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1
Gärtner, Jan Wilhelm, Ye Feng, Andreas Kronenburg, and Oliver T. Stein. "Numerical Investigation of Spray Collapse in GDI with OpenFOAM." Fluids 6, no. 3 (March 4, 2021): 104. http://dx.doi.org/10.3390/fluids6030104.
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During certain operating conditions in spark-ignited direct injection engines (GDI), the injected fuel will be superheated and begin to rapidly vaporize. Fast vaporization can be beneficial for fuel–oxidizer mixing and subsequent combustion, but it poses the risk of spray collapse. In this work, spray collapse is numerically investigated for a single hole and the spray G eight-hole injector of an engine combustion network (ECN). Results from a new OpenFOAM solver are first compared against results of the commercial CONVERGE software for single-hole injectors and validated. The results corroborate the perception that the superheat ratio Rp, which is typically used for the classification of flashing regimes, cannot describe spray collapse behavior. Three cases using the eight-hole spray G injector geometry are compared with experimental data. The first case is the standard G2 test case, with iso-octane as an injected fluid, which is only slightly superheated, whereas the two other cases use propane and show spray collapse behavior in the experiment. The numerical results support the assumption that the interaction of shocks due to the underexpanded vapor jet causes spray collapse. Further, the spray structures match well with experimental data, and shock interactions that provide an explanation for the observed phenomenon are discussed.
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Wu, Wangxia, Bing Wang, and Gaoming Xiang. "Impingement of high-speed cylindrical droplets embedded with an air/vapour cavity on a rigid wall: numerical analysis." Journal of Fluid Mechanics 864 (February 15, 2019): 1058–87. http://dx.doi.org/10.1017/jfm.2019.55.
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The high-speed impingement of hollow droplets embedded with a cavity has fundamental applications in various scenarios, such as in spray coating and biomedical engineering. The impingement dynamics is modulated by the wrapping medium, different from that of denser solid droplets. With air and vapour cavities, the impingement of two kinds of hollow cylindrical droplets is simulated in the present study to investigate the morphology and physical mechanisms regarding droplet and cavity dynamics. The compressible two-phase Eulerian model is used to couple with the phase transition procedure. The results detail the evolution of droplets and collapsing dynamics of the two kinds of cavities. Processes are captured in which the impinging water-hammer shock wave interacts with the cavity, and vertical liquid jets are induced to impact the embedded cavity. For the case of the air cavity, a transmitted shock wave is formed and propagates inside the cavity. The air cavities are compressively deformed and broken into a series of small cavities. Subsequently, a range of intermittent collapsing compression wavelets are generated due to the interface collapse driven by local jets. As for the vapour cavity in the saturated state, initially, once it is impacted by the impinging shock wave, it gradually shrinks accompanied by local condensation but without generation of transmitted waves. Following the first interaction between the lower and upper surfaces of the cavity, the vapour cavity undergoes continuous condensation and collapse with repeated interface fusion. The vapour cavity finally turns into liquid water blended into the surroundings, and the strong collapsing shock waves are expanded inside the droplet. The radius ratios and initial impinging speeds are chosen to analyse the variation of the collapsing time, maximum collapsing pressure and mean pressure on the rigid wall. The pressure withstood by the wall due to the collapsing cavity increases with the initial size of the cavity and initial impinging speed. The maximum local pressures in the entire fluids and the mean pressure on the wall during the collapsing of the vapour cavities are higher than those for the air cavities.
3
Mardoukhi, Ahmad, Mikko Hokka, and Veli-Tapani Kuokkala. "Experimental study of the dynamic indentation damage in thermally shocked granite." Rakenteiden Mekaniikka 51, no. 1 (August 16, 2018): 10–26. http://dx.doi.org/10.23998/rm.69036.
