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Retter JE, Koll M, Dedic CE, Danehy PM, Richardson DR, Kearney SP. Hybrid time-frequency domain dual-probe coherent anti-Stokes Raman scattering for simultaneous temperature and pressure measurements in compressible flows via spectral fitting. APPLIED OPTICS 2023; 62:50-62. [PMID: 36606849 DOI: 10.1364/ao.472831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 11/07/2022] [Indexed: 06/17/2023]
Abstract
We demonstrate a hybrid time-frequency spectroscopic method for simultaneous temperature/pressure measurements in nonreacting compressible flows with known gas composition. Hybrid femtosecond-picosecond, pure-rotational coherent anti-Stokes Raman scattering (CARS), with two independent, time-delayed probe pulses, is deployed for single-laser-shot measurements of temperature and pressure profiles along an ∼5-mm line. The theory of dual-probe CARS is presented, along with a discussion of the iterative fitting of experimental spectra. Temperature is obtained from spectra acquired with an early, near-collision-free probe time delay (τ 1=0p s) and pressure from spectra obtained at probe delays of τ 2=150-1000p s, where collisions significantly impact the spectral profile. Unique solutions for temperature and pressure are obtained by iteratively fitting the two spectra to account for small collisional effects observed for the near zero probe delay spectrum. A dual-probe pure-rotational CARS system, in a 1D line-imaging configuration, is developed to demonstrate effectively the simultaneous temperature and pressure profiles recorded along the axial centerline of a highly underexpanded jet. The underexpanded air jet permits evaluation of this hybrid time-frequency domain approach for temperature and pressure measurements across a wide range of low-temperature-low-pressure conditions of interest in supersonic ground-test facilities. Single-laser-shot measurement precisions in both quantities and pressure measurement accuracy are systematically evaluated in the quiet zone upstream of the Mach disk. Precise thermometry approaching 1%-2% is observed in regions of high CARS signal-to-noise ratios. Pressure measurements are optimized at probe time delays where the ratio of the late probe delay to the Raman lifetime exceeds four (τ 2/τ R>4). The impact of low-temperature Raman linewidths on CARS pressure measurements is evaluated, and comparisons of CARS pressures obtained with our recent low-temperature pure-rotational Raman linewidth data and extrapolated high-temperature Q-branch linewidths are presented. Considering all measurements with τ 2/τ R≥4.0, measured pressures were on average 7.9% of the computed isentropic values with average shot-to-shot deviations representing a combination of instrument noise and fluid fluctuations of 5.0%.
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McCord W, Gragston M, Plemmons D, Zhang Z. O 2 based resonantly ionized photoemission thermometry analysis of supersonic flows. OPTICS EXPRESS 2022; 30:40557-40568. [PMID: 36298986 DOI: 10.1364/oe.471021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 09/16/2022] [Indexed: 06/16/2023]
Abstract
Characterization of the thermal gradients within supersonic and hypersonic flows is essential for understanding transition, turbulence, and aerodynamic heating. Developments in novel, impactful non-intrusive techniques are key for enabling flow characterizations of sufficient detail that provide experimental validation datasets for computational simulations. In this work, Resonantly Ionized Photoemission Thermometry (RIPT) signals are directly imaged using an ICCD camera to realize the techniques 1D measurement capability for the first time. The direct imaging scheme presented for oxygen-based RIPT (O2 RIPT) uses the previously established calibration data to direct excite various resonant rotational peaks within the S-branch of the C3Π, (v = 2) ← X3Σ(v' = 0) absorption band of O2. The efficient ionization of O2 liberates electrons that induce electron avalanche ionization of local N2 molecules generating N2 +, which primarily deexcites via photoemissions of the first negative band of N2+(B 2 Σ u+-X 2 Σ g+). When sufficient lasing energy is used, the ionization region and subsequent photoemission signal is achieved along a 1D line thus, if directly imaged can allow for gas temperature assignments along said line; demonstrated here of up to five centimeters in length. The temperature gradients present within the ensuing shock train of a supersonic under expanded free jet serves as a basis of characterization for this new RIPT imaging scheme. The O2 RIPT results are extensively compared and validated against well-known and established techniques (i.e., CARS and CFD). The direct imaging capability fully realizes the technique's fundamental potential and is expected to be the standard of implementation going forward. The direct imaging capability can play instrumental roles in future scientific studies that rely upon acute characterization of thermal gradients within a medium that cannot be easily resolved by a point. Furthermore, the removal of the spectrometer greatly reduces the cost, complexity, and optical alignment associated with prior RIPT measurements.
