• <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 ?

    Research on active arc-ignition technology as a possible residual-energy-release strategy in electromagnetic rail launch

    2021-08-05 08:29:58XiyuanCAI蔡喜元SaiTAN譚賽JunyongLU魯軍勇XiaoZHANG張曉andYunGUO郭赟
    Plasma Science and Technology 2021年8期
    關(guān)鍵詞:張曉

    Xiyuan CAI (蔡喜元), Sai TAN (譚賽), Junyong LU (魯軍勇),Xiao ZHANG (張曉) and Yun GUO (郭赟)

    National Key Laboratory of Science and Technology on Vessel Integrated Power System,Naval University of Engineering, Wuhan 430033, People’s Republic of China

    Abstract In order to solve the problem of the original residual energy release strategy being unsuitable for high-energy and fast-firing electromagnetic rail launch, this work has explored the applicability of active arc-ignition technology(AAT).The results obtained from the comparison of launching experiments show that AAT has no influence on the acceleration of the armature and is capable of quickly releasing the residual energy.Based on the theory of magnetohydrodynamics, this work has also made numerical simulation of the muzzle arc, analyzed the influence of AAT on the muzzle arc flow field, electromagnetic (EM) field and temperature field, and evaluated the performance of AAT according to the projectile initial disturbance, the EM impact on guidance devices and the rail ablation.The results show that AAT is now one of the most practicable strategies for residual energy release.

    Keywords: muzzle arc, initial disturbance, guidance device, arc ablation, backflow

    1.Introduction

    During the electromagnetic rail launch (EMRL), the energy remaining in the launch system is more than a quarter or even a half of the exit kinetic energy after the armature leaves the bore[1], and it needs to be released.However, the energy level of EMRL is continuously increased to 32 MJ, even 64 MJ, and the speed of continuous firing is up to six shots per minute[2,3].How does one release the residual energy but not affect the launch safety? Firing accuracy and service life of the launcher is one of the key points in the design of high energy level and fast firing rate electromagnetic (EM) rail launchers.

    The main criteria for judging whether a residual energy release strategy is good or not are as follows: (1) the release speed of residual energy; (2) the impact of residual energy release on the acceleration of the projectile in the chamber;(3)the impact on the initial disturbance of the projectile; (4) the electromagnetic impact on the guidance devices; and(5) the ablation of the rails.

    At present, one of the strategies for releasing residual energy is the arc suppression technology [4–7].When the projectile is accelerated in bore, the arc suppression impedance has a shunt effect on the rail current [7], thus reducing the driving force of the projectile.Because of the high energy Joule heat, the arc suppression device must meet the high requirements for temperature resistance and recovery ability.Another strategy is the passive arc-ignition technology [8].This method does not affect the acceleration of the projectile due to the fact that the arc can quickly release a large amount of residual energy and the air medium has strong capacity of recovery, but it has a seriously ablative effect on the rails,thereby affecting the service life of the launcher.The above strategies are not suitable for high-energy and fast continuous-firing EM rail launchers.

    Figure 1.Schematic diagram of the launcher and the AID.

    Active arc-ignition technology (AAT) is a new one for residual energy release.The arc-ignition device (AID) connected in parallel with the rails at the muzzle end releases the residual energy in the form of arc.The metal vapor generated by friction and wear of the aluminum armature in the bore enters the arcing gap and reduces the breakdown strength.Shortly after the armature leaves the bore, the muzzle overvoltage breaks through the gap between the arcing contacts,so that the arc between the armature and the rails will rapidly transfer to the AID.AAT is not used for suppressing the arc—a medium for rapid energy release,but for introducing it into the low-cost and replaceable AID.

    The influence of AAT on the rate of residual energy release and the acceleration of the projectile remains to be examined.What is worth noting is that the influence of AAT on the initial disturbance of the projectile mainly depends on the distribution of the pressure and the velocity of the muzzle arc, the electromagnetic impact caused by AAT on guidance device is determined by the distribution of the EM field, and the ablation caused by AAT to the trajectory is related to the temperature and airflow velocity.Therefore,it is necessary to study the influence of AAT on the launching process as well as the flow field, EM field and temperature field of the muzzle arc.

    In EMRL experiment, the observation of muzzle arc tends to be affected by the radiation of thermal plasma,especially the characteristics of arc flow field are difficult to obtain.Weimeret al[9] used an EM rail launcher with an emission energy level of 12 MJ and a peak current of 1.5 MA as an object of experiment.It is found that a stream of highintensity light, smoke, flame front and luminescent particles flows from the muzzle back to the chamber,with the backflow temperature in the range of 2400–4000 K, and the alkali metals, AlO and CuO existing in the gas.

