PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing ...PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific direction.In this paper,a numerical model of micropump has been proposed,and the fluidic properties of diffuser/nozzle have been simulated with ANSYS.With the method of finite-element analysis,the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously,but the increasing rate of diffuser is faster than that of nozzle.The L/R,ratio of L(length of cone pipe) and R(radius of minimal cross section of cone pipe) plays an important role in fluidic performance of diffuser and nozzle as well,and the mean flow rate will decrease with increment of L/R.The mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or nozzle.The simulation results indicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure,and accordingly determine the efficiency of micropump.展开更多
The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically...The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically studied.A variety of lining composite test methods were innovatively used to ensure the consistency of test conditions.The experimental results showed that the mullite(acidic oxide)has strong reactivity with rare earth inclusions,and the spinel(basic oxide)has stable chemical properties and weak reactivity with rare earth inclusions.Because alumina is one of the main reactants of clogging formation,corundum is not suitable for SEN lining.There are less clogs on the surface of zirconia,but it will be exsoluted and unstable.Therefore,solving the problem of zirconia exsolution will greatly strengthen its application in SEN lining.展开更多
Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,...Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.展开更多
Ultra-precision components have been widely used to produce advanced optoelectronic equipment.The so-called Electric field enhanced UltraViolet-Induced Jet Machining(EUV-INCJM)is an ultra-precision method that can ach...Ultra-precision components have been widely used to produce advanced optoelectronic equipment.The so-called Electric field enhanced UltraViolet-Induced Jet Machining(EUV-INCJM)is an ultra-precision method that can achieve sub-nanometer level surface quality polishing.This study focuses on the application of the EUV-INCJM with different nozzle structures to a single-crystal of silicon.Two kinds of electro-optic-liquid coupling nozzles with single-jet and multi-jet focusing structures are proposed accordingly.Simulations and experiments have been conducted to verify the material removal performance of these nozzles.The simulation results show that,under the same condition,the flow velocity of the single-jet nozzle is 1.05 times higher than that achieved with the multi-jet configuration,while the current density of the latter is 1.63 times higher than that of the single-jet nozzle.For the single-crystal silicon,the material removal efficiency of the multi-jet focusing nozzle exceeds by about 1.4 times that of the single-jet.These results confirm that the material removal ability of the multi-jet configuration is more suitable for ultra-smooth surface polishing.The surface roughness of Si workpiece was reduced from Rq 1.55 to Rq 0.816 nm with valleys and peaks on its surface being almost completely removed.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
Slot nozzle and intensive nozzle can be used in ultra fast cooling equipment. The spray cooling method with higher water pressure can be taken in order to achieve ultra fast cooling for hot rolled strip. Water will be...Slot nozzle and intensive nozzle can be used in ultra fast cooling equipment. The spray cooling method with higher water pressure can be taken in order to achieve ultra fast cooling for hot rolled strip. Water will be diffused after it is sprayed out from ultra fast cooling nozzle. Spray diffusivity will affect water velocity and penetrability of water into residual water layer on top of the strip,and then it will affect strip cooling effect. Water spraying process can be simulated by Fluent and some conclusions were obtained. Slot nozzle width and outlet velocity within setting range could not affect the length of potential core zone and the spray diffusivity. Intensive nozzle diameter and outlet velocity will affect the length of potential core zone and the spray diffusivity with different extent. These conclusions will provide referenced role for confirming ultra fast cooling nozzle size and distance between ultra fast cooling nozzle and hot rolled strip.展开更多
Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient ...Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient penetration depth,caused by excessive jet distances,presents challenges during the perforation process.To overcome this,an optimization design of the nozzle structure is required to enhance the perforation efficiency.In this paper,a computational fluid-dynamic model for conical-cylindrical nozzles has been elaborated.To further improve the rock-breaking efficiency of the jet nozzle,a fillet design is introduced at the nozzle inlet section.The SST k-ωmodel is employed to account for turbulent flow effects in submerged conditions.The results indicate that the nozzle’s geometric parameters greatly influence the flow characteristics.The orthogonal experimental method is employed to optimize the flow channel structure of the nozzle,taking the length of constant velocity core as the evaluation index.The following optimized geometric parameters for the conical-cylindrical nozzle have been determined accordingly:a cylindrical segment diameter of 3.2 mm,a contraction angle of 12°,a contraction segment length of 8 mm,a cylindrical segment length of 6.4 mm,and a fillet radius of 2 mm.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
