Dwarf galaxies,with their shallow gravitational potentials,less evolved assembly histories,and low mass,serve as critical laboratories for studying massive black hole(MBH)formation and growth[1].They preserve signatur...Dwarf galaxies,with their shallow gravitational potentials,less evolved assembly histories,and low mass,serve as critical laboratories for studying massive black hole(MBH)formation and growth[1].They preserve signatures of the primordial processes that shaped early MBH emergence[2].Off-nuclear(or offset)active galactic nucleus(AGN)are increasingly recognized as important laboratories for understanding galactic dynamics and black-hole evolution,with recent studies indicating that they are quite common in various galaxy populations.展开更多
In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Ther...In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Therefore,the fluid evolution characteristics and rock fracture behavior during jet impingement were studied.The results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages:initial fluid-solid contact stage,intense thermal exchange stage,perforation and fracturing stage,and crack propagation and penetration stage.With the increase of rock temperature,the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease,while the number of cracks and crack propagation rate significantly increase,and the rock breaking critical time is shortened by up to 34.5%.Based on numerical simulation results,it was found that the center temperature of granite at 400℃ rapidly decreased from 390 to 260℃ within 0.7 s under jet impact.In addition,a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was established.These findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.展开更多
Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of sh...Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of shaped charge jets in water as well as the underwater penetration effect of concrete need to be studied.In this paper,we introduced a modified forming theory of an underwater hemispherical shaped charge,and investigated the behavior of jet formation and concrete penetration in both air and water experimentally and numerically.The results show that the modified jet forming theory predicts the jet velocity of the hemispherical liner with an error of less than 10%.The underwater jets exhibit at least 3%faster and 11%longer than those in air.Concrete shows different failure modes after penetration in air and water.The depth of penetration deepens at least 18.75%after underwater penetration,accompanied by deeper crater with 65%smaller radius.Moreover,cracks throughout the entire target are formed,whereas cracks exist only near the penetration hole in air.This comprehensive study provides guidance for optimizing the structure of shaped charge and improves the understanding of the permeability effect of concrete in water.展开更多
Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising techn...Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.展开更多
The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure ...The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure variations,potentially causing catastrophic damage to the container.Current studies mainly focus on non-deforming projectiles,such as fragments,with limited exploration of shaped charge jets.In this paper,a uniquely experimental system was designed to record cavity profiles in behind-armor liquid-filled containers subjected to shaped charge jet impacts.The impact process was then numerically reproduced using the explicit simulation program ANSYS LS-DYNA with the Structured Arbitrary Lagrangian-Eulerian(S-ALE)solver.The formation mechanism,along with the dimensional and shape evolution of the cavity was investigated.Additionally,the influence of the impact kinetic energy of the jet on the cavity characteristics was analyzed.The findings reveal that the cavity profile exhibits a conical shape,primarily driven by direct jet impact and inertial effects.The expansion rates of both cavity length and maximum radius increase with jet impact kinetic energy.When the impact kinetic energy is reduced to 28.2 kJ or below,the length-to-diameter ratio of the cavity ultimately stabilizes at approximately 7.展开更多
An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on t...An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on the formation of perforation by AWJ is unclear yet.In this study,we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope(SEM).The results show that when the grain size is doubled,the perforation depth increases by 16.22%under the same type of structure and properties.In general,fractures are more likely to be created at the position of rough surfaces caused by abrasive impact,and the form of fractures is determined by the mineral type.In addition,microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries.The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet,while the lateral extension is controlled by the backflow.The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.展开更多
1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7]...1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7],that indicate their potential for use in actu-ators,sensors,micropumps,energy harvesters,and solid-state re-frigeration[8-10].Among the alloys,Ni-Mn-Sn-based alloys are environment-friendly and cost-effective[6,7,11],and hence,they have received widespread attention.展开更多
