Oxygen-distribution imaging with a novel two-tracer laser-induced fluorescence technique

Koban, W.; Schorr, J. R.; Schulz, Christof

doi:10.1007/s003400100769

Cited by 49 publications

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“…Ketones are the most frequently used class of fluorescent tracers. Their properties have been extensively studied [7][8][9][10] and they have been applied to various practical situations [3][4][5]. The high vapor pressure makes acetone (boiling point 56°C) an ideal tracer for gaseous flows [11].…”

Section: Spectroscopic Conceptmentioning

confidence: 99%

“…For the determination of the fluctuations of mixture formation, many methods have been applied [1]. Methods like LIF (laser-induced fluorescence), infrared absorption, flame luminosity and spectrally-resolved visible and ultraviolet emissions from the flame have been used for measurements of fuel concentration [2], temperature [3] and oxygen concentration [4] in the end gas. Yet, optical sensors for the ultraviolet (UV) spectral range for minimal intrusive measurements on close-to-production engines have not been realized so far.…”

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confidence: 99%

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Fiber optic spark plug sensor for UV-LIF measurements close to the ignition spark

et al. 2005

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Time-resolved observation of the fuel/air mixing process prior to ignition is crucial for the development of modern internal combustion engine concepts. The presented fiber optic sensor is designed for the acquisition of in-cylinder data in the area close to the ignition spark, based on UV-laser-induced fluorescence of organic fuel compounds. Excitation and fluorescence light are separately guided through silica fibers. The detection volume is defined by the optical design of the sensor head. Since the related components are completely integrated into a modified spark plug, the sensor can be applied to unmodified production line engines. We present the fundamental spectroscopic concept, the solution for the minimal invasive access through the spark plug and tracer spectra measured with a prototype.Keywords: Fiber optic sensor, Tracer LIF (laser induced fluorescence), Microoptical sensor, UV-LIF INTRODUCTIONRecent research on modern direct injection spark ignition (DISI) engines opened a promising concept for reducing fuel consumption and CO 2 exhaust. Most engines still provide a homogeneous fuel/air distribution throughout the whole combustion chamber, throttling the airflow to ensure stoichiometric conditions at part-load conditions and thus loosing energy (pumping losses). Modern DISI engines operate nearly unthrottled with a very lean fuel/air mixture to reduce those pumping losses. The safe, clean and reliable operation of any combustion device depends to a large degree on the exact control of the air-fuel mixing process prior to ignition. To insure ignition of the over-all fuel, it is necessary to provide a highly defined (i.e. stratified) distribution of the fuel vapor, which would be too lean for ignition under homogeneous conditions. Because of the spatially inhomogeneous equivalence ratio, the ignition performance is very sensitive to mixture distribution and timing. Therefore, quantitative measurement techniques that characterize the state of the unburned gas mixture are crucial in modern combustion science. The major problem in the development of DISI engines is the cyclic variation of the combustion process, which leads to high raw emissions of soot and hydrocarbons and causes inhomogeneous temperature distributions that are responsible for increased formation of nitric oxide. These emissions can only be partially reduced using state-of-the-art exhaust aftertreatment systems. Especially for the stratified mode the fuel/air composition at the start of combustion is an important factor for the ignition and combustion process of the individual cycle. The equivalence ratio determines ignitability and flame speed. For lean and rich mixtures the flame speed is reduced compared to stoichiometric composition. Thus the fuel/air mixing strongly affects cyclic variations of the combustion process. With the measurement technique presented in this paper we aim to get time-resolved in-situ information about the variations of the equivalence ratio and temperature close to the spark gap region, which are key...

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Section: Spectroscopic Conceptmentioning

confidence: 99%

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confidence: 99%

Fiber optic spark plug sensor for UV-LIF measurements close to the ignition spark

et al. 2005

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“…As tracers for the visualizations of fuel mixing and evaporation processes, an exciplex of TMPD and naphthalene is a prospective candidate because separate measurements of LIF from injected liquid fuel and its vapor may be possible (Melton, 1983). The advantage of the different responses of 3-pentanone and toluene to collisional quenching by molecular oxygen was used for the measurement of oxygen concentration (Koban et al, 2002).…”

Section: Regular Papermentioning

confidence: 99%

Temperature dependence of intensities of laser-induced fluorescences of ethylbenzene and naphthalene seeded in gas flow at atmospheric pressure

