共查询到20条相似文献,搜索用时 0 毫秒
1.
A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase
fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C–H stretching band of vapor
n-decane and liquid n-dodecane near 3.4 μm (3000 cm−1). n-Dodecane film thicknesses <20 μm were accurately measured in the absence of vapor, and simultaneous measurements of n-dodecane liquid film thickness and n-decane vapor mole fraction (300 ppm) were measured with <10% uncertainty for film thicknesses <10 μm. A potential application
of the measurement technique is to provide accurate values of vapor mole fraction in combustion environments where strong
absorption by liquid fuel or oil films on windows make conventional direct absorption measurements of the gas problematic. 相似文献
2.
Liuhao Ma Zhen Wang Kin-Pang Cheong Hongbo Ning Wei Ren 《Proceedings of the Combustion Institute》2019,37(2):1329-1336
We present the first demonstration of heterodyne phase-sensitive dispersion spectroscopy (HPSDS) for in situ, non-intrusive and quantitative CO2 concentration measurements in flames. Dispersion spectroscopy retrieves gas properties by measuring the refractive index in the vicinity of a molecular resonance. The HPSDS scheme features a significant diagnostic advantage of the intrinsic immunity to laser power fluctuations caused by beam steering, thermal radiation and soot scattering in combustion environments, and thus no extra calibration process is required. In this work, we described the spectroscopic fundamentals for measuring heterodyne phase signals in flames. As a proof of principle, we used a mid-infrared interband cascade laser (ICL) near 4183?nm to exploit the strong CO2 transitions in the R-branch of the v3 fundamental band. The HPSDS signals of four CO2 lines, R(76), R(78), R(80) and R(82), were measured in CH4/air flames to obtain CO2 concentrations at different equivalence ratios (Φ?=?0.8–1.2), yielding a good agreement with the simultaneous laser absorption measurements using the same ICL. With its immunity to laser power fluctuations verified experimentally, the HPSDS sensor was successfully implemented to measure CO2 concentrations in C2H4/air sooting flames (Φ?=?1.78–2.38). Laser dispersion spectroscopy proves to be a promising and alternative diagnostic tool for combustion measurements. 相似文献
3.
《Optics and Lasers in Engineering》2002,37(2-3)
We represent the results of our investigations on size distribution of atmospheric aerosol particles by means of a multiwavelength lidar based on Nd : YAG and Ti : Sa lasers equipped with frequency multipliers. The measurements were performed in mountainous areas. 相似文献
4.
R. Schlaf B. Höpfner J. Figueroa E. Tridas E. Welter T. Köhler I. Lauermann Ch.‐H. Fischer 《Journal of synchrotron radiation》2012,19(1):126-128
Spray deposition of thin films and coatings is a widely used manufacturing process owing to its low cost, versatility and simple implementation. The objective of the presented experiments was to investigate whether X‐ray absorption measurements on solutes carried by aerosols are possible, and what count rates can be achieved depending on solution flow through and the resulting mass density in the interrogation volume. The investigated prototypical spray aerosol was InCl3 dissolved in water or ethanol dispersed via an ultrasonic nebulizer. InCl3 spray is essential for the ion layer gas reaction process used for the deposition of In2S3 buffer layers for highly efficient chalcopyrite solar cells. The discussed experiments demonstrate that measurements are possible, but that the achievement of good signal‐to‐noise ratios requires extended sampling times and concentrated solutions. 相似文献
5.
