A shutter-based line-imaging system for single-shot raman scattering measurements of gradients in mixture fraction

Barlow, Robert S.; Miles, Paul C.

doi:10.1016/s0082-0784(00)80220-9

Cited by 26 publications

(4 citation statements)

References 13 publications

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“…So the interference should be considered when using a popular temperature measurement technique that fits the N 2 Q-branch shape (including broadband N 2 CARS). While the integrated intensity of the S (10) branch is less than 2% of that of the N 2 Q-branch in this case, it becomes more important in either higher-temperature, or more fuel-rich, H 2 flames. As seen in figures 8(b), 9(b) and10(b) the calculated vib-H 2 spectra agree well with the measured spectra.…”

Section: Combustion Temperaturementioning

confidence: 71%

“…(1) increased slit width: a 4× signal level increase can be obtained with a 0.1 mm slit instead of the current 0.025 mm slit (we used a narrow slit to observe the detailed spectral shape but it is not necessary for temperature and species concentration measurements via pixel integration method); (2) direct coupling of the collection lens to the spectrograph/CCD camera [10,17]: a 3.14× increase can be achieved since 68% of the collected light is lost when a 400 µm core fibre is imaged onto a 100 µm slit (furthermore, reflection losses at both surfaces of two fibres can be avoided, thus giving about a 1.2× increase);…”

Section: Raman Diagnosticsmentioning

confidence: 99%

“…In particular, spontaneous Raman scattering (SRS) has been a popular method of probing flames because it is one of the few techniques that provides quantitative multi-species, point measurements in turbulent reacting flows [1,2]. Although spontaneous Raman signals are inherently very weak, one can expect high quality SRS data with good signal-to-noise ratio (SNR) using either UV laser excitation [3][4][5][6][7][8] or visible laser excitation in conjunction with a high-performance optical set-up that utilizes a pulse-stretcher, mechanical shutter and high-sensitivity detection methods [9][10][11]. Thus, even single-shot measurements with good SNR can be achieved in turbulent flames using SRS.…”

Section: Introductionmentioning

confidence: 99%

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Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H₂–air flames

Kojima

Nguyen²

2004

Meas. Sci. Technol.

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Rotational and vibrational spontaneous Raman scattering (SRS) spectra of H 2 , N 2 and H 2 O have been measured in H 2 -air flames at pressures up to 30.4 bar as a first step towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in terms of spectral resolution, wavelength coverage and signal-to-noise ratio for use in the development of transferable standards for the cross-talk calibration matrix. The fully resolved Stokes and anti-Stokes shifted spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a spectrograph fitted with a non-intensified CCD detector and a high-speed shutter. Temperatures were determined via the intensity distribution of rotational H 2 lines at stoichiometric and fuel-rich conditions. A discussion of the temperature measurement accuracy in terms of the number of laser shots, including a single-shot measurement, is presented. Theoretical Raman spectra of hydrogen were calculated using a semi-classical anharmonic-oscillator model with recent pressure broadening data and were compared with experimental data. The data and simulation showed good agreement at different equivalence ratios and pressures and indicate that high-J rotational lines of H 2 may interfere with the N 2 vibrational Q-branch lines, which could lead to errors in N 2 -Raman thermometry based on the line-fitting method. In addition, the relative intensities of the O-and S-branches to the Q-branch were determined theoretically and the result indicates that further studies of spectral interferences including contributions from O-and S-branches should be pursued. Finally, from a comparison of N 2 Q-branch spectra in lean H 2 -air flames at nearly atmospheric (1.2 bar) and high pressure (30.4 bar), we found no significant line-narrowing or -broadening effects at a spectral resolution of 0.04 nm.

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Section: Combustion Temperaturementioning

confidence: 71%

Section: Raman Diagnosticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H₂–air flames

Kojima

Nguyen²

2004

Meas. Sci. Technol.

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“…Thus, the Raman spectroscopy has been widely used for the combustion diagnostics of simple laboratory flames such as hydrogen diffusion flames (2) - (4) and premixed flames of various fuels (5), (6) . Furthermore, application of the Raman spectroscopy to diagnostics of practical combustion devices (7), (8) can be found in some recent studies.…”

Section: Introductionmentioning

confidence: 99%

Measurement of Fuel Concentration Distribution in a Sooting Flame through Raman Scattering

Hayashida

Amagai

Satoh

et al. 2006

JSME international journal. Ser. B, Fluids and thermal engineer

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Spontaneous Raman spectroscopy with KrF excimer laser was applied to obtain a fuel concentration distribution in a sooting flame. In the case of sooting flame, fluorescence from polycyclic aromatic hydrocarbons (PAH) and laser-induced incandescence (LII) from soot particles appeared with Raman scattering. These background emissions overlapped on the Raman scattering. In order to separate the Raman scattering and the background emissions, polarization property of laser-induced emissions was utilized. Since the background emissions were depolarized whereas the Raman scattering was highly polarized, it is possible to subtract the background emissions from the overlapping signal of the Raman scattering and the background emissions. Subtracting the emission signals for the electric vector of the laser light perpendicular and parallel to the direction of observation allows to extract the precise Raman signals. By using this technique, detailed fuel concentration distribution in sooting flames could be obtained based on Raman scattering.