This paper mainly studies the well-posedness of steady incompressible impinging jet flow problem through a 3D axisymmetric finitely long nozzle.This problem originates from the physical phenomena encountered in practi...This paper mainly studies the well-posedness of steady incompressible impinging jet flow problem through a 3D axisymmetric finitely long nozzle.This problem originates from the physical phenomena encountered in practical engineering fields,such as in short take-off and vertical landing(STOVL)aircraft.Nowadays many intricate phenomena associated with impinging jet flows remain inadequately elucidated,which limits the ability to optimize aircraft design.Given a boundary condition in the inlet,the impinging jet problem is transformed into a Bernoulli-type free boundary problem according to the stream function.Then the variational method is used to study the corresponding variational problem with one parameter,thereby the wellposedness is established.The main conclusion is as follows.For a 3D axisymmetric finitely long nozzle and an infinitely long vertical wall,given an axial velocity in the inlet of nozzle,there exists a unique smooth incom‑pressible impinging jet flow such that the free boundary initiates smoothly at the endpoint of the nozzle and extends to infinity along the vertical wall at far fields.The key point is to investigate the regularity of the corner where the nozzle and the vertical axis intersect.展开更多
Aiming at the dynamic stall problem that restricts the improvement of aircraft maneuverability,a new dynamic stall control method based on leading-edge Dual Synthetic Jets(DSJ)is proposed in this paper.The aerodynamic...Aiming at the dynamic stall problem that restricts the improvement of aircraft maneuverability,a new dynamic stall control method based on leading-edge Dual Synthetic Jets(DSJ)is proposed in this paper.The aerodynamic control characteristics and flow field evolution process of steady jet,Synthetic Jet(SJ)and DSJ in dynamic stall flow field are analyzed in detail,and the corresponding control mechanism is revealed.The strong"wall attachment effect"and quasisteady"characteristics of DSJ are found.The results show that the leading-edge jet technology can improve the dynamic stall flow field environment.For the whole pitching process,the average lift coefficients of steady jet,SJ and DSJ increased by 3.65%,10.51%and 14.62%respectively,and the average drag coefficients decreased by 9.58%,29.9%and 32.0%respectively.In the downward phase,the average lift coefficient increased by 16.31%,26.72%and 35.88%respectively,and the average drag coefficient decreased by 26.21%,50.46%and 54.28%respectively.Due to its strong"wall attachment effect"and"quasi-steady"characteristics,DSJ exhibits optimal control effect,showing its application potential in dynamic stall control.展开更多
JD Ceramics has been specializing in the field of air interlacing jets,air texturizing jets,and water jets over 29 years.With several years of technical accumulation and continuous equipments upgrades,we have been con...JD Ceramics has been specializing in the field of air interlacing jets,air texturizing jets,and water jets over 29 years.With several years of technical accumulation and continuous equipments upgrades,we have been consistently delivering high-precision,highquality,cost-effective ceramic nozzle solutions to the market.展开更多
Shaoxing Shuifu Reeds is professional on producing all kinds of Air Jet Reeds and Flat Reeds,which has an annual output of 90,000 meters air-jet reeds,300,000,000 pcs of profile dents and 60,000 meters of Flat Reeds,W...Shaoxing Shuifu Reeds is professional on producing all kinds of Air Jet Reeds and Flat Reeds,which has an annual output of 90,000 meters air-jet reeds,300,000,000 pcs of profile dents and 60,000 meters of Flat Reeds,Which has been honored with China Air Jet Profile Reeds Research Center by China Textile Machinery Association in 2015.In order to reach the demands of high quality fabric and industrial textile products,the yarn is developing to high count,multicolor,various fibers,and the fabric is developing to high count,high density,environment protection.So we have researched out high density,multicolor,multinozzle,double energy saving type profile reeds to let you choose.展开更多
Radial jet drilling(RJD)technology is expected to be a technology for the efficient exploitation of geothermal resources.However,the low rock-breaking efficiency is the major obstacle hindering the development of RJD ...Radial jet drilling(RJD)technology is expected to be a technology for the efficient exploitation of geothermal resources.However,the low rock-breaking efficiency is the major obstacle hindering the development of RJD technology.The flow field characteristics and rock breaking ability of cone-straight abrasive jet,rotary abrasive jet,and straight-rotating mixed abrasive jet are analyzed by numerical simulations and experiments.Results show that the axial velocity of the cone-straight abrasive jet is high,the tangential velocity is basically zero,the radial velocity is also small,and the jet impact area is concentrated in the center.A deep hole with a diameter of only 25 mm is formed when the cone-straight abrasive jet breaks the granite.Due to the presence of the guiding impeller,the rotary abrasive jet basically has no axial velocity and has the highest tangential and radial velocity,so it can break the granite to form a hole with a diameter of about 55 mm and a central bulge.The straight-rotating mixed abrasive jet has a large axial/tangential/radial velocity at the same time,so it can break the granite to form a hole with a diameter of about 52 mm with a low bulge.The results show that the straight-rotating mixed abrasive jet combines the advantages of the cone-straight jet and the rotary jet,and is more suitable for the RJD technology.The research results can provide reference for the development of efficient rock-breaking and hole-forming technology,and promote the development of RJD technology in the field of geothermal development.展开更多
