• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Improvement of the spreading effect of atmospheric pressure microplasma jet treatment through shielding-gas-controlled focusing

    2022-08-29 00:42:56LiLV呂櫟JianhangCHEN陳劍航JiahaoWANG汪加豪ShengquanWANG王圣泉MengLI李蒙DeyuTU涂德浴LipingSHI時禮平andTaoWANG王濤
    Plasma Science and Technology 2022年9期
    關(guān)鍵詞:圣泉王濤

    Li LV (呂櫟), Jianhang CHEN (陳劍航), Jiahao WANG (汪加豪),Shengquan WANG (王圣泉), Meng LI (李蒙),3, Deyu TU (涂德浴),Liping SHI (時禮平),3,* and Tao WANG (王濤),3,4,*

    1 Anhui Province Engineering Laboratory of Intelligent Demolition Equipment, Maanshan 243032,People’s Republic of China

    2 School of Mechanical Engineering, Anhui University of Technology, Maanshan 243032, People’s Republic of China

    3 Anhui Province Key Laboratory of Special Heavy Load Robot, Anhui University of Technology,Maanshan 243032, People’s Republic of China

    4 Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials,Ministry of Education, Anhui University of Technology, Maanshan 243032, People’s Republic of China

    Abstract The spreading effect of atmospheric pressure microplasma jets (APμPJ) on the surface of materials will increase the etching area, and controlling the diameter of the jet can improve the precision of surface treatment.In this work,a two-dimensional axisymmetric simulation model is established to analyze the effect of nitrogen (N2) shielding gas on helium (He) from gas dynamics. In addition, by etching the polyethylene terephthalate film, the relationship between the etching effect and aerodynamic analysis is verified. The simulation results are similar to the experimental results,indicating that N2 shielding gas has a focusing effect which is related to the N2 flow rate, distance difference between the inner and outer tubes, and outer tube nozzle diameter. It is hoped that the results of this work can provide a certain reference for the use of shielding gas to control the jet flow of APμPJ.

    Keywords: microplasma jet, nitrogen shielding gas, focusing effect, gas dynamic

    1. Introduction

    Atmospheric pressure cold microplasma jet(APμPJ)is a new plasma-generation technology which is free from the limitation of vacuum environments [1]. APμPJ has low temperature, low cost, and rich reactive species, etc, and has been widely used in sterilization[2-4],surface modification[5,6],biomedicine [7, 8], combustion assistance [9, 10], and other fields.APμPJ can treat complex surfaces,and can modify the surface of a material without affecting the properties of the material itself, providing new solutions and possibilities for the development of surface treatments.

    In the actual plasma discharge process, the plasma jet ejected from the nozzle will increase the diameter of the jet,and,as the gas flow rate increases,the jet diameter will further increase [11, 12]. For high-precision surfaces, the increase in jet diameter will increase the line width on the processed surface, resulting in an actual processing area larger than the expected one, which directly affects the final processing accuracy.

    In order to solve these problems, various methods based on limiting the diffusion of the plasma jet on the surface have been proposed, and their feasibility has been proved. Khan et al[13]adopted the idea of solid shielding and used a quartz tube to reduce the influence of ambient gas on the plasma jet.The results showed that the method was practical and the diameter of the plasma jet was significantly improved.Onyshchenko et al [14] also proposed a solid shielding method to achieve the focusing of an atmospheric pressure low-temperature plasma jet.An additional plate was added at the bottom of the capillary to suppress the lateral diffusion of the jet. As the distance between the baffle and the surface decreased, the extent of the hydrophilic area on the polyethylene terephthalate (PET) surface increased. In order to explore the cause of this phenomenon, the molar concentration distribution of plasma flow at different distances between the baffle and flat surface was simulated. Numerical simulation showed that the smaller the distance between the baffle and the flat surface,the higher the molar concentration of the plasma jet and the wider the distribution range on the flat surface.Schmidt-Bleker et al[15]used a mixture of nitrogen(N2) and oxygen (O2) as the shielding gas curtain to investigate the reaction mechanism of the atmospheric pressure argon cold plasma jet, and obtained better experimental results and simulation data. Kapaldo et al [16] also adopted the idea of shielding gas when studying the influence of atmospheric pressure plasma on cancer cells. Their results proved that the influence of different components of shielding gas on cancer cells was controllable. Shirafuji [17], Pinchuk[18], and Prakash [19] also used experiments to prove that ambient gas could affect the diffusion of plasma jets in the surrounding air, and that shielding gas could inhibit the diffusion of plasma jets. Akishev et al [20] studied the transversal spreading of a plasma jet at its impinging the surface.The results showed that the plasma jet could be symmetrically and stably distributed on the stationary surface. However,when the surface rotated,it was difficult for the plasma jets to keep stable and distribute symmetrically due to the movement of the gas flow.

    The addition of shielding gas to achieve a focusing effect of the plasma jet has become a new technique to suppress the diffusion effect of the plasma jet on a substrate. However, to our knowledge,the effect of shielding gas on the beam effect or the plasma itself has not been investigated systemically.Therefore,a fluid focusing method is proposed in this work to achieve this effect on the plasma plume, and the influence of various parameters on the jet is systematically studied,as well as the influence of the gas flow on the plasma itself.Previous results have shown that the main reason for the expansion is due to the interaction between the plasma jet and the material,as well as the lateral ion waves generated by the charged particles on the wall.

    In this work, a fluid dynamic simulation of neutral gas flow is used to illustrate the effect of shielding gas on the jet ejection. Onyshchenko et al [14] showed that the simulation results of neutral gas fluid dynamics were in good agreement with the actual modified beam spot effect through experiments and simulation studies. The gas flow has a general importance in fluid mechanics owing to the development of turbulence,gas mixing in diffusion flame,gas flow dynamics,and many other applications. The plasma jet discharge at atmospheric gas pressure may contain combined characteristics such as the flow of working gas and electrostatic force among plasma particles [21, 22]. The fluid mechanical property of gas flow may have influence on the discharge phenomena and the electrostatic collective force of plasma may produce or modify the gas flow [23, 24]. Therefore, the simulation method can be used to investigate the focusing effect of the neutral gas. Considering the stability and low cost of N2, this work mainly uses N2as the shielding gas. In this work, a two-dimensional axisymmetric model is established through the COMSOL Multi-physics simulation software, and the focusing mechanism of the shielding gas is analyzed through the computational fluid dynamics (CFD)module and the dilute substance transfer module. By changing the process parameters, the velocity change and concentration distribution of the working gas were analyzed to explore the characteristics of the APμPJ, and experimental verification was carried out. It is hoped that the research results in this work can provide a reference for the use of shielding gas to realize the precision and controllable treatment of APμPJ.