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This paper presents an experimental procedure to study the effects of pre-existing cracks and damage on the rock behavior under dynamic indentation. To gain better understanding on the mechanism involved in percussive-rotary drilling procedure, a modified Split Hopkinson Pressure Bar device was used to carry out dynamic indentation tests, where rock drill buttons were impacted on rock samples with dimensions of 30 cm × 30 cm × 30 cm. Before the mechanical testing, the samples were thermally shocked using a plasma spray gun for periods of 3, 4, and 6 seconds. The plasma gun produces a powerful heat shocks on the rock sample, and even short exposures can change the surface structure of the samples and provide samples with different crack patterns and surface roughness for experimental testing. The effects of the heat shock damage on the dynamic indentation behavior of the rock were characterized with single- and triple-button indentation tests. The specific destruction work was used to characterize the effects of heat shocks on the material removal during dynamic indentation. The results show that the force-displacement response of the rock does not change much even if the rock surface is severely damaged by the heat shock, however, the destruction work decreases significantly. This means that the same loading removes more volume if the material surface is pre-damaged, and that the efficiency of the indentation process cannot be evaluated from the bit-rock interaction forces alone. The presented experimental framework can be a useful tool for the verification of numerical models where the rock microstructure and especially the microcracks are essential.
4
Zhang, Jingyu, Yanfei Li, Hongming Xu, Xiao Ma, and Shijin Shuai. "Investigation into shock-to-shock interactions induced by flash boiling and the impact on spray behaviors." Fuel 337 (April 2023): 127120. http://dx.doi.org/10.1016/j.fuel.2022.127120.
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Quan, Jin, Xinyuan Li, Zewei Li, Meifang Wu, Biao Zhu, Seung-Beom Hong, Jiang Shi, Zhujun Zhu, Liai Xu, and Yunxiang Zang. "Transcriptomic Analysis of Heat Stress Response in Brassica rapa L. ssp. pekinensis with Improved Thermotolerance through Exogenous Glycine Betaine." International Journal of Molecular Sciences 24, no. 7 (March 29, 2023): 6429. http://dx.doi.org/10.3390/ijms24076429.
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Chinese cabbage (Brassica rapa L. ssp. pekinensis) is sensitive to high temperature, which will cause the B. rapa to remain in a semi-dormancy state. Foliar spray of GB prior to heat stress was proven to enhance B. rapa thermotolerance. In order to understand the molecular mechanisms of GB-primed resistance or adaptation towards heat stress, we investigated the transcriptomes of GB-primed and non-primed heat-sensitive B. rapa ‘Beijing No. 3’ variety by RNA-Seq analysis. A total of 582 differentially expressed genes (DEGs) were identified from GB-primed plants exposed to heat stress relative to non-primed plants under heat stress and were assigned to 350 gene ontology (GO) pathways and 69 KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. The analysis of the KEGG enrichment pathways revealed that the most abundantly up-regulated pathways were protein processing in endoplasmic reticulum (14 genes), followed by plant hormone signal transduction (12 genes), ribosome (8 genes), MAPK signaling pathway (8 genes), homologous recombination (7 genes), nucleotide excision repair metabolism (5 genes), glutathione metabolism (4 genes), and ascorbate and aldarate metabolism (4 genes). The most abundantly down-regulated pathways were plant-pathogen interaction (14 genes), followed by phenylpropanoid biosynthesis (7 genes); arginine and proline metabolism (6 genes); cutin, suberine, and wax biosynthesis (4 genes); and tryptophan metabolism (4 genes). Several calcium sensing/transducing proteins, as well as transcription factors associated with abscisic acid (ABA), salicylic acid (SA), auxin, and cytokinin hormones were either up- or down-regulated in GB-primed B. rapa plants under heat stress. In particular, expression of the genes for antioxidant defense, heat shock response, and DNA damage repair systems were highly increased by GB priming. On the other hand, many of the genes involved in the calcium sensors and cell surface receptors involved in plant innate immunity and the biosynthesis of secondary metabolites were down-regulated in the absence of pathogen elicitors in GB-primed B. rapa seedlings. Overall GB priming activated ABA and SA signaling pathways but deactivated auxin and cytokinin signaling pathways while suppressing the innate immunity in B. rapa seedlings exposed to heat stress. The present study provides a preliminary understanding of the thermotolerance mechanisms in GB-primed plants and is of great importance in developing thermotolerant B. rapa cultivars by using the identified DEGs through genetic modification.
6
Barradas, S., V. Guipont, R. Molins, M. Jeandin, M. Arrigoni, M. Boustie, C. Bolis, L. Berthe, and M. Ducos. "Laser Shock Flier Impact Simulation of Particle-Substrate Interactions in Cold Spray." Journal of Thermal Spray Technology 16, no. 4 (September 26, 2007): 548–56. http://dx.doi.org/10.1007/s11666-007-9069-9.