The noise generated by subsonic jet nozzles, commonly encountered in civilian aircraft, is rather significant and propagates in both the upstream and downstream directions due to large-scale and fine-scale turbulence ...The noise generated by subsonic jet nozzles, commonly encountered in civilian aircraft, is rather significant and propagates in both the upstream and downstream directions due to large-scale and fine-scale turbulence structures. In this paper, a distinctive inner wall treatment strategy, denoted as the Azimuthally-distributed Wavy Inner Wall (AWIW), is proposed, which is aimed at mitigating jet noise. Within this strategy, a circumferentially dispersed treatment wall characterized by a minute wavy pattern is substituted for the smooth inner wall in proximity to the nozzle outlet. To assess the effectiveness of the AWIW treatment, we conducted numerical simulations. The unsteady flow field and far-field noise were predicted by employing Large Eddy Simulations (LES) coupled with the Ffowcs Williams and Hawkings (FW-H) integration method. To gain a comprehensive understanding of the mechanism underlying the noise reduction facilitated by the AWIW treatment, it examined physical parameters such as the Lighthill source acoustic source term, the turbulent kinetic energy acoustic source term, and the shear layer instability. The results reveal that the AWIW treatment expedites the instability within the shear layer of the jet, leading to an early disruption of the jet shear layer, and consequently turbulent structures in varying sizes are generated downstream. This process effectively regulates the generation and emission of jet noise. By controlling the minor scale turbulence through the AWIW treatment, the mid- and high-frequency noise within the distant field can be significantly reduced. In the context of the flow field, the introduction of AWIW also leads to a decrease in drag on the inner wall surface of the jet, thereby improving the overall aerodynamic performance of the nozzle. Considering these attributes, the AWIW strategy emerges as a viable technique for the reduction of jet noise.展开更多
Dispersion of Particle-laden Jet in Supersonic Crossflow(PJSC)is an essential process in many applications,experimental study on which,however,has rarely been reported.In order to gain physical insights into PJSC,a sp...Dispersion of Particle-laden Jet in Supersonic Crossflow(PJSC)is an essential process in many applications,experimental study on which,however,has rarely been reported.In order to gain physical insights into PJSC,a specialized experimental setup capable of producing a supersonic crossflow at Mach 2.6 and a particle-laden jet with particle mass loading up to 60%is developed.Visualization of the particles motion is achieved with the help of high-speed planar laser scattering technology.The dispersion characteristics of PJSC within a supersonic channel structured by cavity are systematically analyzed through six experimental cases.The results indicate that the vortices have a significant influence on particle dispersion,leading to preferential concentration of particles.i.e.particle clusters.The particle dispersion is summarized as the"scale dispersion"pattern.The primary pathways for particles entering the cavity are identified as the shear layer above the cavity and collisions at the cavity rear edge.Among the studied factors,the momentum flux ratio exerts the most substantial influence on the dispersion process.Importantly,a reduction in the injection distance is correlated with less particles entering the cavity.The insights gained from this research provide essential references for furthering understanding particle dispersion mechanisms in supersonic flows and developing highly accurate numerical models.展开更多
Electrohydrodynamic(EHD)jet printing represents a novel micro/nano-scale additive manufacturing process that utilises a high-voltage induced electric field between the nozzle and the substrate to print micro/nanoscale...Electrohydrodynamic(EHD)jet printing represents a novel micro/nano-scale additive manufacturing process that utilises a high-voltage induced electric field between the nozzle and the substrate to print micro/nanoscale structures.EHD printing is particularly advantageous for the fabrication on flexible or non-flat substrates and of large aspect ratio micro/nanostructures and composite multi-material structures.Despite this,EHD printing has yet to be fully industrialised due to its low throughput,which is primarily caused by the limitations of serial additive printing technology.The parallel multi-nozzle array-based process has become the most promising option for EHD printing to achieve large-scale printing by increasing the number of nozzles to realise multichannel parallel printing.This paper reviews the recent development of multi-nozzle EHD printing technology,analyses jet motion with multi-nozzle,explains the origins of the electric field crosstalk effect under multi-nozzle and discusses several widely used methods for overcoming it.This work also summarises the impact of different process parameters on multi-nozzle EHD printing and describes the current manufacturing process using multi-nozzle as well as the method by which they can be realised independently.In addition,it presents an additional significant utilisation of multi-nozzle printing aside from enhancing single-nozzle production efficiency,which is the production of composite phase change materials through multi-nozzle.Finally,the future direction of multi-nozzle EHD printing development is discussed and envisioned.展开更多
C-C coupling and hydrodeoxygenation are two important reactions in the production of sustainable aviation fuels(SAFs)with lignocellulose derived oxygenates.However,it is challenging to integrate them into a one-step p...C-C coupling and hydrodeoxygenation are two important reactions in the production of sustainable aviation fuels(SAFs)with lignocellulose derived oxygenates.However,it is challenging to integrate them into a one-step process because the necessity of oxygen containing functional groups in the C-C coupling reactions.Herein,jet fuel range polycycloalkanes and branched alkanes were directly synthesized by a cascade self-aldol condensation/hydrodeoxygenation reaction of lignocellulosic ketones over a zirconium phosphate loaded calcium modified nickel catalyst(NiCa/ZrP)that was prepared by a simple incipient impregnation method.Compared with the catalyst systems that have been reported in literature,the NiCa/ZrP catalyst have many advantages such as fewer step,easier operation and preparation,lower equipment investment and cost,wider applicability,etc.Moreover,the NiCa/ZrP is also applicable for the direct production of jet fuel range alkanes with lignocellulosic ketones and/or alcohols by a cascade dehydrogenation/aldol condensation/hydrodeoxygenation reaction.This work gives a new idea about the reduction of energy consumption and cost by catalyst designing in the manufacture of SAFs from lignocellulose.展开更多
Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show ...Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show significant characteristic differences and couple each other.This paper designs and conducts experiments with shaped charges to analyze the complicated process.The effects of liner angle and weight of shaped charge on the characteristics of metal jets,waves,and bubbles are discussed.It is found that in underwater explosions,the shaped charge generates the metal jet accompanied by the ballistic wave.Then,the shock wave propagates and superimposes with the ballistic wave,and the generated bubble pulsates periodically.It is revealed that the maximum head velocity of the metal jet versus the liner angle a and length-to-diameter ratio k of the shaped charge follows the laws of 1/(α/180°)^(0.55)andλ^(0.16),respectively.The head shape and velocity of the metal jet determine the curvature and propagation speed of the initial ballistic wave,thus impacting the superposition time and region with the shock wave.Our findings also reveal that the metal jet carries away some explosion products,which hinders the bubble development,causing an inward depression of the bubble wall near the metal jet.Therefore,the maximum bubble radius and pulsation period are 5.2%and 3.9%smaller than the spherical charge with the same weight.In addition,the uneven axial energy distribution of the shaped charge leads to an oblique bubble jet formation.展开更多
Impinging jet arrays are extensively used in numerous industrial operations,including the cooling of electronics,turbine blades,and other high-heat flux systems because of their superior heat transfer capabilities.Opt...Impinging jet arrays are extensively used in numerous industrial operations,including the cooling of electronics,turbine blades,and other high-heat flux systems because of their superior heat transfer capabilities.Optimizing the design and operating parameters of such systems is essential to enhance cooling efficiency and achieve uniform pressure distribution,which can lead to improved system performance and energy savings.This paper presents two multi-objective optimization methodologies for a turbulent air jet impingement cooling system.The governing equations are resolved employing the commercial computational fluid dynamics(CFD)software ANSYS Fluent v17.The study focuses on four controlling parameters:Reynolds number(Re),swirl number(S),jet-to-jet separation distance(Z/D),and impingement height(H/D).The effects of these parameters on heat transfer and impingement pressure distribution are investigated.Non-dominated Sorting Genetic Algorithm(NSGA-II)and Weighted Sum Method(WSM)are employed to optimize the controlling parameters for maximum cooling performance.The aim is to identify optimal design parameters and system configurations that enhance heat transfer efficiency while achieving a uniform impingement pressure distribution.These findings have practical implications for applications requiring efficient cooling.The optimized design achieved a 12.28%increase in convective heat transfer efficiency with a local Nusselt number of 113.05 compared to 100.69 in the reference design.Enhanced convective cooling and heat flux were observed in the optimized configuration,particularly in areas of direct jet impingement.Additionally,the optimized design maintained lower wall temperatures,demonstrating more effective thermal dissipation.展开更多
Electrohydrodynamic(EHD)jet printing is a promising method for high-resolution manufacturing;however,it often suffers from jet deflection owing to the accumulation of residual charges within printed structures.These r...Electrohydrodynamic(EHD)jet printing is a promising method for high-resolution manufacturing;however,it often suffers from jet deflection owing to the accumulation of residual charges within printed structures.These residual charges lead to jet deflection.This study introduces a novel noncontact electric field-driven(NEFD)jet micro 3D printing technique to address these challenges.By decoupling the high-voltage power supply from both the printing material and substrate,NEFD jet micro 3D printing eliminates the pathway for charge injection into the printing material,reducing residual charges by a factor of five or more compared to EHD jet printing.Our research revealed an inherent attractive force between the material jet and previously deposited material,regardless of the material used.Furthermore,we demonstrate that employing a pre-defined allowance printing strategy during fabrication reduces the standard deviation of actual fiber spacing values from 11.4μm to 1.5μm,thereby improving the fiber spacing consistency.This enhanced control enabled the successful fabrication of line patterns with 20±1μm fiber diameters and 61.1±1.9μm fiber spacing,demonstrating the feasibility of NEFD jet micro 3D printing.This technique offers a novel solution for mitigating the challenges associated with electric fields and charge accumulation in EHD jet printing,paving the way for enhanced resolution and material compatibility in micro-/nanoscale additive manufacturing.展开更多
基金supported by the National SKA Program of China(2022SKA0120102 and 2022SKA0130103)the National Natural Science Foundation of China(NSFC)(12403023)+6 种基金FAST special Program(NSFC)(12041301)China Postdoctoral Science Foundation(2023M733625 and 2024T170968)supported by the Shanghai Post-doctoral Excellence Program and Shanghai Sailing Program(23YF1455700)support from the Xinjiang Tianchi Talent ProgramMar Mezcua acknowledges support from the Spanish Ministry of Science and Innovation through the project PID2021-124243NB-C22partially supported by the program Unidad de Excelencia Marła de Maeztu CEX2020-001058-MThis work used resources of China SKA Regional Centre funded by the Ministry of Science and Technology of China and the Chinese Academy of Sciences.The National Radio Astronomy Observatory(NRAO)is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities,Inc.This paper makes use of the VLBA data from the program BA158.