    The increase of the computing capability by computer leads to the continuous progress in the numerical simulation of arc plasma.Using the magnetohydrodynamics (MHD)model of arc, it is possible to give a good description of the characteristics of the distribution of arc temperature field,EM field and flow field [10].Gaoet al[11] conducted a simulation study on the muzzle arc, but the muzzle arc root in their model only exists between the rails, and the current is only about 200 A, which is much lower than the magnitude of current 100 kA of the EMRL when AAT is adopted.This case is quite different from the muzzle arc produced in the use of AAT.The muzzle arc behavior needs to be further studied.

    This paper has described the current characteristics of the EM rail launcher in experiment when AAT is adopted and not, investigated the influence of AAT on the release rate of residual energy and the acceleration of the projectile and simulated the muzzle arc.According to the characteristics of muzzle arc, an MHD model has been established, and the finite volume method is adopted for solution.The model can be used to analyze the flow field, EM field and temperature field of the muzzle arc, and to evaluate the influence of AAT on the initial disturbance of the projectile, the EM impact of the guidance device and the rail ablation.

    2.Experiment

    An EM rail launcher with the caliber of 30 mm×30 mm and an AID,as shown in figure 1,has been designed.The AID is mainly composed of two pairs of arcing contacts and two copper connection boards, and the arcing contacts are connected with the rails via the connection board.After the armature leaves the bore, the current will be transferred from the rails to the arcing contacts, and the arc between the armature and the rails will be switched to the arcing gap.Two groups of comparative launching experiments are carried out respectively with and without the AID.Rogowski coils are used to measure the currents of the breech and the arcing contacts.

    Figure 2 shows the currents of the breech, the AID and the armature during the launching.It can be seen that the breech current is the same when the AID is used or not.The discharge characteristics of the power supply are not affected.Before the armature leaves the bore,there is no current in the device.Attout, the total current in the device rapidly rises from zero to the magnitude of the breech current.Aftertout,both the currents are basically the same.This shows that(1)in the acceleration process of the armature,the AID which is in a dormant state, does not affect the driving force of the armature; (2) at the moment of the armature leaving the bore, the device is quickly activated and receives all the current in the rail to ensure the safe disconnection between the armature and the rails;and(3)after the armature comes out of the bore,the device continues to work to finish releasing the residual energy in a short time.

    Figure 2.Current curves in experiment.

    3.Calculation model

    3.1.Hypotheses

    As the physical and chemical processes in the muzzle arc of an EM rail launcher are too complex for simulation calculation, it is necessary to simplify the physical process by introducing some reasonable hypotheses.The specific hypotheses are as follows:

    ? The arc plasma is considered to be in the local thermodynamic equilibrium (LTE) state.

    ? Ignoring the interaction between the arc and the electrode as well as the electrode sheath,considering the air area at the muzzle as the calculation domain.

    3.2.Governing equations

    MHD basic equations include mass conservation,momentum conservation,energy conservation,electric field and magnetic field equations.All these equations are unified in the steady form of the Patankar equation:

    where Φ is the variable to be solved,ΓΦis the diffusion term,andSΦis the source term.The variables and parameters of the MHD equations are listed in table 1.Among them,P,Hand V are respectively the plasma pressure, specific enthalpy and velocity vector;u,vandware the velocity components inx,yandzdirections, respectively;Ax,AyandAzare the magnetic vector potential components;Jx,JyandJzare the current density components;Bx,By,Bzare the magnetic field strength components; ρ,Cp, λ, μ and σ are respectively the plasma density, specific heat at constant pressure, thermal conductivity and viscosity;kbis Boltzmann constant,eis the electron charge, μ0is the permeability;qradis the radiation source term, which is related to the radiation model.

    The net emission coefficient εNis used to describe the radiation heat loss of plasma per unit volume, which is regarded as the source term of energy conservation equation,namely

    The realizablek-ε model is used to describe the turbulent flow state of muzzle arc.The related parameters and expressions can be obtained from [12] and [13].

    The temperature and the pressure near the wall are the highest and the gradient is large.Therefore,the enhanced wall function method is used for treatment.

    3.3.Geometry and mesh

    The geometry and calculation domain is shown in figure 3.According to the symmetry, a quarter of the air area is taken for the calculation model, in which the in-bore length is 1000 mm,and the radius and length of the air area outside the bore are both 1000 mm.The bolts are neglected.The cuboid is the arcing contact and L-type geometry is half of the armature.According to the features of the geometrical model,the computational domain is divided by the multi-block structural mesh.In order to increase the convergence of the calculation model and the calculation accuracy, the core area is super-refined.According to the requirements of the selected turbulence model and the adjacent-wall method on they+value, repeated trial calculations as well as grid adjustment are conducted and finally they+ value is about 1.They+value is within five,near the insulator wall in the breech end.Considering that the Reynolds number is small and far away from the muzzle end in this place,they+value is considered to be acceptable.The grids with the quality of 0.85–0.90 and 0.90–0.95 account for 0.032% and 6.379% respectively, and the quality of the other grids is above 0.95.The orthogonality of the mesh is greater than 36 degrees,and finally the number of grids is up to 10 million.

