• <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 ?

    Investigation on the deformation of aluminum and alumina droplet during its impact on the wall①

    2019-01-18 10:58:22WUGuanjieRENQuanbinFUYuLIUYuanminHUChunbo
    固體火箭技術(shù) 2018年6期

    WU Guanjie, REN Quanbin,, FU Yu, LIU Yuanmin, HU Chunbo

    (1. Science and Technology on Combustion, Internal Flow and Thermal-structure Laboratory, Northwestern Polytechnical University, Xi'an 710072, China; 2. The Fourth Academy of CASC, Xi'an 710025, China)

    Abstract:The micrometer-size alumina droplets usually impact on the wall of solid rocket motor during combustion process. Considering the high melting point of alumina, the droplet-wall impingement experiments were carried out by the molten aluminum as a demonstration. The volume of fluid (VOF) and adaptive grid methods have been used to numerically simulate the aluminum droplet-wall impingement experiments, which have been used to validate the numerical models. The deformation process of micrometer-size alumina droplets that impacted on the wall have been calculated by the validated model under different droplet velocities and sizes. The results show that the numerical simulation process is basically in accordance with the experiment. With the increase of the initial impacting velocity, alumina droplet would rebound, stick, and breakup successively after impacting on the wall. With the increase of the diameter, the critical Weber number of alumina droplet between rebound and stick, stick and breakup decreases accordingly. The rebound-stick critical We number of 20 μm, 50 μm and 100 μm alumina droplet vertically impacting on the wall are 170, 84 and 50 respectively, and the stick-breakup critical We number of impacting alumina droplet in diameters of 50 μm and 100 μm are 141 and 129. The droplet breakup must have sufficient kinetic energy to overcome the energy consumed by viscous flow and surface tension.

    Key words:alumina droplet;directly numerical simulations;self-adaptive grid method;critical We number

    0 Introduction

    Alumina droplet impacting on the wall is a common phenomenon in the combustion chamber and nozzle convergence section of solid rocket motor[1]. Aluminum/alumina droplets will impact on the surface of insulation layer and lead to particle deposition and erosion, which is a unique phenomenon of combustion gas flow in aluminized rocket motor[2-3]. The process of droplets impacting on the wall has been a very important physical process to research.

    The previous researches of droplet impacting on the wall mainly focused on the water droplet impacting on the wall. Leidenfrost[4]performed the experiments of water droplets impacting on the hot iron spoon, and the water droplets kept suspending for few seconds over the iron spoon. Wathers[5]found whether the droplet rebound or stick after impacting the hot wall mainly depended on Weber number, and the criticalWevalue of bounce and stick was 40. Zhang[6]summarized that the glycerol droplet impacting on the wall was a viscous impact whenRewas less than 20, but an inertial impact when theRewas over 230.

    However, previous studies on droplets impacting on the wall were mainly on the low-melting-point droplets[7-9]. The alumina droplet has higher surface tension than the droplet at normal temperature. Therefore, in the study of droplet-wall impacting regulation, the low-melting-point droplet cannot be used to replace the alumina droplet, but the properties of molten aluminum droplet are much similar to that of the alumina droplet. In this paper, the experimental device for aluminum droplet impacting on the wall was set up, and the open-source program Gerris was used to directly simulate the experiments of aluminum droplet impacting on the wall. Meanwhile, a lot of numerical simulations about the alumina droplet impacting on the wall were carried out by Gerris. Furthermore, the influence of velocity and diameter on the droplet impacting on wall was researched.

    1 Approach

    1.1 Experimental apparatus

    In consideration of the high melting point of alumina, it is very difficult to conduct the experimental research on alumina directly. However, the aluminum has high surface tension, which is similar to alumina, and their physical parameters are very approximate. Therefore, the experiment of aluminum droplet impacting on the graphite wall was carried out in this paper, and the accuracy of numerical calculation was verified by the experimental results. The experimental system of molten aluminum droplet impacting on the wall is mainly made up of the heating system, cooling system, gas supply system, control system, acquisition system and the obturation device. The heating system is a high-frequency induction heater, which is mainly used for melting the metal aluminum; the gas supply system mainly adopts argon, which can be used as the driving gas for the generation of aluminum droplets and the environmental protection gas; the cooling system provides the temperature protection for some components by water cooling; the control system with the high-response control hardware and professional software, is mainly used to control the high-frequency solenoid valve, whose working time is in milliseconds, so that the single metal droplet can be generated; the acquisition system mainly includes pressure and temperature acquisition, and the high-speed photography; the obturation device contains a closed container used for argon environment, and a graphite crucible for molten aluminum. A transparent quartz window is inset into the closed container for observing the deformation process of aluminum droplet-wall impingement. The whole experimental system is shown as follows in Fig.1.