文摘Dwarf galaxies,with their shallow gravitational potentials,less evolved assembly histories,and low mass,serve as critical laboratories for studying massive black hole(MBH)formation and growth[1].They preserve signatures of the primordial processes that shaped early MBH emergence[2].Off-nuclear(or offset)active galactic nucleus(AGN)are increasingly recognized as important laboratories for understanding galactic dynamics and black-hole evolution,with recent studies indicating that they are quite common in various galaxy populations.
基金supported by National Natural Science Foundation of China (No.U23A20597)National Major Science and Technology Project of China (No.2024ZD1003803)+1 种基金Chongqing Science Fund for Distinguished Young Scholars of Chongqing Municipality (No.CSTB2022NSCQ-JQX0028)Natural Science Foundation of Chongqing (No.CSTB2024NSCQ-MSX0503)。
文摘In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Therefore,the fluid evolution characteristics and rock fracture behavior during jet impingement were studied.The results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages:initial fluid-solid contact stage,intense thermal exchange stage,perforation and fracturing stage,and crack propagation and penetration stage.With the increase of rock temperature,the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease,while the number of cracks and crack propagation rate significantly increase,and the rock breaking critical time is shortened by up to 34.5%.Based on numerical simulation results,it was found that the center temperature of granite at 400℃ rapidly decreased from 390 to 260℃ within 0.7 s under jet impact.In addition,a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was established.These findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.
基金supported by the National Science Foundation of China(Grant Nos.12372361,12102427,12372335 and 12102202)the Fundamental Research Funds for the Central Universities(Grant No.30923010908)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX23_0520).
文摘Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of shaped charge jets in water as well as the underwater penetration effect of concrete need to be studied.In this paper,we introduced a modified forming theory of an underwater hemispherical shaped charge,and investigated the behavior of jet formation and concrete penetration in both air and water experimentally and numerically.The results show that the modified jet forming theory predicts the jet velocity of the hemispherical liner with an error of less than 10%.The underwater jets exhibit at least 3%faster and 11%longer than those in air.Concrete shows different failure modes after penetration in air and water.The depth of penetration deepens at least 18.75%after underwater penetration,accompanied by deeper crater with 65%smaller radius.Moreover,cracks throughout the entire target are formed,whereas cracks exist only near the penetration hole in air.This comprehensive study provides guidance for optimizing the structure of shaped charge and improves the understanding of the permeability effect of concrete in water.
基金the National Natural Science Foundation of China(No.52205468)China Postdoctoral Science Foundation(No.2022M710061 and No.2023T160277)Natural Science Foundation of Jiangsu Province(No.BK20210755)。
文摘Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.
基金financial support from the National Natural Science Foundation of China(Grant No.11572159).
文摘The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure variations,potentially causing catastrophic damage to the container.Current studies mainly focus on non-deforming projectiles,such as fragments,with limited exploration of shaped charge jets.In this paper,a uniquely experimental system was designed to record cavity profiles in behind-armor liquid-filled containers subjected to shaped charge jet impacts.The impact process was then numerically reproduced using the explicit simulation program ANSYS LS-DYNA with the Structured Arbitrary Lagrangian-Eulerian(S-ALE)solver.The formation mechanism,along with the dimensional and shape evolution of the cavity was investigated.Additionally,the influence of the impact kinetic energy of the jet on the cavity characteristics was analyzed.The findings reveal that the cavity profile exhibits a conical shape,primarily driven by direct jet impact and inertial effects.The expansion rates of both cavity length and maximum radius increase with jet impact kinetic energy.When the impact kinetic energy is reduced to 28.2 kJ or below,the length-to-diameter ratio of the cavity ultimately stabilizes at approximately 7.
基金supported by the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20233326)the Chongqing Science Fund for Distinguished Young Scholars(Grant No.CSTB2022NSCQJQX0028)the National Natural Science Foundation of China(Grant Nos.U23A20597,52274112).
文摘An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on the formation of perforation by AWJ is unclear yet.In this study,we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope(SEM).The results show that when the grain size is doubled,the perforation depth increases by 16.22%under the same type of structure and properties.In general,fractures are more likely to be created at the position of rough surfaces caused by abrasive impact,and the form of fractures is determined by the mineral type.In addition,microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries.The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet,while the lateral extension is controlled by the backflow.The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.
基金supported by the National Key R&D Pro-gram of China(No.2022YFB3805701)National Natural Science Foundation of China(NSFC)(No.52371182,51701052,52192592,52192593)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2019QNRC001)the Heilongjiang Touyan Innovation Team Program.