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Retter JE, Koll M, Richardson D, Kearney SP. Time-Domain Self-Broadened and Air-Broadened Nitrogen S-Branch Raman Linewidths at 80-200 K Recorded in an Underexpanded Jet. J Chem Phys 2022; 156:194201. [DOI: 10.1063/5.0090613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report pure-rotational N2-N2, N2-air, and O2-air S-branch linewidths for temperatures of 80-200 K by measuring the time-dependent decay of rotational Raman coherences in an isentropic free-jet expansion from a sonic nozzle. We recorded pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) spectra along the axial centerline of the underexpanded jet, within the barrel shock region upstream of the Mach disk. Dephasing of the pure-rotational Raman coherence was monitored using probe-time-delay scans at different axial positions in the jet, corresponding to varying local temperatures and pressures. The local temperature was obtained by fitting CARS spectra acquired at zero probe time delay, where the impact of collisions was minimal. The measured decay of each available Raman transition was fit to a dephasing constant and corrected for the local pressure, which was obtained from the CARS-measured static temperature and thermodynamic relationships for isentropic expansion from the known stagnation state. Nitrogen self-broadened transitions decayed more rapidly than those broadened in air for all temperatures, corresponding to higher Raman linewidths. In general, the measured S-branch linewidths deviated significantly in absolute and relative magnitudes from those predicted by extrapolating the modified exponential gap (MEG) model to low temperatures. The temperature dependence of the Raman linewidth for each measured rotational state of nitrogen ( J {less than or equal to} 10) and oxygen ( N {less than or equal to} 11) was fit to a temperature-dependent power-law over the measurable temperature domain (80-200 K) and extrapolated to both higher rotational states and to room temperature.
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Affiliation(s)
- Jonathan E Retter
- National Institute of Aerospace, United States of America
- Sandia National Laboratories
| | - Matthew Koll
- Aerospace Engineering, University of Illinois at Urbana-Champaign, United States of America
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Wu Y, Zhuzou M, Zhao T, Ding P, Sun S, Wang J, Liu Z, Hu B. Gas-phase pressure measurement using femtosecond laser-induced grating scattering technique. OPTICS LETTERS 2022; 47:1859-1862. [PMID: 35363754 DOI: 10.1364/ol.454045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 03/09/2022] [Indexed: 06/14/2023]
Abstract
Gas-phase pressure measurements remain challenging in situations where local pressure rapidly changes or in hostile environments such as turbulent combustion. In this work, we demonstrate the implementation of the recently developed femtosecond laser-induced grating scattering (fs-LIGS) technique for pressure measurement in ambient air. With an overall femtosecond laser pulse energy of 185 μJ, fs-LIGS signals were generated for various gas pressure ranging from 0.2 to 3.0 bar. By theoretically fitting the signal and extracting the time constant of the stationary density modulation damping, the pressure is successfully derived. The derived values were compared to the gauge pressure, which shows a quasi-linear dependence with a slope of 0.96, suggesting the feasibility of the fs-LIGS technique for gas-phase pressure measurements.
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Rodrigues NS, Brown AD, Meyer TR, Lucht RP. 0.1-5 MHz ultrahigh-speed gas density distributions using digital holographic interferometry. APPLIED OPTICS 2022; 61:28-34. [PMID: 35200798 DOI: 10.1364/ao.434725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 11/16/2021] [Indexed: 06/14/2023]
Abstract
Gas density distributions for an underexpanded jet at several different pressure ratios were measured at ultrahigh speeds in this work using digital holographic interferometry (DHI). DHI measurements have generally been performed on the order of several Hz in the literature, although some recent groups report measurements at 10 and 100 kHz. We demonstrate 2D imaging of gas density distributions at imaging rates up to 5 MHz, which is an increase by a factor of 50 compared to the previous DHI literature. A narrow-linewidth, continuous-wave laser was used in a Mach-Zehnder configuration, and the holograms were recorded using one of two different CMOS cameras. The interferograms were analyzed using the Fourier method, and a phase unwrapping was performed. Axisymmetric flow was assumed for the region near the nozzle exit, and an Abel inversion was performed to generate a planar-slice gas density distribution from the line-of-sight unwrapped phase. The challenges and opportunities associated with performing DHI measurements at ultrahigh speeds are discussed.