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
The nozzle is a critical component responsible for generating most of the net thrust in a scramjet engine.The quality of its design directly affects the performance of the entire propulsion system.However,most turbule...The nozzle is a critical component responsible for generating most of the net thrust in a scramjet engine.The quality of its design directly affects the performance of the entire propulsion system.However,most turbulence models struggle to make accurate predictions for subsonic and supersonic flows in nozzles.In this study,we explored a novel model,the algebraic stress model k-kL-ARSM+J,to enhance the accuracy of turbulence numerical simulations.This new model was used to conduct numerical simulations of the design and off-design performance of a 3D supersonic asymmetric truncated nozzle designed in our laboratory,with the aim of providing a realistic pattern of changes.The research indicates that,compared to linear eddy viscosity turbulence models such as k-kL and shear stress transport(SST),the k-kL-ARSM+J algebraic stress model shows better accuracy in predicting the performance of supersonic nozzles.Its predictions were identical to the experimental values,enabling precise calculations of the nozzle.The performance trends of the nozzle are as follows:as the inlet Mach number increases,both thrust and pitching moment increase,but the rate of increase slows down.Lift peaks near the design Mach number and then rapidly decreases.With increasing inlet pressure,the nozzle thrust,lift,and pitching moment all show linear growth.As the flight altitude rises,the internal flow field within the nozzle remains relatively consistent due to the same supersonic nozzle inlet flow conditions.However,external to the nozzle,the change in external flow pressure results in the nozzle exit transitioning from over-expanded to under-expanded,leading to a shear layer behind the nozzle that initially converges towards the nozzle center and then diverges.展开更多
Understanding the motion behaviors of non-metallic inclusions in the liquid metal is important for clean steel production.High-temperature confocal laser scanning microscopy is applied to investigate the effect of dif...Understanding the motion behaviors of non-metallic inclusions in the liquid metal is important for clean steel production.High-temperature confocal laser scanning microscopy is applied to investigate the effect of different Ti and Al contents on the agglomeration behavior of non-metallic inclusions in low carbon steels.Furthermore,the agglomeration mechanism of inclusions was investigated through quantitative analysis of in-situ observation experiments and a modified Kralchevsky-Paunov model.The obtained results indicate that Al_(2)O_(3)is the main type inclusion in the low-alloys steels with both Al and Ti addition.This type of inclusion is more likely to absorb surrounding small-size inclusion particles,leading to a further growth for the cluster formation and contributing to a serious engineering problem,nozzle clogging.Besides,TiO_(x)is the main type inclusion in the molten steel with only Ti addition,and this type of inclusion is less likely to agglomerate and the individual inclusion particles show a‘free’motion with the fluid of molten steel.The difference between these two types of inclusions is due to the difference in attractive force and action distance at the meniscus created by the inclusion/steel/Ar multiple interfaces and influenced by the physical parameters,e.g.,contact angle and interface energy between inclusion and steel,and surface tension of the melt.展开更多
The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the res...The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the results are reliable.Nozzle fluid is influenced by pipe structure,causing pressure and density to drop as speed increases.Differences in pressure and velocity between the jet and surrounding gas lead to jet velocity attenuation,flow expansion,deflection,and eddy currents.The optimal top blowing pressure is 0.6 MPa,and the center velocity and width of the jet are 345 m/s and 0.124 m,respectively,at 20De(De is the nozzle exit diameter).It achieves a maximum jet velocity of 456 m/s.The optimal nozzle Mach number is 1.75,with a maximum jet velocity of 451 m/s.At 20D_(e),the jet center velocity is 338 m/s,with a width of 0.12 m.展开更多