文摘1.Introduction.Ni-Mn-X(X=Ga,In,Sn,or Sb)Heusler alloys have versatile properties[1-4],such as shape memory effect[1],superelastic-ity[5],magnetocaloric effect[3],elastocaloric effect[6],and even multicaloric effect[7],that indicate their potential for use in actu-ators,sensors,micropumps,energy harvesters,and solid-state re-frigeration[8-10].Among the alloys,Ni-Mn-Sn-based alloys are environment-friendly and cost-effective[6,7,11],and hence,they have received widespread attention.
文摘This paper mainly studies the well-posedness of steady incompressible impinging jet flow problem through a 3D axisymmetric finitely long nozzle.This problem originates from the physical phenomena encountered in practical engineering fields,such as in short take-off and vertical landing(STOVL)aircraft.Nowadays many intricate phenomena associated with impinging jet flows remain inadequately elucidated,which limits the ability to optimize aircraft design.Given a boundary condition in the inlet,the impinging jet problem is transformed into a Bernoulli-type free boundary problem according to the stream function.Then the variational method is used to study the corresponding variational problem with one parameter,thereby the wellposedness is established.The main conclusion is as follows.For a 3D axisymmetric finitely long nozzle and an infinitely long vertical wall,given an axial velocity in the inlet of nozzle,there exists a unique smooth incom‑pressible impinging jet flow such that the free boundary initiates smoothly at the endpoint of the nozzle and extends to infinity along the vertical wall at far fields.The key point is to investigate the regularity of the corner where the nozzle and the vertical axis intersect.
基金supported by the National Natural Science Foundation of China(Nos.52075538,92271110)Hunan Provincial Natural Science Foundation,China(No.2023JJ30622)the National Science and Technology Major Project,China(Nos.J2019-II-0016-0037,J2019-III-0010-0054).
文摘Aiming at the dynamic stall problem that restricts the improvement of aircraft maneuverability,a new dynamic stall control method based on leading-edge Dual Synthetic Jets(DSJ)is proposed in this paper.The aerodynamic control characteristics and flow field evolution process of steady jet,Synthetic Jet(SJ)and DSJ in dynamic stall flow field are analyzed in detail,and the corresponding control mechanism is revealed.The strong"wall attachment effect"and quasisteady"characteristics of DSJ are found.The results show that the leading-edge jet technology can improve the dynamic stall flow field environment.For the whole pitching process,the average lift coefficients of steady jet,SJ and DSJ increased by 3.65%,10.51%and 14.62%respectively,and the average drag coefficients decreased by 9.58%,29.9%and 32.0%respectively.In the downward phase,the average lift coefficient increased by 16.31%,26.72%and 35.88%respectively,and the average drag coefficient decreased by 26.21%,50.46%and 54.28%respectively.Due to its strong"wall attachment effect"and"quasi-steady"characteristics,DSJ exhibits optimal control effect,showing its application potential in dynamic stall control.
文摘JD Ceramics has been specializing in the field of air interlacing jets,air texturizing jets,and water jets over 29 years.With several years of technical accumulation and continuous equipments upgrades,we have been consistently delivering high-precision,highquality,cost-effective ceramic nozzle solutions to the market.
文摘Shaoxing Shuifu Reeds is professional on producing all kinds of Air Jet Reeds and Flat Reeds,which has an annual output of 90,000 meters air-jet reeds,300,000,000 pcs of profile dents and 60,000 meters of Flat Reeds,Which has been honored with China Air Jet Profile Reeds Research Center by China Textile Machinery Association in 2015.In order to reach the demands of high quality fabric and industrial textile products,the yarn is developing to high count,multicolor,various fibers,and the fabric is developing to high count,high density,environment protection.So we have researched out high density,multicolor,multinozzle,double energy saving type profile reeds to let you choose.
基金funded by the National Natural Science Foundation of China(No.52374018)Science Foundation of China University of Petroleum,Beijing(No.2462021YJRC009)。
文摘Radial jet drilling(RJD)technology is expected to be a technology for the efficient exploitation of geothermal resources.However,the low rock-breaking efficiency is the major obstacle hindering the development of RJD technology.The flow field characteristics and rock breaking ability of cone-straight abrasive jet,rotary abrasive jet,and straight-rotating mixed abrasive jet are analyzed by numerical simulations and experiments.Results show that the axial velocity of the cone-straight abrasive jet is high,the tangential velocity is basically zero,the radial velocity is also small,and the jet impact area is concentrated in the center.A deep hole with a diameter of only 25 mm is formed when the cone-straight abrasive jet breaks the granite.Due to the presence of the guiding impeller,the rotary abrasive jet basically has no axial velocity and has the highest tangential and radial velocity,so it can break the granite to form a hole with a diameter of about 55 mm and a central bulge.The straight-rotating mixed abrasive jet has a large axial/tangential/radial velocity at the same time,so it can break the granite to form a hole with a diameter of about 52 mm with a low bulge.The results show that the straight-rotating mixed abrasive jet combines the advantages of the cone-straight jet and the rotary jet,and is more suitable for the RJD technology.The research results can provide reference for the development of efficient rock-breaking and hole-forming technology,and promote the development of RJD technology in the field of geothermal development.
