Thermal characterization of a flashing jet by planar laser-induced fluorescence

Vetrano, Maria Rosaria; Simonini, Alessia; Steelant, Johan; Rambaud, Patrick

doi:10.1007/s00348-013-1573-8

Cited by 34 publications

(22 citation statements)

References 15 publications

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“…With the great progress in both camera sensor technology and illumination sources over the past two decades, imaging techniques such as microscopic imaging (Crua et al 2015), X-ray absorption imaging (Halls et al 2014), ballistic imaging (Linne et al 2009), optical connectivity (Charalampous et al 2009), and a variety of laser sheet imaging techniques have been created and extensively used. One of the main benefits of laser sheet imaging-wherein only a thin plane is illuminated-is its versatility regarding which quantities it can extract: flow velocities using particle image velocimetry (PIV) (Adrian and Westerweel 2011;Westerweel et al 2013), droplet Sauter mean diameter (SMD) using LIF/Mie ratio techniques (Le Gal et al 1999;Domann and Hardalupas 2003), and spray temperatures using the ratio of two spectral bands from either laser-induced fluorescence (Bruchhausen et al 2005;Vetrano et al 2013) or phosphorescence (Brübach et al 2006;Omrane et al 2004) emissions. Nearly all quantitative imaging techniques are based on the single scattering approximation, which assumes that the detected photons have experienced only one scattering event prior to reaching the detector.…”

Section: Introductionmentioning

confidence: 99%

Comparison between two-phase and one-phase SLIPI for instantaneous imaging of transient sprays

et al. 2017

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images with an intensity profile close to the corresponding single scattering case. Experimentally, this suppression renders both an improvement in image contrast and the removal of undesired stray light components that could be interpreted as signal. However, while 2p-SLIPI preserves most of the initial spatial resolution, 1p-SLIPI results in a loss of spatial resolution, where high-frequency image information is not visible anymore. Thus, there is a tradeoff between preserving the most detailed information of the spray structure-with 2p-SLIPI-and being able to record an SLIPI image from a single modulated image only-with 1p-SLIPI. The comparison and technical overview of these two methods presented in this paper can facilitate in selecting which approach is the most suitable for a given application for spray visualization.

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Section: Introductionmentioning

confidence: 99%

Comparison between two-phase and one-phase SLIPI for instantaneous imaging of transient sprays

et al. 2017

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“…In contrast, it is difficult to map temperature fields with resolution comparable to that of PIV. Optical techniques such as laser-induced fluorescence are available 3,4 , but they require cameras and relatively high-power lasers, and are unsuitable for opaque fluids.…”

Section: Introductionmentioning

confidence: 99%

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

Lomperski

Gerardi

Lisowski

2016

JoVE

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The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists chiefly of velocity and temperature readings, both ideally having high spatial and temporal resolution to facilitate rigorous code validation. While high resolution velocity data is readily obtained through optical measurement techniques such as particle image velocimetry, it has proven difficult to obtain temperature data with similar resolution. Traditional sensors such as thermocouples cannot fill this role, but the recent development of distributed sensing based on Rayleigh scattering and swept-wave interferometry offers resolution suitable for CFD code validation work. Thousands of temperature measurements can be generated along a single thin optical fiber at hundreds of Hertz. Sensors function over large temperature ranges and within opaque fluids where optical techniques are unsuitable. But this type of sensor is sensitive to strain and humidity as well as temperature and so accuracy is affected by handling, vibration, and shifts in relative humidity. Such behavior is quite unlike traditional sensors and so unconventional installation and operating procedures are necessary to ensure accurate measurements. This paper demonstrates implementation of a Rayleigh scattering-type distributed temperature sensor in a thermal mixing experiment involving two air jets at 25 and 45 °C. We present criteria to guide selection of optical fiber for the sensor and describe installation setup for a jet mixing experiment. We illustrate sensor baselining, which links readings to an absolute temperature standard, and discuss practical issues such as errors due to flow-induced vibration. This material can aid those interested in temperature measurements having high data density and bandwidth for fluid dynamics experiments and similar applications. We highlight pitfalls specific to these sensors for consideration in experiment design and operation.

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“…For example, for producing a very fine spray of droplets of a uniform 30 size distribution that improve combustion efficiency (Sher et al, 2008). This is desirable in some applications such as fuel injectors (Chen et al, 2013; ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T Vetrano et al, 2013;Lamanna et al, 2014;Bohon et al, 2015;Ju et al, 2015), but also necessary when driving pressures cannot exceed certain limit (Sher et al, 2008;Zeigerson-Katz and Sher, 1998). Flashboiling atomization usually coexists simultaneously with other mechanisms of spray formation, such as turbulence, bubbles within the flow and coax-40 ial gas flows.…”

Section: Introductionmentioning

confidence: 99%

“…The vapor densities shown in Table 2 were evaluated at ambient pressure and at injec-170 tion temperature (Kitamura et al, 1986), using the ideal gas equation (P ∞ /ρ v = RT l /M ), where M is the molar mass in kg/mol. The Jacob number establishes the limits for a phase change to occur and therefore it has been used to estimate the onset of 175 flash-boiling (Vetrano et al, 2013). On a jet with a fixed Jacob number, a liquid with an agitated interphase has a higher flashing potential than an unperturbed surface.…”

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Ultra-high speed visualization of a flash-boiling jet in a low-pressure environment

Alghamdi

Thoroddsen

Hernández-Sánchez

2019

International Journal of Multiphase Flow

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Highlights• We visualized flash-boiling jets at an unprecedented frame rate of 5 Million frames per second. At such high frame rate we observed for the first time the evolution of the bubble expansion and the burst mechanisms, responsible for the jet atomization.• For developed flash-boiling conditions, minimum pixel intensity profiles revealed that droplets are ejected in all directions from the nozzle. This crucial fact was translated into spray angles larger than 300• .• The detailed close up to the nozzle revealed that the droplet size distribution of the spray is wide, contrary to the common belief. Using a simple argument we infer that the smallest droplets are on the hundreds of nanometer range. This means that the drop size distribution extends trough almost four orders of magnitude.• We measured velocities up to 140 m/s during the expansion of bubbles from the core of the jet. Such velocity is a bit less than half of the speed of a 0.22 bullet, an unprecedented velocity for expanding bubbles. AbstractWe visualize the flash-boiling atomization of liquid jets released into a low-pressure environment at frame rates of up to five million frames per second using a long distance microscope. Such temporal resolution allowed us to capture the details of the bubble expansion mechanism, responsible for the jet atomization, for the first time. We document an abrupt transition from a laminar to a fully external flashing jet by systematically reducing the ambient pressure. We perform experiments with different volatile liquids, ejected through micro-nozzles with different inner diameters. Surprisingly, minimum pixel intensity projections revealed spray angles close to θ s ∼ 360• and speeds of bubble expansion up to 140 m/s. Particle tracking shows that ejected droplets achieve speeds much larger than the jet velocity and drop sizes order of magnitude smaller than the diameter of the nozzle. Furthermore, hole growth speeds measured on the bubbles film in combination with to Taylor-Culick predictions suggests that the smallest droplet sizes are on the hundreds of nanometer or submicron range, which contravenes the general belief that flash-boiling atomization results in uniform drop sizes.

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Thermal characterization of a flashing jet by planar laser-induced fluorescence

Cited by 34 publications

References 15 publications

Comparison between two-phase and one-phase SLIPI for instantaneous imaging of transient sprays

Comparison between two-phase and one-phase SLIPI for instantaneous imaging of transient sprays

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

Ultra-high speed visualization of a flash-boiling jet in a low-pressure environment

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