Enhancing the fermentation efficiency of waste in waste warehouses is pivotal for accelerating the pyrolysis process and minimizing harmful gas emissions.This study proposes an integrated approach,combining hot air in...Enhancing the fermentation efficiency of waste in waste warehouses is pivotal for accelerating the pyrolysis process and minimizing harmful gas emissions.This study proposes an integrated approach,combining hot air injection with dual atomizing nozzles,for the thermal treatment of waste piles.Numerical simulations are employed to investigate the influence of various parameters,namely,nozzle height,nozzle tilt angle,inlet air velocity and air temperature,on the droplet diffusion process,spread area,droplet temperature,and droplet size distribution.The results show that reducing the nozzle height increases the temperature of droplets upon their deposition on the waste pile.Specifically,when the nozzle height is lowered to 1.5 m,the temperature of the droplets reaching the waste pile is 1℃higher than when the nozzle height is set at 2 m.Furthermore,an increase in the nozzle tilt angle expands the overlapping heating area.For instance,when the nozzle angle is increased from 15°to 30°,the overlapping spread area expands by 3.21 m2.Additionally,increasing the inlet air velocity enhances the droplet diffusion range.At an air velocity of 2 m/s,the droplet diffusion range grows to 14.4 m,representing a 6.7%increase compared to the nowind condition.While the average droplet diameter decreases to 1.53 mm,the droplet temperature decreases by 1℃.Moreover,the droplet temperature is found to become smaller as the ambient temperature inside the waste warehouse declines.Specifically,a 5℃reduction in the ambient temperature results in a 1℃decrease in the average temperature of the atomized droplets.The study concludes that a nozzle height of 1.5 m and a nozzle tilt angle of 30°effectively meet practical heating requirements.展开更多
Semisolid ZL101 aluminum slurry was prepared by a micro fused-casting process.The nozzle temperature has great effects on the microstructure and mechanical properties,which are primarily influenced through changing co...Semisolid ZL101 aluminum slurry was prepared by a micro fused-casting process.The nozzle temperature has great effects on the microstructure and mechanical properties,which are primarily influenced through changing cooling conditions of the fused-casting area.With the decline of nozzle temperatures,the microstructure of semisolid ZL101 aluminum slurry tends to be more homogeneous,delivering smaller grains.Temperatures of liquids and solids were measured by differential scanning calorimetry(DSC).Distribution and characteristics of microstructure were examined by scanning electron microscopy(SEM)equipped with energy dispersive spectrometer(EDS)and optical microscope(OM).It is found that uniform shape and good grain size are observed for semisolid samples fabricated by micro fused-casting under conditions including nozzle temperature of 592℃,bucket temperature of 600℃,stirring velocity of 600 r/min and channel diameter of 3 mm.Due to the smaller average grain size of 53μm and shape factor of 0.71 for the fine grains,the ultrahigh average tensile strength and Vickers hardness can reach(181±1.25)MPa and(87.95±1.18)HV for the optimized semisolid ZL101 aluminum slurry,respectively.展开更多
Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ...Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.展开更多
The characteristics of flow and thrust evolution of an annular Expansion-Deflection(ED)nozzle are numerically investigated under varying backpressure changing rates during ascending and descending trajectories.The obj...The characteristics of flow and thrust evolution of an annular Expansion-Deflection(ED)nozzle are numerically investigated under varying backpressure changing rates during ascending and descending trajectories.The objective is to test the sensitivity of unsteady behaviors of shock waves in the ED nozzle to backpressure changing rate,and to further elucidate the thrust evolution mechanism and mode transition hysteresis.The movement of shock reflection points on the nozzle wall follows two flow mechanisms,namely,shock self-excited oscillations and rapid backpressure changes.A low backpressure changing rate enables shock self-excited oscillations,leading to a reciprocating motion of the shock waves accompanied by thrust oscillations,while a high backpressure changing rate suppresses the shock self-excited oscillations,leading to a unidirectional motion of the wave system on the nozzle shroud wall.A criterion for distinguishing ED nozzle operation modes is proposed,which relies on the loading inflection points of the nozzle pintle base and exhibits a fast and user-friendly feature.A dual-wake mode hysteresis region is defined to quantify the hysteresis in nozzle mode transition,with the span of the region decreasing as the backpressure changing rate slows down.The present work helps in understanding the unsteady flow mechanism and thrust evolution in ED nozzles.展开更多