    2. Simulation model and experimental equipment

    2.1. Simulation model

    In this work, the simulation model adopts a two-dimensional axisymmetric structure. The model size is AB=BR=QR=AQ=50 mm, AC=25 mm, CD=45 mm, AE=0.4 mm, AF=0.6 mm, AG=1 mm, AH=2 mm, MN=OP=0.5 mm, NP=8 mm, IJ=0.2 mm, JK=0.4 mm, and KL=1 mm.AQ is the axis of symmetry,BR and QR are set as open boundaries,and CD simulates a substrate surface.AE is the radius of the inner tube, EF is the wall thickness of the inner tube; AG is the radius of the outer tube, and GH is the wall thickness of the outer tube. The model is composed of a concentric tube structure;the inner tube is fed with working gas He,and the outer tube is fed with shielding gas N2. The distance between the outlet port and the surface is set to 2 mm. MNPO simulates a copper foil electrode wrapped on the outer tube.Three two-dimensional transversals and a three-dimensional section are marked in figure 1. Transverse line 1 represents the gas junction, transverse line 2 represents the central axis,transverse line 3 represents the substrate, and section 1 represents the entire substrate surface.The speed of natural flow is set to 0.025 m s-1. The remaining boundaries are walls, and the operating temperature in the entire simulation is set to 25 °C.

    2.2. Neutral gas flow dynamics model

    Figure 1.Two-dimensional axisymmetric geometric model.

    The state in any flow field needs to satisfy the mass conservation equation (continuity equation) and momentum conservation equation (Navier-Stokes equation). That is, the increase in the mass of the fluid element per unit time is equal to the mass flowing into the fluid element at the same time,and the rate of change of momentum in the fluid element with respect to time is equal to the sum of the external force vector acting on the fluid element.

    The continuity equation is as follows:

    where

    In the formula,ρis the density;tis the time;andu,v,ware the components of the velocity vector in the x, y, and z directions,respectively.If the fluid is in a stable state and the densityρdoes not change with time, the equation can be simplified to

    The Navier-Stokes equation is as follows:

    where

    In the formula,pis the static pressure;xiandxjare the coordinate points;uiandujare the shear viscosity coefficients in the directions ofxiandxj;δijis the Knecker;τijis the stress tensor;cjis the fluid length;ρgiandFiare the gravitational volume force and other volume forces,respectively;the subscripts i,j indicate the i, j substances.

    The convection-diffusion equation is as follows:

    where

    Figure 2. Schematic diagram of APμPJ generator.

    In the formula,ciis the molar concentration of particle i;uis the mass average velocity of the gas mixture;Jiis the mass flux of particle i relative to the mass average velocity;Riis the net productivity of particle i;Diis the diffusion coefficient of gas.

    2.3. Simulation hypothesis

    (1) Generally speaking, the dimensionless Reynolds number (Re) is used to distinguish between laminar and turbulent flow[25].The Reynolds number is calculated as follows:In the formula, V is the average gas velocity; D is the inner diameter of the nozzle;v is the kinematic viscosity of the gas flow;ρis the gas density; μ is the gas viscosity. In the simulation process of this work, it is assumed that the flow field is always in a laminar state.

    (2) It is assumed that the plasma forms a free jet in the atmosphere without considering the chemical reactions between the plasma and other components in the atmosphere, and ignoring the influence of secondary factors such as mass force, volume force, and electromagnetic force of the plasma.

    (3) He/O2working gas was used in the experiment,and the O2content was 1%.To simplify the simulation,pure He was used instead.

    2.4. Experimental materials and setup

    2.4.1. Materials. PET is one of the most common thermoplastic polymers. It has excellent properties such as chemical resistance, corrosion resistance, dimensional stability, and easy recycling, which has been widely used in the surface modification of polymers [26]. The PET film used in the experiment is a rectangular block with dimensions10 mm×10 mm ×5 mm.

    Figure 3.He molar concentration distributions under different N2 flow rates;(a)-(h)correspond to N2 of 0,100,200,300,400,500,600,and 700 sccm, respectively.

    2.4.2.Experimental setup. The APμPJ generator used in the experiment is shown in figure 2, which includes discharge,gas circuit, test, and control systems. Detailed information about the experimental setup is available in our previous work [27].

    The working gas is high-purity helium (He (99.999%))and high-purity oxygen (O2(99.999%)). Due to the electronegativity of O2, free electrons in the space will be adsorbed, resulting in suppression of discharge and reduced jet length. The total flow of working gas is 400 sccm, of which the flow of He is 396 sccm, and the remaining 1% is O2. Due to the chemical inertness and low cost of N2, highpurity nitrogen(N2(99.99%))is selected as the shielding gas,and the flow rate is controlled at 0-700 sccm. Through the calculation of Reynolds number, it can be known that the working gas and shielding gas are in laminar flow.

    3. Results and discussions

    3.1. Effect of N2 flow rate

    The N2flow rate is one of the main influencing parameters of the shielding gas on the plasma jet.As shown in figure 3,it is the effect of different N2flow rates on the He molar concentration distribution in the range of 0-700 sccm,and the He concentration gradually decreases from the center to the outside. When no shielding gas is introduced, it can be observed from figure 3(a) that after He is ejected from the outlet,there is an obvious diffusion phenomenon in the space,with diffusion even into the N2tube. As the N2flow rate increases, the surrounding N2gas mixes (through laminar convective diffusion)into the He jet when He flows out of the tube, resulting in a decrease in the mole fraction of He[28, 29]. There is an obvious non-concentration area below the N2outlet,and the size of this area is positively correlated with the N2flow rate, indicating that N2forms a layer of air curtain which restricts the exchange of He and ambient gases.At the same time, the N2shielding gas not only limits the distribution of the high He concentration area, but also weakens the He concentration in the central region, and the weakening degree is positively correlated with the N2flow rate.

    Although the N2flow rate has a greater effect on the He concentration of the central axis, it has less effect on the He velocity of the central axis. The influence of velocity is mainly concentrated at the intersection of gas,and the change trend of velocity of the central axis is relatively stable. The concentration of He remained stable in the tube, the velocity decreased after being ejected from the outlet, and the concentration reached the minimum after reaching the substrate.The higher the N2flow rate, the lower the concentration at that location.

