The reduction of oxygen consumption is a key factor to improve the energy density of underwater Stirling engine.A series of fundamental experiments are carried out to elucidate the spray characteristics of soybean oil...The reduction of oxygen consumption is a key factor to improve the energy density of underwater Stirling engine.A series of fundamental experiments are carried out to elucidate the spray characteristics of soybean oil/2,5-dimethylfuran(DMF)blended fuel in an underwater Stirling engine.Spray characteristics such as spray penetration,spray angle,spray area,and light intensity level under low injection and ambient pressures are obtained using image post-processing method.The results show that the effects of injection pressure,ambient pressure,and nozzle diameter on the transient spray characteristics of underwater Stirling engine are similar to those of diesel engine.However,in the steady spray process,the injection pressure has little effect on spray near angle,and the spray far angle increases with the increase of the injection pressure.Compared with the spray far angle at injection pressure of 3 MPa,the spray far angle at 5 MPa and 7 MPa increased by 11.38%and 18.14%respectively.The addition of DMF can obviously improve the atomization of soybean oil/DMF blended fuel.The spray angle of blended fuel in transient process increases with the increase of the DMF concentration.The spray near angle has exceeded that of diesel(46.21°)when the DMF volume fraction exceeds 25%.The spray far angle is equivalent to that of diesel when the DMF volume fraction reaches 75%.Moreover,the spray with gas ejection no longer keeps conical,the droplet diameter distribution is more dispersed,and the droplet diameter is smaller.展开更多
The high-speed digital imaging technique is applied to observe the developing process of flash boiling spray of dimethyl ether at low ambient pressure, and the effects of nozzle opening pressure and nozzle hole diamet...The high-speed digital imaging technique is applied to observe the developing process of flash boiling spray of dimethyl ether at low ambient pressure, and the effects of nozzle opening pressure and nozzle hole diameter on the spray shape, spray tip penetration and spray angle during the injection are investigated. The experimental results show that the time when the vortex ring structure of flash boiling spray forms and its developing process are determined by the combined action of the bubble growth and breakup in the spray and the air drag on the leading end of spray; with the enhancement of nozzle opening pressure, the spray tip penetration increases and the spray angle decreases. The influence of nozzle hole diameter on the spray tip penetration is relatively complicated, the spray tip penetration is longer with a smaller nozzle hole diameter at the early stage of injection, while the situation is just opposite at the later stage of injection. This paper establishes that the variation of spray angle is consistent with that of nozzle hole diameter.展开更多
The spray behaviors of the combined trapezoid spray tray(CTST) have a significant effect on the gas-liquid interface. In this paper, the spray process of CTST in a column, 570 mm in diameter, was experimentally invest...The spray behaviors of the combined trapezoid spray tray(CTST) have a significant effect on the gas-liquid interface. In this paper, the spray process of CTST in a column, 570 mm in diameter, was experimentally investigated by using a high-speed camera, and a theoretical model of the average droplet size was established according to the unstable wave theory. The results demonstrated that gas velocity passing through the hole is the key factor affecting the spray angle, which increases gradually with an increase in the gas velocity. When the gas velocity exceeds 7.5 m/s, the spray angle becomes stable at around 55°. The average flow velocity of the liquid sheet at the spray-hole increases significantly with an increase in the gas velocity, and decreases slightly with an increase in the liquid flow rate; moreover, it increases from the bottom of spray hole upward to the top. The density of liquid drops distribution in the spray area can be described by the RosinRammler function. In addition, the liquid drops are mainly concentrated in the area of spray angle ranging from 20° to 40°, and they gradually become uniform with the increase in the gas velocity and the liquid flow rate. The average liquid drop size deceases with an increase in the gas velocity, and increases slightly with an increasing liquid flow rate. In the normal working range, the average liquid drop size is about 1.0 mm to 2.5 mm in diameter.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
In order to analyze the spray characteristics of non-circular nozzle holes based on the air-assisted spray system, the spray characteristics of circular and non-circular nozzles were studied under the pressure of 0.2-...In order to analyze the spray characteristics of non-circular nozzle holes based on the air-assisted spray system, the spray characteristics of circular and non-circular nozzles were studied under the pressure of 0.2-0.6 MPa and the spray volume of 1000-5000 mL/h. Elliptical nozzle and triangular nozzle are classified as non-circular geometries. The spray cone angle was measured by processing the spray image captured by a CCD camera. The measured spray cone angles of the circular nozzles were analyzed, and the axis switching phenomenon of minor plane of elliptical nozzle was found during the test. Among the three shapes of nozzles, the elliptical nozzle had the largest spray cone angle, and the triangular nozzle had the smallest. The velocity field obtained depended on the PIV system. The results show that for axial velocity, elliptical orifice spray has greater kinetic energy and smaller droplet size under the same working parameters. Compared with the circular and elliptical nozzles, triangular orifice reached maximum spray velocity the fastest, but its velocity decay was the fastest. For radial velocity, away from the axis, the spray velocity of the elliptical orifice was less affected by the injection parameters, and the velocity was less than that of circular orifice and triangle orifice. Increasing air pressure will weaken radial propagation. The increase of liquid spraying rate had no remarkable effect on the increase of spraying rate. The results of particle size analysis show that the particle size of the non-circular orifice is reduced compared with that of the circular orifice, which promotes the breakup of droplets to a certain extent and enhances the atomization effect.展开更多