    The working principle of the experimental device is that a high-frequency induction heater is used for heating the graphite crucible, and the solid aluminum in the crucible is melted; then the molten aluminum is ejected from the nozzle at the end of the graphite crucible by controlling the mass flow rate of argon gas in the graphite crucible, and the molten aluminum droplet was generated by the precise working time of high-frequency solenoid valve. Subsequently, the aluminum droplet with a certain speed impacts on the smooth graphite wall, and the impacting process is shot by the high-speed photography. The deformation process of aluminum droplet impacting on the wall is obtained.

    1.2 Numerical method

    The phenomenon of droplet impacting on the wall is the typical two-phase flow. In this paper, Gerris[10], a computational fluid dynamics program based on the VOF interface tracking method, is used to perform the direct numerical calculations on the droplet impacting on the wall. In the method of VOF, the volume rate functionC(x,t) is used to describe the volume fraction of the fluid in a grid cell: the grid cell is completely occupied by a certain liquid whenC=1, and it doesn't have liquid whenC=0, while the liquid and gas occur simultaneously in one grid when 0

    ?tC+·(Cu)=0

    (1)

    The control equations used in this paper include non-stationary incompressible continuity equations and the Navier-Stokes equations. The time-interleaving method is used to perform the discrete on the equations of volume fraction, density and pressure, and the surface tension and gravity are added as source terms to the N-S equations. The equations are as follows:

    ρ(?tu+u·u)= -p+·(2μD)+

    σκδsn+ρg

    (2)

    ?tρ+·(ρu)=0

    (3)

    ?tC+·(Cu)=0

    (4)

    whereu(u,v,w) is the fluid velocity,ρis the fluid density,μis the dynamic viscosity,σis the surface tension,κis the droplet curvature,nis the normal vector of wall, andDis the deformation tensor;δsshows that the surface tension term only exists at the two-phase interface, andρgis the gravity term.

    The density and viscosity can be expressed by the VOF functions as follows:

    ρ(C)=ρ1(C)+ρ2(1-C)

    (5)

    μ(C)=μ1(C)+μ2(1-C)

    (6)

    whereρ1is the density of the liquid,ρ2is the density of the gas,μ1is the dynamic viscosity of the liquid, andμ2is the dynamic viscosity of the gas.

    1.3 Research proposal

    In the aluminum droplet-wall impingement experiment, the temperature of molten aluminum is controlled at 977 K, and the graphite wall will be heated to 933 K, while the argon environment temperature of the aluminum droplet impingement part is around 473 K. The whole impacting process is performed in an argon atmosphere to ensure that the aluminum droplet surface does not oxidize, and the whole deformation process of the droplet impacting on the wall surface is photographed by high-speed photography. Table 1 shows the experimental parameters of aluminum droplet impacting on the graphite wall vertically, and the contact angle between the aluminum droplet and the graphite wall is 161°.

    Table 1 Experimental parameters of aluminum dropletimpacting on the graphite wall

    The VOF method was used to directly simulate the experimental process of aluminum droplet impacting on the wall, so as to verify the reliability of the numerical model. According to the experimental parameters in Table 1, Gerris was used to perform the numerical calculations of aluminum impacting on the wall.

    Considering that the particle sizes of alumina droplets in the combustion chamber of solid rocket motors are mainly below 100 μm and the gas flow velocity is generally not higher than 60 m/s, the Weber number of alumina droplets is 10~450, and theRenumber is 38.85 ~ 253.25. In this paper, the influence of particle size and velocity of alumina droplet on the behavior pattern of droplet-wall impingement process is studied. Therefore, the diameter of the alumina droplet is set as 20~100 μm, and the impacting velocity is 6.7~69.78 m/s. The physical property parameters of alumina droplets and gas phase are as shown in Table 2.

    In the solid rocket motor, as surface of the heat-insulating material is greatly influenced by the operating mode, it is very complicated to judge the wettability between the droplet and the insulating surface, thus the solid wall contact angleθis set as 90°, namely the dividing angle of the wetting property.

    Table 2 Parameters of alumina droplet and gas phase

    2 Results and discussion

    2.1 Aluminum deformation process analysis

    The experiment and simulation result of 730 μm aluminum droplet impacting on the graphite wall at a velocity of 1.01 m/s are shown in Fig.2. It can be seen that both the results of numerical simulation and experiment on the aluminum droplet-wall impacting process are very similar. The aluminum droplet is symmetrically spread over the impacting point under the inertia force, and it reaches the maximum spreading length at 0.36 ms. Then, the aluminum droplet begins to shrink to the center part. The height of aluminum droplet bulge increases continuously during the retracting process, and the aluminum droplet gains an upward speed. Finally, the droplet is completely rebounded by resistance to the gravity under the effect of kinetic energy and surface tension.

