrated using detection speeds 100 times greater than previously attained with a femtosecond laser source. The increase in repetition rate makes time-resolved Kr PLIF relevant for high-speed flows in particular.
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Sun C, Jia Y. Rapid diagnosis and measurement of explosively formed projectiles based on high-quality sequential images. APPLIED OPTICS 2020; 59:3959-3966. [PMID: 32400667 DOI: 10.1364/ao.383410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 04/03/2020] [Indexed: 06/11/2023]
Abstract
The explosively formed projectile (EFP) is an important type of warhead technology. To verify and evaluate its design and performance, EFP testing is an essential procedure. This work applies a newly developed dual-color laser photographic system (DCLPS) to diagnose the EFP in a flight. The main concepts of the DCLPS and image measurement theory are introduced in detail. The states of the EFP in flight are recorded via experiments at the Nanshan Test Center. High-quality sequential images are obtained by the DCLPS, and the measured key parameters agree well with the simulation results. Test time is only a few minutes, and the measurement error is less than 10%. This work demonstrates the considerable capability of the DCLPS for rapid diagnosis and measurement of an ultrafast EFP, and its great potential in similar observation applications.
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Jiang N, Hsu PS, Grib SW, Roy S. Simultaneous high-speed imaging of temperature, heat-release rate, and multi-species concentrations in turbulent jet flames. OPTICS EXPRESS 2019; 27:17017-17026. [PMID: 31252919 DOI: 10.1364/oe.27.017017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 05/16/2019] [Indexed: 06/09/2023]
Abstract
We report the high-speed imaging of multi-species and multi-parameter combustion diagnostics for turbulent non-premixed jet flames using a three-legged burst-mode laser system. Simultaneous OH/CH2O planar laser-induced fluorescence and Rayleigh-scattering imaging measurements at a 10-kHz rate are obtained. OH and CH2O concentrations, flame temperatures, and heat-release rates are simultaneously acquired in two-dimensions at 10 kHz.
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Yang X, Fu C, Wang G, Li Z, Li T, Gao Y. Simultaneous high-speed SO 2 PLIF imaging and stereo-PIV measurements in premixed swirling flame at 20 kHz. APPLIED OPTICS 2019; 58:C121-C129. [PMID: 31045082 DOI: 10.1364/ao.58.00c121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 03/20/2019] [Indexed: 06/09/2023]
Abstract
Interactions between flow structures and premixed swirling flame were investigated using simultaneous sulfur dioxide (SO2) planar laser induced fluorescence (PLIF) and stereoscopic particle imaging velocimetry (PIV) with high temporal resolution at 20 kHz. In this work, a premixed swirling flame was operated with methane and air doped with 0.5% (volume fraction) SO2 at ambient pressure under different equivalence ratios (ϕ=0.7-1.2). The results show that global SO2 PLIF signal shows a consistent response to the density ratio with the change of equivalence ratio, making it a good indicator for the high temperature zone and a very useful tool to study the global effect of equivalence ratio. In addition, the three-component flow structure is affected by the varying equivalence ratio and the structure of the inner recirculation zone changes accordingly. The transient results show that the circumferential velocity of some vortices outside the flame zone is inconsistent with that of the main flow and these vortices cause local flame contour curling and shedding. The high temporal resolution measurements provide more details for the study of the evolution of some isolated flame isles.
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Wang S, Liu X, Wang G, Xu L, Li L, Liu Y, Huang Z, Qi F. High-repetition-rate burst-mode-laser diagnostics of an unconfined lean premixed swirling flame under external acoustic excitation. APPLIED OPTICS 2019; 58:C68-C78. [PMID: 31045033 DOI: 10.1364/ao.58.000c68] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 01/25/2019] [Indexed: 06/09/2023]
Abstract
Lean premixed swirling flames are important in practical combustors, but a commonly encountered problem of practical swirl combustors is thermo-acoustic instability, which may cause internal structure damage to combustors. In this research, a high-repetition-rate burst-mode laser is used for simultaneous particle image velocimetry and planar laser-induced fluorescence measurement in an unconfined acoustically excited swirl burner. The time-resolved flow field and transient flame response to the acoustic perturbation are visualized at 20 kHz, offering insight into the heat release rate oscillation. The premixed mixture flow rate and acoustic modulation are varied to study the effects of Reynolds number, Strouhal number, and acoustic modulation amplitude on the swirling flame. The results suggest that the Strouhal number has a notable effect on the periodic movements of the inner recirculation zone and swirling flame configuration.
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Liu N, Ma L. Hybrid diagnostic for optimizing domain size and resolution of 3D measurements. OPTICS LETTERS 2018; 43:3842-3845. [PMID: 30106897 DOI: 10.1364/ol.43.003842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 07/09/2018] [Indexed: 06/08/2023]
Abstract
This Letter reports a hybrid three-dimensional (3D) visualization approach for turbulent flows at the kilohertz range. The approach, named scanning volumetric laser induced fluorescence (SVLIF), combines 3D tomography with scanning to significantly enhance spatial resolution of 3D measurements in a given domain (or equivalently, to enlarge the domain size under a given resolution) compared to past tomographic approaches. The SVLIF technique (1) divides a large measurement domain into smaller sub-domains, (2) performs 3D tomographic measurement in each sub-domain by scanning the excitation laser pulses across them consecutively, and (3) combines the measurements in all sub-domains to form a final measurement. This hybrid approach enables the conversion of temporal resolution into spatial resolution or domain size to optimize 3D measurements in a wider design space. In this work, the SVLIF was demonstrated and validated at a scanning rate of 1.86 kHz in a volume of 38.4 mm×26.5 mm×25.2 mm with 7.1 million voxels, representing a ∼5 times enhancement in the number of voxels or the domain size compared to past tomographic techniques.
