The saturation of the fluorescence and its consequences for laser-induced fluorescence thermometry in liquid flows

Chaze, William; Caballina, Ophélie; Castanet, Guillaume; Lemoine, Fabrice

doi:10.1007/s00348-016-2142-8

Cited by 71 publications

(93 citation statements)

References 37 publications

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“…Although different temperatures can clearly be distinguished, an unexpected inhomogeneity pattern is evident for each measured temperature. The inhomogeneity explains the standard deviation of the calibration that corresponds to about 3 to 4 K. Locally increased temperatures are found to be nonphysical, because the laser pulse itself causes only a negligible temperature change of ∆T=0.07 K for the given experimental configuration 10 . The cause of the emerged inhomogeneity pattern is more likely caused by a locally changed laser excitation intensity that affects the fluorescence spectrum of one detection wavelength band stronger than the other.…”

Section: Development Steps Of Pulsed 2d-2clif With Mdr-enhanced Energmentioning

confidence: 99%

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Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays

Palmer

Reddemann

Kirsch

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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A new method for instantaneous measurement of temperature, size and velocity of micro-droplets has been developed. The method is based on the well-known 2-color laser-induced fluorescence (2cLIF) technique, but uses a pulsed laser for 2-dimensional imaging without motion blur and an adjusted dye mixture for suppression of LIFMDRs by utilizing the MDR-enhanced energy transfer effect. This work presents the development steps that are necessary to verify feasibility of pulsed 2D-2cLIF-EET for micro droplet and hollow-cone spray applications.

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Section: Development Steps Of Pulsed 2d-2clif With Mdr-enhanced Energmentioning

confidence: 99%

“…different types of fluorophores for various liquids [6,7] or a third PMT for an additional wavelength band that accounts for self-absorption effects of a single dye [8]. More interestingly, latest 2cLIF publications consider a pulsed laser for fluorescence excitation [2,9,10]. Pulsed lasers solve the issue of motion blur.…”

Section: Introductionmentioning

confidence: 99%

Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays

Palmer

Reddemann

Kirsch

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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“…However, for the purpose of instantaneous imaging, it is very advantageous using pulsed laser sources, which allow delivering a considerable amount of energy over a very short period of time (typically a few ns). According to Chaze et al [8], the fluorescence F λ signal emitted at a wavelength λ in an elementary volume V of liquid can be expressed by:…”

Section: Droplet Temperature Measurementsmentioning

confidence: 99%

“…Examples of temperature measurements based on 2cLIF can be found in the literature. Application are related to single-phase liquid flows [8], monosized droplet streams [7] and sprays [5]. In most of these applications, a CW laser was used to induce fluorescence.…”

Section: Droplet Temperature Measurementsmentioning

confidence: 99%

“…Light intensity within the laser sheet was not sufficient to shorten the exposure time of the cameras enough to obtain instantaneous images of the impinging droplets. More recently, several improvements to the 2cLIF technique were made by [8] to achieve single shot measurements of the temperature using nanosecond pulse laser. The present study relies on these previous works for the development of optical diagnostics adapted to the characterization of heat and mass transfers at the drop impact on heated solid surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Instantaneous heat transfers at the impact of a droplet onto a hot surface in the film boiling regime

Chaze¹,

Castanet²,

Caballina³

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Heat and mass transfers at the impact of a droplet onto a hot solid surface are investigated experimentally. Millimetersized water droplets impinges onto a perfectly flat sapphire surface heated at 600°C. The temperature of the liquid inside the droplet is measured using the two-color laser-induced fluorescence (2cLIF) technique. Water is seeded with a temperature-sensitive fluorescent dye, while a nanosecond pulsed laser is used for the excitation of the fluorescence. The ratio of fluorescence signal detected in two appropriate spectral bands allows to determine the liquid temperature. One advantage of this non-intrusive optical technique is that it eliminates adverse effects associated with signal variations caused by droplet shape during its impact. In parallel, the temperature of the solid surface is characterized using infrared thermography. The latter measurements are made possible by the deposition of a nanosize coating of titanium aluminium nitride (TiAlN) on the upper surface of the sapphire window. Thanks to the high frame rate of the IR camera, the time evolution of the heat flux distribution at the solid surface can be reconstructed. A comparison of IR and 2cLIF techniques enable to correlate the heating of the liquid with the cooling of the wall. This reveals that most of the heat removed from the solid surface is devoted to the heating of the liquid, the energy used for liquid vaporization being significantly lower. IntroductionMany industrial applications require a rapid cooling of surfaces from high temperatures. Among the cooling technologies, spray cooling is certainly one of the most attractive for the thermal management of high heat flux systems. Compared to jet impingement, it has the capability of cooling a relatively wider surface area with a single nozzle. It also has an unrivalled cooling efficiency, meaning that significant quantities of coolant liquid can be saved to remove the same amount of heat. These features explain why it is widely employed in many industrial applications, especially in metal production and processing industry. However, while it is applied for decades, its integration remains a complex and cumbersome process because of still incomplete knowledge of the fluid flow and heat transfer characteristics. In particular, scientific investigations focused on individual droplets are still required to understand the underlying physics behind the interactions between droplets and a hot solid surface. When a drop impacts a hot wall, different behaviours are observed. The drop can spread over the solid surface and remain attached to it due to wettability forces. It can splash and creates several smaller secondary droplets or simply rebounds. Extensive experimental investigations were carried out in the past to characterize the parameters influencing the drop behavior at the impact. Among them, some can be related to the dynamic of the impacting droplets (velocity, diameter, etc.), the physical properties of the liquid (viscosity, surface tension, etc.), and the solid su...

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Saturated laser-induced fluorescence in liquid kerosene seeded with a dye: influence of temperature and excitation intensity

et al. 2019

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Fluorescence-based techniques are commonly implemented to characterize droplet sprays in flows at temperature above 293 K. Nevertheless, in the case of gas turbine altitude relight, aeroengines are exposed to critical operating conditions where the liquid fuel temperature can reach values as low as-40°C. As a result, it is necessary to address the influence of this parameter on fluorescence intensity for temperatures below room values. In this paper, an innovative SLIF (Saturated Laser-Induced Fluorescence) excitation scheme is proposed in order to overcome the strong temperature dependence of fluorescence in liquid kerosene seeded with a dye. The findings of this work are based on gated sequential images recorded with an intensified camera during and after the laser pulse duration so as to sample the temporal evolution of the fluorescence emission. The results show that, for low laser excitation intensity, the fluorescence intensity remains proportional to the laser power. However, a non-linear response is observed in the case of high excitation intensity. This difference can be used to limit the fluorescence dependence on temperature by carefully selecting the temporal window where fluorescence is detected. Finally, although the method presented in this paper is applied to cold liquid kerosene, its range of application can be extended to other liquids and other temperature ranges.

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The saturation of the fluorescence and its consequences for laser-induced fluorescence thermometry in liquid flows

Cited by 71 publications

References 37 publications

Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays

Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays

Instantaneous heat transfers at the impact of a droplet onto a hot surface in the film boiling regime

Saturated laser-induced fluorescence in liquid kerosene seeded with a dye: influence of temperature and excitation intensity

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