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Zhang, Jingyu, Yanfei Li, Hongming Xu, Yang Liu, Xiao Ma, and Shijin Shuai. "General understanding on spray collapse process of an asymmetrical multi-hole direct injection gasoline injector under wide flash-boiling conditions." International Journal of Engine Research, December 14, 2023. http://dx.doi.org/10.1177/14680874221149244.
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How the under-expansion impacts the flash-boiling spray collapse process over wide superheat levels ( Rp, defined as the ratio of saturation pressure to ambient pressure) is not well understood. In the present study, n-hexane flash-boiling sprays issued from a five-hole asymmetrical injector were experimentally and numerically studied to obtain a more general understanding of the spray collapse with wide Rp variation. The experimental results proved that the collapse in the transitional region occurs in the far field, unlike the fully collapse that occurred in the near-nozzle region. The numerical results demonstrated the complexity of individual jet evolutions and their interactions over wide Rp. For individual flash-boiling jets, there were different behaviors in the near-nozzle region. In the case with Rp slightly larger than 1, no shock waves can be observed, but a set of compression-expansion chains. The further increase in Rp caused the generation of shock waves, and resultantly the primary cells were established. For the multi-jet sprays, the further increase in Rp enlarged the primary cells, leading to their interactions and the generation of secondary cells. When Rp was sufficiently higher, the further interactions among primary and secondary cells could cause the generation of tertiary cell. Orderly interactions of shock cells were observed with increasing Rp, that is, the interactions initially occur between the adjacent jets with smaller distances, and then other jets were involved. Based on the results: It was found that the compression-expansion chains caused the low- Rp flash-boiling spray collapse in the far field; With the increase in Rp, the shock waves and shock-to-shock interaction become the main contributor to spray collapse, leading collapse appearing in the near-nozzle region.
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Takana, Hidemasa, Kazuhiro Ogawa, Tetsuo Shoji, and Hideya Nishiyama. "Computational Simulation on Performance Enhancement of Cold Gas Dynamic Spray Processes With Electrostatic Assist." Journal of Fluids Engineering 130, no. 8 (July 30, 2008). http://dx.doi.org/10.1115/1.2907417.
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A real-time computational simulation on the entire cold spray process is carried out by the integrated model of compressible flow field, splat formation model, and coating formation model, in order to provide the fundamental data for the advanced high performance cold gas dynamic spray process with electrostatic acceleration. In this computation, viscous drag force, flow acceleration added mass, gravity, Basset history force, Saffman lift force, Brownian motion, thermophoresis, and electrostatic force are all considered in the particle equation of motion for the more realistic prediction of in-flight nano∕microparticle characteristics with electrostatic force and also for the detailed analysis of particle-shock-wave-substrate interaction. Computational results show that electrostatic acceleration can broaden the smallest size of applicable particle diameter for successful adhesion; as a result, wider coating can be realized. The utilization of electrostatic acceleration enhances the performance of cold dynamic spray process even under the presence of unavoidable shock wave.
9
Siddappa, C., O. Thomine, M. S. Shadloo, G. Gai, and A. Hadjadj. "Interactions of shock waves with polydisperse particle clouds: Effects on mitigation and topological heterogeneity." Physics of Fluids 36, no. 5 (May 1, 2024). http://dx.doi.org/10.1063/5.0205854.
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This study explores the efficiency of employing a particle-spray cloud to mitigate shock wave propagation, which is essential in various industrial applications, especially in preventing potential hydrogen explosions within nuclear reactor containment buildings. Numerical simulations, primarily in one- and two-dimensional configurations, are utilized to examine the interaction between shock waves and a cloud of polydisperse particles, considering both air and hydrogen–air mixtures as carrier gases. A novel reduced-order theoretical model is developed to analyze the dispersion pattern of polydisperse particles, with validation conducted through direct numerical simulations. Results demonstrate that the polydispersion of cloud particles significantly reduces shock wave propagation compared to monodisperse particles. Notably, particles with smaller diameters and higher standard deviations (σ) show increased attenuation effects. Additionally, scenarios with higher particle volume fractions (τv,0) contribute to enhanced shock wave attenuation. A critical incident Mach number is identified, indicating a significant change in shock wave transmission from supersonic to subsonic when Ms<2.8.