    3.4.Plasma properties

    The aluminum vapor tends to affect the physical properties of plasma medium in the AID.In this paper, the proportion of aluminum and air in the muzzle arc medium are assumed to be 10% and 90%, respectively.Murphy and others [14–19]offered the data,such as thermodynamic properties,transport coefficients and net emission coefficients of Al-air plasma,in the temperature range of 300–50000 K and in the pressure range of 0.01–20 MPa.Plasma properties are related to temperature and pressure.The binary three-point interpolation is adopted to obtain the physical parameters of plasma under the condition of specific temperature and pressure.

    Table 1.MHD basic equations.

    Figure 3.Calculation domain.

    3.5.Boundary conditions

    Simonyan’s and Kats’studies[20]show that,under the action of plasma, the maximum temperature on the surface of the electrode is close to the boiling point of electrode material.Based on that, the surface temperature of the rail, armature and arcing contact is set as the corresponding material boiling point (2500 K).In experiment, the insulation material was found to be hardly ablated, so it could be treated as the adiabatic wall [21].The outlet pressure is 101.325 kPa and the temperature is 300 K.

    After the armature leaves the bore,the arcing contacts on the single side each share half of the rail current.The current is distributed on the interface between the arcing contact and the arcing gap.The current is distributed parabolically.The potential of the armature surface is set to be zero.The potential and magnetic vector components of the outlet are zero,and the magnetic field on the wall is calculated by Biot–Savart law.

    4.Results and analysis

    The equations mentioned above are solved by the adapted commercial code Fluent, which is based on the finite volume method.For convenience, the forward direction of the armature is defined as thexaxis, and the launcher end is the plane ofx=0.The horizontal direction is set asyaxis, and the symmetry of left and right is the plane ofy=0.The vertical direction is the forward direction of thezaxis.

    Figure 4.Airflow rate distribution of the muzzle area.

    4.1.Flow field distribution

    Figure 4 shows the flow rate distribution at the muzzle area with and without AAT.When AAT is not adopted, the airflow outside the chamber rushes to the end of the rails and dashes upon the wall,thereby forming a complex turbulence.A part of airflow is emitted in the forward direction of the armature, and another part flows back to the inner chamber.The high-velocity region of the muzzle arc plasma is near the end of the rails, and the velocity is up to 8400 m s?1.When AAT is adopted, the airflow above the arc contacts will flow to the arcing gap.It will emit after it is offset in the arcing gap and the airflow moving to the plane ofy=0 will flow out along the vertical center of the launcher.The high velocity region of the muzzle arc plasma is in the arcing gap, and its magnitude will decrease to 5700 m s?1.The velocity of the airflow near the armature and rail end will drop down to 300 m s?1.

    Figure 5 shows the distribution of pressure in the muzzle area with and without AAT.When AAT is not used, the maximum pressure is 282 kPa and the pressure difference is 214 kPa,which appear near the muzzle end of the rails.When AAT is adopted,the maximum pressure and pressure gradient in the muzzle area will be shown in the arcing gap.The maximum pressure is 245 kPa and the pressure difference is 161 kPa.Furthermore, the pressure at the armature and rail end is uniform, being very close to the atmosphere.

    Airflow is the main reason that the initial disturbance of the projectile is affected by the muzzle arc.The use of AAT can lead to a decrease in the airflow velocity, turbulence,pressure and pressure difference in the muzzle area,especially around the armature, which will be beneficial to the stability of the projectile and reduce its initial disturbance, thereby improving the firing accuracy.

    4.2.EM field distribution

    Figures 6 and 7 show the distributions of EM field with and without AAT.When AAT is not applied,the EM field of the muzzle arc is mainly concentrated near the armature and rail end,with the peak current density up to 300 MA m?2and the magnitude of the magnetic field up to 0.67 T.When AAT is used,the muzzle arc is transferred to the AID.The maximum current density of the arcing gap is 230 MA m?2and the peak magnetic field is 0.41 T.The current near the armature is greatly reduced to about 0.2 MA m?2, and the magnetic field drops down to about 0.03 T.

    Figure 5.Pressure distribution of the muzzle area.

    Figure 6.Current distribution of the muzzle area.

    Figure 7.Magnetic distribution of the muzzle area.

    The AID has the ability to shunt the current, transfer the muzzle arc.When AAT is not adopted, the current flows directly from one rail to the other, and the current is more concentrated.But if it is applied, each of the two pairs of arcing contacts will share only a half of the residual current.As a result, the arc current on the single side will be greatly reduced.In addition, the arcing contacts are distributed on both sides of the rail,so the muzzle arc is enlarged.The AID expands the muzzle arc from two aspects of current and space,and reduces the EM field in the muzzle area,especially near the armature.Therefore, the application of AAT can reduce the EM impact on the internal guidance device of the projectile to prevent it from losing its vitality.