    The evolution of the pressure and velocity is shown in Fig.3. Whent=0.1 ms, the colliding is in the spreading stage, the internal pressure of aluminum droplet is concentrated on the surface between the droplet and the wall, and it gradually decreases along the normal direction. Then the droplet is gradually spreading under the inertia force, and the pressure on both sides of the droplet increases gradually. Whent=0.38 ms, the kinetic energy of the droplet is completely converted to the surface energy, and the droplet begins to shrink under the surface tension. Whent=0.60 ms, the pressure at the bottom of the droplet is less than that oft=0.1 ms, which is mainly because the droplet is subjected to the upward inertial force. Subsequently, the kinetic energy counteracts the viscous dissipation energy, and the droplet bounces off the wall.

    (a)Experimental result (b)Simulation result

    (a)Spreading stage (b)Retraction stage

    In order to describe the changing process of different energies in the impact process of aluminum droplet, each energy is tracked and calculated, including the kinetic energy (KE), the surface energy (SE), the viscous dissipation energy (VDE) and the total energy (TE). The total kinetic energy of the droplet is calculated by the integration of the kinetic energy and the volume rate function. The droplet surface energy can be calculated by the product of the surface tension coefficient and the surface area of the droplet. The viscous dissipation energy is calculated by the time integral of the viscous dissipation rate (VDR), which belongs to the cumulative viscous dissipation energy. The total energy is the summation of kinetic energy, surface energy and viscous dissipation energy. The formulation ofVDRunder two-dimensional axisymmetric condition is shown as follows[13]:

    (7)

    In Fig.4, theKE,SE,VDEandTEat an instant are nondimensionalized by initialTE. It can be seen that the balance of the original droplet surface tension is broken when the aluminum droplet contacts the wall surface, and the liquid interface is deformed and the bottom is compressed. TheKEkeeps decreasing, andSEandVDEkeep increasing during 0 ms to 0.4 ms, which is the aluminum droplet spreading stage, and the kinetic energy of the droplet is transformed into surface energy and viscous dissipation energy.

    Fig.4 Relationship between differentenergy and contact time

    At this time, the deformation of droplet is sharp, which lead to the high viscous dissipation rate; from 0.4 ms to 0.7 ms, theSEdecreases continuously, andKEandVDEincrease slowly, and the surface energy of the droplet transforms into kinetic energy and viscous dissipation energy. At this time, the viscous dissipation rate of droplets is lower than that of the spreading stage. In addition, it can be seen that the kinetic energy of the droplet is higher than the viscous dissipation energy during the deformation process, and the droplet leaves the wall under the action of the residual kinetic energy.

    2.2 The effect of the initial velocity

    As the initial velocity of alumina droplet impacting on the wall changes, the appearance of droplets impacting on the wall changes correspondingly. In Fig.5, it shows the deformation and rebound process of 20 μm alumina droplets impacting on the wall at the impacting parameter Weber number is 10, 100 and 170 respectively, and the initial velocity is 10.70, 33.85, 44.13 and 69.78 m/s.

    Fig.5 20 μm alumina droplet impacting on the wallwith different Weber number

    The calculation results of 20 μm alumina droplet vertically impacting on the wall in the Fig.5 shows that, the droplet rebounds in the low velocity, and it will stick on the wall when the velocity is high. When the Weber number is 10 and 100, the alumina droplets spread and retract after impacting on the wall, and it rebound off the wall at the end. When the Weber number is 170 and 425, the movement process can be divided into four periods: rapid spreading, retraction, oscillation and stabilization. After stabilization, the droplets stably adhere on the wall. However, no breakup or spattering occurred in the calculation range of 20 μm alumina droplet vertically impacting on the wall in this paper.

    Fig.6 shows theWe-Redistribution diagram of rebound and stick of 20 μm alumina droplet vertically impacting on the horizontal wall. The critical Weber number of rebound and stick is 170. This is mainly due to the high viscosity and surface tension, and it is different from the water droplet, which has low viscosity and surface tension.

    2.3 The effect of the initial diameter

    During the working process of the rocket motor, the size of the alumina droplets ranges from submicron to several hundred microns. Because of the unevenness of the size distribution, the influence of droplet size on the impingement results needs to be investigated[14].

    The numerical calculation results of 50 μm alumina droplet impact on the wall is shown in Fig.7. When the Weber number is 83, 84, 140 and 141 respectively, the initial velocity is 19.50, 19.62, 25.33 and 25.42 m/s. It can be seen that 50 μm alumina droplet-wall impingement results have three types: rebound, stick and breakup. When the Weber number is lower than 83, the alumina droplet will rebound after impacting on the wall; when it ranges from 84 to 140, the droplet will stick; when it is more than 500, the droplet will breakup. This is different from the types of impingement results of 20 μm alumina droplet, which is due to the larger diameter.