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Ahamed, Sheikh, and Song-Charng Kong. "Analysis of Thermomechanical Stress of High-Temperature Ignition Surface Caused by Drop-Wall Interaction at Engine Conditions." Journal of Thermal Science and Engineering Applications, February 20, 2024, 1–28. http://dx.doi.org/10.1115/1.4064820.
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Abstract Drop-wall interaction is an important phenomenon in various industrial applications. The liquid droplets can impinge on the high-temperature wall, causing thermal shock because of a sudden temperature change. The change in temperature in the solid wall can induce thermal stress. When the thermal stress exceeds the strength of the material in that stress mode, failure can occur. Hence, it is essential to investigate the temperature evolution on the high-temperature surface to optimize the durability of the material. In this paper, drop-wall interactions in the engine environment are studied. The Smoothed Particle Hydrodynamics (SPH) method is used to simulate the impingement of fuel droplets on an ignition plug with different materials to characterize the heat transfer, thermal penetration, and temperature distributions in the heated wall. This paper also investigates the behavior of ceramic material (i.e., silicon nitride) for thermomechanical stress and its durability based on the stress-number of cycles (S-N) curve. Thermal stress is calculated based on the temperature gradient and material properties, while mechanical stress is evaluated based on the bending momentum and momentum flux induced by the spray. A parametric study was conducted for various materials, including wolfram carbide, iron, stainless steel, carbon steel, and aluminum. Results show that ceramic materials have the lowest thermal stress distribution and best durability.
11
Wang, Zhijian, Yanfei Li, Zhijie Li, Jingshan Wang, Xiao Ma, and Shijin Shuai. "Experimental investigation on effect of gas/spray interactions on transient diesel spray behaviors." International Journal of Engine Research, February 12, 2023, 146808742211507. http://dx.doi.org/10.1177/14680874221150710.
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The ever-increasing rail pressure in diesel engines may cause the injection induced shock waves. In the present study, different gases (N2 and CO2) were used as the ambient mediums in order to understand the effect of shock waves induced by the high-speed jets on the near-field spray penetration. The tests were carried out in an optically-accessible constant volume vessel and a single-hole diesel injector was used. The injection pressure ( Pinj) ranged from 80 to 150 MPa and the ambient density ( ρambient) are 11.25, 22.52, and 33.81 kg/m3, respectively. Schlieren imaging was used to capture the shock waves ahead of the sprays with a frame speed of 100,000 fps and high-speed imaging was used to capture the spray penetration evolution with a frame speed of 300,000 fps in order to provide sufficient high temporal and spatial resolutions of the spray development. Shock waves can be observed under CO2 atmosphere over all the tested conditions and almost invisible under N2 atmosphere. The timings of occurrence and detachment of the shock waves are advanced with the increase in ρambient, but less sensitivity to Pinj. The difference in penetration lengths for N2 and CO2 atmosphere are not consistent as Pinj and ρambient varied, indicating the complicated role of shock waves in influencing the spray behaviors. Several mechanisms for the generation of shock waves were discussed, as well the physical meaning of the timing to the peak velocity of the spray tip with breakup time.
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Lang, Fengyong, Zhenrui Zhou, Jia Liu, Meng Cui, and Zhongqing Zhang. "Review on the impact of marine environment on the reliability of electronic packaging materials." Frontiers in Materials 12 (April 15, 2025). https://doi.org/10.3389/fmats.2025.1584349.
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Marine environments pose significant challenges to the reliability of electronic packaging materials. This review summarizes the main degradation mechanisms and reliability impacts of electronic packaging materials under marine conditions, including salt spray corrosion, high humidity, thermal cycling, and mechanical shock. Salt spray corrosion initiates localized galvanic corrosion through chloride ion (Cl−) diffusion, creating corrosion pits and stress concentration, thereby accelerating electrochemical-mechanical coupled failures. High humidity promotes moisture ingress into polymer packaging materials, resulting in hygroscopic plasticization, weakened interfacial adhesion, and delamination failure. Thermal cycling, due to mismatched coefficients of thermal expansion (CTE), induces growth of interfacial intermetallic compound (IMC) layers at solder joints and creep-fatigue interactions, further promoting interfacial crack propagation. Mechanical shock generates transient, high-strain-rate loading, rapidly initiating and propagating cracks within brittle packaging structures, ultimately leading to structural failure. Additionally, this paper discusses the current status and limitations of Physics of Failure (PoF)-based reliability models such as the Coffin-Manson and Arrhenius models for evaluating electronic packaging reliability in marine environments. Finally, it suggests that future studies should further develop multiphysics coupling models to more accurately predict long-term material performance under extreme marine conditions.