As the core equipment in power systems,ultra-high voltage(UHV)transformers pose a high fire risk.The compressed-air foam spray nozzle is a novel end-release device that,due to its high efficiency and excellent suppres...As the core equipment in power systems,ultra-high voltage(UHV)transformers pose a high fire risk.The compressed-air foam spray nozzle is a novel end-release device that,due to its high efficiency and excellent suppression effect on oil-based fires,has been increasingly applied in UHV substations.This study is based on a self-developed experimental platform for compressed-air foam firefighting systems.To meet practical engineering needs,the longitudinal maximum of the contour line at the threshold of 12 L/(min·m²)was selected as the spray range.The study systematically explored the factors influencing the spray range of the spray nozzle.Experimental results revealed that when the hole elevation angle was 60°,the average spray range increased by 59%compared to 0°.When the nozzle aperture was 10 mm and the outlet pressure was 0.15 MPa,the spray range improved by 17%.Additionally,as the outlet pressure increased,the foam spray range grew significantly,with a 35.2% increase at 0.3 MPa compared to 0.1 MPa,indicating that the outlet pressure had a substantial effect on the spray range.To predict the spray range increase,an empirical model is developed for the outlet pressure versus the spray range.After analyzing the above three influencing factors,all the data of various working conditions were integrated into a single dataset,a prediction model of the spray range was established,and the importance of the factors affecting the range was ranked.These findings provide a theoretical foundation for the optimized design and engineering application of compressed-air foam systems(CAFSs).展开更多
The structure of the pressure swirl nozzle is an important factor affecting its spray performance.This work aims to study pressure swirl nozzles with different structures by experiment and simulation.In the experiment...The structure of the pressure swirl nozzle is an important factor affecting its spray performance.This work aims to study pressure swirl nozzles with different structures by experiment and simulation.In the experiment,10 nozzles with different structures are designed to comprehensively cover various geometric factors.In terms of simulation,steady-state simulation with less computational complexity is used to study the flow inside the nozzle.The results show that the diameter of the inlet and outlet,the direction of the inlet,the diameter of the swirl chamber,and the height of the swirl chamber all affect the atomization performance,and the diameter of the inlet and outlet has a greater impact.It is found that under the same flow rate and pressure,the geometric differences do have a significant impact on the atomization characteristics,such as spray angle and SMD(Sauter mean diameter).Specific nozzle structures can be customized according to the actual needs.Data analysis shows that the spray angle is related to the swirl number,and the SMD is related to turbulent kinetic energy.Through data fitting,the equations for predicting the spray angle and the SMD are obtained.The error range of the fitting equation for the prediction of spray angle and SMD is within 15% and 10% respectively.The prediction is expected to be used in engineering to estimate the spray performance at the beginning of a real project.展开更多
Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles.Rebounded concrete amount cause a significant difference between the initial mix de...Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles.Rebounded concrete amount cause a significant difference between the initial mix design and emplaced mix compositions.Apart from the structural differences,it comes with a cost increase which was resulted by the splashed concrete amount.Many factors such as viscosity and quantity of mixes dominate this rebound amount in sprayed glass fibre reinforced concrete applications depending on production technologies and processes;however,this research focuses on the spray distance and the angle of the spray gun which mainly effects the rebound amount in glass fibre reinforced concrete production.This paper aims to understand the required angle and distance for glass fibre reinforced concrete mixes having on-site plastic viscosity values.Glass fibre reinforced mixtures were also modelled with a finite element method based software and,the analysis results were compared with production line results.Results of the analysis and on-site studies showed a decisive correlation between,discharge distance,discharge angle and the viscosity of the concrete.展开更多