    Fig.6 20 μm alumina droplet impacting on the wallwith different Weber number

    Fig.7 50 μm alumina droplet impactingon the wall with different We

    The results of 100 μm alumina droplet impacting on the wall are similar to that of 50 μm droplet, but the critical Weber numbers between rebound and stick is 50, and that of stick and breakup is 129. The morphological changes of alumina droplet with the same impingement results at different impacting velocities are approximately similar. The regional distribution diagram of 20~100 μm alumina-wall impingement result is shown in Fig.8. It can be seen that with the diameter of the alumina droplet increases, the conversion critical Weber number between rebound and stick, stick and breakup decrease correspondingly. This is because the Weber number actually is the ratio of inertial force and surface tension, and with the increase of diameter, the increasing rate of inertial force is higher than that of surface tension, it is easier to breakup for bigger droplet in lower Weber number.

    Fig.8 We-D distribution diagram of the results inthe alumina droplet impacting on the wall

    2.4 The evolution of the energy

    The energy evolution in alumina droplet impacting on the wall during the 50 μm alumina droplet deformation is shown in Fig.9, and the value ofSEandKEat an instant are the ratio of initialSEandKE, respectively.

    The temporal evolution ofKEandSEfor different impingement results is shown in Fig.9.

    Fig.9 Energy evolution of 50 μm aluminadroplet impact on the wall

    The maximum surface energy of droplets increases with the increase of dropletWenumber, and the final surface energy of the droplet is basically consistent with the initial surface energy in the rebound and stick results. While, the final surface energy of the droplet increases 12% in the breakup result. This is because that the small droplets separated increase the surface area of the droplets. However, the droplet still has a certain kinetic energy in the rebound result, and the kinetic energy of droplets gradually approaches zero in stick and breakup results. In conclusion, the viscous movements of droplets dissipate most of the energy in the impacting process. Therefore, the breakup of droplet must have sufficient kinetic energy to overcome the energy consumed by viscous flow and surface tension.

    3 Conclusions

    In view of the phenomenon of alumina droplet impacting on the wall, the direct numerical simulation of micrometer alumina droplet-wall impingement process is carried out by the VOF interface tracing method and the adaptive mesh discrete program. With the increase of the initial velocity, the alumina droplet has the phenomena of rebound, stick and breakup after the vertically impacting on the wall.

    The morphology changes of the droplets impacting on the wall with different diameters are basically similar. It is easier for alumina droplets with large diameter to have the phenomenon of breakup than the small droplets. The droplet breakup must have sufficient kinetic energy to overcome the energy consumed by viscous flow and surface tension. With the droplet diameter increases, the critical Weber number of rebound-stick and stick-breakup decreases accordingly.