    4.3.Temperature distribution

    Figure 8 shows the distribution of temperature in the muzzle area with and without AAT.When AAT is not used, the muzzle arc concentrates between the armature and the rails,with less expansion in the direction perpendicular to the armature movement.In the direction of the armature movement, the muzzle arc covers the armature when expanding forward and forms a backflow in the bore when expanding backwards, with its maximum temperature being 28000 K.When AAT is applied, the muzzle arc is concentrated in the arcing gap.Its maximum temperature is 25000 K, while the temperature of the backflow at the end of the rails and in the chamber is greatly reduced to 6000 K or so.

    The application of AAT can alleviate the ablation of the rails in the muzzle end.When subjected to the high-temperature arc plasma, the rail surface will undergo evaporation erosion and droplet splashing, which lead to a loss of materials.Because of the arc transfer of the AID,the arc column is shifted from between the rails to the arcing gap.Besides, the shunting effect of the AID can reduce the current and the temperature of single-sided arc, so the heat flux to the rail surface will be greatly reduced.According to the analysis in section 4.1, the adoption of AAT makes it possible to reduce the airflow velocity around the rails,and to weaken the impact of the thermal flow on the rail surface as well.Thus, the alleviation of the rail ablation will help prolong the service life of the device.

    5.Conclusions

    Because the original strategy of residual energy release is not suitable for high-energy and rapid EMRL, this paper proposed a new approach named AAT and investigated its performance.Through experiments and numerical calculations,AAT is proved to be applicable for dealing with the residual energy release, the acceleration of the armature, the initial disturbance of the projectile, the EM impact on the guidance devices, and the ablation of rail materials.

    Figure 8.Temperature distribution of the muzzle area.

    AAT has the following characteristics: when the armature accelerates in the bore, AID is in a dormant state; when the armature leaves the bore, the device quickly transfers the current, without affecting the power discharge and the armature acceleration.What is more, the residual energy can be released shortly after the armature leaves the bore.

    AAT has the ability to transfer the muzzle arc.It reduces the airflow velocity and pressure in the area around the rail end and armature, distributes the pressure more uniformly,weakens the EM field,and decreases the temperature greatly.As a result,it is possible to decrease the initial disturbance of the projectile,weaken the EM impact on the guidance device inside the projectile and alleviate the rail ablation, thereby improving the performance and firing accuracy of the launcher and prolonging the service life of the rail.In short,AAT is now one of the most practicable strategies of releasing the residual energy for high-energy, and rapid EMRL.

    Acknowledgments

    This work was supported in part by National Natural Science Foundation of China (Nos.51522706, 51877214 and 51607187) and in part by the National Basic Research Program of China (973 Program) (No.613262).