Air-atomized fog cooling is particularly suitable for the after-pot cooling of galvanized steel strips.With air and water serving as working media,an experimental study was conducted on the atomization characteristics...Air-atomized fog cooling is particularly suitable for the after-pot cooling of galvanized steel strips.With air and water serving as working media,an experimental study was conducted on the atomization characteristics of a newly-developed cross-flow type of fog nozzles.The water flux distribution,spray angle and pressure of water and air were measured.The results show that the water droplet size was small and insensitive to the water flow rate.The spray angle was small and the water flow rate slightly affected the air pressure in the chamber.An empirical correlation between the pressure in the chamber and the gas flow rate was obtained for the purpose of equipment design.展开更多
A pintle injector is advantageous for throttling a liquid rocket engine and reducing engine weight. This study ex- plores the effects of momentum ratio and Weber number at various injection conditions on spray charact...A pintle injector is advantageous for throttling a liquid rocket engine and reducing engine weight. This study ex- plores the effects of momentum ratio and Weber number at various injection conditions on spray characteristics of the pintle injector for liquid-gas propellants. A liquid sheet is injected from a center pintle nozzle and it is broken by a gas jet from an annular gap. The pressure drops of propellants, and the pintle opening distance were consi- dered as control variables; using 0.1 -1.0 as a bar for the pressure drop of the liquid injection, a 0.01-4）.2 bar for the pressure drop of gas jet and a 0.2 - 1.0 mm for the pintle opening distance. The discharge coefficient was de- creased linearly before the pintle opening distance of 0.75 mm and then, the coefficient was slightly increased. Spray images were captured by a CMOS camera with high resolution. Then, the shadow and reflected images were analyzed. Spray distributions were measured by a pattemator with an axial distance of 50 mm from a pintle tip. Finally, the spray half angles had an exponentially decreasing correlation as a momentum ratio divided by the Weber number. Also, the spray half angles from the spray distribution were underestimated compared to those measured from the captured images.展开更多
In this work, the effects of injecting an evaporating liquid jet into solid-gas flow are experimentally investigated. A new model （SHED model） and a supplementary model （spray model） have also been proposed to inv...In this work, the effects of injecting an evaporating liquid jet into solid-gas flow are experimentally investigated. A new model （SHED model） and a supplementary model （spray model） have also been proposed to investigate some flow-field characteristics in three-phase fluidized bed with the mean relative error 4.3% between model and measured results. Some experiments were conducted to study the influences of flow-field parameters such as liquid volumetric flow rate, injection velocity, jet angle and gas superficial velocity as well as solid mass flux on the jet penetration depth （JPD）. In addition, independent variables were experimentally employed to propose two empirical correlations for JPD by using multiple regression method and spray cone angle （SCA） by using dimensional analysis technique. The mean relative errors between the JPD and SCA correlations versus ex- perimental data were 7.5% and 3.9%, respectively. In addition, in order to identify the variable effect, a parametric study was carried out. Applying the proposed model can avoid direct use of expensive devices to measureJPD and to nredict dronlet size.展开更多
A Pulse-Width-Modulation-based(PWM-based)continuously variable sprayer was developed using a proportional regulating solenoid valve.Variable flow-rate was obtained by varying the duty cycle of the actuating signal wit...A Pulse-Width-Modulation-based(PWM-based)continuously variable sprayer was developed using a proportional regulating solenoid valve.Variable flow-rate was obtained by varying the duty cycle of the actuating signal with 24 kHz frequency.Flow-rate regulating ranges of the PWM-based continuously variable spray(i.e.the turndown ratio responding to 100%-40%duty cycle)are 7.14:1,3.57:1,and 3.70:1 for flat-fan,hollow-cone and solid-cone nozzles,respectively.The purpose of the study was to evaluate the PWM-based continuously variable spray.The method was to quantify the effects of flow-rate control on spray characteristics in terms of droplet size spectra,spray distribution patterns,and spray angle for flat-fan,hollow-cone,solid-cone nozzles.For all nozzles tested,spray distribution concentrated on the center of the spray field with the decrease of flow-rate.But the spray shape is still symmetrical.The sensitivities of the spray angles to flow-rate were 0.83,0.67,and 0.58(o)/%respectively for flat-fan,hollow-cone and solid-cone nozzles.Compared with the sensitivities of spray angle for PWM-based intermittent variable spray,they are somewhat larger.As flow-rate was reduced from the maximum(100%flow-rate)to the minimum controllable rate,the observed median diameter of spray droplets decreased by 5.4%,9.8%,and 9.9%for flat-fan,hollow-cone and solid-cone nozzles,respectively.This indicates that spray droplet size was affected slightly by flow-rate control.展开更多