    成人av在线播放网站| 国产高清视频在线播放一区| 婷婷六月久久综合丁香| 亚洲aⅴ乱码一区二区在线播放 | 黄色 视频免费看| 18禁黄网站禁片免费观看直播| 国产一区二区激情短视频| 最近最新免费中文字幕在线| 欧美中文综合在线视频| 曰老女人黄片| 久久这里只有精品中国| 久久天躁狠狠躁夜夜2o2o| 欧美成人免费av一区二区三区| 国产亚洲精品综合一区在线观看 | 成人国语在线视频| 亚洲一区二区三区不卡视频| 一区二区三区高清视频在线| 美女高潮喷水抽搐中文字幕| 两性夫妻黄色片| 亚洲第一电影网av| 亚洲精品一卡2卡三卡4卡5卡| 一级a爱片免费观看的视频| 极品教师在线免费播放| 欧美黄色淫秽网站| 两性午夜刺激爽爽歪歪视频在线观看 | 免费观看人在逋| 久久这里只有精品19| 免费观看精品视频网站| 亚洲专区中文字幕在线| 淫秽高清视频在线观看| 久久久久久亚洲精品国产蜜桃av| 天天一区二区日本电影三级| 久久亚洲精品不卡| 日韩高清综合在线| 在线播放国产精品三级| 熟女电影av网| 久久久久久久久久黄片| 在线观看日韩欧美| 黑人操中国人逼视频| 午夜视频精品福利| 精品久久久久久久毛片微露脸| 在线观看免费午夜福利视频| 在线国产一区二区在线| av天堂在线播放| 九九热线精品视视频播放| 女警被强在线播放| 亚洲av成人一区二区三| 丁香欧美五月| 最近最新免费中文字幕在线| 国产高清videossex| 午夜激情av网站| 国产又色又爽无遮挡免费看| 欧美在线一区亚洲| 在线观看免费午夜福利视频| 女警被强在线播放| 国产精品久久久人人做人人爽| 黄片小视频在线播放| 欧美zozozo另类| 婷婷丁香在线五月| 日本成人三级电影网站| 国产精品久久久人人做人人爽| 亚洲五月天丁香| 国产成人啪精品午夜网站| 老熟妇乱子伦视频在线观看| 亚洲,欧美精品.| 亚洲精品久久国产高清桃花| 亚洲在线自拍视频| 国产亚洲av高清不卡| 久久久久久人人人人人| 国产视频内射| 国产日本99.免费观看| 亚洲一区高清亚洲精品| 精品久久久久久成人av| 淫妇啪啪啪对白视频| 好看av亚洲va欧美ⅴa在| 久久国产精品影院| 国产精品影院久久| 1024香蕉在线观看| a级毛片a级免费在线| 99riav亚洲国产免费| 成年免费大片在线观看| 九色国产91popny在线| 国产免费男女视频| 少妇被粗大的猛进出69影院| 好男人在线观看高清免费视频| 久久久精品大字幕| 精品人妻1区二区| 久久中文字幕人妻熟女| 可以免费在线观看a视频的电影网站| 欧美性长视频在线观看| 国产精品免费一区二区三区在线| 国产精品美女特级片免费视频播放器 | 蜜桃久久精品国产亚洲av| 欧美日韩精品网址| 久久久久免费精品人妻一区二区| 久久精品人妻少妇| 免费搜索国产男女视频| 怎么达到女性高潮| 成人国产一区最新在线观看| 两个人视频免费观看高清| 国产激情久久老熟女| 又紧又爽又黄一区二区| 国产一区二区在线av高清观看| 无人区码免费观看不卡| 搡老熟女国产l中国老女人| 亚洲成人精品中文字幕电影| 狠狠狠狠99中文字幕| 美女扒开内裤让男人捅视频| 999久久久精品免费观看国产| 天堂动漫精品| 国产69精品久久久久777片 | 精品国产美女av久久久久小说| 99riav亚洲国产免费| 亚洲欧美日韩高清在线视频| 欧美日本亚洲视频在线播放| 性色av乱码一区二区三区2| 特大巨黑吊av在线直播| 精品一区二区三区视频在线观看免费| 亚洲九九香蕉| 成人亚洲精品av一区二区| 国产精品1区2区在线观看.| 午夜免费观看网址| 日本撒尿小便嘘嘘汇集6| 国产伦一二天堂av在线观看| 久久精品夜夜夜夜夜久久蜜豆 | 亚洲欧美日韩东京热| av欧美777| 一本久久中文字幕| 成人永久免费在线观看视频| 在线观看一区二区三区| 在线观看免费午夜福利视频| 欧美乱色亚洲激情| 岛国视频午夜一区免费看| 久9热在线精品视频| 看黄色毛片网站| 亚洲国产精品sss在线观看| 男女视频在线观看网站免费 | 中文字幕熟女人妻在线| √禁漫天堂资源中文www| 欧美成人午夜精品| 国产精品一区二区三区四区久久| 国产成人欧美在线观看| 一区二区三区激情视频| 亚洲人成77777在线视频| www国产在线视频色| 亚洲欧美精品综合一区二区三区| 视频区欧美日本亚洲| 欧美黄色淫秽网站| 一级黄色大片毛片| 欧美日韩中文字幕国产精品一区二区三区| 成人亚洲精品av一区二区| 亚洲熟女毛片儿| 麻豆国产97在线/欧美 | 