    猜你喜歡
    張曉
    Photothermal-chemical synthesis of P–S–H ternary hydride at high pressures
    Synthesis of ternary compound in H–S–Se system at high pressures?
    Investigation of electronic,elastic,and optical properties of topological electride Ca3Pb via first-principles calculations*
    Dielectric breakdown properties of Al-air mixtures
    “你可以逼我代孕,那為什么我不能借精生子?”
    Quaternary antiferromagnetic Ba2BiFeS5 with isolated FeS4 tetrahedra
    煮餃子
    春雨
    THE BEACH PARADOX
    考霸
    一卡2卡三卡四卡精品乱码亚洲| 亚洲性久久影院| 免费看光身美女| h日本视频在线播放| 村上凉子中文字幕在线| 国产精品日韩av在线免费观看| 一区二区三区四区激情视频 | 日韩国内少妇激情av| 22中文网久久字幕| 亚洲欧洲日产国产| 国产精品嫩草影院av在线观看| 99久久人妻综合| 少妇熟女aⅴ在线视频| 国产极品天堂在线| 欧美一区二区国产精品久久精品| 51国产日韩欧美| 天堂影院成人在线观看| av天堂中文字幕网| 国产精品国产三级国产av玫瑰| 亚洲精品影视一区二区三区av| 日本撒尿小便嘘嘘汇集6| 亚洲丝袜综合中文字幕| 91午夜精品亚洲一区二区三区| 久久婷婷人人爽人人干人人爱| 五月玫瑰六月丁香| 国内揄拍国产精品人妻在线| 黄片无遮挡物在线观看| 国产极品天堂在线| 美女大奶头视频| 亚洲精品亚洲一区二区| 91久久精品国产一区二区成人| 久久6这里有精品| 99久久无色码亚洲精品果冻| 卡戴珊不雅视频在线播放| 嫩草影院新地址| 亚洲av熟女| 亚洲va在线va天堂va国产| 午夜激情欧美在线| 久久99热6这里只有精品| 午夜精品国产一区二区电影 | 国产色婷婷99| 亚洲精品乱码久久久久久按摩| 国产黄a三级三级三级人| 在现免费观看毛片| 精品久久久久久久人妻蜜臀av| 国产精品一区二区性色av| 一本—道久久a久久精品蜜桃钙片 精品乱码久久久久久99久播 | 国产午夜精品一二区理论片| 国产精品一区二区性色av| 国产高清视频在线观看网站| 禁无遮挡网站| 插阴视频在线观看视频| 在现免费观看毛片| 国产91av在线免费观看| 18+在线观看网站| ponron亚洲| 国产国拍精品亚洲av在线观看| 精品一区二区三区视频在线| 欧美高清成人免费视频www| 男女啪啪激烈高潮av片| 校园人妻丝袜中文字幕| 亚洲国产精品国产精品| 悠悠久久av| 天堂√8在线中文| 国产精华一区二区三区| 黄色欧美视频在线观看| 国产免费一级a男人的天堂| 午夜a级毛片| 亚洲欧美日韩卡通动漫| 亚洲国产精品久久男人天堂| 不卡一级毛片| 久久久精品94久久精品| 一本一本综合久久| 国产亚洲精品av在线| 中文字幕av成人在线电影| 麻豆国产97在线/欧美| 成人av在线播放网站| 黄色欧美视频在线观看| 村上凉子中文字幕在线| 亚洲av熟女| 国产久久久一区二区三区| 国产白丝娇喘喷水9色精品| 久久精品国产亚洲av香蕉五月| 亚洲欧美日韩卡通动漫| 亚洲久久久久久中文字幕| 不卡视频在线观看欧美| 日韩欧美精品v在线| 国产av不卡久久| 欧美激情在线99| 日韩av在线大香蕉| 久久久色成人| 久久国内精品自在自线图片| 男女啪啪激烈高潮av片| 亚洲av中文av极速乱| 免费电影在线观看免费观看| 成人漫画全彩无遮挡| 色播亚洲综合网| 非洲黑人性xxxx精品又粗又长| 熟女人妻精品中文字幕| 色尼玛亚洲综合影院| 青春草视频在线免费观看| 国产成人一区二区在线| 久久久久久久久久成人| 欧美日韩综合久久久久久| 美女脱内裤让男人舔精品视频 | 日韩三级伦理在线观看| 亚洲国产欧美人成| videossex国产| 少妇人妻精品综合一区二区 | 欧美日韩综合久久久久久| 国产av在哪里看| 听说在线观看完整版免费高清| 中出人妻视频一区二区| 亚洲成人av在线免费| 国产精品国产三级国产av玫瑰| 在现免费观看毛片| 特级一级黄色大片| 国产高清激情床上av| 美女cb高潮喷水在线观看| 国产成人精品一,二区 | 特大巨黑吊av在线直播| 