    Due to the low density of He,the buoyancy in the air also has a certain influence [30, 31]. However, the velocity changes in different processes.He enters the tube from the inlet,and the speed increases rapidly and then remains stable. The velocity increases slightly near the outlet,decreases rapidly after leaving the outlet, and returns to zero when He reaches the substrate.These results can be drawn from figure 4(c).

    In order to analyze the effect of the intersection of the two gases,the concentration and velocity changes at the intersection of the gases are plotted in figures 5 and 6. It can be seen from figure 5 that in the absence of shielding gas, the He concentration is always kept close to 1 mol m-3.When the shielding gas is introduced, the He concentration at the gas junction changes significantly compared to that without shielding gas. In the vicinity of the outlet,the He concentration is low,and gradually leaves the outlet, and the concentration gradually increases and reaches the maximum on the substrate.Under different N2flow rates,the concentration change process is similar,but the larger the flow rate, the smaller the He concentration at the same position.Compared to the concentration at the gas junction,the velocity trends at the gas junction are similar,with or without the shielding gas. After leaving the outlet, the velocity increases continuously, the increase trend of the velocity is the largest at the 0 and 1.6 mm positions,and the velocity decreases rapidly to 0 near the substrate. Between 0 and 1.6 mm, the larger the N2flow rate,the faster the velocity increase,which is mainly due to the result of the larger N2velocity at the gas junction.

    Figure 4.Velocity distributions with the N2 flow rate of(a)0 sccm and(b)700 sccm;(c)velocity and concentration curve at the center axis with N2 flow rate of 700 sccm.

    Figure 5.He molar concentration variation curve at gas junction.

    Figure 6.He velocity variation curve at gas junction.

    After the He hits the substrate surface, it diffuses into a ring-shaped concentration distribution on the substrate, as shown in figure 7(a). In the central area of the jet, the concentration of He is the largest, diffuses outward, and the concentration gradually decreases. Figure 7 shows the molar concentration distribution of He on the substrate under the action of different N2flow rates, of which the top curve corresponds to figure 7(a), which is the result without shielding gas. Combining the two figures 7(a) and (b), it can be found that the areas with high He concentration are mainly concentrated in a 10 mm diameter range.Breden et al[32]has also showed that He plasma jets will extend a certain radial distance outward after contacting the target surface, and eventually mix into the air;the farther the radial distance,the lower the mole fraction concentration, which is consistent with the simulation results in this paper. When the N2flow rate is less than 400 sccm, the concentration at 5 mm has a slight upward trend,which may be due to the strong collision between the working gas He and the shielding gas N2at this position.

    To sum up,within the scope of this study,the increase of shielding gas N2flow rate will further limit the distribution of the high-concentration He region.

    Figure 7. (a) He molar concentration distribution on the substrate without N2 shielding gas, and (b) concentration change curve on the substrate under different N2 flow rates.

    Figure 8. Influence of distance difference x on He molar concentration distribution without shielding gas. (a) x=+1, (b) x=+0.5, (c)x=0, (d) x=-0.5, and (e) x=-1.

    After comprehensive consideration, in the following study of distance difference x and outlet diameter D,with the participation of N2shielding gas, the N2flow rate is selected to be 300 sccm.

    3.2.Influence of distance difference x between inner and outer tubes

    The distance difference between the inner and outer tubes is represented by x,where the inner tube is the reference and the outer tube is extended as positive. First, in order to exclude the influence of structure on the results, figure 8 plots the He molar concentration distribution under each structure without shielding gas. In figure 8, under each structure, the diffusion degree of He concentration is similar,and it is difficult to find the difference.

    Figure 9.Molar distribution of He at different positions under the influence of distance x without shielding gas(a)at gas junction,and(b)on the substrate.

    Figure 10.Influence of distance difference x on He molar concentration distribution with N2 shielding gas of 300 sccm. (a) x=+1, (b)x=+0.5, (c) x=0, (d) x=-0.5, and (e) x=-1.

    The difference visible to the naked eye may be that there is a small lightening of the dark red area below the concentric tubes as x goes from large to small. The influence of the structure on the He concentration distribution can be clearly seen from figure 9.The outer tube protrudes outward relative to the inner tube, limiting the outward diffusion of the high-concentration He, which is similar to the result in Onyshchenko’s work[14].The greater the distance difference x, the greater the limiting effect. However, the He concentration at the gas junction is always greater than 0.92 mol m-3. The concentration distribution difference on the substrate is mainly concentrated in the 0-5 mm range, as shown in figure 9(b),and the concentration curves almost overlap.In general,the distance difference x can have a certain influence on the results without shielding gas, but the influence is limited and can be ignored.

    As shown in figure 10, when the N2shielding gas is introduced,it is obvious that the diffusion of He concentration in the space is significantly reduced, and the concentration is only higher in the central axis region. Compared with the distance difference x=0,when x>0,the outer tube restricts the outward diffusion of N2and intensifies the inward diffusion.As the distance difference x increases,the concentrationfree area increases toward the center axis. When x<0, the space for N2to diffuse outwards increases, resulting in the increase of the non-concentration area outwards. Due to the change of structure,the change of He concentration at the gas junction is more complicated after the shielding gas is introduced.However,from the results at the end point(on the substrate) at the gas junction, it can be seen that as x decreases, the He concentration on the substrate increases, as shown in figure 11(a). This conclusion is consistent with the results in figure 11(b). As the distance difference x increases,the outward diffusion of N2is restricted, the interaction between N2and He is intensified,and the He concentration is reduced.

    Figure 11.Molar distribution of He at different positions under the influence of distance x with shielding gas(a)at gas junction,and(b)on the substrate.

    Figure 12.He concentration distribution under the conical structure. (a) No N2, (b) N2 flow rate of 300 sccm, (1) D=1.4 mm, (2) D=1.6 mm, (3) D=1.8 mm, (4) D=2.0 mm.

    3.3. Effect of outlet diameter of outer tube

    In the research of existing plasma jet devices, a structure composed of a special-shaped nozzle or a syringe and glass tube is used to realize the gas shielding of the plasma jet[33,34].In this work,the shape of the outlet is controlled by changing the outlet diameter D of the casing, and the influence of N2shielding gas under different structures is analyzed. Considering the low practicability of the complex model and the complicated simulation process, the casing shapes in this section are mainly divided into trumpet,cylindrical, and conical shapes. The difference in shape is limited to the diameter D of the outlet nozzle.