基金support from the National Natural Science Foundation of China(Nos.12372256,12072186).
文摘The noise generated by subsonic jet nozzles, commonly encountered in civilian aircraft, is rather significant and propagates in both the upstream and downstream directions due to large-scale and fine-scale turbulence structures. In this paper, a distinctive inner wall treatment strategy, denoted as the Azimuthally-distributed Wavy Inner Wall (AWIW), is proposed, which is aimed at mitigating jet noise. Within this strategy, a circumferentially dispersed treatment wall characterized by a minute wavy pattern is substituted for the smooth inner wall in proximity to the nozzle outlet. To assess the effectiveness of the AWIW treatment, we conducted numerical simulations. The unsteady flow field and far-field noise were predicted by employing Large Eddy Simulations (LES) coupled with the Ffowcs Williams and Hawkings (FW-H) integration method. To gain a comprehensive understanding of the mechanism underlying the noise reduction facilitated by the AWIW treatment, it examined physical parameters such as the Lighthill source acoustic source term, the turbulent kinetic energy acoustic source term, and the shear layer instability. The results reveal that the AWIW treatment expedites the instability within the shear layer of the jet, leading to an early disruption of the jet shear layer, and consequently turbulent structures in varying sizes are generated downstream. This process effectively regulates the generation and emission of jet noise. By controlling the minor scale turbulence through the AWIW treatment, the mid- and high-frequency noise within the distant field can be significantly reduced. In the context of the flow field, the introduction of AWIW also leads to a decrease in drag on the inner wall surface of the jet, thereby improving the overall aerodynamic performance of the nozzle. Considering these attributes, the AWIW strategy emerges as a viable technique for the reduction of jet noise.
基金co-supported by the National Natural Science Foundation of China (No. 12272409)the Scientific Research and Innovation Project of Hunan Province, China (Nos. CX20230058, kq2107001, 2022RC1233 and QL20230015)
文摘Dispersion of Particle-laden Jet in Supersonic Crossflow(PJSC)is an essential process in many applications,experimental study on which,however,has rarely been reported.In order to gain physical insights into PJSC,a specialized experimental setup capable of producing a supersonic crossflow at Mach 2.6 and a particle-laden jet with particle mass loading up to 60%is developed.Visualization of the particles motion is achieved with the help of high-speed planar laser scattering technology.The dispersion characteristics of PJSC within a supersonic channel structured by cavity are systematically analyzed through six experimental cases.The results indicate that the vortices have a significant influence on particle dispersion,leading to preferential concentration of particles.i.e.particle clusters.The particle dispersion is summarized as the"scale dispersion"pattern.The primary pathways for particles entering the cavity are identified as the shear layer above the cavity and collisions at the cavity rear edge.Among the studied factors,the momentum flux ratio exerts the most substantial influence on the dispersion process.Importantly,a reduction in the injection distance is correlated with less particles entering the cavity.The insights gained from this research provide essential references for furthering understanding particle dispersion mechanisms in supersonic flows and developing highly accurate numerical models.
基金National Natural Science Foundation of China(Grant Nos.52275345,52175331)the Support plan for Outstanding Youth Innovation Team in Universities of Shandong Province,China(2021KJ044)Natural Science Foundation of Shandong Province,China(Granted No.ZR2020ZD04)。
文摘Electrohydrodynamic(EHD)jet printing represents a novel micro/nano-scale additive manufacturing process that utilises a high-voltage induced electric field between the nozzle and the substrate to print micro/nanoscale structures.EHD printing is particularly advantageous for the fabrication on flexible or non-flat substrates and of large aspect ratio micro/nanostructures and composite multi-material structures.Despite this,EHD printing has yet to be fully industrialised due to its low throughput,which is primarily caused by the limitations of serial additive printing technology.The parallel multi-nozzle array-based process has become the most promising option for EHD printing to achieve large-scale printing by increasing the number of nozzles to realise multichannel parallel printing.This paper reviews the recent development of multi-nozzle EHD printing technology,analyses jet motion with multi-nozzle,explains the origins of the electric field crosstalk effect under multi-nozzle and discusses several widely used methods for overcoming it.This work also summarises the impact of different process parameters on multi-nozzle EHD printing and describes the current manufacturing process using multi-nozzle as well as the method by which they can be realised independently.In addition,it presents an additional significant utilisation of multi-nozzle printing aside from enhancing single-nozzle production efficiency,which is the production of composite phase change materials through multi-nozzle.Finally,the future direction of multi-nozzle EHD printing development is discussed and envisioned.