The atomization characteristics play a key role in the highly efficient combustion of pyrolysis oil derived from waste tires.In this study,the fuel properties of tire pyrolysis oil(TPO)were initially studied,and then ...The atomization characteristics play a key role in the highly efficient combustion of pyrolysis oil derived from waste tires.In this study,the fuel properties of tire pyrolysis oil(TPO)were initially studied,and then a high-speed camera and a phase Doppler particle analyzer were employed to characterize the atomization feature of TPO.The influence of pressure and nozzle orifice diameter on atomization characteristics such as spray angle,droplet velocity,and droplet size distribution was investigated.The results showed that TPO had a high calorific value of about 43.6 MJ/kg and a low viscosity of 3.84×10^(–6)m^(2)/s at 40℃,which made it have the potential to be used as an alternative fuel.Higher pressure expanded the spray angle and extended the spray in both the axial and radial directions.With increasing pressure,spray angle and droplet velocity raised,and the increase in crushing effect of air reduced the Sauter mean diameter(SMD)of the droplets.To obtain proper atomization quality for combustion,the pressure is expected to be higher than 1.25 MPa.With increasing nozzle orifice diameter,droplet velocity increased,and the SMD of the droplets increased as well due to weakened crushing effect of the orifice.Therefore,the pressure must be increased to maintain the atomization quality when using a nozzle with a larger orifice.Due to the lower viscosity,the velocity and particle size distribution of TPO droplets after atomization were smaller than those of diesel droplets.The extremely small carbon black contained in TPO also contributed to the breaking of droplets and played a certain role in the size reduction of the oil droplets,but it may cause the risk of nozzle blockage.In summary,TPO showed great atomization characteristics for alternative fuel applications.展开更多
This study discusses the development of a mathematical model that is capable ofpredicting the drop size mean diameter of the spray generated by a pressure swirl atomizer,considering the effects of the liquid’s viscos...This study discusses the development of a mathematical model that is capable ofpredicting the drop size mean diameter of the spray generated by a pressure swirl atomizer,considering the effects of the liquid’s viscosity and the geometrical parameters of this typeof injector, as well as the angle of incidence of the inlet channels (j and b) and atomizationparameters (k, 8), obtained from hyperbolic relations. Additionally, this model investigatesthe phenomena of rupture and stability that are observed in the conical liquid film, in whichthe importance of a new geometrical parameter of atomization, “8”, which immediately influences the drop size diameter of the spray, should be highlighted. The results that are obtainedusing this model are compared with analytical results of Couto, Wang and Lefebvre, Jasuja,Radcliffe and Lefebvre, experimental results and numerics (Hollow cone atomization model),using the Ansys Fluent software for the validation and consistency of the model proposed in Rivas (2015). This model yields good approximations as compared to that yielded using otheralternative mathematical models, demonstrating that the new atomization geometric parameter“8” is an “adjustment” factor that exhibits considerable significance while designing pressureswirl atomizers according to the required SMD. Furthermore, this model is easy to use, withreliable results, and has the advantage of saving computational time.展开更多
Equations of dynamic systems in droplet distribution at high pressure and boundary value flows in the swirl chamber of a swirl nozzle were used in conjunction with momentum equations of forces on moving curved vanes t...Equations of dynamic systems in droplet distribution at high pressure and boundary value flows in the swirl chamber of a swirl nozzle were used in conjunction with momentum equations of forces on moving curved vanes to develop mathematical models.A computer program in C++language was developed and used to simulate the effect of some flow and geometric parameters,including flow rate,pressure and swirl chamber diameter,on the spray performance of a high pressure agro-forestry swirl nozzle.Each of the three performance parameters of axial flow rate,spray cone angle and output discharge(or performance)coefficient were studied as a function of any two combinations of the nozzle supply pressure,exit orifice diameter and swirl chamber diameter.The study established that the spray cone angle of the discharge flow pattern varied from the minimum value of 40°for a swirl chamber diameter of 90 mm to 220°for 40 mm as the exit orifice diameter varied from the minimum value of 0.5 mm to 4.0 mm.The simulated nozzle output discharge coefficient could be varied from 0.98,when the nozzle supply pressure was 400 kPa to the minimum value of 0.001 at any of the other six simulated nozzle supply pressure values of 200,250,300,350,450 and 500 kPa by varying the exit orifice diameter from 0.5 mm to 4.0 mm.The pattern of variation of the simulated nozzle discharge coefficient values were similar to those obtained by measurement during the validation exercise in the laboratory although their sensitivities to the independent variables were different.The results indicated that the range of nozzle discharge coefficient of 0.80 to 0.98 required for a well designed high pressure agro-forestry swirl nozzle has been simulated.With the successful development of the C++computer program,a useful tool that will cut down on the rigor encountered and time spent by nozzle designers and evaluators during nozzle development process has been developed in the study.展开更多
