Diode laser absorption sensors for gas-dynamic and combustion flows

Allen, Mark G.

doi:10.1088/0957-0233/9/4/001

Cited by 498 publications

(206 citation statements)

References 92 publications

(89 reference statements)

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“…The distance from the source of sound to the microphone differs slightly along the pathlength, and the effect of this on the signal generation process may merit further investigation. Nevertheless, the one-dimensional nature of this measurement technique should not be viewed as a critical limitation since this is an inherent feature of absorption spectroscopy, which has found very widespread application to combustion diagnostics [27,28]. Tomographic methods are sometimes used to extract spatially precise information from absorption measurements [29,30], and it is possible that similar approaches could also be applied to photoacoustic data.…”

Section: Discussionmentioning

confidence: 99%

A simple photoacoustic method for the in situ study of soot distribution in flames

et al. 2015

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of soot formation during combustion is a key step in developing soot reduction strategies [3,4].Optical measurement techniques are ideally suited for combustion environments because they generally cause negligible perturbation to the combustion process. One of the most widely used optical techniques for the study of particulate matter in flames is laser-induced incandescence (LII). Typical LII experimental schemes use a high-power pulsed laser source (such as a solid-state Nd:YAG laser) [5] to heat the soot particles. The resulting thermal emission is then detected, usually over a narrow range of wavelengths selected using either a system of optical filters [6] or a monochromator [7]. The peak signal level provides a measure of the relative soot volume fraction. The absolute soot volume fraction is found either by calibration based on optical extinction measurements [8,9] or by a two-colour approach in which a second filtered detector collects light from the same measurement volume, and the ratio of signals is used to determine the peak particle temperature [10,11]. A feature of this type of experimental set-up is that a high-power pulsed laser source and relatively fast photodetectors or intensified cameras are required.Photoacoustic (PA) detection has been used to make highly sensitive laser absorption measurements in a number of applications, such as IR spectroscopy [12]. The principle of photoacoustic detection of particles is that absorption of the incident laser energy leads to an increase in the temperature of the particle. Heat is transferred from the particles to the surrounding gas, resulting in the expansion of the gas [13]. A change in laser intensity leads to a change in the rate of heat transfer, and an acoustic pressure wave can therefore be established by modulating the intensity of the laser [14]. The pressure wave can be detected using a microphone, and its amplitude measured using a lock-in amplifier. This method of detection has a further advantage Abstract This paper presents a simple photoacoustic technique capable of quantifying soot volume fraction across a range of flame conditions. The output of a highpower (30 W) 808-nm cw-diode laser was modulated in order to generate an acoustic pressure wave via laser heating of soot within the flame. The generated pressure wave was detected using a micro-electro-mechanical microphone mounted close to a porous-plug flat-flame burner. Measurements were taken using the photoacoustic technique in flames of three different equivalence ratios and were compared to laser-induced incandescence. The results presented here show good agreement between the two techniques and show the potential of the photoacoustic method as a way to measure soot volume fraction profiles in this type of flame. We discuss the potential to implement this technique with much lower laser power than was used in the experiments presented here.

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Section: Discussionmentioning

confidence: 99%

A simple photoacoustic method for the in situ study of soot distribution in flames

et al. 2015

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“…Coherent anti-Stokes Raman spectroscopy (CARS) is widely used for gas phase temperature measurements in the combustion field and is capable of both 2D (Bohlin and Kliewer 2014) and 1D (Kulatilaka et al 2011) mapping, though it is more commonly used for point measurements since three overlapping laser light fields are needed for the measurement volume. Tuneable diode laser absorption spectroscopy (TDLAS) measures narrow line absorption of gas species such as water vapor along the path of a laser beam (Cai et al 2009;Allen 1998), providing an average temperature over the beam path. And 1D profiles can be obtained through wavelength multiplexing across multiple absorption bands (Liu et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Fiber optic distributed temperature sensor mapping of a jet-mixing flow field

2015

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“…The combination of two strong lines in the spectral ranges 1.39 μ and 1.34 μ was selected as the optimal one. The efficiency of the developed technique was exemplified in the first set of the experiments in conditions of real propulsion in Zhukovsky Central Aerohydrodynamic Institute (TsAGI) for the temperatures within (500-2200) К range and total pressure up to 3 atm.Absorption spectroscopy with diode lasers (DLAS) is widely used for diagnostics of gases [1][2][3][4][5][6]. It is particulary the most popular technique for contactless probing of different combustion zones in mixing gas flows because any traditional thermocouples being inserted in a flow strongly modifies the structure of the flow.…”

mentioning

confidence: 99%

“…Absorption spectroscopy with diode lasers (DLAS) is widely used for diagnostics of gases [1][2][3][4][5][6]. It is particulary the most popular technique for contactless probing of different combustion zones in mixing gas flows because any traditional thermocouples being inserted in a flow strongly modifies the structure of the flow.…”

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confidence: 99%

Measurement of the parameters of non-stationary gas flows by diode laser absorption spectroscopy in case of high temperature and high pressure

et al. 2016

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Abstract. Experimental version of diode laser absorption spectrometer (DLAS) for contactless measurements of temperature and water vapor concentration in supersonic gas flows is developed. The spectrometer can be used for the measurements of temperature up to 2500 K and total pressure up to 3 atm. The technique is based on the registration of the transient absorption spectra of a target molecules and fitting of the experimental spectra by the simulated ones constructed using the spectroscopic databases. The temperature is inferred from the ratio of the intensities of the absorption lines with different low energy levels. In gas media with the above parameters the absorption lines are broadened which demands the use of two diode lasers (DL) working in different spectral ranges. The software for selection of the optimal line combinations was developed. The combination of two strong lines in the spectral ranges 1.39 μ and 1.34 μ was selected as the optimal one. The efficiency of the developed technique was exemplified in the first set of the experiments in conditions of real propulsion in Zhukovsky Central Aerohydrodynamic Institute (TsAGI) for the temperatures within (500-2200) К range and total pressure up to 3 atm.Absorption spectroscopy with diode lasers (DLAS) is widely used for diagnostics of gases [1][2][3][4][5][6]. It is particulary the most popular technique for contactless probing of different combustion zones in mixing gas flows because any traditional thermocouples being inserted in a flow strongly modifies the structure of the flow.General approach of DLAS technique is based on the measurement of the integral intensities of two lines of a test molecule with different energies of low levels. Assuming the termodynamic equilibrium the ratio of the line intensities S(T) depends only on gas kinetic temperature. In case of low pressure (<1 atm.) and temperature (<1500 K) the absorption lines are relatively narrow and can be spectrally resolved. One can find a spectral interval in near-ir with different absorption lines of water molecules lieing within a

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Diode laser absorption sensors for gas-dynamic and combustion flows

Cited by 498 publications

References 92 publications

A simple photoacoustic method for the in situ study of soot distribution in flames

A simple photoacoustic method for the in situ study of soot distribution in flames

Fiber optic distributed temperature sensor mapping of a jet-mixing flow field

Measurement of the parameters of non-stationary gas flows by diode laser absorption spectroscopy in case of high temperature and high pressure

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