亚洲成人中文字幕在线播放| 禁无遮挡网站| 国产亚洲精品综合一区在线观看 | 人妻丰满熟妇av一区二区三区| 亚洲av成人不卡在线观看播放网| 精品久久久久久久末码| 精品国内亚洲2022精品成人| 在线观看一区二区三区| 久久久精品国产亚洲av高清涩受| 国产亚洲av高清不卡| 久久精品综合一区二区三区| 国产av一区在线观看免费| 12—13女人毛片做爰片一| 我要搜黄色片| 国产探花在线观看一区二区| 男女下面进入的视频免费午夜| 亚洲成av人片免费观看| 久久久久国产精品人妻aⅴ院| 国产私拍福利视频在线观看| 欧美黄色淫秽网站| 国产精品综合久久久久久久免费| 99国产精品一区二区蜜桃av| 亚洲av中文字字幕乱码综合| 国产免费av片在线观看野外av| 欧美人与性动交α欧美精品济南到| 成人永久免费在线观看视频| 日韩三级视频一区二区三区| 国产久久久一区二区三区| 日本黄大片高清| 国产精品精品国产色婷婷| 欧洲精品卡2卡3卡4卡5卡区| 国产精品综合久久久久久久免费| 中亚洲国语对白在线视频| 脱女人内裤的视频| 国产男靠女视频免费网站| av有码第一页| 久久久久久国产a免费观看| 国产三级在线视频| 国产欧美日韩一区二区三| 国产精品精品国产色婷婷| 免费在线观看黄色视频的| 黑人欧美特级aaaaaa片| 欧美精品亚洲一区二区| 中文字幕人成人乱码亚洲影| 露出奶头的视频| 欧美人与性动交α欧美精品济南到| 男女那种视频在线观看| 国产乱人伦免费视频| 18禁黄网站禁片免费观看直播| 极品教师在线免费播放| 亚洲成人久久爱视频| 亚洲在线自拍视频| 老熟妇乱子伦视频在线观看| 国产亚洲精品第一综合不卡| 中文字幕熟女人妻在线| 久久草成人影院| 特级一级黄色大片| 亚洲国产高清在线一区二区三| 日韩欧美在线乱码| 免费在线观看影片大全网站| 男女做爰动态图高潮gif福利片| 黄色视频,在线免费观看| 亚洲九九香蕉| 美女 人体艺术 gogo| 欧美3d第一页| 国产av麻豆久久久久久久| 老司机靠b影院| 在线免费观看的www视频| 老鸭窝网址在线观看| www.精华液| 老司机在亚洲福利影院| 国产又色又爽无遮挡免费看| 99国产精品一区二区蜜桃av| 亚洲国产中文字幕在线视频| 婷婷亚洲欧美| 黄色女人牲交| 国产69精品久久久久777片 | 在线观看一区二区三区| 亚洲免费av在线视频| 午夜影院日韩av| 亚洲精华国产精华精| 国产av麻豆久久久久久久| 亚洲片人在线观看| 久久久久性生活片| 少妇粗大呻吟视频| a级毛片在线看网站| 99国产精品99久久久久| 久久久久久久久久黄片| 日韩欧美在线二视频| 亚洲精品在线观看二区| 午夜免费激情av| 香蕉久久夜色| 岛国视频午夜一区免费看| 欧美日韩一级在线毛片| 欧美极品一区二区三区四区| 老熟妇乱子伦视频在线观看| 九九热线精品视视频播放| 中文字幕最新亚洲高清| 亚洲自拍偷在线| 最近在线观看免费完整版| 国内精品一区二区在线观看| 天天添夜夜摸| 丁香六月欧美| 国产欧美日韩一区二区三| 久久久久久亚洲精品国产蜜桃av| 18禁黄网站禁片免费观看直播| 真人一进一出gif抽搐免费| 757午夜福利合集在线观看| 女生性感内裤真人,穿戴方法视频| 国产激情久久老熟女| 男人舔奶头视频| 国产精华一区二区三区| 欧美 亚洲 国产 日韩一| www.999成人在线观看| 精品日产1卡2卡| 精品电影一区二区在线| 欧美乱妇无乱码| 曰老女人黄片| 欧美性猛交╳xxx乱大交人| 50天的宝宝边吃奶边哭怎么回事| 国产高清激情床上av| 国内精品久久久久久久电影| 999久久久国产精品视频| 亚洲精华国产精华精| 国产成+人综合+亚洲专区| www.999成人在线观看| 午夜成年电影在线免费观看| 国产在线观看jvid| 国产区一区二久久| 亚洲专区中文字幕在线| 麻豆成人午夜福利视频| 精品国产亚洲在线| 男插女下体视频免费在线播放| 少妇熟女aⅴ在线视频| 亚洲国产欧美人成| 国产探花在线观看一区二区| 午夜免费观看网址| 国产精品久久电影中文字幕| 国产又色又爽无遮挡免费看| 狂野欧美激情性xxxx| 好男人电影高清在线观看| 日韩大码丰满熟妇| 国语自产精品视频在线第100页| 欧美日韩亚洲综合一区二区三区_| 久久久久久久久免费视频了| 男人舔女人下体高潮全视频| 色综合欧美亚洲国产小说| av天堂在线播放| 亚洲一卡2卡3卡4卡5卡精品中文| 国产午夜福利久久久久久| 99久久无色码亚洲精品果冻| 国内精品一区二区在线观看| 黄频高清免费视频| 