In this paper,the atomization characteristics of Si3N4 ceramic dry granulation affect the performance of Si3N4 ceramic bearing balls.In order to improve the dry granulation characteristics and the comprehensive perfor...In this paper,the atomization characteristics of Si3N4 ceramic dry granulation affect the performance of Si3N4 ceramic bearing balls.In order to improve the dry granulation characteristics and the comprehensive performance of Si3N4 ceramic bearing balls,the atomization mechanism of the spinning nozzle used for Si3N4 dry granulation was studied in detail.The interaction between air and binder in the pressure-swirl nozzle is analyzed based on VOF method,the modified realizable k−εturbulence model is used to simulate the flow field inside and outside the pressure-swirl nozzle,the effects of nozzle inlet parameters including the number of tangential inlets and the deflection angle of tangential inlets on the binder volume fraction,velocity distribution and pressure distribution are analyzed.The results show that when the number of tangential inlets increases from 1 to 4,the swirl strength of gas–liquid two-phase in the nozzle increases,the mean diameter of air core increases from 1.51 mm to 2.01 mm,and the spray cone angle increases from 18.5◦to 26.4◦.Besides,when the deflection angle of tangential inlet increases from 0◦to 15◦,the swirl strength of gas–liquid two-phase in the nozzle with the deflection angle of tangential inlet of 10◦is the largest,and the mean diameter of air core and spray cone angle is 3.04 mm and 30.7◦,respectively.Based on the atomization experiment platform of the electric control fuel system,the mean diameter of air core and spray cone angle are measured,the micromorphology of Si3N4 particles is observed,which verifies the correctness of numerical simulation.When the Si3N4 particles are prepared by dry granulation,taking the atomization performance of nozzle into consideration,the pressure-swirl nozzle with 4 tangential inlets and 10◦deflection angle should be selected.展开更多
基金the Natural Science Foundation of Jiangsu Province(No.BK20220588)the Initial Scientific Research Fund of Yangzhou University(No.137012553)and the Public Welfare Technology Research Program of Zhejiang Province(Nos.LGG19E060001 and LGG 21E090001)。
文摘The reduction of oxygen consumption is a key factor to improve the energy density of underwater Stirling engine.A series of fundamental experiments are carried out to elucidate the spray characteristics of soybean oil/2,5-dimethylfuran(DMF)blended fuel in an underwater Stirling engine.Spray characteristics such as spray penetration,spray angle,spray area,and light intensity level under low injection and ambient pressures are obtained using image post-processing method.The results show that the effects of injection pressure,ambient pressure,and nozzle diameter on the transient spray characteristics of underwater Stirling engine are similar to those of diesel engine.However,in the steady spray process,the injection pressure has little effect on spray near angle,and the spray far angle increases with the increase of the injection pressure.Compared with the spray far angle at injection pressure of 3 MPa,the spray far angle at 5 MPa and 7 MPa increased by 11.38%and 18.14%respectively.The addition of DMF can obviously improve the atomization of soybean oil/DMF blended fuel.The spray angle of blended fuel in transient process increases with the increase of the DMF concentration.The spray near angle has exceeded that of diesel(46.21°)when the DMF volume fraction exceeds 25%.The spray far angle is equivalent to that of diesel when the DMF volume fraction reaches 75%.Moreover,the spray with gas ejection no longer keeps conical,the droplet diameter distribution is more dispersed,and the droplet diameter is smaller.
文摘The high-speed digital imaging technique is applied to observe the developing process of flash boiling spray of dimethyl ether at low ambient pressure, and the effects of nozzle opening pressure and nozzle hole diameter on the spray shape, spray tip penetration and spray angle during the injection are investigated. The experimental results show that the time when the vortex ring structure of flash boiling spray forms and its developing process are determined by the combined action of the bubble growth and breakup in the spray and the air drag on the leading end of spray; with the enhancement of nozzle opening pressure, the spray tip penetration increases and the spray angle decreases. The influence of nozzle hole diameter on the spray tip penetration is relatively complicated, the spray tip penetration is longer with a smaller nozzle hole diameter at the early stage of injection, while the situation is just opposite at the later stage of injection. This paper establishes that the variation of spray angle is consistent with that of nozzle hole diameter.
基金supported by the Science and Technology Research and Development Plan of Hebei Province, China (12276710D)
文摘The spray behaviors of the combined trapezoid spray tray(CTST) have a significant effect on the gas-liquid interface. In this paper, the spray process of CTST in a column, 570 mm in diameter, was experimentally investigated by using a high-speed camera, and a theoretical model of the average droplet size was established according to the unstable wave theory. The results demonstrated that gas velocity passing through the hole is the key factor affecting the spray angle, which increases gradually with an increase in the gas velocity. When the gas velocity exceeds 7.5 m/s, the spray angle becomes stable at around 55°. The average flow velocity of the liquid sheet at the spray-hole increases significantly with an increase in the gas velocity, and decreases slightly with an increase in the liquid flow rate; moreover, it increases from the bottom of spray hole upward to the top. The density of liquid drops distribution in the spray area can be described by the RosinRammler function. In addition, the liquid drops are mainly concentrated in the area of spray angle ranging from 20° to 40°, and they gradually become uniform with the increase in the gas velocity and the liquid flow rate. The average liquid drop size deceases with an increase in the gas velocity, and increases slightly with an increasing liquid flow rate. In the normal working range, the average liquid drop size is about 1.0 mm to 2.5 mm in diameter.