基金supported by the National Key R&D Program of China(2022YFB4201802)the National Natural Science Foundation of China(22178335)DICP(DICP I202448)。
文摘C-C coupling and hydrodeoxygenation are two important reactions in the production of sustainable aviation fuels(SAFs)with lignocellulose derived oxygenates.However,it is challenging to integrate them into a one-step process because the necessity of oxygen containing functional groups in the C-C coupling reactions.Herein,jet fuel range polycycloalkanes and branched alkanes were directly synthesized by a cascade self-aldol condensation/hydrodeoxygenation reaction of lignocellulosic ketones over a zirconium phosphate loaded calcium modified nickel catalyst(NiCa/ZrP)that was prepared by a simple incipient impregnation method.Compared with the catalyst systems that have been reported in literature,the NiCa/ZrP catalyst have many advantages such as fewer step,easier operation and preparation,lower equipment investment and cost,wider applicability,etc.Moreover,the NiCa/ZrP is also applicable for the direct production of jet fuel range alkanes with lignocellulosic ketones and/or alcohols by a cascade dehydrogenation/aldol condensation/hydrodeoxygenation reaction.This work gives a new idea about the reduction of energy consumption and cost by catalyst designing in the manufacture of SAFs from lignocellulose.
基金funded by the National Natural Science Founda-tion of China(52071109).
文摘Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show significant characteristic differences and couple each other.This paper designs and conducts experiments with shaped charges to analyze the complicated process.The effects of liner angle and weight of shaped charge on the characteristics of metal jets,waves,and bubbles are discussed.It is found that in underwater explosions,the shaped charge generates the metal jet accompanied by the ballistic wave.Then,the shock wave propagates and superimposes with the ballistic wave,and the generated bubble pulsates periodically.It is revealed that the maximum head velocity of the metal jet versus the liner angle a and length-to-diameter ratio k of the shaped charge follows the laws of 1/(α/180°)^(0.55)andλ^(0.16),respectively.The head shape and velocity of the metal jet determine the curvature and propagation speed of the initial ballistic wave,thus impacting the superposition time and region with the shock wave.Our findings also reveal that the metal jet carries away some explosion products,which hinders the bubble development,causing an inward depression of the bubble wall near the metal jet.Therefore,the maximum bubble radius and pulsation period are 5.2%and 3.9%smaller than the spherical charge with the same weight.In addition,the uneven axial energy distribution of the shaped charge leads to an oblique bubble jet formation.
文摘Impinging jet arrays are extensively used in numerous industrial operations,including the cooling of electronics,turbine blades,and other high-heat flux systems because of their superior heat transfer capabilities.Optimizing the design and operating parameters of such systems is essential to enhance cooling efficiency and achieve uniform pressure distribution,which can lead to improved system performance and energy savings.This paper presents two multi-objective optimization methodologies for a turbulent air jet impingement cooling system.The governing equations are resolved employing the commercial computational fluid dynamics(CFD)software ANSYS Fluent v17.The study focuses on four controlling parameters:Reynolds number(Re),swirl number(S),jet-to-jet separation distance(Z/D),and impingement height(H/D).The effects of these parameters on heat transfer and impingement pressure distribution are investigated.Non-dominated Sorting Genetic Algorithm(NSGA-II)and Weighted Sum Method(WSM)are employed to optimize the controlling parameters for maximum cooling performance.The aim is to identify optimal design parameters and system configurations that enhance heat transfer efficiency while achieving a uniform impingement pressure distribution.These findings have practical implications for applications requiring efficient cooling.The optimized design achieved a 12.28%increase in convective heat transfer efficiency with a local Nusselt number of 113.05 compared to 100.69 in the reference design.Enhanced convective cooling and heat flux were observed in the optimized configuration,particularly in areas of direct jet impingement.Additionally,the optimized design maintained lower wall temperatures,demonstrating more effective thermal dissipation.
基金supported by National Natural Science Foundation of China(Grant Nos.52275345,52175331,51875300)Support Plan for Outstanding Youth Innovation Team in Universities of Shandong Province,China(Grant No.2021KJ044)Natural Science Foundation of Shandong Province,China(Grant No.ZR2020ZD04).
文摘Electrohydrodynamic(EHD)jet printing is a promising method for high-resolution manufacturing;however,it often suffers from jet deflection owing to the accumulation of residual charges within printed structures.These residual charges lead to jet deflection.This study introduces a novel noncontact electric field-driven(NEFD)jet micro 3D printing technique to address these challenges.By decoupling the high-voltage power supply from both the printing material and substrate,NEFD jet micro 3D printing eliminates the pathway for charge injection into the printing material,reducing residual charges by a factor of five or more compared to EHD jet printing.Our research revealed an inherent attractive force between the material jet and previously deposited material,regardless of the material used.Furthermore,we demonstrate that employing a pre-defined allowance printing strategy during fabrication reduces the standard deviation of actual fiber spacing values from 11.4μm to 1.5μm,thereby improving the fiber spacing consistency.This enhanced control enabled the successful fabrication of line patterns with 20±1μm fiber diameters and 61.1±1.9μm fiber spacing,demonstrating the feasibility of NEFD jet micro 3D printing.This technique offers a novel solution for mitigating the challenges associated with electric fields and charge accumulation in EHD jet printing,paving the way for enhanced resolution and material compatibility in micro-/nanoscale additive manufacturing.