Minimum quantity lubrication(MQL)is a technique that achieves effective lubrication and cooling of the cutting zone by using a minimal amount of cutting fluid.This results in a decrease in the cutting temperature,exte...Minimum quantity lubrication(MQL)is a technique that achieves effective lubrication and cooling of the cutting zone by using a minimal amount of cutting fluid.This results in a decrease in the cutting temperature,extending the cutting tool life and improving the surface quality of the workpiece.Optimizing the nozzle settings can enhance the cooling and lubrication performance of MQL,leading to increased processing efficiency and product quality.Nozzles with different shapes are fabricated,and different outlet diameters and wall thicknesses are set.The cutting process takes into account the impact of spindle speed and feed rate.An experimental study is conducted to investigate the atomization cone angle and particle size distribution of different nozzles.The circular nozzle is more conducive to the concentrated injection of an atomized liquid beam.The atomization cone angle is the largest when the nozzle outlet diameter is 1.2 mm.Enlarging the nozzle outlet diameter will increase the diameter of the atomized droplets.The atomization cone angle increases while the droplet diameter decreases with the increase of outlet wall thickness.Properly increasing the outlet wall thickness is beneficial to improving the atomization quality.The droplet diameter increases firstly and then decreases with the increase of spindle speed and feed rate.Increasing the MQL gas supply pressure and reducing the lubricating oil flow rate will improve the atomization quality of the nozzle.Studies on the influence of the MQL nozzle processing technology on the atomization effect can help to enhance the cooling and lubrication performance of the MQL technology,leading to improved processing efficiency and quality.展开更多
The serpentine convergent-divergent nozzle represents an optimal configuration for nextgeneration fighter aircraft characterized by low detectability and high thrust-to-weight ratio.In contrast to the serpentine conve...The serpentine convergent-divergent nozzle represents an optimal configuration for nextgeneration fighter aircraft characterized by low detectability and high thrust-to-weight ratio.In contrast to the serpentine convergent nozzle,such configuration offers increased design flexibility with additional parameters,leading to heightened interactions among these parameters.As such,it is crucial to reveal the influence of design parameters on the aerodynamic performance of the serpentine convergent-divergent nozzle and the multifactor interaction,as well as its mechanism.Therefore,the influence,interaction and sensitivity of parameters on the aerodynamic performance of the nozzle were numerically investigated using the orthogonal test method.Additionally,the influence mechanism of the convergence angle,throat aspect ratio,and axial length to inlet diameter on the flow characteristics of the nozzle was investigated in detail.The results show that the convergence angle is identified as the main factor affecting the aerodynamic parameters of the nozzle.As the convergence angle increases,the thrust coefficient,total pressure recovery coefficient and discharge coefficient gradually decrease.The interaction between throat aspect ratio and other parameters is obvious.Different design parameters affect the local loss and the friction loss by affecting the curvature and wetted perimeter area,resulting in different aerodynamic characteristics of serpentine convergent-divergent nozzle.展开更多
This study utilizes a visualization nozzle and spray experimental platform to experimentally investigate the flow focusing/blurring nozzle.It is found that the working mode of the nozzle transitions from flow focusing...This study utilizes a visualization nozzle and spray experimental platform to experimentally investigate the flow focusing/blurring nozzle.It is found that the working mode of the nozzle transitions from flow focusing to flow transition and eventually to flow blurring as the gas flow rate increases or the tube hole distance decreases.Conversely,an increase in liquid flow rate only facilitates the transition from flow focusing to flow transition.Changes in the gas/liquid flow rate or tube hole distance influence the gas shear effect and the gas inertial impact effect inside the nozzle,which in turn alters the working mode.An increase in gas flow rate results in a shift of the droplet size distribution towards smaller particle sizes in the flow blurring mode,whereas an increase in liquid flow rate produces the opposite effect.Notably,the impact of the gas flow rate on these changes is more pronounced than that of the liquid flow rate.展开更多
基金Supported by′111′Project and Chongqing Natural Science Foundation(2006BB2043,2006BB2142)
文摘PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific direction.In this paper,a numerical model of micropump has been proposed,and the fluidic properties of diffuser/nozzle have been simulated with ANSYS.With the method of finite-element analysis,the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously,but the increasing rate of diffuser is faster than that of nozzle.The L/R,ratio of L(length of cone pipe) and R(radius of minimal cross section of cone pipe) plays an important role in fluidic performance of diffuser and nozzle as well,and the mean flow rate will decrease with increment of L/R.The mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or nozzle.The simulation results indicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure,and accordingly determine the efficiency of micropump.