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Sponsored by the National Key R&D Project(Grant No.2019YFD1002500)the Key Projects of Science and Technology Support Plan of JiangsuP rovince(Grant No.BE2016341)the Open Fund of State Key Laboratory of Internal Combustion Engine(Grant No.GKF2015-004)。
文摘In order to analyze the spray characteristics of non-circular nozzle holes based on the air-assisted spray system, the spray characteristics of circular and non-circular nozzles were studied under the pressure of 0.2-0.6 MPa and the spray volume of 1000-5000 mL/h. Elliptical nozzle and triangular nozzle are classified as non-circular geometries. The spray cone angle was measured by processing the spray image captured by a CCD camera. The measured spray cone angles of the circular nozzles were analyzed, and the axis switching phenomenon of minor plane of elliptical nozzle was found during the test. Among the three shapes of nozzles, the elliptical nozzle had the largest spray cone angle, and the triangular nozzle had the smallest. The velocity field obtained depended on the PIV system. The results show that for axial velocity, elliptical orifice spray has greater kinetic energy and smaller droplet size under the same working parameters. Compared with the circular and elliptical nozzles, triangular orifice reached maximum spray velocity the fastest, but its velocity decay was the fastest. For radial velocity, away from the axis, the spray velocity of the elliptical orifice was less affected by the injection parameters, and the velocity was less than that of circular orifice and triangle orifice. Increasing air pressure will weaken radial propagation. The increase of liquid spraying rate had no remarkable effect on the increase of spraying rate. The results of particle size analysis show that the particle size of the non-circular orifice is reduced compared with that of the circular orifice, which promotes the breakup of droplets to a certain extent and enhances the atomization effect.
基金supported by the Science and Technology Project of State Grid Anhui Electric Corporation of China(Grant No.52120523000L).
文摘As the core equipment in power systems,ultra-high voltage(UHV)transformers pose a high fire risk.The compressed-air foam spray nozzle is a novel end-release device that,due to its high efficiency and excellent suppression effect on oil-based fires,has been increasingly applied in UHV substations.This study is based on a self-developed experimental platform for compressed-air foam firefighting systems.To meet practical engineering needs,the longitudinal maximum of the contour line at the threshold of 12 L/(min·m²)was selected as the spray range.The study systematically explored the factors influencing the spray range of the spray nozzle.Experimental results revealed that when the hole elevation angle was 60°,the average spray range increased by 59%compared to 0°.When the nozzle aperture was 10 mm and the outlet pressure was 0.15 MPa,the spray range improved by 17%.Additionally,as the outlet pressure increased,the foam spray range grew significantly,with a 35.2% increase at 0.3 MPa compared to 0.1 MPa,indicating that the outlet pressure had a substantial effect on the spray range.To predict the spray range increase,an empirical model is developed for the outlet pressure versus the spray range.After analyzing the above three influencing factors,all the data of various working conditions were integrated into a single dataset,a prediction model of the spray range was established,and the importance of the factors affecting the range was ranked.These findings provide a theoretical foundation for the optimized design and engineering application of compressed-air foam systems(CAFSs).
基金supported by the National Key Research and Development Program(2022YFB3504000)the National Natural Science Foundation of China(22122815,21978296)the NSFC-EU project(31961133018)。
文摘The structure of the pressure swirl nozzle is an important factor affecting its spray performance.This work aims to study pressure swirl nozzles with different structures by experiment and simulation.In the experiment,10 nozzles with different structures are designed to comprehensively cover various geometric factors.In terms of simulation,steady-state simulation with less computational complexity is used to study the flow inside the nozzle.The results show that the diameter of the inlet and outlet,the direction of the inlet,the diameter of the swirl chamber,and the height of the swirl chamber all affect the atomization performance,and the diameter of the inlet and outlet has a greater impact.It is found that under the same flow rate and pressure,the geometric differences do have a significant impact on the atomization characteristics,such as spray angle and SMD(Sauter mean diameter).Specific nozzle structures can be customized according to the actual needs.Data analysis shows that the spray angle is related to the swirl number,and the SMD is related to turbulent kinetic energy.Through data fitting,the equations for predicting the spray angle and the SMD are obtained.The error range of the fitting equation for the prediction of spray angle and SMD is within 15% and 10% respectively.The prediction is expected to be used in engineering to estimate the spray performance at the beginning of a real project.
文摘Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles.Rebounded concrete amount cause a significant difference between the initial mix design and emplaced mix compositions.Apart from the structural differences,it comes with a cost increase which was resulted by the splashed concrete amount.Many factors such as viscosity and quantity of mixes dominate this rebound amount in sprayed glass fibre reinforced concrete applications depending on production technologies and processes;however,this research focuses on the spray distance and the angle of the spray gun which mainly effects the rebound amount in glass fibre reinforced concrete production.This paper aims to understand the required angle and distance for glass fibre reinforced concrete mixes having on-site plastic viscosity values.Glass fibre reinforced mixtures were also modelled with a finite element method based software and,the analysis results were compared with production line results.Results of the analysis and on-site studies showed a decisive correlation between,discharge distance,discharge angle and the viscosity of the concrete.
文摘Air-atomized fog cooling is particularly suitable for the after-pot cooling of galvanized steel strips.With air and water serving as working media,an experimental study was conducted on the atomization characteristics of a newly-developed cross-flow type of fog nozzles.The water flux distribution,spray angle and pressure of water and air were measured.The results show that the water droplet size was small and insensitive to the water flow rate.The spray angle was small and the water flow rate slightly affected the air pressure in the chamber.An empirical correlation between the pressure in the chamber and the gas flow rate was obtained for the purpose of equipment design.