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Laser‐Based Combustion Diagnostics*Update based on original article by Jürgen Wolfrum, Thomas Dreier, Volker Ebert, and Christof Schulz, Encyclopedia of Analytical Chemistry, ©2000, John Wiley & Sons Ltd.

Dreier

Ebert

Schulz

2011

Encyclopedia of Analytical Chemistry

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In laser spectroscopy, the interaction of light emitted from various types of laser sources — tunable or nontunable in their output frequency — with the atomic or molecular species of interest is used to probe the sample through a variety of spectral responses. In order to perform laser spectroscopy, suitable laser sources must be selected, which meet the requirements of the chosen spectroscopic method. This means that the laser has to provide radiation in the wavelength range of interest, has the appropriate emission characteristics (lineshape), and has a suitable energy to perform the measurements. Further requirements are pulse length (milliseconds to femtoseconds or continuous wave), repetition rate, and beam profile. Nowadays, laser radiation can be generated with most of the required parameters necessary for the respective spectroscopic application, either directly or by generating new radiation frequencies by frequency mixing of one or several laser beams in a nonlinear medium (gas, liquid, and solid). As an example, the most direct interrogation technique is absorption of laser radiation (LAS, laser absorption spectroscopy) by suitable spectroscopically allowed transitions in atoms or molecules, which are known from conventional spectroscopic methods. The increase or decrease in the laser radiation transmitted through the sample is then a measure of the amount of substance probed in the sample, which characteristically absorbs at the required wavelength. Laser light scattering methods, elastic (Rayleigh scattering (RS)) and inelastic (spontaneous Raman scattering (SRS)), are other techniques to probe the medium. In the first method, which is not species specific, the density of the medium can be interrogated, whereas the second is able to probe all species with Raman‐active vibration‐rotation transitions. There are several advantages in using laser spectroscopy instead of conventional spectroscopic techniques using conventional thermal light sources. The spectral brightness of laser beams is many orders of magnitude higher than that of thermal radiation sources, which correspondingly increase the detection sensitivity of laser spectroscopic techniques. In addition, the small linewidth of the emitted radiation dramatically increases the spectral resolution such that minor details of the spectroscopic branch investigated can be resolved. This enables more quantitative interpretations of all parameters influencing the lineshape and line intensity of the probed transition, and as such the physical and chemical environments of the probed species: temperature, pressure, velocity, chemical species, and so on. It makes laser spectroscopic techniques much more selective than conventional methods, which often are not able to separate closely spaced spectral features from different species. A third advantage of laser spectroscopic techniques is connected with the variable pulse duration and repetition frequency of lasers: the very short pulse lengths can be used successfully to probe the sample within time periods that are short compared to any other physical or chemical time development — flow, chemical reaction, pressure changes, and so on. Finally, the small spatial regions that can be probed by focusing diffraction‐limited laser beams makes laser spectroscopic techniques ideally suited for applications where high spatial resolution is required. All these advantages of laser spectroscopy are beneficial when the various techniques are applied as a diagnostic tool in combustion processes: flames constitute a complex interaction of fast chemistry with flow fields and surfaces, and therefore, a detailed understanding of combustion events often needs in situ, species‐specific optical diagnostics with high spatial and temporal resolution. In many recent applications, laser spectroscopy has become a developed technique that can even be performed by nonlaser specialists. However, numerous laser spectroscopic techniques require detailed theoretical knowledge of the spectroscopy underlying the respective technique and the use of sophisticated equipment in order to obtain meaningful results. Future development is aimed toward simplifying experimental set‐ups, data evaluation, and maintenance. This development runs parallel to the breathtaking development in laser technology that continuously increases available wavelength ranges, simplicity of use, pulse power, and repetition rates.

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A shutter-based line-imaging system for single-shot raman scattering measurements of gradients in mixture fraction

Cited by 26 publications

References 13 publications

Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H₂–air flames

Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H₂–air flames

Measurement of Fuel Concentration Distribution in a Sooting Flame through Raman Scattering

Laser‐Based Combustion Diagnostics*Update based on original article by Jürgen Wolfrum, Thomas Dreier, Volker Ebert, and Christof Schulz, Encyclopedia of Analytical Chemistry, ©2000, John Wiley & Sons Ltd.

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A shutter-based line-imaging system for single-shot raman scattering measurements of gradients in mixture fraction

Cited by 26 publications

References 13 publications

Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H2–air flames

Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H2–air flames

Measurement of Fuel Concentration Distribution in a Sooting Flame through Raman Scattering

Laser‐Based Combustion Diagnostics*Update based on original article by Jürgen Wolfrum, Thomas Dreier, Volker Ebert, and Christof Schulz, Encyclopedia of Analytical Chemistry, ©2000, John Wiley & Sons Ltd.

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Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H₂–air flames

Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H₂–air flames