    As shown in figure 12, when the shielding gas is not introduced,the high concentration of He mainly concentrates on the outlet of the outer tube and the vicinity of the central axis, and diffuses on the substrate only after hitting the substrate. After injecting N2, it can be observed that the concentration of He decreases significantly after the injection,and there is a clear gap with the inner wall of the outer tube.It can be seen from figure 13(a)that the larger the diameter,the stronger the diffusion effect of He and the smaller the concentration on the substrate;this change is only effective in the high-concentration region. The concentration distribution on the substrate was similar after the shielding gas was introduced.However,when D=1.8 mm at the outlet of the inner tube, the concentration at this position is the largest.

    Figure 13. He concentration distribution on the substrate under the conical structure. (a) No N2, (b) N2 flow rate of 300 sccm.

    Figure 14.He concentration distribution under the flared structure. (a) No N2, (b) N2 flow rate of 300 sccm, (1) D=2.0 mm, (2) D=3.0 mm, (3) D=4.0 mm, (4) D=5.0 mm.

    Figure 15.He concentration distribution on the substrate under the flared structure. (a) No N2, (b) N2 flow rate of 300 sccm.

    Figure 16.Observation and measurement PET etching results. The corresponding etching conditions are the influence of N2 flow, no shielding gas. (a) 2D morphology, (b) 3D morphology.

    Figure 17.Etching depth change at the center position under the influence of N2 flow rate.

    Figure 18.Etching results with the influence of N2 flow rate.

    There is a clear difference between the results of the conical structure and the flared structure without shielding gas. In the flared structure, after He is ejected from the inner tube,it is mainly concentrated near the central axis but a small part of the gas still flows into the outer tube, as shown in figure 14.When the shielding gas is introduced,the diffusion of this small part of He disappears. It can be seen from figure 15 that with the increase of the diameter D, the He concentration in the high-concentration region on the substrate gradually decreases, and the maximum concentration when D=2 mm is much larger than that in other cases.When N2is introduced, the region of the high-concentration He is restricted, the concentration on the substrate decreases,and the smaller the diameter, the more the concentration decreases. It is shown that the larger the outlet diameter, the worse the inhibitory effect of the N2shielding gas.

    4. Experimental verification

    The preceding simulation study is limited to gas dynamic analysis; in order to prove the feasibility of the simulation results,PET etching experiments are carried out. The surface etching morphology was observed through the two-dimensional (2D)and three-dimensional (3D) etching results, as shown in figures 16(a) and (b). As presented in figure 16(a), the depth variation path is drawn from the central position so as to obtain the change curve of etching depth. Furthermore, a systematic analysis of the contact line width and the maximum etch depth was carried out.

    It can be found from figure 17 that when there is no N2shielding gas,the contact line width and etching depth remain relatively large, and when N2is introduced, the contact line width and etching depth gradually decrease. Among them, in the experiment, when the N2flow rate reaches 700 sccm, the contact line width and etching depth are significantly reduced,and this result can be obtained in figure 18. The weakening effect on the He intensity increases with increasing N2flow rate, resulting in a high concentration of He only kept just below the outlet orifice.There are obvious contact line widths and etching depths near the position with high He concentration, and the contact line widths and etching depths gradually decrease when the He concentration decreases in the central region.

    Figure 19.Etching depth change at the center position under the influence of distance difference x.

    Figure 20.Etching results with the influence of distance difference x.

    It can be seen from this simulation that as the distance difference x increases,the distance between the outer tube and the substrate as well as the He concentration in the central area gradually decrease. Referring to figure 19, when the distance difference x is the same, the contact line width and etching depth are obviously reduced after the shielding gas is introduced. By comparing the cases with and without shielding gas in figure 20, it is found that the contact line width decreases gradually with the increase of x, and increases slightly when x=1.The etch depth decreases to the smallest extent when x=0, and the decrease is similar in other cases. In general, the regions with larger etching depth are mainly concentrated in the position with higher He concentration.

    Figure 21.Etching depth change at the center position under the influence of nozzle outlet diameter D=2, 3, 4, and 5 mm.

    Figure 22.Etching results with the influence of nozzle outlet diameter D=2, 3, 4, and 5 mm.

    Consistent with the simulation, when exploring the influence of N2under different structures, the cylindrical shape is used as a reference, and the experimental results under the conical shape and the trumpet shape are discussed.It can be seen from figures 21 and 22 that the maximum contact line width and etching depth occur when the nozzle outlet diameter D is 4 mm without the presence of N2.Although in the presence of N2shielding gas,the contact line width and etching depth are smaller than those without N2,the actual influence law is more complicated.The diameter of the outlet is greater than 2 mm. In the absence of N2, the larger the diameter of the outlet,the larger the diffusion space of the working gas and the larger diffusion space after the jet flows out of the outlet,resulting in a larger actual contact line width and etching depth. However, when the outlet diameter was increased to 3 mm after adding N2shielding gas, the increase of the contact line width was smaller. When the outlet diameter increases to 4 mm, the contact line width reaches the maximum value.As the outlet diameter increases to 3 mm, the inhibitory effect of N2on the jet increases,resulting in a smaller etching depth.When the outlet diameter is 4 mm, the outward diffusion space of N2increases, the inhibition effect on the jet intensity is reduced, and the etching depth of the jet reaches the maximum value. After that, due to more air entering the jet, both the contact line width and etching depth decrease, but the contact line width varies more.

    Figure 23.Etching depth change at the center position under the influence of nozzle outlet diameter D=1.4, 1.6, 1.8, and 2 mm.

    Figure 24.Etching results with the influence of nozzle outlet diameter D=1.4, 1.6, 1.8, and 2 mm.

    In the experiments above, the suppression of the plasma jet by the shielding gas resulted in a reduction in the actual contact line width and etch depth. However, different experimental results appeared when the outlet diameter is too small.In the absence of N2, the contact line width decreases gradually with the decrease of the outlet diameter, but when the outlet diameter is less than 1.6 mm, the contact line width tends to fluctuate steadily, as presented in figure 23 and figure 24. The outlet diameter decreases from 2 to 1.8 mm,and the etching depth decreases sharply.After that,the outlet diameter continues to decrease,and the etching depth changes slowly, but there is still a decreasing trend. After N2is introduced,the contact line width fluctuates around 2.4 mm as the outlet diameter decreases. When the outlet diameter is 1.6 mm,the contact line width with N2is larger than that without N2. In the presence of N2, as the outlet diameter decreases, the etching depth decreases slightly, and finally tends to be stable.However, it has been found through experiments that when the diameter of the outlet is less than 2 mm,the etching depth with N2is greater than that without N2. The reason may be that the outlet diameter is too small and the flow rate becomes the main influencing factor, which requires further research and demonstration. In general, under the same conditions, the contact line width of the trumpet shape is larger than that of the conical shape, consistent with Taiana’s work [35].