基金supported by Advanced Research Center Program(NRF-2013R1A5A1073861)through the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)contracted through Advanced Space Propulsion Research Center at Seoul National University
文摘A pintle injector is advantageous for throttling a liquid rocket engine and reducing engine weight. This study ex- plores the effects of momentum ratio and Weber number at various injection conditions on spray characteristics of the pintle injector for liquid-gas propellants. A liquid sheet is injected from a center pintle nozzle and it is broken by a gas jet from an annular gap. The pressure drops of propellants, and the pintle opening distance were consi- dered as control variables; using 0.1 -1.0 as a bar for the pressure drop of the liquid injection, a 0.01-4）.2 bar for the pressure drop of gas jet and a 0.2 - 1.0 mm for the pintle opening distance. The discharge coefficient was de- creased linearly before the pintle opening distance of 0.75 mm and then, the coefficient was slightly increased. Spray images were captured by a CMOS camera with high resolution. Then, the shadow and reflected images were analyzed. Spray distributions were measured by a pattemator with an axial distance of 50 mm from a pintle tip. Finally, the spray half angles had an exponentially decreasing correlation as a momentum ratio divided by the Weber number. Also, the spray half angles from the spray distribution were underestimated compared to those measured from the captured images.
文摘In this work, the effects of injecting an evaporating liquid jet into solid-gas flow are experimentally investigated. A new model （SHED model） and a supplementary model （spray model） have also been proposed to investigate some flow-field characteristics in three-phase fluidized bed with the mean relative error 4.3% between model and measured results. Some experiments were conducted to study the influences of flow-field parameters such as liquid volumetric flow rate, injection velocity, jet angle and gas superficial velocity as well as solid mass flux on the jet penetration depth （JPD）. In addition, independent variables were experimentally employed to propose two empirical correlations for JPD by using multiple regression method and spray cone angle （SCA） by using dimensional analysis technique. The mean relative errors between the JPD and SCA correlations versus ex- perimental data were 7.5% and 3.9%, respectively. In addition, in order to identify the variable effect, a parametric study was carried out. Applying the proposed model can avoid direct use of expensive devices to measureJPD and to nredict dronlet size.
文摘A Pulse-Width-Modulation-based(PWM-based)continuously variable sprayer was developed using a proportional regulating solenoid valve.Variable flow-rate was obtained by varying the duty cycle of the actuating signal with 24 kHz frequency.Flow-rate regulating ranges of the PWM-based continuously variable spray(i.e.the turndown ratio responding to 100%-40%duty cycle)are 7.14:1,3.57:1,and 3.70:1 for flat-fan,hollow-cone and solid-cone nozzles,respectively.The purpose of the study was to evaluate the PWM-based continuously variable spray.The method was to quantify the effects of flow-rate control on spray characteristics in terms of droplet size spectra,spray distribution patterns,and spray angle for flat-fan,hollow-cone,solid-cone nozzles.For all nozzles tested,spray distribution concentrated on the center of the spray field with the decrease of flow-rate.But the spray shape is still symmetrical.The sensitivities of the spray angles to flow-rate were 0.83,0.67,and 0.58(o)/%respectively for flat-fan,hollow-cone and solid-cone nozzles.Compared with the sensitivities of spray angle for PWM-based intermittent variable spray,they are somewhat larger.As flow-rate was reduced from the maximum(100%flow-rate)to the minimum controllable rate,the observed median diameter of spray droplets decreased by 5.4%,9.8%,and 9.9%for flat-fan,hollow-cone and solid-cone nozzles,respectively.This indicates that spray droplet size was affected slightly by flow-rate control.
基金the National Natural Science Foundation of China(No.52076190)Zhejiang Provincial Key Research and Development Program(No.2023C03129).
文摘The atomization characteristics play a key role in the highly efficient combustion of pyrolysis oil derived from waste tires.In this study,the fuel properties of tire pyrolysis oil(TPO)were initially studied,and then a high-speed camera and a phase Doppler particle analyzer were employed to characterize the atomization feature of TPO.The influence of pressure and nozzle orifice diameter on atomization characteristics such as spray angle,droplet velocity,and droplet size distribution was investigated.The results showed that TPO had a high calorific value of about 43.6 MJ/kg and a low viscosity of 3.84×10^(–6)m^(2)/s at 40℃,which made it have the potential to be used as an alternative fuel.Higher pressure expanded the spray angle and extended the spray in both the axial and radial directions.With increasing pressure,spray angle and droplet velocity raised,and the increase in crushing effect of air reduced the Sauter mean diameter(SMD)of the droplets.To obtain proper atomization quality for combustion,the pressure is expected to be higher than 1.25 MPa.With increasing nozzle orifice diameter,droplet velocity increased,and the SMD of the droplets increased as well due to weakened crushing effect of the orifice.Therefore,the pressure must be increased to maintain the atomization quality when using a nozzle with a larger orifice.Due to the lower viscosity,the velocity and particle size distribution of TPO droplets after atomization were smaller than those of diesel droplets.The extremely small carbon black contained in TPO also contributed to the breaking of droplets and played a certain role in the size reduction of the oil droplets,but it may cause the risk of nozzle blockage.In summary,TPO showed great atomization characteristics for alternative fuel applications.