基金supported by the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China(52302031)National Natural Science Foundation of China(51932008 and 51772277)Central China Thousand Talents Project(204200510011).
文摘The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically studied.A variety of lining composite test methods were innovatively used to ensure the consistency of test conditions.The experimental results showed that the mullite(acidic oxide)has strong reactivity with rare earth inclusions,and the spinel(basic oxide)has stable chemical properties and weak reactivity with rare earth inclusions.Because alumina is one of the main reactants of clogging formation,corundum is not suitable for SEN lining.There are less clogs on the surface of zirconia,but it will be exsoluted and unstable.Therefore,solving the problem of zirconia exsolution will greatly strengthen its application in SEN lining.
基金supported by the Fundamental Research Funds for the Central Universities(No.FRF-BD-23-01).
文摘Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.
基金supported by the National Natural Science Foundation of China(52365056).
文摘Ultra-precision components have been widely used to produce advanced optoelectronic equipment.The so-called Electric field enhanced UltraViolet-Induced Jet Machining(EUV-INCJM)is an ultra-precision method that can achieve sub-nanometer level surface quality polishing.This study focuses on the application of the EUV-INCJM with different nozzle structures to a single-crystal of silicon.Two kinds of electro-optic-liquid coupling nozzles with single-jet and multi-jet focusing structures are proposed accordingly.Simulations and experiments have been conducted to verify the material removal performance of these nozzles.The simulation results show that,under the same condition,the flow velocity of the single-jet nozzle is 1.05 times higher than that achieved with the multi-jet configuration,while the current density of the latter is 1.63 times higher than that of the single-jet nozzle.For the single-crystal silicon,the material removal efficiency of the multi-jet focusing nozzle exceeds by about 1.4 times that of the single-jet.These results confirm that the material removal ability of the multi-jet configuration is more suitable for ultra-smooth surface polishing.The surface roughness of Si workpiece was reduced from Rq 1.55 to Rq 0.816 nm with valleys and peaks on its surface being almost completely removed.
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State"1025"Science and Technology Support Projects,China(No.2012BAF04B01)
文摘Slot nozzle and intensive nozzle can be used in ultra fast cooling equipment. The spray cooling method with higher water pressure can be taken in order to achieve ultra fast cooling for hot rolled strip. Water will be diffused after it is sprayed out from ultra fast cooling nozzle. Spray diffusivity will affect water velocity and penetrability of water into residual water layer on top of the strip,and then it will affect strip cooling effect. Water spraying process can be simulated by Fluent and some conclusions were obtained. Slot nozzle width and outlet velocity within setting range could not affect the length of potential core zone and the spray diffusivity. Intensive nozzle diameter and outlet velocity will affect the length of potential core zone and the spray diffusivity with different extent. These conclusions will provide referenced role for confirming ultra fast cooling nozzle size and distance between ultra fast cooling nozzle and hot rolled strip.
基金The authors gratefully acknowledge the financial support by the National Natural Science Foundation of China(No.52405272)the CNOOC’s major project during the 14th Five-Year Plan period“Key Technologies and Equipment for Measurement,Recording,and Testing-Development and Engineering of Integrated Perforation Technology Equipment Based on Reservoir Geology”and the National Science Foundation of Jiangsu Province(No.BK20220533).