13
Samareh, B., and A. Dolatabadi. "Dense Particulate Flow in a Cold Gas Dynamic Spray System." Journal of Fluids Engineering 130, no. 8 (July 30, 2008). http://dx.doi.org/10.1115/1.2957914.
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The effect of particle-gas and particle-particle interactions in a cold spray process is studied when the particle loading is high. To examine the effect of the presence of a dense particulate flow on the supersonic gas, an Eulerian-Eulerian approach is used. It is found that when the volume fraction of the injected particles is increased, the turbulence of the gas phase will be augmented by the motion of particles and consequently, the shape, the strength, and the location of the compression and expansion waves will be altered. Shock-particle interactions are demonstrated for various volume fractions. Another important parameter, which will affect the spraying deposition efficiency, is the substrate stand-off distance. It is found that the stagnation pressure alternates for different stand-off distances because of the formation of compression and expansion waves outside the nozzle exit. The particle normal velocity on impact is a strong function of the stagnation pressure on the substrate as particles must pierce through the bow shock formed on that region. The effect of the particle size and number density are also studied for different loading conditions. It is found that small and large particles behave differently as they pass through shock diamonds and the bow shock, i.e., in the case of very small particles, as the loading increases, the impact velocity increases, while, for the large particles, the trend is reversed.
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Ralls, Alessandro, Bo Mao, and Pradeep Menezes. "Tribological Performance of Laser Shock Peened Cold Spray Additive Manufactured 316L Stainless Steel." Journal of Tribology, March 8, 2023, 1–28. http://dx.doi.org/10.1115/1.4062102.
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Abstract In recent years, cold spray additive manufacturing (CSAM) has become an attractive technology for surface modification and protection. However, due to the intrinsic porous nature of CSAM coatings, they suffer from rapid material degradation due to premature brittle fracturing induced by tribological interactions. In this work, laser shock peening (LSP) was utilized as a post-processing technology to mitigate the surface porosity and augment the surface characteristics of CSAM 316L SS. Due to the synergistic influence of severe plastic deformation and rapid surface heating, the surface porosities were effectively healed, thus reducing the surface roughness. Combined with the surface strengthening effects of LSP, the frictional resistance and transfer layer formation on the CSAM LSP surfaces were reduced. The underlying mechanisms for these findings were discussed by correlating the atomic, microstructural, and physical features of the LSP surfaces. Based on these findings, it can be suggested that LSP is indeed a useful technique to control the surface characteristics of CSAM 316L SS coatings.
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Miki, Kenji, Thomas Wey, and Jeffrey Moder. "Computational Study on Fully Coupled Combustor–Turbine Interactions." Journal of Propulsion and Power, January 3, 2023, 1–14. http://dx.doi.org/10.2514/1.b38501.
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Combustor–turbine interactions are investigated by modeling the unsteady flowfields inside a realistic combustor and high-pressure turbine configuration from the Energy Efficient Engine program. We perform three-dimensional unsteady simulations to capture a liquid-spray fuel/air combustion and relative motions between the combustor and turbine using the Open National Combustion Code. To understand combustor–turbine interactions, we perform both sequential single-component simulations (step 1: [Formula: see text] stator of turbine; step 2: the turbine imposing the time-averaged flow solution from step 1 as the inflow) and a fully coupled combustor–turbine simulation (step 3) at two operating conditions: the simulated sea-level takeoff (SLTO) condition ([Formula: see text]) and a more realistic SLTO ([Formula: see text]). Although the mean flowfields inside the combustor predicted by steps 1 and 3 are similar, there is a noticeable difference in the hot-streak distributions at the first-stage stator. In addition, the shock wave appears at the first-stage stator only for steps 2 and 3 for the low-pressure condition and for step 3 for the high-pressure condition. The calculated turbine efficiencies from step 2 and step 3 differ by about 7%. From both conditions, it is consistently observed that fully coupling the combustor and turbine enhances temporal oscillations of the turbine efficiency through the temperature fluctuations generated in the combustor.