成年女人看的毛片在线观看| 国产精品日韩av在线免费观看| 成年免费大片在线观看| 免费av不卡在线播放| 久久中文看片网| 亚洲最大成人手机在线| 亚洲欧美成人精品一区二区| 18禁黄网站禁片免费观看直播| 日日摸夜夜添夜夜爱| 亚洲不卡免费看| 免费观看在线日韩| 黄色视频,在线免费观看| 国产精品久久久久久久久免| 欧美不卡视频在线免费观看| 哪里可以看免费的av片| 亚洲欧美精品综合久久99| 国产精品一区二区在线观看99 | 国产精品久久久久久久电影| 久久精品综合一区二区三区| 成熟少妇高潮喷水视频| 欧美最新免费一区二区三区| 欧美bdsm另类| 日本免费a在线| 国产精品国产三级国产av玫瑰| 国产伦精品一区二区三区视频9| 麻豆国产97在线/欧美| 禁无遮挡网站| 国产一区二区三区av在线 | 国产亚洲av嫩草精品影院| 久久人人爽人人片av| 久久久久久久亚洲中文字幕| 欧美最新免费一区二区三区| 精品久久久久久久久亚洲| 国产精品爽爽va在线观看网站| 最近手机中文字幕大全| 国产中年淑女户外野战色| 又爽又黄a免费视频| 久久亚洲国产成人精品v| 国产精品.久久久| 边亲边吃奶的免费视频| 久久久成人免费电影| 亚洲最大成人av| av卡一久久| 免费在线观看成人毛片| 日韩欧美国产在线观看| 天天一区二区日本电影三级| av在线亚洲专区| 精华霜和精华液先用哪个| 男女做爰动态图高潮gif福利片| 嫩草影院新地址| 又爽又黄a免费视频| 午夜福利高清视频| 亚洲精品影视一区二区三区av| 99热精品在线国产| 激情 狠狠 欧美| 热99re8久久精品国产| 人妻制服诱惑在线中文字幕| 国产成人精品婷婷| 蜜桃亚洲精品一区二区三区| 成人毛片60女人毛片免费| 免费观看人在逋| 国产精品永久免费网站| 日产精品乱码卡一卡2卡三| 亚洲aⅴ乱码一区二区在线播放| 最近最新中文字幕大全电影3| 天天躁夜夜躁狠狠久久av| 超碰av人人做人人爽久久| 久久久国产成人免费| 成人一区二区视频在线观看| av在线蜜桃| 爱豆传媒免费全集在线观看| 两个人的视频大全免费| 亚洲无线观看免费| 欧美日韩一区二区视频在线观看视频在线 | 亚洲四区av| 亚洲国产精品久久男人天堂| 精品国内亚洲2022精品成人| 免费无遮挡裸体视频| 欧美区成人在线视频| 国产 一区精品| av女优亚洲男人天堂| 日韩av在线大香蕉| 国产单亲对白刺激| 三级经典国产精品| eeuss影院久久| 国产精品一区二区三区四区久久| 美女cb高潮喷水在线观看| 天堂影院成人在线观看| 成人欧美大片| 青春草视频在线免费观看| 国产伦一二天堂av在线观看| 亚洲无线观看免费| 三级国产精品欧美在线观看| 国产一区二区三区在线臀色熟女| 韩国av在线不卡| 日韩一区二区视频免费看| 成人亚洲欧美一区二区av| 小蜜桃在线观看免费完整版高清| 中文资源天堂在线| 精品不卡国产一区二区三区| 只有这里有精品99| 亚州av有码| а√天堂www在线а√下载| 免费看av在线观看网站| 久久久久国产网址| 亚州av有码| 国产单亲对白刺激| 亚洲精品亚洲一区二区| 天天躁日日操中文字幕| 久久这里有精品视频免费| 久久人人精品亚洲av| 国产一区二区在线av高清观看| 国产精品久久久久久久久免| 国产乱人视频| 亚洲精品国产av成人精品| 日韩在线高清观看一区二区三区| 国产精品,欧美在线| 国产精品一二三区在线看| 夜夜看夜夜爽夜夜摸| 免费观看人在逋| 成人综合一区亚洲| 男女做爰动态图高潮gif福利片| 三级毛片av免费| .国产精品久久| 欧美一区二区国产精品久久精品| 亚洲在线观看片| 91av网一区二区| 亚洲国产精品成人久久小说 | or卡值多少钱| 国产精品电影一区二区三区| 最近视频中文字幕2019在线8| 天天躁日日操中文字幕| 久久韩国三级中文字幕| 高清日韩中文字幕在线| 最近手机中文字幕大全| 如何舔出高潮| 伦理电影大哥的女人| 麻豆久久精品国产亚洲av| 久久久久性生活片| 十八禁国产超污无遮挡网站| 婷婷亚洲欧美| 亚洲欧洲国产日韩| 亚洲av一区综合| 久久久国产成人免费| 欧美色欧美亚洲另类二区| 欧美最黄视频在线播放免费| 国产又黄又爽又无遮挡在线| 我的老师免费观看完整版| 99在线人妻在线中文字幕| 日本一二三区视频观看| 直男gayav资源| 亚洲人成网站在线播放欧美日韩| 深夜精品福利| 久久久久网色| 免费人成在线观看视频色| 日本黄色视频三级网站网址| 国产精品日韩av在线免费观看| 99热这里只有是精品在线观看| 国产免费男女视频| 日韩精品青青久久久久久| 国产高清视频在线观看网站| 国产亚洲精品久久久com| 欧美高清成人免费视频www| 草草在线视频免费看| 久久午夜亚洲精品久久| 麻豆成人av视频| 亚洲精品成人久久久久久| a级毛片a级免费在线| 午夜亚洲福利在线播放| 亚洲国产色片| 99热这里只有是精品50| 国产精品久久久久久久电影| av免费在线看不卡| 一本久久中文字幕| 啦啦啦观看免费观看视频高清| 人妻夜夜爽99麻豆av| 免费不卡的大黄色大毛片视频在线观看 | 亚洲av一区综合| 国产日本99.