    5. Discussions

    In this work, the He concentration distribution under various conditions with or without N2shielding gas is mainly considered,and the ultimate goal is to limit the processing area of the plasma jet. In addition to suppressing the transverse ion waves of the plasma, N2shielding gas can also achieve a shielding effect on the ambient gas (air). Kawasaki et al [36]explored the effects of the surrounding gas on the plasmainduced downward liquid flow and found that a higher nitrogen-oxygen concentration ratio in the surrounding gas can reduce the oxidation reaction during the plasma radiation process. When the plasma jet diffuses in the air, a large number of air molecules enter the atom and ion stream,which will cause a large number of charged particles and excited state substances, such as metastable states, to be lost in the interaction between the He plasma jet and the ambient gas.By shielding the influence of ambient gas by N2, the loss of charged particles can be greatly reduced [37].

    In this work, the focusing effect of the N2shielding gas and the structural parameters of the outer tube on the working gas are analyzed from the perspective of aerodynamics through simulation. Since the effects of the thermal field and discharge process in the plasma jet are not considered in the simulation, the final etching effect cannot be strictly described.In order to illustrate the feasibility of the simulation,PET etching experiments were carried out corresponding to the simulation parameters. The area with larger working gas concentration corresponds to the area with larger contact line width and etching depth in the experiment, and the change rule is similar after changing the parameters. It is shown that the simulation in this paper has certain feasibility. In the follow-up research,adding the thermal and electric fields into the simulation model is proposed as a way to simulate the plasma jet more accurately.

    6. Conclusion

    In this study,a two-dimensional axisymmetric simulation model of plasma jet gas dynamics is established to simulate the influence of N2flow rate,distance difference x,and outer tube nozzle diameter D on the molar concentration distribution of working gas He with or without N2shielding gas.The focusing effect of N2is analyzed by the simulation results, and the experimental results are verified. The results show that:

    (1) The actual etched area is mainly concentrated in the high-concentration He area.

    (2) Compared with the absence of shielding gas, shielding gas N2will restrict the distribution of He in the highconcentration region so that it only maintains a higher concentration in the central region, and this effect is continuously enhanced with the increase of the N2flow rate. The experimental results show that the larger the N2flow rate, the smaller the contact line width and etching depth.

    (3) As the distance difference x between the inner and outer tube increases, the He molar concentration on the substrate decreases more under the action of shielding gas. The experimental results show that as the distance difference x increases, the contact line width and etching depth are smaller, and the focusing effect is more obvious.

    (4) With the increase of the outlet diameter,the smaller the He molar concentration in the high-concentration region, the less obvious the focusing effect of N2. The experimental results show that with the increase of the outlet diameter, the focusing effect of N2will reduce the contact line width and etching depth, but when the outlet diameter D<2, the abnormal phenomenon of increasing etching depth will appear. In general, a cylindrical outlet is more suitable.

    It is hoped that the results in this paper can provide a certain reference for the use of shielding gas to achieve precise and controllable etching of APμPJ.

    Acknowledgments

    This work is supported by National Natural Science Foundation of China (No. 51905002), Anhui Provincial Natural Science Foundation (Nos.2008085QE230,2108085ME174),Open Project of Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials (No.GFST2021KF06), Open Project of Anhui Province Key Laboratory of Special and Heavy Load Robot (No.TZJQRO03-2021) and Open Project of Anhui Province Engineering Laboratory of Intelligent Demolition Equipment(No. APELIDE2021B001).

