Noncontact optoacoustic monitoring of flame temperature profiles

Zapka, Werner; Pokrowsky, P.; Tam, A. C.

doi:10.1364/ol.7.000477

Cited by 29 publications

(4 citation statements)

References 8 publications

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“…In this way, the whole acoustic wave front arrives simultaneously at the focused probe beam, (6) surement at two separations is presently used to derive the ultrasonic absorption spectrum. A much faster measurement is possible by use of two probe beams 12 at separations x and x' from the target surface for single-shot detection of the deflections.…”

Section: Optical Generation and Detection Of Acoustic Pulse Profiles mentioning

confidence: 99%

Optical Generation and Detection of Acoustic Pulse Profiles in Gases for Novel Ultrasonic Absorption Spectroscopy

Tam

Leung

1984

Phys. Rev. Lett.

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We demonstrate a new all-optical, frequency-multiplexed, and fast technique for gas-phase ultrasonic absorption spectroscopy. A pulsed laser produces a short-duration acoustic pulse in the gas sample, and the acoustic pulse profiles at two distances are monitored by focused continuous probe beams. Fourier decompositions of these probe deflection signals provide the absorption spectrum, and examples for C0 2 and a C0 2 + H 2 0 mixture are given. Ultrasonic propagation speeds in the megahertz regime are also obtained for several gases. PACS numbers: 42.60.-v, 34.50.-s, 43.85.+fConventional acoustic absorption spectroscopy 1 " 5 in gases has been performed with transducers such as quartz plates, microphones, etc. The use of transducers for gases causes several limitations. The frequency response is usually limited to < 1 MHz. Also, the frequencies are scanned point by point, and the procedure is thus slow and unsuitable for transient conditions. Short-pulsed measurements are difficult because of transducer ringing. Furthermore, transducers cannot be used in hostile environments like flames. We describe here a new all-optical, pulsed, and multiplexed technique that avoids the above limitations, and is useful for acoustic absorption spectroscopy of gases. This technique relies on the use of a short-duration laser pulse to generate reliably a narrow acoustic pulse containing a broad Fourier frequency spectrum; as this pulse propagates, the various Fourier components are absorbed differently, resulting in pulse distortion that is probed by a focused cw laser beam. Fast Fourier transform of the transient probe deflection signal provides the acoustic absorption spectrum; this is much faster than the conventional pointwise frequency measurement. Our technique can be called "optoacoustic spectroscopy of the second kind" (OAS II) because it exploits optoacoustic pulse generation 6 " 8 for acoustic spectroscopy. This should be distinguished from the well-known optoacoustic spectroscopy 9 (understood to be the first kind), which exploits optoacoustic pulse generation for optical spectroscopy.Our experimental demonstration of OAS II is shown in Fig.

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Section: Optical Generation and Detection Of Acoustic Pulse Profiles mentioning

confidence: 99%

Optical Generation and Detection of Acoustic Pulse Profiles in Gases for Novel Ultrasonic Absorption Spectroscopy

Tam

Leung

1984

Phys. Rev. Lett.

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“…In addition, the corresponding optical paths are arranged, and the operation process has a certain complexity. It is challenged to use laser spectroscopy for temperature measurement in some high-vibration and high-dust industrial environments [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Determination of Non-Uniform Soot Temperature and Volume Fraction from Flame Images

Liu¹,

Liu²,

Sun³

et al. 2023

HSET

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This paper presents a method to invert the two-dimensional distribution of temperature and volume fraction of soot particles from flame images. The temperature field and particle volume concentration field of the non-uniform soot flame are simultaneously reconstructed using the wide response spectrum of the color CCD camera without adding monochromatic filters. The influences of the number of cameras, error of cameras position angle, measurement noise and different reconstruction algorithms on the measurement accuracy, are analyzed. The numerical simulation results demonstrate that the error of cameras position angle plays a crucial role in the reconstruction accuracy. In addition, increasing the number of cameras can improve the reconstruction results accuracy. Compared with the least squares algorithm, the Tikhonov regularization algorithm has a stronger anti-noise ability, which can resist 39 dB of noise. The conclusions obtained in this paper are helpful to guide the following experimental studies.

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“…In addition, corresponding optical paths are arranged, and the operation process has a certain complexity. It is challenging to use laser spectroscopy for temperature measurement in some high-vibration and high-dust industrial environments [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Numerical Simultaneous Determination of Non-Uniform Soot Temperature and Volume Fraction from Visible Flame Images

Yan

et al. 2022

Energies

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This paper presents a method to invert the two-dimensional distribution of a temperature and volume concentration of soot particles from color images. By using numerical simulation, the temperature field and particle volume-concentration field of a non-uniform soot flame are simultaneously reconstructed using the wide-response spectrum of a color CCD camera without adding monochromatic filters. The influence of number of cameras, error of camera position angle, measurement noise and different reconstruction algorithms on measurement accuracy are analyzed. The numerical-simulation results demonstrate that camera-position angle errors play a crucial role in the reconstruction accuracy. In addition, increasing the number of cameras can improve the reconstruction result accuracy. Compared with the least squares algorithm, the Tikhonov-regularization algorithm has a stronger anti-noise ability and can resist 39 dB of noise. The conclusions obtained in this paper are helpful to guide following experimental studies.

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Noncontact optoacoustic monitoring of flame temperature profiles

Cited by 29 publications

References 8 publications

Optical Generation and Detection of Acoustic Pulse Profiles in Gases for Novel Ultrasonic Absorption Spectroscopy

Optical Generation and Detection of Acoustic Pulse Profiles in Gases for Novel Ultrasonic Absorption Spectroscopy

Simultaneous Determination of Non-Uniform Soot Temperature and Volume Fraction from Flame Images

Numerical Simultaneous Determination of Non-Uniform Soot Temperature and Volume Fraction from Visible Flame Images

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