文摘Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient penetration depth,caused by excessive jet distances,presents challenges during the perforation process.To overcome this,an optimization design of the nozzle structure is required to enhance the perforation efficiency.In this paper,a computational fluid-dynamic model for conical-cylindrical nozzles has been elaborated.To further improve the rock-breaking efficiency of the jet nozzle,a fillet design is introduced at the nozzle inlet section.The SST k-ωmodel is employed to account for turbulent flow effects in submerged conditions.The results indicate that the nozzle’s geometric parameters greatly influence the flow characteristics.The orthogonal experimental method is employed to optimize the flow channel structure of the nozzle,taking the length of constant velocity core as the evaluation index.The following optimized geometric parameters for the conical-cylindrical nozzle have been determined accordingly:a cylindrical segment diameter of 3.2 mm,a contraction angle of 12°,a contraction segment length of 8 mm,a cylindrical segment length of 6.4 mm,and a fillet radius of 2 mm.
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.
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.
基金supported by the Zhejiang Provincial Key Research and Development Program of China(No.2020C01020).
文摘The nozzle is a critical component responsible for generating most of the net thrust in a scramjet engine.The quality of its design directly affects the performance of the entire propulsion system.However,most turbulence models struggle to make accurate predictions for subsonic and supersonic flows in nozzles.In this study,we explored a novel model,the algebraic stress model k-kL-ARSM+J,to enhance the accuracy of turbulence numerical simulations.This new model was used to conduct numerical simulations of the design and off-design performance of a 3D supersonic asymmetric truncated nozzle designed in our laboratory,with the aim of providing a realistic pattern of changes.The research indicates that,compared to linear eddy viscosity turbulence models such as k-kL and shear stress transport(SST),the k-kL-ARSM+J algebraic stress model shows better accuracy in predicting the performance of supersonic nozzles.Its predictions were identical to the experimental values,enabling precise calculations of the nozzle.The performance trends of the nozzle are as follows:as the inlet Mach number increases,both thrust and pitching moment increase,but the rate of increase slows down.Lift peaks near the design Mach number and then rapidly decreases.With increasing inlet pressure,the nozzle thrust,lift,and pitching moment all show linear growth.As the flight altitude rises,the internal flow field within the nozzle remains relatively consistent due to the same supersonic nozzle inlet flow conditions.However,external to the nozzle,the change in external flow pressure results in the nozzle exit transitioning from over-expanded to under-expanded,leading to a shear layer behind the nozzle that initially converges towards the nozzle center and then diverges.
基金National Natural Science Foundation of China(Nos.U21A20116,U21A20117 and 52304347)National Natural Science Foundation of Liaoning(Nos.2023-MSBA-135 and 2023-BSBA-107)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.N2409006 and N2409008)are acknowledged to support this workSwedish Foundation for International Cooperation in Research and Higher Education(STINT,Project No.IB2022-9228)is acknowledged by W.Mu to support his visit between KTH(Sweden)and NEU(China).
文摘Understanding the motion behaviors of non-metallic inclusions in the liquid metal is important for clean steel production.High-temperature confocal laser scanning microscopy is applied to investigate the effect of different Ti and Al contents on the agglomeration behavior of non-metallic inclusions in low carbon steels.Furthermore,the agglomeration mechanism of inclusions was investigated through quantitative analysis of in-situ observation experiments and a modified Kralchevsky-Paunov model.The obtained results indicate that Al_(2)O_(3)is the main type inclusion in the low-alloys steels with both Al and Ti addition.This type of inclusion is more likely to absorb surrounding small-size inclusion particles,leading to a further growth for the cluster formation and contributing to a serious engineering problem,nozzle clogging.Besides,TiO_(x)is the main type inclusion in the molten steel with only Ti addition,and this type of inclusion is less likely to agglomerate and the individual inclusion particles show a‘free’motion with the fluid of molten steel.The difference between these two types of inclusions is due to the difference in attractive force and action distance at the meniscus created by the inclusion/steel/Ar multiple interfaces and influenced by the physical parameters,e.g.,contact angle and interface energy between inclusion and steel,and surface tension of the melt.