Séan J. Cassady Christopher L. Strand Christopher S. Goldenstein R. Mitchell Spearrin Christopher M. Brophy Jay B. Jeffries Ronald K. Hanson 《Proceedings of the Combustion Institute》2019,37(2):1435-1443
A novel single-ended mid-infrared laser-absorption sensor for time-resolved measurements of water mole fraction and temperature was developed and deployed within the annulus of a hydrogen/air-fed rotating detonation engine (RDE). The sensor transmitted two laser beams targeting mid-infrared water transitions through a single optical port on the outer wall of the cylindrical RDE annulus and measured the backscattered radiation from the RDE inner surface using a photodetector for a round-trip path of 1.52?cm. Optimizing the sensor's optical arrangement using numerical ray tracing to minimize interference from optical emission, beam steering, and scattered laser light from window surfaces was essential to sensor performance. Scanned-wavelength-modulation spectroscopy with second-harmonic detection and first-harmonic normalization was implemented to allow for frequency-domain multiplexing of the two lasers and to suppress non-absorbing interference sources such as beam-steering and emission. Tunable diode lasers near 2551 and 2482?nm were modulated at 100 and 122?kHz, respectively, and sinusoidally scanned across the peaks of their respective water transitions at 10?kHz to provide a measurement rate of 20?kHz and detection limit of 0.5% water by mole. Experimentally derived spectroscopic parameters enabled water and temperature sensing with respective uncertainties of 7.3% and 5.3% relative to the measured values. Time-resolved and time-averaged sensor measurements of gas temperature and water vapor mole fraction allow quantitative evaluation of the combustion progress at the measurement location and thus provide a design tool for RDE optimization. Broadly, this single-ended laser sensor should find applications in other combustion systems where optical access is limited. 相似文献
6.
7.
Yingying Ma Pucai Wang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(2):338-6598
Classification is a critical step in the backscatter lidar data processing to accurately retrieve extinction and backscatter profiles of atmospheric aerosols and clouds. Different schemes, such as the probability distribution functions (PDFs) method, have been used in the cloud and aerosol classification. In this paper, we attempt to use the support vector machine (SVM) to discriminate aerosols from clouds, with a focus on dust aerosol classification in China. To demonstrate the feasibility of the SVM classifier, we chose dust storms that occurred in the Gobi and Taklimakan deserts and observed by the CALIPSO lidar in spring time 2007. The results show that the SVM can correctly identify the dust storms. 相似文献
8.
9.
10.
N. A. Myslitskaya A. V. Khitrin A. M. Ivanov I. G. Samusev V. V. Bryukhanov 《Russian Physics Journal》2012,54(11):1280-1285
The method of photon correlation spectroscopy is used to investigate the distribution of the diffusion coefficient of silver
nanoparticles in an evaporating water drop given that the drop base area remains unchanged (the pinning condition). It is
established that the capillary flow dominates over the diffusion nanoparticle motion in redistribution of concentration of
the dissolved nanoparticles. 相似文献
11.
A pre-selected 21 MHz ultrasonic transducer was used to produce characteristic pulses, arbitrarily similar to the quantum-mechanical concept of a phonon, describable as having a single-frequency modulated Gaussian shape. The propagation of such pulses in water-acoustic channels was studied in conjunction with nonlinear regression analysis and an Erlangian model for size distribution of molecular aggregates. Experimental results obtained distinguish between surface and bulk phenomena and provide quantitative measures of an average molecular cluster size in water. The relevance of the Erlangian model, in studying the near front of the channel, provides a significant distinction between the behavior of pure water and Ringer's solution of water. The inherent consistency between the various results re-enforces the theoretical approach, implying new venues for future research. 相似文献
12.
Evaporation is ubiquitous in nature, but very few attempts have been made in the past to couple the effects of evaporation with fluid flow behavior. In this theoretical paper we have discussed the effects of evaporation on the dynamics of steady state thermocapillary convection in a two-dimensional rectangular container. The liquid is heated by differentially heated sidewalls and mass loss from the interface due to evaporation is compensated by the liquid entering into the container through a lower inlet, thus keeping the thickness of the liquid layer constant. We show that for an evaporating liquid one can obtain a plane parallel base state profile which depends on the evaporative mass flux. 相似文献
13.
14.
Dissipative instability in a weakly ionized aerosol plasma has been studied with allowance for a finite electric conductivity of the medium, electron and ion diffusion, and friction of the aerosol component against a neutral gas. Instability is caused by the relative drift of the aerosol and ion components. Estimates of the basic parameters of instability (threshold, characteristic wavelengths, and increments) in experiments with dust crystals indicate that this instability can be an important additional factor upon the formation of regular structures in an aerosol plasma. 相似文献
15.