亚洲中文日韩欧美视频| 琪琪午夜伦伦电影理论片6080| xxx96com| 国产av一区二区精品久久| 少妇的丰满在线观看| 久久精品人妻少妇| 香蕉国产在线看| 又紧又爽又黄一区二区| 成人午夜高清在线视频| 在线十欧美十亚洲十日本专区| videosex国产| 亚洲av成人一区二区三| 亚洲av电影在线进入| 午夜精品一区二区三区免费看| av欧美777| 老司机午夜福利在线观看视频| 嫩草影视91久久| 国产熟女午夜一区二区三区| 色哟哟哟哟哟哟| 18禁裸乳无遮挡免费网站照片| 亚洲av五月六月丁香网| 久久精品国产亚洲av高清一级| 欧美日本视频| 最近视频中文字幕2019在线8| 一级毛片女人18水好多| 亚洲熟妇中文字幕五十中出| 久久久久久久久免费视频了| www.999成人在线观看| 欧美大码av| 一区福利在线观看| 欧美国产日韩亚洲一区| 国产蜜桃级精品一区二区三区| 99久久综合精品五月天人人| 国产不卡一卡二| 狂野欧美激情性xxxx| ponron亚洲| 欧美zozozo另类| 啦啦啦观看免费观看视频高清| 老司机福利观看| 久久国产精品影院| 久久久水蜜桃国产精品网| 97超级碰碰碰精品色视频在线观看| 一本大道久久a久久精品| 宅男免费午夜| 亚洲人成伊人成综合网2020| 老司机在亚洲福利影院| 亚洲精品美女久久av网站| 欧美3d第一页| 一区二区三区激情视频| 天天添夜夜摸| 久久人妻av系列| 亚洲成人精品中文字幕电影| 国产午夜福利久久久久久| 亚洲精品国产精品久久久不卡| 中出人妻视频一区二区| 两个人的视频大全免费| 欧美成人性av电影在线观看| 免费观看精品视频网站| 五月伊人婷婷丁香| 亚洲人成电影免费在线| 91大片在线观看| 国产亚洲精品一区二区www| 国产私拍福利视频在线观看| 欧美日韩福利视频一区二区| 亚洲一区中文字幕在线| 91成年电影在线观看| 色尼玛亚洲综合影院| 此物有八面人人有两片| 一个人观看的视频www高清免费观看 | 亚洲美女黄片视频| 男人的好看免费观看在线视频 | 长腿黑丝高跟| 老司机午夜福利在线观看视频| 国产99白浆流出| 啪啪无遮挡十八禁网站| 免费在线观看视频国产中文字幕亚洲| 国产亚洲欧美在线一区二区| 国产av一区在线观看免费| 神马国产精品三级电影在线观看 | 亚洲一区中文字幕在线| 九色成人免费人妻av| 特大巨黑吊av在线直播| 亚洲成人久久性| 欧美成人性av电影在线观看| 精品国产美女av久久久久小说| av片东京热男人的天堂| 日韩中文字幕欧美一区二区| 叶爱在线成人免费视频播放| 人妻丰满熟妇av一区二区三区| 他把我摸到了高潮在线观看| 欧美3d第一页| 91字幕亚洲| 黄片大片在线免费观看| 午夜日韩欧美国产| 亚洲激情在线av| 国产97色在线日韩免费| 在线观看www视频免费| 亚洲欧美一区二区三区黑人| 窝窝影院91人妻| 婷婷六月久久综合丁香| 老司机午夜十八禁免费视频| 日本成人三级电影网站| 午夜亚洲福利在线播放| 高潮久久久久久久久久久不卡| 啦啦啦免费观看视频1| bbb黄色大片| 久久精品91蜜桃| cao死你这个sao货| 国产熟女xx| 长腿黑丝高跟| 99久久99久久久精品蜜桃| 叶爱在线成人免费视频播放| 国产精品一区二区三区四区免费观看 | 国产野战对白在线观看| 精品欧美一区二区三区在线| 丰满的人妻完整版| 一级毛片女人18水好多| 舔av片在线| 亚洲va日本ⅴa欧美va伊人久久| cao死你这个sao货| 欧美三级亚洲精品| 18禁黄网站禁片午夜丰满| 此物有八面人人有两片| 99久久综合精品五月天人人| 久久天堂一区二区三区四区| 窝窝影院91人妻| 久久久精品欧美日韩精品| 两性午夜刺激爽爽歪歪视频在线观看 | 高潮久久久久久久久久久不卡| 变态另类丝袜制服| 国产午夜精品论理片| 欧美成人性av电影在线观看| 国产精品久久久久久久电影 | 国产精品 国内视频| 一边摸一边做爽爽视频免费| 亚洲人成电影免费在线| 国产野战对白在线观看| 国产久久久一区二区三区| 精品国产美女av久久久久小说| 国产成人av激情在线播放| 国产一区二区激情短视频| 韩国av一区二区三区四区| 亚洲精品中文字幕一二三四区| 亚洲精品一卡2卡三卡4卡5卡| 禁无遮挡网站| 久久欧美精品欧美久久欧美| 亚洲av电影不卡..