    猜你喜歡
    圣泉王濤
    綿師學(xué)人
    ——王濤
    Transition to chaos in lid–driven square cavity flow?
    圣泉
    王濤 李佳星作品
    大眾文藝(2020年22期)2020-12-13 11:37:16
    過武陵山區(qū)
    圣泉集團(tuán)堅(jiān)守創(chuàng)新基因
    英才(2020年5期)2020-05-22 12:48:47
    ONE-DIMENSIONAL VISCOUS RADIATIVE GAS WITH TEMPERATURE DEPENDENT VISCOSITY?
    圣泉英賽德歐洲有限公司正式開工建設(shè)
    王濤作品
    STABILITY OF VISCOUS SHOCK WAVES FOR THE ONE-DIMENSIONAL COMPRESSIBLE NAVIER-STOKES E QUATIONS WITH DENSITY-DEPENDENT VISCOSITY?
    a级片在线免费高清观看视频| 下体分泌物呈黄色| 老司机亚洲免费影院| 午夜激情av网站| 国产精品久久久久久精品古装| 成人av一区二区三区在线看| av免费在线观看网站| 在线观看66精品国产| 国产精品综合久久久久久久免费 | 久久精品人人爽人人爽视色| 99国产精品一区二区蜜桃av | av电影中文网址| 国产免费男女视频| 国产精品1区2区在线观看. | 1024香蕉在线观看| 日本精品一区二区三区蜜桃| 亚洲精品国产精品久久久不卡| 老司机影院毛片| 黑丝袜美女国产一区| 精品国产乱码久久久久久男人| 一本一本久久a久久精品综合妖精| 天天躁夜夜躁狠狠躁躁| 女人被躁到高潮嗷嗷叫费观| 久久久精品区二区三区| 精品福利观看| 国产1区2区3区精品| 国产精品欧美亚洲77777| 亚洲熟女精品中文字幕| 操出白浆在线播放| 十八禁人妻一区二区| 日韩欧美免费精品| 99精品欧美一区二区三区四区| 免费看a级黄色片| 国产精品久久久久成人av| 免费av中文字幕在线| 性少妇av在线| 十分钟在线观看高清视频www| 国产伦人伦偷精品视频| 亚洲成人国产一区在线观看| 久久精品aⅴ一区二区三区四区| 一级a爱片免费观看的视频| 精品一区二区三卡| 午夜福利一区二区在线看| 欧美黑人欧美精品刺激| 国产亚洲欧美在线一区二区| 黑丝袜美女国产一区| 亚洲av熟女| 在线观看日韩欧美| 日韩欧美在线二视频 | 亚洲精品在线观看二区| 亚洲少妇的诱惑av| 欧美黄色淫秽网站| 丰满迷人的少妇在线观看| 自拍欧美九色日韩亚洲蝌蚪91| 精品少妇久久久久久888优播| 丁香六月欧美| 757午夜福利合集在线观看| 久久久久久久国产电影| 国产精品香港三级国产av潘金莲| 天堂动漫精品| 久久人妻熟女aⅴ| 欧美日韩福利视频一区二区| 日韩欧美在线二视频 | 91麻豆精品激情在线观看国产 | 成人手机av| 久久久久视频综合| 日日摸夜夜添夜夜添小说| 精品福利观看| 国产日韩欧美亚洲二区| 91精品三级在线观看| 狠狠婷婷综合久久久久久88av| 后天国语完整版免费观看| 99久久综合精品五月天人人| 窝窝影院91人妻| 一级a爱视频在线免费观看| 纯流量卡能插随身wifi吗| 国产高清激情床上av| 大香蕉久久网| 中国美女看黄片| 中出人妻视频一区二区| 在线观看免费高清a一片| 变态另类成人亚洲欧美熟女 | 天天躁日日躁夜夜躁夜夜| 亚洲精品在线美女| 久久精品熟女亚洲av麻豆精品| 女人高潮潮喷娇喘18禁视频| 欧美在线黄色| 女人久久www免费人成看片| 一夜夜www| 无人区码免费观看不卡| 国产精品一区二区免费欧美| 国产在视频线精品| 久久人人97超碰香蕉20202| 91麻豆精品激情在线观看国产 | 午夜亚洲福利在线播放| 欧美成狂野欧美在线观看| 伦理电影免费视频| 一本大道久久a久久精品| 久久精品国产a三级三级三级| 美女高潮到喷水免费观看| 超色免费av| 免费av中文字幕在线| 欧美国产精品va在线观看不卡| 午夜影院日韩av| 成在线人永久免费视频| a在线观看视频网站| 99热网站在线观看| 国产精品欧美亚洲77777| 91在线观看av| 日韩欧美国产一区二区入口| 国产精品一区二区在线观看99| 国产精品成人在线| 久久久国产一区二区| 91精品国产国语对白视频| 一区二区三区激情视频| 欧美在线黄色| 黄色视频,在线免费观看| 日本一区二区免费在线视频| 99久久综合精品五月天人人| 国产成+人综合+亚洲专区| 999久久久国产精品视频| 亚洲久久久国产精品| 久久久久国内视频| 久久这里只有精品19| 久久久国产一区二区| 女人爽到高潮嗷嗷叫在线视频| 日韩制服丝袜自拍偷拍| 午夜免费观看网址| 午夜福利,免费看| 中国美女看黄片| 精品无人区乱码1区二区| 午夜成年电影在线免费观看| 成人精品一区二区免费| 欧美成人午夜精品| 国产精品香港三级国产av潘金莲| 国产成人精品在线电影| 久99久视频精品免费| 91麻豆av在线| xxxhd国产人妻xxx| 少妇猛男粗大的猛烈进出视频| 成年版毛片免费区| 欧美精品高潮呻吟av久久| 国产在线观看jvid| 久久香蕉国产精品| 一个人免费在线观看的高清视频| 中亚洲国语对白在线视频| 美女 人体艺术 gogo| 免费久久久久久久精品成人欧美视频| 日韩免费高清中文字幕av| 亚洲成人免费av在线播放| 啦啦啦 在线观看视频| 大香蕉久久成人网| 黑人猛操日本美女一级片| 色老头精品视频在线观看| 免费少妇av软件| 人人妻人人澡人人爽人人夜夜| 后天国语完整版免费观看| 国产片内射在线| 久久久久国产精品人妻aⅴ院 | 99精品久久久久人妻精品| 国产精品 欧美亚洲| 久99久视频精品免费| 在线观看免费日韩欧美大片| 女人被狂操c到高潮| 亚洲精品久久午夜乱码| 一级毛片高清免费大全| 亚洲成a人片在线一区二区| 午夜免费鲁丝| 日韩中文字幕欧美一区二区| 巨乳人妻的诱惑在线观看| 久久中文字幕一级| 精品熟女少妇八av免费久了| 精品一区二区三区av网在线观看| 国产精品国产高清国产av | 亚洲精品自拍成人| 大码成人一级视频| 激情在线观看视频在线高清 | 欧洲精品卡2卡3卡4卡5卡区| 