免费观看| 国产精品人妻久久久久久| 此物有八面人人有两片| 黄色视频,在线免费观看| 在线播放国产精品三级| 欧美变态另类bdsm刘玥| 国产精品免费一区二区三区在线| 亚洲第一电影网av| 中文欧美无线码| 能在线免费观看的黄片| 日本黄大片高清| 18禁在线无遮挡免费观看视频| 欧美人与善性xxx| 亚洲欧洲日产国产| 青春草视频在线免费观看| 丰满的人妻完整版| 内地一区二区视频在线| 最新中文字幕久久久久| 99久国产av精品| 国产三级在线视频| 能在线免费观看的黄片| 大型黄色视频在线免费观看| 一本精品99久久精品77| 此物有八面人人有两片| 国产一区二区激情短视频| 99久国产av精品| 日本五十路高清| 国内精品宾馆在线| 九九在线视频观看精品| 97热精品久久久久久| 99久久九九国产精品国产免费| 我要搜黄色片| 免费看光身美女| 亚洲av一区综合| 亚洲国产日韩欧美精品在线观看| 久久久精品94久久精品| 99久久精品一区二区三区| 91久久精品电影网| 成人国产麻豆网| 久久精品国产99精品国产亚洲性色| 人妻夜夜爽99麻豆av| 午夜精品在线福利| 身体一侧抽搐| 亚洲av免费高清在线观看| 在线观看免费视频日本深夜| 好男人视频免费观看在线| 久久久久久久久久久免费av| 亚洲婷婷狠狠爱综合网| 婷婷亚洲欧美| av卡一久久| 国产真实伦视频高清在线观看| 在线观看午夜福利视频| 国产精品久久久久久久电影| 禁无遮挡网站| 我的老师免费观看完整版| 插阴视频在线观看视频| 中文亚洲av片在线观看爽| 亚洲精品影视一区二区三区av| 九草在线视频观看| 亚洲国产精品成人综合色| 亚洲,欧美,日韩| 欧美一区二区亚洲| 久久亚洲国产成人精品v| 久久久久久大精品| 国产精品不卡视频一区二区| 偷拍熟女少妇极品色| 欧美高清成人免费视频www| 丰满乱子伦码专区| 日韩成人伦理影院| 一级二级三级毛片免费看| 在线国产一区二区在线| av在线天堂中文字幕| 看黄色毛片网站| 国产亚洲91精品色在线| 小蜜桃在线观看免费完整版高清| 精品人妻一区二区三区麻豆| 亚洲美女视频黄频| 亚洲国产精品久久男人天堂| 高清日韩中文字幕在线| 成人综合一区亚洲| 色综合站精品国产| 中文资源天堂在线| 久久综合国产亚洲精品| 不卡视频在线观看欧美| 色播亚洲综合网| 婷婷亚洲欧美| 一本久久精品| ponron亚洲| 午夜激情福利司机影院| 国产极品天堂在线| 秋霞在线观看毛片| 亚洲真实伦在线观看| 欧美色视频一区免费| 天堂网av新在线| 在线免费观看的www视频| 十八禁国产超污无遮挡网站| 波多野结衣高清作品| 黄色欧美视频在线观看| 九九热线精品视视频播放| 少妇的逼水好多| 亚洲天堂国产精品一区在线| 国产成人精品婷婷| 午夜视频国产福利| 免费看美女性在线毛片视频| 看免费成人av毛片| 卡戴珊不雅视频在线播放| av福利片在线观看| 欧美性猛交╳xxx乱大交人| 99热这里只有是精品50| 26uuu在线亚洲综合色| 日韩三级伦理在线观看| 最近的中文字幕免费完整| 欧美最新免费一区二区三区| 成人漫画全彩无遮挡| 大又大粗又爽又黄少妇毛片口| 日本色播在线视频| 熟女人妻精品中文字幕| 欧美三级亚洲精品| 亚洲国产精品成人综合色| 色尼玛亚洲综合影院| 你懂的网址亚洲精品在线观看 | 亚洲一级一片aⅴ在线观看| 婷婷色av中文字幕| 久久热精品热| 男人的好看免费观看在线视频| 尾随美女入室| 变态另类丝袜制服| 亚洲天堂国产精品一区在线| 只有这里有精品99| 久久久国产成人免费| 亚洲av二区三区四区| 成人漫画全彩无遮挡| 联通29元200g的流量卡| 国产私拍福利视频在线观看| 国产v大片淫在线免费观看| 国产极品天堂在线| 亚洲欧美中文字幕日韩二区| www.av在线官网国产| 黄色视频,在线免费观看| 一个人看视频在线观看www免费| 一个人免费在线观看电影| 国产精品乱码一区二三区的特点| 亚洲高清免费不卡视频| 12—13女人毛片做爰片一| 人妻系列 视频| 97人妻精品一区二区三区麻豆| 色尼玛亚洲综合影院| 亚洲国产欧美在线一区| 天堂av国产一区二区熟女人妻| 欧美精品一区二区大全| 亚洲欧洲日产国产| 中文资源天堂在线| 夜夜爽天天搞| 亚洲中文字幕日韩| av女优亚洲男人天堂| 亚洲真实伦在线观看| .