P. V. Lebedev-Stepanov S. P. Molchanov T. A. Karabut S. A. Rybak 《Acoustical Physics》2010,56(5):651-653
The nature of the self-oscillations of shape that occur in a meniscus of an evaporating colloidal solution (or a microdrop) is investigated. The concentration self-oscillations resulting in the formation of a solid film with a periodic and jumpwise decreasing thickness are considered. 相似文献
16.
F. Immler 《Applied physics. B, Lasers and optics》2003,76(5):593-596
Aerosols can introduce significant errors in measurements of trace gas concentration profiles with differential absorption
lidar (DIAL). Here, a solution to counteract the aerosol effect is introduced, which does not depend on additional measurements
and is applicable when absorption at the off-wavelength is not negligible. It is based on a numerical solution of the coupled
lidar equations and calculates the trace-gas concentration and the aerosol backscatter ratio simultaneously. Consequently,
most of the errors introduced by aerosols to DIAL measurements are inherently corrected and, additionally, the aerosol backscatter
profiles at the DIAL wavelengths are obtained.
Received: 23 December 2002 / Revised version: 24 March 2003 / Published online: 14 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-331/288-2178, E-mail: fimmler@awi-bremerhaven.de Present address: AWI Bremerhaven, Am
Handelshafen 12, 27570 Bremerhaven, Germany 相似文献
17.
Improvements for ground-based remote sensing of atmospheric aerosol properties by additional polarimetric measurements 总被引:1,自引:0,他引:1
Zhengqiang Li Philippe Goloub Oleg Dubovik Luc Blarel Wenxing Zhang Thierry Podvin Alexander Sinyuk Mikhail Sorokin Hongbin Chen Brent Holben Didier Tanr Marius Canini Jean-Pierre Buis 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(17):1954-1961
We discuss the improvements in the aerosol properties characterization resulting from the additional multi-wavelength polarization measurements measured by a new CIMEL polarized sun/sky-photometer, CE318-DP. In order to process direct-sun, sky and polarization measurements in a wide spectral range (340–1640 nm), we developed new calibration methods and strategies, e.g. using the Langley plot method to calibrate both direct-sun irradiance and sky radiance, as well as combining laboratory facilities with a vicarious method to calibrate the polarized sky measurements. For studying the impact of new polarimetric measurements on the retrievals of aerosol properties, we have processed an extensive record of field measurements using an updated Dubovik and King retrieval algorithm [Dubovik O, Sinyuk A, Lapyonok T, Holben BN, Mishchenko MI, et al. Application of spheroid models to account for aerosol particle nonsphericity in remote sensing of desert dust. J Geophys Res 2006;111:D11208.]. A preliminary analysis shows that adding polarization in the inversion can reduce possible errors (notably for about 30% of our field cases) in the fine mode size distribution, real part of refractive index and particle shape parameter retrievals, especially for small particles. 相似文献
18.
The performance of an electrical aerosol detector (EAD; TSI Model 3070A) was experimentally evaluated for measuring the integral parameters of particles (i.e., total length concentration of particles, and the total surface area concentrations of particles deposited in a human lung). The EAD consists of a unipolar diffusion charger with an ion trap, and aerosol electrometer. We first evaluated the performance of the EAD charger. Both polydisperse and monodisperse particles of Ag, NaCl, and oleic acid (with the dielectric constants of infinite, 6.1 and 2.5) were then generated to evaluate the particle material effect on the EAD readout. 相似文献
19.
20.
M.A. Mélières M. Chenevier F. Stoeckel 《Journal of Quantitative Spectroscopy & Radiative Transfer》1985,33(4):337-345
Quantitative measurements of intensities and widths were made for individual rotational lines of the atmospheric oxygen γ band by using a recently developed, highly sensitive, intracavity laser-absorption spectroscopic technique (ICLAS) at 300 torr m. The total band intensity derived from the line intensities is (STP). Self-broadening collision coefficients for the PP and PQ branch lines have been determined from the absorption line width and were found to vary from 0.055 cm?1 atm?1 at N″ = 1 to 0.037 cm?1 atm?1 at N″ = 27. 相似文献