Effect of Nozzle Exit Turbulence on the Column Trajectory and Breakup Location of a Transverse Liquid Jet in a Gaseous Flow

Broumand, Mohsen; Rigby, G.A.; Birouk, Madjid

doi:10.1007/s10494-017-9806-1

Cited by 16 publications

(5 citation statements)

References 27 publications

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“…% only, the dynamics observed for water are comparable to the actual feedstock used for deposition and other low concentration feedstock in general, as their liquid columns have comparable momenta. The graphs showing the feedstock penetration into the jet have been carried out tracing the upstream side of the liquid column [18] using ImageJ (NIH, USA); the images were first converted to black and white by applying the same threshold of 90% to each image.…”

Section: In-flight Measurementsmentioning

confidence: 99%

Radial Injection in Suspension High Velocity Oxy-Fuel (S-HVOF) Thermal Spray of Graphene Nanoplatelets for Tribology

Venturi

Hussain

2019

J Therm Spray Tech

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Friction is a major issue in energy efficiency of any apparatus composed of moving mechanical parts, affecting durability and reliability. Graphene nanoplatelets (GNPs) are good candidates for reducing friction and wear, and suspension high velocity oxy-fuel (SHVOF) thermal spray is a promising technique for their scalable and fast deposition, but it can expose them to excessive heat. In this work, we explore radial injection of GNPs in SHVOF thermal spray as a means of reducing their interaction with the hot flame, while still allowing a high momentum transfer and effective deposition. Feedstock injection parameters, such as flowrate, injection angle and position, were studied using high-speed imaging and particles temperature and velocity monitoring at different flame powers using Accuraspray 4.0.Unlubricated ball-on-flat sliding wear tests against an alumina counterbody ball showed a friction coefficient reduction up to a factor 10 compared to the bare substrate, down to 0.07. The deposited layer of GNPs protects the underlying substrate by allowing low-friction dry sliding. A Transmission Electron Microscopy study showed GNPs preserved crystallinity after spray, and became amorphised and wrinkled upon wear. This study focused on GNPs but is relevant to other heat-and oxidation-sensitive materials such as polymers, nitrides and 2D materials. The unprecedented mechanical [1] and tribological [2] properties of graphene have attracted a wide range of interests in using it as a solid lubricant [3]. The lubricating effect favors a lowering of the coefficient of friction and a delay in damaging the lubricated surfaces. This can effectively improve the durability of moving mechanical parts, by reducing localized heating and subsequent wear. Some small-scale deposition techniques [4, 5] can be hardly employed for covering large areas with a considerable amount of graphene. Simple techniques like drop casting and airbrush spray [6] would allow the deposition;however, they do not provide a good bonding with the substrate. Conversely, spray techniques such as supersonic cold spray [7] proved suitable for large scale graphene coverage and enhanced the bonding with the substrate due to the high velocity at impact. An even better graphene-substrate adhesion could be reached with thermal spray, as it gives not only high kinetic energy but also a higher amount of heat to the particles. In particular, Suspension High Velocity Oxy Fuel (S-HVOF) thermal spray [8] is a good candidate for this task. This relatively new technique allows the injection and spray of suspension in HVOF instead of powders, thus allowing to handle finer particles, down to the micro-to-nano scale. Overall, this technique provides high acceleration and has a relatively low flame temperature compared to plasma spray. Graphene is known to be stable at high temperatures in an inert environment, however in air it starts degrading at around 250 °C, and a consistent mass loss can occur at around 500 °C, according to thermogravimetric analyses (TGA) [9]. The use ...

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Section: In-flight Measurementsmentioning

confidence: 99%

Radial Injection in Suspension High Velocity Oxy-Fuel (S-HVOF) Thermal Spray of Graphene Nanoplatelets for Tribology

Venturi

Hussain

2019

J Therm Spray Tech

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“…Lb is measured through laser-induced fluorescence (LIF) (Charalampous et al 2009a,b) or is estimated photographically (Jiang et al 2019;Sridhara and Raghunandan 2010). There are several prediction equations for Lb presented in literature based on experimental investigations (Broumand et al 2017;Engelbert et al 1995;Eroglu et al 1991;Lasheras et al 1998;Leroux et al 2007;Porcheron et al 2002). Although a satisfactory agreement with the specific experimental data is demonstrated in each case, these equations cannot be used for the prediction of other spraying configurations.…”

Section: Introductionmentioning

confidence: 99%

A Spraying Model of Non-atomizing Sprinkler based on Jet Fragmentation

2022

JAFM

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“…On the one hand, it is the imbalance between the pressure gradient and the density gradient caused by the disturbance of the liquid column surface at the nozzle outlet, namely the Rayleigh-Taylor (RT) instability mechanism [5,6] ; on the other hand, the Kelvin-Helmholtz (KH) instability is caused by the tangential velocity gradient at the gas-liquid interface [7,8] . The R-T instability and the K-H instability or the instability effect produced by the coupling of the two have an important influence on the breaking length of the liquid jet, the droplet size distribution, and the subsequent atomization characteristics in Figure 1 [9] . Based on the above instability principle, it is found that under high gas Weber number, the transverse jet will be subjected to the azimuthal shear effect on the lateral surface to cause surface cracking [10] , which can be divided into primary crushing and secondary crushing according to different crushing mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Research on the Numerical Effect of VTD Model in Cross Jet

Gao

Zhang²

2022

J. Phys.: Conf. Ser.

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To deeply study the specific characteristics of the cross-scale phenomenon of fragmentation and atomization in the cross-jet process, this paper is based on the adaptive grid technology, using the RANS model, RNG k-ε model, LES model turbulence models, and VOF models, DPM model, VTD model multiphase flow models have carried out numerical calculations on the lateral jet process, and compared and analyzed the results to better solve the cross-scale problem and obtain more suitable research methods for the phenomenon of lateral jet breaking and atomization. It is found that: compared to the RANS model and RNG k-ε model, the LES model is more suitable for jet breaking; compared with the VOF model and DPM model, the VTD model is closer to the actual physical phenomenon in the cross jet breaking shape, and the initial surface of the liquid column is broken, the columnar broken and the band-shaped liquid filament is broken by a series of broken and atomized phenomena. And a large number of banded or filamentous liquid lumps can be captured in the continuous liquid film stage and the primary crushing stage of the jet, while discrete misty droplets can also be captured in the secondary crushing area. Based on this, this paper finds that the cross-scale VTD model is combined the phase gradient adaptive grid technology can couple the advantages of the VOF model and the DPM model to better solve the transition problem between the continuous phase and the discrete phase, thereby obtaining more accurate jet atomization characteristics.

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Effect of Nozzle Exit Turbulence on the Column Trajectory and Breakup Location of a Transverse Liquid Jet in a Gaseous Flow

Cited by 16 publications

References 27 publications

Radial Injection in Suspension High Velocity Oxy-Fuel (S-HVOF) Thermal Spray of Graphene Nanoplatelets for Tribology

Radial Injection in Suspension High Velocity Oxy-Fuel (S-HVOF) Thermal Spray of Graphene Nanoplatelets for Tribology

A Spraying Model of Non-atomizing Sprinkler based on Jet Fragmentation

Research on the Numerical Effect of VTD Model in Cross Jet

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