On the sensitivity of rotational CARS N<sub>2</sub> thermometry to the Herman–Wallis factor

Bohlin, Alexis; Bengtsson, Per-Erik; Marrocco, Michele

doi:10.1002/jrs.2869

Cited by 38 publications

(32 citation statements)

References 16 publications

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“…Although this formulation has been recently questioned, the error associated with this assumption is minimal (<3 K) for the temperatures explored in the current work [35]. The population difference is a strong function of temperature, T, based on the Boltzmann distribution and also a function of the degeneracy of the lower energy state, J.…”

Section: T I T I P T Dt Dt Dt R T T T E T T E T T T E T T T T E E Ementioning

confidence: 91%

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Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

Miller¹,

Roy²,

Slipchenko³

et al. 2011

Opt. Express

104

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High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate singleshot, purerotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time-and frequencydomain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N 2 -RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows. KeywordsFriedrich-Alexander University Erlangen-Nürnberg, aerodynamics, probes, Raman scattering, Raman spectroscopy, temperature measurement, thermometers, dephasing, femtoseconds, frequency domains, Fs laser, gasphase, high repetition rate, laser sources, species concentration, equipment design, optics and photonics, Fourier analysis Abstract: High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate singleshot, pure-rotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time-and frequency-domain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N 2 -RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows.

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Section: T I T I P T Dt Dt Dt R T T T E T T E T T T E T T T T E E Ementioning

confidence: 91%

“…This correction for vibrational-rotational interaction is the so-called Herman-Wallis factor [35] and is defined in the current model using the formulation of Martinsson as shown in Eq. (7), …”

Section: T I T I P T Dt Dt Dt R T T T E T T E T T T E T T T T E E Ementioning

confidence: 99%

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

Miller¹,

Roy²,

Slipchenko³

et al. 2011

Opt. Express

104

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show abstract

“…These J-dependent corrections have recently been evaluated by Bohlin et al[61] for rotational CARS, from which we use the expression recommended by Martinsson et al[62],…”

mentioning

confidence: 99%

Hybrid fs/ps rotational CARS temperature and oxygen measurements in the product gases of canonical flat flames

Kearney

2015

Combustion and Flame

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a b s t r a c tA hybrid fs/ps pure-rotational coherent anti-Stokes Raman scattering (CARS) scheme is systematically evaluated over a wide range of flame conditions in the product gases of two canonical flat-flame burners. Near-transform-limited, broadband femtosecond pump and Stokes pulses impulsively prepare a rotational Raman coherence, which is later probed using a high-energy, frequency-narrow picosecond beam generated by the second-harmonic bandwidth compression scheme that has recently been demonstrated for rotational CARS generation in H 2 /air flat flames. The measured spectra are free of collision effects and nonresonant background and can be obtained on a single-shot basis at 1 kHz. The technique is evaluated for temperature/oxygen measurements in near-adiabatic H 2 /air flames stabilized on the Hencken burner for equivalence ratios of u = 0.20-1.20. Thermometry is demonstrated in hydrocarbon/air products for u = 0.75-3.14 in premixed C 2 H 4 /air flat flames on the McKenna burner. Reliable spectral fitting is demonstrated for both shot-averaged and single-laser-shot data using a simple phenomenological model. Measurement accuracy is benchmarked by comparison to adiabatic-equilibrium calculations for the H 2 /air flames, and by comparison with nanosecond CARS measurements for the C 2 H 4 /air flames. Quantitative accuracy comparable to nanosecond rotational CARS measurements is observed, while the observed precision in both the temperature and oxygen data is extraordinarily high, exceeding nanosecond CARS, and on par with the best published thermometric precision by femtosecond vibrational CARS in flames, and rotational femtosecond CARS at low temperature. Threshold levels of signal-to-noise ratio to achieve 1-2% precision in temperature and O 2 /N 2 ratio are identified. The results show that pure-rotational fs/ps CARS is a robust and quantitative tool when applied across a wide range of flame conditions spanning lean H 2 /air combustion to fuel-rich sooting hydrocarbon flames.

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“…The routine is built on a nonlinear interpolating Levenberg-Marquardt algorithm to minimize the sum square of the residuals (SSQ) between experimental and theoretical spectra. The theoretical spectra were calculated using an inhouse-developed RCARS code, 21 updated with more recent N 2 Herman-Wallis factors, 22,23 to improve the accuracy in evaluated data. In Ref.…”

Section: Implementation For Rcars Thermometrymentioning

confidence: 99%

Direct measurement of S-branch N2-H2 Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy

Bohlin¹,

Nordström²,

Patterson³

et al. 2012

The Journal of Chemical Physics

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S-branch N2-H2 Raman linewidths have been measured in the temperature region 294–1466 K using time-resolved dual-broadband picosecond pure rotational coherent anti-Stokes Raman spectroscopy (RCARS). Data are extracted by mapping the dephasing rates of the CARS signal temporal decay. The J-dependent coherence decays are detected in the time domain by following the individual spectral lines as a function of probe delay. The linewidth data set was employed in spectral fits of N2 RCARS spectra recorded in binary mixtures of N2 and H2 at calibrated temperature conditions up to 661 K using a standard nanosecond RCARS setup. In this region, the set shows a deviation of less than 2% in comparison with thermocouples. The results provide useful knowledge for the applicability of N2 CARS thermometry on the fuel-side of H2 diffusion flames.

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On the sensitivity of rotational CARS N₂ thermometry to the Herman–Wallis factor

Cited by 38 publications

References 16 publications

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

Hybrid fs/ps rotational CARS temperature and oxygen measurements in the product gases of canonical flat flames

Direct measurement of S-branch N2-H2 Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy

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On the sensitivity of rotational CARS N2 thermometry to the Herman–Wallis factor

Cited by 38 publications

References 16 publications

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

Hybrid fs/ps rotational CARS temperature and oxygen measurements in the product gases of canonical flat flames

Direct measurement of S-branch N2-H2 Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy

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On the sensitivity of rotational CARS N₂ thermometry to the Herman–Wallis factor