文摘This study discusses the development of a mathematical model that is capable ofpredicting the drop size mean diameter of the spray generated by a pressure swirl atomizer,considering the effects of the liquid’s viscosity and the geometrical parameters of this typeof injector, as well as the angle of incidence of the inlet channels (j and b) and atomizationparameters (k, 8), obtained from hyperbolic relations. Additionally, this model investigatesthe phenomena of rupture and stability that are observed in the conical liquid film, in whichthe importance of a new geometrical parameter of atomization, “8”, which immediately influences the drop size diameter of the spray, should be highlighted. The results that are obtainedusing this model are compared with analytical results of Couto, Wang and Lefebvre, Jasuja,Radcliffe and Lefebvre, experimental results and numerics (Hollow cone atomization model),using the Ansys Fluent software for the validation and consistency of the model proposed in Rivas (2015). This model yields good approximations as compared to that yielded using otheralternative mathematical models, demonstrating that the new atomization geometric parameter“8” is an “adjustment” factor that exhibits considerable significance while designing pressureswirl atomizers according to the required SMD. Furthermore, this model is easy to use, withreliable results, and has the advantage of saving computational time.
文摘Equations of dynamic systems in droplet distribution at high pressure and boundary value flows in the swirl chamber of a swirl nozzle were used in conjunction with momentum equations of forces on moving curved vanes to develop mathematical models.A computer program in C++language was developed and used to simulate the effect of some flow and geometric parameters,including flow rate,pressure and swirl chamber diameter,on the spray performance of a high pressure agro-forestry swirl nozzle.Each of the three performance parameters of axial flow rate,spray cone angle and output discharge(or performance)coefficient were studied as a function of any two combinations of the nozzle supply pressure,exit orifice diameter and swirl chamber diameter.The study established that the spray cone angle of the discharge flow pattern varied from the minimum value of 40°for a swirl chamber diameter of 90 mm to 220°for 40 mm as the exit orifice diameter varied from the minimum value of 0.5 mm to 4.0 mm.The simulated nozzle output discharge coefficient could be varied from 0.98,when the nozzle supply pressure was 400 kPa to the minimum value of 0.001 at any of the other six simulated nozzle supply pressure values of 200,250,300,350,450 and 500 kPa by varying the exit orifice diameter from 0.5 mm to 4.0 mm.The pattern of variation of the simulated nozzle discharge coefficient values were similar to those obtained by measurement during the validation exercise in the laboratory although their sensitivities to the independent variables were different.The results indicated that the range of nozzle discharge coefficient of 0.80 to 0.98 required for a well designed high pressure agro-forestry swirl nozzle has been simulated.With the successful development of the C++computer program,a useful tool that will cut down on the rigor encountered and time spent by nozzle designers and evaluators during nozzle development process has been developed in the study.
基金The author would like to thank the National Natural Science Foundation of China(NSFC)for its grant to this research.The number of the fund is 51964022.
文摘In this paper,the atomization characteristics of Si3N4 ceramic dry granulation affect the performance of Si3N4 ceramic bearing balls.In order to improve the dry granulation characteristics and the comprehensive performance of Si3N4 ceramic bearing balls,the atomization mechanism of the spinning nozzle used for Si3N4 dry granulation was studied in detail.The interaction between air and binder in the pressure-swirl nozzle is analyzed based on VOF method,the modified realizable k−εturbulence model is used to simulate the flow field inside and outside the pressure-swirl nozzle,the effects of nozzle inlet parameters including the number of tangential inlets and the deflection angle of tangential inlets on the binder volume fraction,velocity distribution and pressure distribution are analyzed.The results show that when the number of tangential inlets increases from 1 to 4,the swirl strength of gas–liquid two-phase in the nozzle increases,the mean diameter of air core increases from 1.51 mm to 2.01 mm,and the spray cone angle increases from 18.5◦to 26.4◦.Besides,when the deflection angle of tangential inlet increases from 0◦to 15◦,the swirl strength of gas–liquid two-phase in the nozzle with the deflection angle of tangential inlet of 10◦is the largest,and the mean diameter of air core and spray cone angle is 3.04 mm and 30.7◦,respectively.Based on the atomization experiment platform of the electric control fuel system,the mean diameter of air core and spray cone angle are measured,the micromorphology of Si3N4 particles is observed,which verifies the correctness of numerical simulation.When the Si3N4 particles are prepared by dry granulation,taking the atomization performance of nozzle into consideration,the pressure-swirl nozzle with 4 tangential inlets and 10◦deflection angle should be selected.