基金supported by the National Key Research and Development Project of China(No.2022YFC3902001)the National Natural Science Foundation of China(No.52004340)the Guangxi Innovation-driven Development Project,China(Nos.Gui 2021AA12006 and 2021AB26024)。
文摘The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the results are reliable.Nozzle fluid is influenced by pipe structure,causing pressure and density to drop as speed increases.Differences in pressure and velocity between the jet and surrounding gas lead to jet velocity attenuation,flow expansion,deflection,and eddy currents.The optimal top blowing pressure is 0.6 MPa,and the center velocity and width of the jet are 345 m/s and 0.124 m,respectively,at 20De(De is the nozzle exit diameter).It achieves a maximum jet velocity of 456 m/s.The optimal nozzle Mach number is 1.75,with a maximum jet velocity of 451 m/s.At 20D_(e),the jet center velocity is 338 m/s,with a width of 0.12 m.
文摘Enhancing the fermentation efficiency of waste in waste warehouses is pivotal for accelerating the pyrolysis process and minimizing harmful gas emissions.This study proposes an integrated approach,combining hot air injection with dual atomizing nozzles,for the thermal treatment of waste piles.Numerical simulations are employed to investigate the influence of various parameters,namely,nozzle height,nozzle tilt angle,inlet air velocity and air temperature,on the droplet diffusion process,spread area,droplet temperature,and droplet size distribution.The results show that reducing the nozzle height increases the temperature of droplets upon their deposition on the waste pile.Specifically,when the nozzle height is lowered to 1.5 m,the temperature of the droplets reaching the waste pile is 1℃higher than when the nozzle height is set at 2 m.Furthermore,an increase in the nozzle tilt angle expands the overlapping heating area.For instance,when the nozzle angle is increased from 15°to 30°,the overlapping spread area expands by 3.21 m2.Additionally,increasing the inlet air velocity enhances the droplet diffusion range.At an air velocity of 2 m/s,the droplet diffusion range grows to 14.4 m,representing a 6.7%increase compared to the nowind condition.While the average droplet diameter decreases to 1.53 mm,the droplet temperature decreases by 1℃.Moreover,the droplet temperature is found to become smaller as the ambient temperature inside the waste warehouse declines.Specifically,a 5℃reduction in the ambient temperature results in a 1℃decrease in the average temperature of the atomized droplets.The study concludes that a nozzle height of 1.5 m and a nozzle tilt angle of 30°effectively meet practical heating requirements.
基金Funded by the Natural Science Foundation of Henan Province(No.252300420256)。
文摘Semisolid ZL101 aluminum slurry was prepared by a micro fused-casting process.The nozzle temperature has great effects on the microstructure and mechanical properties,which are primarily influenced through changing cooling conditions of the fused-casting area.With the decline of nozzle temperatures,the microstructure of semisolid ZL101 aluminum slurry tends to be more homogeneous,delivering smaller grains.Temperatures of liquids and solids were measured by differential scanning calorimetry(DSC).Distribution and characteristics of microstructure were examined by scanning electron microscopy(SEM)equipped with energy dispersive spectrometer(EDS)and optical microscope(OM).It is found that uniform shape and good grain size are observed for semisolid samples fabricated by micro fused-casting under conditions including nozzle temperature of 592℃,bucket temperature of 600℃,stirring velocity of 600 r/min and channel diameter of 3 mm.Due to the smaller average grain size of 53μm and shape factor of 0.71 for the fine grains,the ultrahigh average tensile strength and Vickers hardness can reach(181±1.25)MPa and(87.95±1.18)HV for the optimized semisolid ZL101 aluminum slurry,respectively.
基金supported by the National Natural Science Foundation of China(No.12002102)。
文摘Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.
基金the National Natural Science Foundation of China(No.12002102)。
文摘The characteristics of flow and thrust evolution of an annular Expansion-Deflection(ED)nozzle are numerically investigated under varying backpressure changing rates during ascending and descending trajectories.The objective is to test the sensitivity of unsteady behaviors of shock waves in the ED nozzle to backpressure changing rate,and to further elucidate the thrust evolution mechanism and mode transition hysteresis.The movement of shock reflection points on the nozzle wall follows two flow mechanisms,namely,shock self-excited oscillations and rapid backpressure changes.A low backpressure changing rate enables shock self-excited oscillations,leading to a reciprocating motion of the shock waves accompanied by thrust oscillations,while a high backpressure changing rate suppresses the shock self-excited oscillations,leading to a unidirectional motion of the wave system on the nozzle shroud wall.A criterion for distinguishing ED nozzle operation modes is proposed,which relies on the loading inflection points of the nozzle pintle base and exhibits a fast and user-friendly feature.A dual-wake mode hysteresis region is defined to quantify the hysteresis in nozzle mode transition,with the span of the region decreasing as the backpressure changing rate slows down.The present work helps in understanding the unsteady flow mechanism and thrust evolution in ED nozzles.