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Retzer U, Pan R, Werblinski T, Huber FJT, Slipchenko MN, Meyer TR, Zigan L, Will S. Burst-mode OH/CH 2O planar laser-induced fluorescence imaging of the heat release zone in an unsteady flame. OPTICS EXPRESS 2018; 26:18105-18114. [PMID: 30114090 DOI: 10.1364/oe.26.018105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 05/29/2018] [Indexed: 06/08/2023]
Abstract
The paper presents simultaneous high-speed (7.5 kHz) planar laser-induced fluorescence (PLIF) of formaldehyde (CH2O) and the hydroxyl-radical (OH) for visualization of the flame structure and heat release zone in a non-premixed unsteady CH4/O2/N2 flame. For this purpose, a dye laser designed for high-speed operation is pumped by the second-harmonic 532 nm output of a Nd:YAG burst-mode laser to produce a tunable, 566 nm beam. After frequency doubling a high-energy kHz-rate narrowband pulse train of approximately 2.2 mJ/pulse at 283 nm is used for excitation of the OH radical. Simultaneously, CH2O is excited by the frequency-tripled output of the same Nd:YAG laser, providing a high-frequency pulse train over 10 ms in duration at high pulse energies (>100 mJ/pulse). The excitation energies enable signal-to-noise ratios (SNRs) of ~10 and ~60 for CH2O and OH PLIF, respectively, using a single high-speed intensified CMOS camera equipped with an image doubler. This allows sufficient SNR for investigation of the temporal evolution of the primary heat release zone and the local flame structure at kHz rates from the spatial overlap of the OH- and CH2O-PLIF signals.
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Li Y, Jia H, Chen S, Tian J, Liang L, Yuan F, Yu H, Li DDU. Single-shot time-gated fluorescence lifetime imaging using three-frame images. OPTICS EXPRESS 2018; 26:17936-17947. [PMID: 30114076 DOI: 10.1364/oe.26.017936] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 06/14/2018] [Indexed: 06/08/2023]
Abstract
Qualitative and quantitative measurements of complex flows demand for fast single-shot fluorescence lifetime imaging (FLI) technology with high precision. A method, single-shot time-gated fluorescence lifetime imaging using three-frame images (TFI-TGFLI), is presented. To our knowledge, it is the first work to combine a three-gate rapid lifetime determination (RLD) scheme and a four-channel framing camera to achieve this goal. Different from previously proposed two-gate RLD schemes, TFI-TGFLI can provide a wider lifetime range 0.6 ~ 13ns with reasonable precision. The performances of the proposed approach have been examined by both Monte-Carlo simulations and toluene seeded gas mixing jet diagnosis experiments. The measured average lifetimes of the whole excited areas agree well with the results obtained by the streak camera, and they are 7.6ns (N2 = 7L/min; O2 < 0.1L/min) and 2.6ns (N2 = 19L/min; O2 = 1L/min) with the standard deviations of 1.7ns and 0.8ns among the lifetime image pixels, respectively. The concentration distributions of the quenchers and fluorescent species were further analyzed, and they are consistent with the experimental settings.
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Gragston M, Smith CD, Zhang Z. High-speed flame chemiluminescence imaging using time-multiplexed structured detection. APPLIED OPTICS 2018; 57:2923-2929. [PMID: 29714296 DOI: 10.1364/ao.57.002923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 03/12/2018] [Indexed: 06/08/2023]
Abstract
In this work, high-speed flame chemiluminescence has been obtained by using the time-multiplexed structured detection (TMSD) imaging method from a single snapshot. TMSD sheers the time lapse into the spatial frequency shifts, which allows multiple high-speed images to be frequency upshifted into distinct spatial frequency regions from the original image. A cumulative exposure captured in a single snapshot image contains distinct time evolution. Each distinct image is demultiplexed and recovered by hyperdyne mixing with the modulation frequency. TMSD is an optical frequency domain analog to carrier frequency modulation in radio and microwave detections. Specifically, a digital micromirror device (DMD) spatially modulates flame chemiluminescence just prior to the camera. Spatial frequency of each distinct image is mixed between the original spatial frequency components and DMD modulation pattern frequency, resulting in a coded snapshot. The high-speed flame chemiluminescence image is recovered by demodulation. TMSD is similar to structured illumination used in super-resolution microscopy, but offers more advantages, for it does not alternate incident illumination light. Since DMDs are available with speeds up to 40 kHz, this technique shows promise as a cost-effective means of high-speed imaging and diagnostics of combustion phenomena.
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