国产精品1区2区在线观看. | 操出白浆在线播放| 男男h啪啪无遮挡| 午夜精品国产一区二区电影| 女性生殖器流出的白浆| 精品无人区乱码1区二区| 国产成+人综合+亚洲专区| 美女午夜性视频免费| 久久亚洲真实| 制服人妻中文乱码| 亚洲精品在线美女| 久久香蕉国产精品| 免费在线观看亚洲国产| 国产成+人综合+亚洲专区| 久久国产精品男人的天堂亚洲| 黄频高清免费视频| 亚洲成国产人片在线观看| 欧美国产精品va在线观看不卡| 国产主播在线观看一区二区| 18禁裸乳无遮挡免费网站照片 | 老司机在亚洲福利影院| 人妻 亚洲 视频| 国产黄色免费在线视频| 黄色a级毛片大全视频| 亚洲专区中文字幕在线| 色在线成人网| 久热这里只有精品99| 啦啦啦 在线观看视频| 国产成人精品无人区| 国产精品偷伦视频观看了| 三级毛片av免费| 亚洲欧洲精品一区二区精品久久久| 日日摸夜夜添夜夜添小说| 777久久人妻少妇嫩草av网站| 每晚都被弄得嗷嗷叫到高潮| 免费黄频网站在线观看国产| 国产av一区二区精品久久| 五月开心婷婷网| 亚洲aⅴ乱码一区二区在线播放 | 亚洲成人免费av在线播放| 亚洲成人国产一区在线观看| 国产精品自产拍在线观看55亚洲 | 又黄又粗又硬又大视频| 国产精品久久久久久精品古装| 丝瓜视频免费看黄片| 国产xxxxx性猛交| 一本一本久久a久久精品综合妖精| 叶爱在线成人免费视频播放| 桃红色精品国产亚洲av| 久久精品国产99精品国产亚洲性色 | 国产欧美日韩综合在线一区二区| 成人三级做爰电影| 久久青草综合色| 欧美人与性动交α欧美软件| 天堂俺去俺来也www色官网| 女人高潮潮喷娇喘18禁视频| 免费在线观看完整版高清| 中文字幕另类日韩欧美亚洲嫩草| 嫁个100分男人电影在线观看| 波多野结衣一区麻豆| 国产成人免费观看mmmm| 最新美女视频免费是黄的| 久久精品国产综合久久久| 亚洲欧美日韩另类电影网站| 男女午夜视频在线观看| 亚洲第一青青草原| 91av网站免费观看| 国产色视频综合| 久久久国产成人精品二区 | 久久草成人影院| 久久久久久久久免费视频了| 成人永久免费在线观看视频| 不卡一级毛片| 天天影视国产精品| 亚洲精品美女久久久久99蜜臀| 在线看a的网站| 女警被强在线播放| 黄色丝袜av网址大全| 成年版毛片免费区| 精品人妻1区二区| 亚洲久久久国产精品| 啪啪无遮挡十八禁网站| 精品无人区乱码1区二区| 国产在线精品亚洲第一网站| 亚洲自偷自拍图片 自拍| 欧美 日韩 精品 国产| 午夜福利乱码中文字幕| 亚洲久久久国产精品| 亚洲av日韩在线播放| 国产免费现黄频在线看| 人人妻人人澡人人爽人人夜夜| 麻豆av在线久日| 18禁黄网站禁片午夜丰满| 国产精品永久免费网站| 成人精品一区二区免费| 一区二区三区激情视频| 国产不卡一卡二| 极品教师在线免费播放| 国产熟女午夜一区二区三区| 在线播放国产精品三级| 美国免费a级毛片| 男人舔女人的私密视频| 在线永久观看黄色视频| 欧美激情极品国产一区二区三区| 亚洲五月天丁香| av片东京热男人的天堂| 黄色丝袜av网址大全| 美国免费a级毛片| 精品电影一区二区在线| 欧美黑人精品巨大| 叶爱在线成人免费视频播放| 免费在线观看黄色视频的| 大片电影免费在线观看免费| 午夜日韩欧美国产| 精品国产亚洲在线| 极品少妇高潮喷水抽搐| 捣出白浆h1v1| 狠狠狠狠99中文字幕| av网站在线播放免费| 老司机在亚洲福利影院| 午夜免费观看网址| 欧美乱码精品一区二区三区| 999久久久精品免费观看国产| 国产精品二区激情视频| 亚洲一卡2卡3卡4卡5卡精品中文| 成人精品一区二区免费| 免费看a级黄色片| 51午夜福利影视在线观看| 一级片'在线观看视频| 国产精品99久久99久久久不卡| a级片在线免费高清观看视频| 久久久国产成人免费| 黑人操中国人逼视频| 国产精品香港三级国产av潘金莲| 这个男人来自地球电影免费观看| 中出人妻视频一区二区| 黑人操中国人逼视频| 男人舔女人的私密视频| 久久久久精品人妻al黑| 黄片大片在线免费观看| 成人18禁在线播放| 曰老女人黄片| 亚洲国产看品久久| 搡老岳熟女国产| 建设人人有责人人尽责人人享有的| 午夜福利乱码中文字幕| 男女免费视频国产| 99久久精品国产亚洲精品| 中文字幕av电影在线播放| 日本黄色视频三级网站网址 | bbb黄色大片| 夜夜躁狠狠躁天天躁| 天堂俺去俺来也www色官网| 一进一出好大好爽视频| 天天操日日干夜夜撸| 欧美丝袜亚洲另类 | 久久性视频一级片| 亚洲综合色网址| 午夜福利影视在线免费观看| 精品电影一区二区在线| 天堂动漫精品| 亚洲色图 男人天堂 中文字幕| xxx96com| 中文亚洲av片在线观看爽 | 美女扒开内裤让男人捅视频| 老司机亚洲免费影院| 国产一区有黄有色的免费视频| 男女免费视频国产| 久久久久国产一级毛片高清牌| 超碰成人久久| 丁香欧美五月| 久久人妻熟女aⅴ| 99久久综合精品五月天人人| 国产视频一区二区在线看| 久久久久精品人妻al黑| 亚洲精品乱久久久久久| 黄网站色视频无遮挡免费观看| 国产有黄有色有爽视频| 久久 成人 亚洲| av视频免费观看在线观看| 三级毛片av免费| 国产视频一区二区在线看| 99国产综合亚洲精品| 制服人妻中文乱码| 免费黄频网站在线观看国产| 如日韩欧美国产精品一区二区三区| 亚洲午夜理论影院| 久久久精品免费免费高清| 18禁黄网站禁片午夜丰满| 色老头精品视频在线观看| 欧美黑人欧美精品刺激| 一进一出抽搐动态| 岛国在线观看网站| 亚洲成人国产一区在线观看| 日韩一卡2卡3卡4卡2021年| 精品一区二区三区四区五区乱码| 亚洲欧美日韩高清在线视频| 飞空精品影院首页| 99在线人妻在线中文字幕 | 欧美精品亚洲一区二区| 人妻一区二区av| 国产欧美日韩一区二区精品| 久久 成人 亚洲| 亚洲精品在线观看二区| 少妇裸体淫交视频免费看高清 | 亚洲三区欧美一区| 99国产精品免费福利视频| 在线观看日韩欧美| 久久青草综合色| 韩国精品一区二区三区| 欧美日韩亚洲综合一区二区三区_| 在线av久久热| 曰老女人黄片| 1024香蕉在线观看| 亚洲熟女精品中文字幕| 精品高清国产在线一区| 婷婷精品国产亚洲av在线 | 亚洲午夜理论影院| 无遮挡黄片免费观看| 日本a在线网址| 