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Willman C, Le Page LM, Ewart P, Williams BAO. Pressure measurement in gas flows using laser-induced grating lifetime. APPLIED OPTICS 2021; 60:C131-C141. [PMID: 34143134 DOI: 10.1364/ao.419973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 04/07/2021] [Indexed: 06/12/2023]
Abstract
Optical diagnostics of gas-phase pressure are relatively unusual. In this work, we demonstrate a novel, rapid, and robust method to use laser-induced grating scattering (LIGS) to derive this property in real time. Previous pressure measurements with LIGS have employed a signal fitting method, but this is relatively time-consuming and requires specialist understanding. In this paper, we directly measure a decay lifetime from a LIGS signal and then employ a calibration surface constructed using a physics-based model to convert this value to pressure. This method was applied to an optically accessible single-cylinder internal combustion engine, yielding an accuracy of better than 10% at all tested conditions above atmospheric pressure. This new approach complements the existing strength of LIGS in precisely and accurately deriving temperature with a simple analysis method, by adding pressure information with a similarly simple method.
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Kearney SP, Scoglietti DJ, Kliewer CJ. Hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering temperature and concentration measurements using two different picosecond-duration probes. OPTICS EXPRESS 2013; 21:12327-12339. [PMID: 23736451 DOI: 10.1364/oe.21.012327] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A hybrid fs/ps pure-rotational CARS scheme is characterized in furnace-heated air at temperatures from 290 to 800 K. Impulsive femtosecond excitation is used to prepare a rotational Raman coherence that is probed with a ps-duration beam generated from an initially broadband fs pulse that is bandwidth limited using air-spaced Fabry-Perot etalons. CARS spectra are generated using 1.5- and 7.0-ps duration probe beams with corresponding coarse and narrow spectral widths. The spectra are fitted using a simple phenomenological model for both shot-averaged and single-shot measurements of temperature and oxygen mole fraction. Our single-shot temperature measurements exhibit high levels of precision and accuracy when the spectrally coarse 1.5-ps probe beam is used, demonstrating that high spectral resolution is not required for thermometry. An initial assessment of concentration measurements in air is also provided, with best results obtained using the higher resolution 7.0-ps probe. This systematic assessment of the hybrid CARS technique demonstrates its utility for practical application in low-temperature gas-phase systems.
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Affiliation(s)
- Sean P Kearney
- Engineering Sciences Center, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
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Narayanaswamy V, Burns R, Clemens NT. Kr-PLIF for scalar imaging in supersonic flows. OPTICS LETTERS 2011; 36:4185-4187. [PMID: 22048359 DOI: 10.1364/ol.36.004185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Experiments were performed to explore the use of two-photon planar laser-induced fluorescence (PLIF) of krypton gas for applications of scalar imaging in supersonic flows. Experiments were performed in an underexpanded jet of krypton, which exhibited a wide range of conditions, from subsonic to hypersonic. Excellent signal-to-noise ratios were obtained, showing the technique is suitable for single-shot imaging. The data were used to infer the distribution of gas density and temperature by correcting the fluorescence signal for quenching effects and using isentropic relations. The centerline variation of the density and temperature from the experiments agree very well with those predicted with an empirical correlation and a CFD simulation (FLUENT). Overall, the high signal levels and quantifiable measurements indicate that Kr-PLIF could be an effective scalar marker for use in supersonic and hypersonic flow applications.
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Affiliation(s)
- V Narayanaswamy
- Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, Texas 78712, USA
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Vestin F, Nilsson K, Bengtsson PE. Validation of a rotational coherent anti-Stokes Raman spectroscopy model for carbon dioxide using high-resolution detection in the temperature range 294-1143 K. APPLIED OPTICS 2008; 47:1893-1901. [PMID: 18404188 DOI: 10.1364/ao.47.001893] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Experiments were performed in the temperature range of 294-1143 K in pure CO(2) using high-resolution rotational coherent anti-Stokes Raman spectroscopy (CARS), in the dual-broadband approach. Experimental single-shot spectra were recorded with high spectral resolution using a single-mode Nd:YAG laser and a relay imaging lens system on the exit of a 1 m spectrometer. A theoretical rotational CARS model for CO(2) was developed for evaluation of the experimental spectra. The evaluated mean temperatures of the recorded single-shot dual-broadband rotational coherent anti-Stokes Raman spectroscopy (DB-RCARS) spectra using this model showed good agreement with thermocouple temperatures, and the relative standard deviation of evaluated single-shot temperatures was generally 2-3%. Simultaneous thermometry and relative CO(2)/N(2)-concentration measurements were demonstrated in the product gas of premixed laminar CO/air flames at atmospheric pressure. Although the model proved to be accurate for thermometry up to 1143 K, limitations were observed at flame temperatures where temperatures were overestimated and relative CO(2)/N(2) concentrations were underestimated. Potential sources for these discrepancies are discussed.