文摘Minimum quantity lubrication(MQL)is a technique that achieves effective lubrication and cooling of the cutting zone by using a minimal amount of cutting fluid.This results in a decrease in the cutting temperature,extending the cutting tool life and improving the surface quality of the workpiece.Optimizing the nozzle settings can enhance the cooling and lubrication performance of MQL,leading to increased processing efficiency and product quality.Nozzles with different shapes are fabricated,and different outlet diameters and wall thicknesses are set.The cutting process takes into account the impact of spindle speed and feed rate.An experimental study is conducted to investigate the atomization cone angle and particle size distribution of different nozzles.The circular nozzle is more conducive to the concentrated injection of an atomized liquid beam.The atomization cone angle is the largest when the nozzle outlet diameter is 1.2 mm.Enlarging the nozzle outlet diameter will increase the diameter of the atomized droplets.The atomization cone angle increases while the droplet diameter decreases with the increase of outlet wall thickness.Properly increasing the outlet wall thickness is beneficial to improving the atomization quality.The droplet diameter increases firstly and then decreases with the increase of spindle speed and feed rate.Increasing the MQL gas supply pressure and reducing the lubricating oil flow rate will improve the atomization quality of the nozzle.Studies on the influence of the MQL nozzle processing technology on the atomization effect can help to enhance the cooling and lubrication performance of the MQL technology,leading to improved processing efficiency and quality.
基金supported by the National Science and Technology Major Project of China(No.J2019-Ⅲ-0009-0053)。
文摘The serpentine convergent-divergent nozzle represents an optimal configuration for nextgeneration fighter aircraft characterized by low detectability and high thrust-to-weight ratio.In contrast to the serpentine convergent nozzle,such configuration offers increased design flexibility with additional parameters,leading to heightened interactions among these parameters.As such,it is crucial to reveal the influence of design parameters on the aerodynamic performance of the serpentine convergent-divergent nozzle and the multifactor interaction,as well as its mechanism.Therefore,the influence,interaction and sensitivity of parameters on the aerodynamic performance of the nozzle were numerically investigated using the orthogonal test method.Additionally,the influence mechanism of the convergence angle,throat aspect ratio,and axial length to inlet diameter on the flow characteristics of the nozzle was investigated in detail.The results show that the convergence angle is identified as the main factor affecting the aerodynamic parameters of the nozzle.As the convergence angle increases,the thrust coefficient,total pressure recovery coefficient and discharge coefficient gradually decrease.The interaction between throat aspect ratio and other parameters is obvious.Different design parameters affect the local loss and the friction loss by affecting the curvature and wetted perimeter area,resulting in different aerodynamic characteristics of serpentine convergent-divergent nozzle.
基金the National Natural Science Foundation of China(52276026).
文摘This study utilizes a visualization nozzle and spray experimental platform to experimentally investigate the flow focusing/blurring nozzle.It is found that the working mode of the nozzle transitions from flow focusing to flow transition and eventually to flow blurring as the gas flow rate increases or the tube hole distance decreases.Conversely,an increase in liquid flow rate only facilitates the transition from flow focusing to flow transition.Changes in the gas/liquid flow rate or tube hole distance influence the gas shear effect and the gas inertial impact effect inside the nozzle,which in turn alters the working mode.An increase in gas flow rate results in a shift of the droplet size distribution towards smaller particle sizes in the flow blurring mode,whereas an increase in liquid flow rate produces the opposite effect.Notably,the impact of the gas flow rate on these changes is more pronounced than that of the liquid flow rate.