国产精品久久| 欧美一区二区亚洲| 亚洲色图av天堂| 禁无遮挡网站| 日韩精品青青久久久久久| 免费看av在线观看网站| 亚洲综合色惰| 大又大粗又爽又黄少妇毛片口| 最近视频中文字幕2019在线8| 亚洲国产精品合色在线| 午夜福利在线观看吧| 寂寞人妻少妇视频99o| 国产乱人偷精品视频| 看非洲黑人一级黄片| 午夜久久久久精精品| 国产国拍精品亚洲av在线观看| 免费av观看视频| 亚洲av熟女| 国产精品久久久久久久电影| 午夜激情欧美在线| 成人国产麻豆网| 久久久a久久爽久久v久久| 国产一区二区亚洲精品在线观看| 看免费成人av毛片| 久久久久九九精品影院| 国产精品久久久久久亚洲av鲁大| 国产精品久久电影中文字幕| 亚洲自偷自拍三级| 久久亚洲国产成人精品v| 天天躁日日操中文字幕| 亚洲中文字幕一区二区三区有码在线看| 最近2019中文字幕mv第一页| 3wmmmm亚洲av在线观看| 丝袜喷水一区| 亚州av有码| 国产亚洲av片在线观看秒播厂 | 国产成人a∨麻豆精品| 黄色一级大片看看| 深爱激情五月婷婷| a级一级毛片免费在线观看| 五月伊人婷婷丁香| 春色校园在线视频观看| eeuss影院久久| 亚州av有码| 乱码一卡2卡4卡精品| 少妇被粗大猛烈的视频| 嘟嘟电影网在线观看| 免费看a级黄色片| 一级黄片播放器| 久久久久久九九精品二区国产| 亚洲欧美中文字幕日韩二区| 麻豆久久精品国产亚洲av| 亚洲av免费高清在线观看| 精品一区二区三区人妻视频| 日本一二三区视频观看| 国产熟女欧美一区二区| 一边摸一边抽搐一进一小说| 一级黄色大片毛片| 国模一区二区三区四区视频| 欧美区成人在线视频| 亚洲精品久久国产高清桃花| 小说图片视频综合网站| 国模一区二区三区四区视频| 国产高清不卡午夜福利| 免费观看的影片在线观看| 在线观看av片永久免费下载| 晚上一个人看的免费电影| 亚洲av免费在线观看| 在线播放无遮挡| 午夜福利在线观看吧| 久久久久久久久久黄片| 久久亚洲国产成人精品v| 欧美xxxx黑人xx丫x性爽| 欧美一区二区精品小视频在线| 又爽又黄无遮挡网站| 丰满人妻一区二区三区视频av| 91精品一卡2卡3卡4卡| 欧美成人一区二区免费高清观看| 亚洲精品亚洲一区二区| 国产精品永久免费网站| 久久久精品欧美日韩精品| 女同久久另类99精品国产91| 午夜激情欧美在线| 久久精品国产亚洲av香蕉五月| 国产激情偷乱视频一区二区| 久久6这里有精品| 午夜福利在线观看免费完整高清在 | 午夜精品一区二区三区免费看| 午夜亚洲福利在线播放| 国产免费一级a男人的天堂| 如何舔出高潮| 久久人人爽人人爽人人片va| 久久精品国产亚洲av涩爱 | 国产精品无大码| 亚洲人成网站高清观看| 乱人视频在线观看| 成人亚洲欧美一区二区av| 精品无人区乱码1区二区| 草草在线视频免费看| 看黄色毛片网站| 18禁在线无遮挡免费观看视频| 男人舔奶头视频| 亚洲天堂国产精品一区在线| 免费看美女性在线毛片视频| 国产午夜福利久久久久久| 日韩一区二区三区影片| 99热网站在线观看| 可以在线观看毛片的网站| 成人漫画全彩无遮挡| 亚洲国产精品合色在线| 少妇人妻一区二区三区视频| 久久人人精品亚洲av| 国产一区二区在线av高清观看| 亚洲国产精品成人久久小说 | 美女国产视频在线观看| 午夜久久久久精精品| 天堂√8在线中文| 中文资源天堂在线| 日日干狠狠操夜夜爽| 九草在线视频观看| 性色avwww在线观看| 色哟哟哟哟哟哟| 嫩草影院入口| 插逼视频在线观看| 一本一本综合久久| ponron亚洲| 亚洲成a人片在线一区二区| 深夜a级毛片| 欧美极品一区二区三区四区| 男女下面进入的视频免费午夜| 亚洲图色成人| 国产蜜桃级精品一区二区三区| av黄色大香蕉| 亚洲国产欧美在线一区| 99精品在免费线老司机午夜| 亚洲国产欧美人成| 久久亚洲国产成人精品v| 狠狠狠狠99中文字幕| 三级男女做爰猛烈吃奶摸视频| 一本一本综合久久| 2022亚洲国产成人精品| 国产精品蜜桃在线观看 | 国国产精品蜜臀av免费| 日韩欧美在线乱码| 性色avwww在线观看| 日产精品乱码卡一卡2卡三| 天堂网av新在线| 丝袜美腿在线中文| 日韩精品青青久久久久久| 国产色爽女视频免费观看| 91在线精品国自产拍蜜月| 三级国产精品欧美在线观看| 亚洲美女搞黄在线观看| a级毛片a级免费在线| 国产亚洲精品久久久久久毛片| 极品教师在线视频| 男女边吃奶边做爰视频| 国产熟女欧美一区二区| 亚洲欧美精品综合久久99| 有码 亚洲区|