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Affiliation(s)
- Fredrik Vestin
- Division of Combustion Physics, Lund Institute of Technology, P.O. Box 118, 221 00 Lund, Sweden
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van Veen EH, Roekaerts D. Thermometry for turbulent flames by coherent anti-Stokes Raman spectroscopy with simultaneous referencing to the modeless excitation profile. APPLIED OPTICS 2005; 44:6995-7004. [PMID: 16294976 DOI: 10.1364/ao.44.006995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
An optimal system for temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) in turbulent flames and flows is presented. In addition to a single-mode pump laser and a modeless dye laser, an echelle spectrometer with a cross disperser is used. This system permits simultaneous measurement of the N2 CARS spectrum and the broadband dye laser profile. A procedure is developed to use software to transform this profile into the excitation profile by which the spectrum is referenced. Simultaneous shot-to-shot referencing is compared to sequential averaged referencing for data obtained in flat flames and in room air. At flame temperatures, the resultant 1.5% imprecision is limited by flame fluctuations, indicating that the system may have a single-shot imprecision below 1%. At room temperature, the 3.8% single-shot imprecision is of the same order as the best values reported for dual-broadband pure-rotational CARS. Using the unique shot-to-shot excitation profiles, simultaneous referencing eliminates systematic errors. At 2000 and 300 K, the 95% confidence intervals are estimated to be +/- 20 and +/- 10 K, respectively.
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Affiliation(s)
- Eric H van Veen
- Department of Multi-Scale Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
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Kuehner JP, Woodmansee MA, Lucht RP, Dutton JC. High-resolution broadband N2 coherent anti-Stokes Raman spectroscopy: comparison of measurements for conventional and modeless broadband dye lasers. APPLIED OPTICS 2003; 42:6757-6767. [PMID: 14658480 DOI: 10.1364/ao.42.006757] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We have performed high-resolution N2 coherent anti-Stokes Raman spectroscopy (CARS) measurements using a modeless dye laser (MDL) as the Stokes beam source to determine the effects of a reduction in mode noise on the accuracy and precision of the method. These results are compared with previous research that employed a conventional broadband dye laser (CBDL) as the Stokes beam source. A new spectral-fitting procedure was developed to avoid starting-point bias in the least-squares fitting results, which possibly had altered the previous measurements. Single-shot measurements of pressure were performed in a static-pressure vessel over the range of 0.1-4.0 atm to examine the pressure sensitivity of the technique. The precision of these measurements is a measure of the baseline noise level of the system, which sets the detection limit for flow-field pressure fluctuations. Centerline measurements of pressure and temperature in an underexpanded jet (Mj = 1.85) were also used to determine the performance of the technique in a compressible flow field. Our study represents the first known application, to our knowledge, of a MDL CARS system in a low-temperature, low-pressure supersonic environment. Improvements in accuracy for mean single-shot measurements and increased precision were found for pressure vessel conditions above 1.0 atm. For subatmospheric pressure vessel conditions (0.1-1.0 atm) and the underexpanded jet measurements, there was a decrease in accuracy and precision compared with the CBDL results. A comparison with the CBDL study is included, along with a discussion of the MDL system behavior.
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Affiliation(s)
- Joel P Kuehner
- Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, Illinois 61801, USA.
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Roy S, Ray G, Lucht RP. Interline Transfer CCD Camera for Gated Broadband Coherent Anti-Stokes Raman-Scattering Measurements. APPLIED OPTICS 2001; 40:6005-6011. [PMID: 18364895 DOI: 10.1364/ao.40.006005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Use of an interline transfer CCD camera for the acquisition of broadband coherent anti-Stokes Raman-scattering (CARS) spectra is demonstrated. The interline transfer CCD has alternating columns of imaging and storage pixels that allow one to acquire two successive images by shifting the first image in the storage pixels and immediately acquiring the second image. We have used this dual-image mode for gated CARS measurements by acquiring a CARS spectral image and shifting it rapidly from the imaging pixel columns to the storage pixel columns. We have demonstrated the use of this dual-image mode for gated single-laser-shot measurement of hydrogen and nitrogen CARS spectra at room temperature and in atmospheric pressure flames. The performance of the interline transfer CCD for these CARS measurements is compared directly with the performance of a back-illuminated unintensified CCD camera.
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