Hirasawa

Kaneba

Kamata

et al. 2007

J Vis

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The present study has been carried out with the aim of developing a technique for measuring two-dimensional gas temperature profiles based on two-color fluorescence induced by a one-color laser. The laser sheet of the fourth harmonic (266 nm) from a Nd:YAG laser induced fluorescence in species doped in a nitrogen gas flow. The LIF spectra of seven fluorescent species, namely acetone, methylethylketone, acetaldehyde ethylbenzene, anisole, aniline, and naphthalene, were measured to select the best prospective pair of fluorescent species for this technique. Ethylbenzene and naphthalene show relatively high LIF intensities and their LIF spectra overlap less with each other than with other species. Also, ethylbenzene has a high temperature dependence while naphthalene has a low temperature dependence. Thus by selecting one portion of wavelengths in the range where ethylbenzene or naphthalene is dominant, the temperature of the gas can be determined using the ratio of LIF intensities of the mixture at the two wavelengths with good temperature sensitivity. In addition, a general principle is presented for finding out an optimum pair of wavelengths to obtain a good temperature sensitivity in those LIF spectra.

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“…Some of the challenges (particularly related to pressure effects) on the use of toluene for fuel/air ratio measurements have also been identified [12,15,20,21]. The properties of oxygen quenching on fluorescence have also been exploited for a direct measure of oxygen concentration in both single-tracer [22] and dual-tracer [23] configurations. Furthermore, because of the relatively large fluorescence quantum yield, toluene PLIF has also been successfully used for high-framing-rate imaging configurations where laser pulse energies are typically limited [14,20,24].…”

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Temperature and number density measurement in non-uniform supersonic flowfields undergoing mixing using toluene PLIF thermometry

et al. 2015

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visualization and quantification of many flow properties, including scalar concentration and temperature measurements, and it has been long used in both low-and highspeed flows. PLIF imaging based on a variety of tracers has been considered through the literature [1]. Historically, acetone and 3-pentanone [2, 3] have been widely used for scalar and temperature imaging, and more recently, naphthalene [4,5], krypton [6], 1-methylnaphthalene [7], and anisole [8] have been utilized in a variety of applications.Toluene has been identified as a versatile candidate for PLIF studies owing to its large fluorescence quantum yield and strong temperature sensitivity [9][10][11][12][13]. Toluene PLIF has found many applications for the study of mixing, especially in internal combustion engine studies [10,12,[14][15][16][17] where the strong oxygen quenching [18] has been used to obtain a direct measurement of air/fuel ratio [1,12,19]. Some of the challenges (particularly related to pressure effects) on the use of toluene for fuel/air ratio measurements have also been identified [12,15,20,21]. The properties of oxygen quenching on fluorescence have also been exploited for a direct measure of oxygen concentration in both single-tracer [22] and dual-tracer [23] configurations. Furthermore, because of the relatively large fluorescence quantum yield, toluene PLIF has also been successfully used for high-framing-rate imaging configurations where laser pulse energies are typically limited [14,20,24].Toluene PLIF has proven to be a particularly robust approach for temperature measurements. Both singleand dual-band-detection schemes have been proposed [10, 13] and applied [16,[25][26][27][28][29]. Its use as a thermometry technique stems from the strong temperature dependence of the integrated fluorescence quantum yield and the temperature-induced red shift of the spectral fluorescence Abstract Single-excitation, dual-band-collection toluene planar laser-induced fluorescence (PLIF) is used to measure temperature and number density (or partial pressure) fields in non-uniform supersonic complex flows in the presence of mixing and compressibility. The study provides a quantitative evaluation of the technique in transverse jets in supersonic crossflow (JISCF). It is found that toluene PLIF is highly effective in visualizing the structure of supersonic flows and that temperature can be accurately inferred with acceptable signal-to-noise ratios (of order 30) even when mixing occurs. The technique was applied to several JISCFs that differ by jet fluid properties with resulting different structures. In the presence of compressibility and mixing, it is found that the PLIF signal is non-unique, a feature that is used to identify the mixing region of the transverse jet. Measurement errors due to camera registration errors have also been quantified. Because of the complexity of the flowfield, it is found that minute misalignment (<0.1 pixels) between the two PLIF images can introduce measurable errors on the order of tens of Kelvins and significa...

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Oxygen-distribution imaging with a novel two-tracer laser-induced fluorescence technique

Cited by 49 publications

References 0 publications

Fiber optic spark plug sensor for UV-LIF measurements close to the ignition spark

Fiber optic spark plug sensor for UV-LIF measurements close to the ignition spark

Temperature dependence of intensities of laser-induced fluorescences of ethylbenzene and naphthalene seeded in gas flow at atmospheric pressure

Temperature and number density measurement in non-uniform supersonic flowfields undergoing mixing using toluene PLIF thermometry

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