在线观看| 91麻豆精品激情在线观看国产| 精品国产乱子伦一区二区三区| 国产午夜精品久久久久久| 亚洲午夜理论影院| 久久亚洲真实| 日本黄大片高清| 午夜老司机福利片| 巨乳人妻的诱惑在线观看| 在线播放国产精品三级| 麻豆国产97在线/欧美 | av有码第一页| 欧美绝顶高潮抽搐喷水| 丝袜人妻中文字幕| 99久久久亚洲精品蜜臀av| 久久久久性生活片| 欧美在线黄色| 国产精品一区二区免费欧美| 舔av片在线| 亚洲va日本ⅴa欧美va伊人久久| 麻豆av在线久日| 我的老师免费观看完整版| 精品一区二区三区四区五区乱码| 久久精品夜夜夜夜夜久久蜜豆 | 午夜a级毛片| 两个人看的免费小视频| 国产精品自产拍在线观看55亚洲| 亚洲午夜精品一区,二区,三区| 在线观看免费日韩欧美大片| 日韩欧美 国产精品| 欧美色欧美亚洲另类二区| 久久精品夜夜夜夜夜久久蜜豆 | 男人舔女人下体高潮全视频| 精品久久久久久久久久免费视频| 听说在线观看完整版免费高清| 成人国产综合亚洲| 午夜精品久久久久久毛片777| av天堂在线播放| 欧美成人午夜精品| 免费在线观看黄色视频的| 国产在线观看jvid| 国产精品一区二区免费欧美| 欧美性猛交╳xxx乱大交人| 午夜激情av网站| 99在线视频只有这里精品首页| 亚洲精品一区av在线观看| 国产精品 欧美亚洲| АⅤ资源中文在线天堂| 无限看片的www在线观看| 久久精品成人免费网站| 波多野结衣高清无吗| xxxwww97欧美| 久久精品国产亚洲av香蕉五月| 亚洲,欧美精品.| 校园春色视频在线观看| 少妇人妻一区二区三区视频| 99久久精品国产亚洲精品| 97碰自拍视频| 国产成人av教育| 国内少妇人妻偷人精品xxx网站 | 亚洲av熟女| 又黄又爽又免费观看的视频| 日本a在线网址| 老司机深夜福利视频在线观看| 我要搜黄色片| 亚洲专区字幕在线| 国产伦人伦偷精品视频| 一本大道久久a久久精品| 黄频高清免费视频| 亚洲va日本ⅴa欧美va伊人久久| 91av网站免费观看| 国产精品乱码一区二三区的特点| 亚洲七黄色美女视频| 欧美成人午夜精品| 桃色一区二区三区在线观看| 国产私拍福利视频在线观看| 看黄色毛片网站| 99久久无色码亚洲精品果冻| 一区二区三区高清视频在线| 人妻久久中文字幕网| 波多野结衣高清作品| 欧美绝顶高潮抽搐喷水| 精品欧美国产一区二区三| 成人三级黄色视频| 人妻丰满熟妇av一区二区三区| 国产黄色小视频在线观看| 动漫黄色视频在线观看| 国产单亲对白刺激| 长腿黑丝高跟| 婷婷亚洲欧美| 亚洲人与动物交配视频| 97人妻精品一区二区三区麻豆| 成人三级做爰电影| 色综合亚洲欧美另类图片| 波多野结衣巨乳人妻| 人成视频在线观看免费观看| 久热爱精品视频在线9| 黄片大片在线免费观看| 成人国产一区最新在线观看| 国产精品 欧美亚洲| 91成年电影在线观看| 三级男女做爰猛烈吃奶摸视频| 黄色片一级片一级黄色片| 99久久精品热视频| 国产亚洲精品av在线| 十八禁人妻一区二区| 国产野战对白在线观看| 亚洲av成人精品一区久久| 男女之事视频高清在线观看| 12—13女人毛片做爰片一| 校园春色视频在线观看| 欧美日韩中文字幕国产精品一区二区三区| 欧美日韩精品网址| 久久久久性生活片| 欧美黄色片欧美黄色片| 欧美日韩国产亚洲二区| 亚洲欧美日韩高清专用| 国产精品香港三级国产av潘金莲| 国产激情偷乱视频一区二区| 在线观看午夜福利视频| 色在线成人网| 成人一区二区视频在线观看| 欧美黑人巨大hd| 久久久久亚洲av毛片大全| 精品第一国产精品| 日日干狠狠操夜夜爽| 午夜福利高清视频| 伦理电影免费视频| 91av网站免费观看| 99久久久亚洲精品蜜臀av| 法律面前人人平等表现在哪些方面| 欧美一区二区国产精品久久精品 | 久久国产乱子伦精品免费另类| 午夜精品一区二区三区免费看| 最近最新中文字幕大全免费视频| 国产精品综合久久久久久久免费| 欧美中文综合在线视频| 极品教师在线免费播放| 国产一区二区三区视频了| 亚洲男人的天堂狠狠| 一个人免费在线观看的高清视频| 日韩中文字幕欧美一区二区| 中出人妻视频一区二区| 琪琪午夜伦伦电影理论片6080| 又紧又爽又黄一区二区| www国产在线视频色| 国产午夜精品久久久久久| av福利片在线观看| 性欧美人与动物交配| 久久精品影院6| 欧美日韩精品网址| 97超级碰碰碰精品色视频在线观看| 天堂动漫精品| 欧美精品亚洲一区二区| 亚洲免费av在线视频| 国产高清视频在线观看网站| 久久精品亚洲精品国产色婷小说| 午夜精品在线福利| 久久亚洲精品不卡| 国产亚洲精品综合一区在线观看 | 悠悠久久av| 亚洲国产精品久久男人天堂| 90打野战视频偷拍视频|