精品午夜福利视频在线观看一区| 欧美 亚洲 国产 日韩一| 久久精品熟女亚洲av麻豆精品| 香蕉国产在线看| 脱女人内裤的视频| 新久久久久国产一级毛片| 久久人妻熟女aⅴ| 久久影院123| 婷婷精品国产亚洲av在线 | 欧美乱码精品一区二区三区| 国产不卡av网站在线观看| 18在线观看网站| 国产精品一区二区免费欧美| 飞空精品影院首页| 午夜福利免费观看在线| 欧美丝袜亚洲另类 | 久久国产精品大桥未久av| 国产精品亚洲av一区麻豆| 精品久久久精品久久久| 免费少妇av软件| 一边摸一边抽搐一进一小说 | 巨乳人妻的诱惑在线观看| 国产精品久久久久久人妻精品电影| 色播在线永久视频| 精品国产美女av久久久久小说| 很黄的视频免费| 欧美成人午夜精品| 国产av精品麻豆| 欧美大码av| 国产男靠女视频免费网站| 黄片大片在线免费观看| 午夜91福利影院| 一进一出好大好爽视频| 黄色片一级片一级黄色片| 亚洲国产精品合色在线| 午夜福利,免费看| 色视频www国产| 精品福利观看| 床上黄色一级片| 欧美另类亚洲清纯唯美| 国内少妇人妻偷人精品xxx网站| 69av精品久久久久久| 麻豆一二三区av精品| 国产伦精品一区二区三区视频9 | 韩国av一区二区三区四区| 亚洲精品色激情综合| 成熟少妇高潮喷水视频| 亚洲 国产 在线| 中国美女看黄片| 好看av亚洲va欧美ⅴa在| 91麻豆精品激情在线观看国产| 久久久久性生活片| 日本黄色视频三级网站网址| 免费观看人在逋| 国产色婷婷99| 国产精品香港三级国产av潘金莲| 在线观看免费午夜福利视频| 国产精品影院久久| 在线观看美女被高潮喷水网站 | 午夜精品在线福利| 精品不卡国产一区二区三区| 亚洲五月婷婷丁香| 欧美日韩黄片免| 美女cb高潮喷水在线观看| 精品不卡国产一区二区三区| 午夜老司机福利剧场| 国产精品99久久99久久久不卡| 日本 欧美在线| 成人国产综合亚洲| 搡老妇女老女人老熟妇| 香蕉久久夜色| 长腿黑丝高跟| 国产又黄又爽又无遮挡在线| 3wmmmm亚洲av在线观看| 亚洲avbb在线观看| 一进一出抽搐gif免费好疼| 每晚都被弄得嗷嗷叫到高潮| 亚洲精华国产精华精| 亚洲国产欧美网| 麻豆久久精品国产亚洲av| 国产精品精品国产色婷婷| 亚洲男人的天堂狠狠| 人人妻人人澡欧美一区二区| 午夜精品久久久久久毛片777| 国内精品一区二区在线观看| 国产一区二区激情短视频| 国产单亲对白刺激| 午夜激情欧美在线| 欧美不卡视频在线免费观看| АⅤ资源中文在线天堂| 亚洲精品乱码久久久v下载方式 | 变态另类丝袜制服| 亚洲不卡免费看| 亚洲 国产 在线| 欧美性猛交╳xxx乱大交人| 国产精品电影一区二区三区| 精华霜和精华液先用哪个| 女警被强在线播放| 五月玫瑰六月丁香| 一本久久中文字幕| 欧美绝顶高潮抽搐喷水| 久久久久久人人人人人| 日韩有码中文字幕| 久久精品亚洲精品国产色婷小说| 亚洲精品国产精品久久久不卡| 午夜视频国产福利| 精品久久久久久,| 久99久视频精品免费| 国产精品久久久久久久电影 | 国内久久婷婷六月综合欲色啪| 国产乱人伦免费视频| 亚洲av熟女| 一级毛片女人18水好多| 国产不卡一卡二| 欧美日韩亚洲国产一区二区在线观看| 国产高清视频在线播放一区| 中文字幕人妻丝袜一区二区| 国产精品久久久久久久久免 | 精品欧美国产一区二区三| 又黄又爽又免费观看的视频| 制服丝袜大香蕉在线| 欧美最黄视频在线播放免费| 精品人妻1区二区| 叶爱在线成人免费视频播放| 一级毛片高清免费大全| 国产主播在线观看一区二区| 国产精品久久电影中文字幕| 波野结衣二区三区在线 | 男人的好看免费观看在线视频| 精品不卡国产一区二区三区| 老司机深夜福利视频在线观看| 精品久久久久久久末码| 又粗又爽又猛毛片免费看| 国产成人啪精品午夜网站| 国产一区二区激情短视频| 国产精品国产高清国产av| 一区二区三区免费毛片| 日韩欧美国产一区二区入口| 最新在线观看一区二区三区| 一进一出好大好爽视频| 啦啦啦观看免费观看视频高清| 亚洲av第一区精品v没综合| 国产精品98久久久久久宅男小说| 午夜激情欧美在线| 美女大奶头视频| 怎么达到女性高潮| 精品久久久久久久毛片微露脸| 又紧又爽又黄一区二区| 午夜精品在线福利| 精华霜和精华液先用哪个| 国内久久婷婷六月综合欲色啪| 亚洲av电影在线进入| 搞女人的毛片| 99在线视频只有这里精品首页| 亚洲av成人不卡在线观看播放网| 尤物成人国产欧美一区二区三区| 长腿黑丝高跟| 白带黄色成豆腐渣| 午夜免费激情av| 欧美av亚洲av综合av国产av| 国产精品永久免费网站| 听说在线观看完整版免费高清| 韩国av一区二区三区四区| 日本一二三区视频观看| 一区二区三区高清视频在线| 色综合欧美亚洲国产小说| 亚洲美女视频黄频| 亚洲国产欧美网| 69人妻影院| 午夜福利高清视频| 久久久久性生活片| 97超视频在线观看视频| 国产伦精品一区二区三区四那| 亚洲精华国产精华精| 999久久久精品免费观看国产| 色综合欧美亚洲国产小说| 精品国产美女av久久久久小说| 好看av亚洲va欧美ⅴa在| 最近最新中文字幕大全免费视频| 亚洲专区中文字幕在线| 国产亚洲欧美98| 男女床上黄色一级片免费看| 久久久久久久久中文| 男人的好看免费观看在线视频| 欧美一区二区精品小视频在线| 欧美国产日韩亚洲一区| 天堂√8在线中文| 白带黄色成豆腐渣| 两个人视频免费观看高清| 久久久久久人人人人人| 国产视频内射| 亚洲熟妇中文字幕五十中出| 一区二区三区国产精品乱码| 嫁个100分男人电影在线观看| 精华霜和精华液先用哪个| 国产在视频线在精品| 久久精品夜夜夜夜夜久久蜜豆| 久久久精品大字幕| 母亲3免费完整高清在线观看| 麻豆久久精品国产亚洲av| 国产久久久一区二区三区| 亚洲熟妇中文字幕五十中出| 一个人看的www免费观看视频| www.www免费av| 日韩免费av在线播放| www.熟女人妻精品国产| 老汉色av国产亚洲站长工具| 国产黄片美女视频| 桃色一区二区三区在线观看| 国产伦精品一区二区三区视频9 | 91九色精品人成在线观看| 成人特级av手机在线观看| 成年版毛片免费区| 十八禁人妻一区二区| 久久精品国产自在天天线| 亚洲国产日韩欧美精品在线观看 | 99视频精品全部免费 在线|