• <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 ?

    Effect of some parameters on the performance of anchor impellers for stirring shear-thinning fluids in a cylindrical vessel*

    2016-10-18 01:45:36HouariAMEUR

    Houari AMEUR

    Institut des Sciences et Technologies, Centre Universitaire Salhi Ahmed, CUN-SA, BP 66, Naama 45000, Algeria,E-mail: houari_ameur@yahoo.fr

    ?

    Effect of some parameters on the performance of anchor impellers for stirring shear-thinning fluids in a cylindrical vessel*

    Houari AMEUR

    Institut des Sciences et Technologies, Centre Universitaire Salhi Ahmed, CUN-SA, BP 66, Naama 45000, Algeria,E-mail: houari_ameur@yahoo.fr

    The 3-D hydrodynamics of shear thinning fluids in a stirred tank with an anchor impeller were numerically simulated. By using a computational fluid dynamics code (CFX 13.0), the obtained results give a good prediction of the hydrodynamics such as the velocity fields and cavern size. The multiple reference frames (MRF) technique was employed to model the rotation of the impellers. The rheology of the fluid was approximated using the Ostwald model. To validate the CFD model, some predicted results were compared with the experimental data and a satisfactory agreement was found. The effects of impeller speed, fluid rheology, and some design parameters on the flow pattern, cavern size and power consumption were explored.

    CFD, computer simulation, stirred tank, anchor impeller, shear thinning fluid

    Introduction

    Mixing operations with non-Newtonian fluids are frequently employed in areas such as the paint, polymer, food or pharmaceutical industries. Additional difficulties for the optimization of processes often occur with such fluids. Shear thinning fluids are a common class of non-Newtonian fluids, the agitation of such fluids results in the formation of well-mixed zone (known as cavern) around the impeller with essentially stagnant and/or slow moving fluids elsewhere. The formation of the stagnant regions gives rise to poor mass and heat transfer rates, which lead to poor quality of the end products[1]. Thus, the mixing of such fluids is a difficult operation and considered as a key step in the chemical industry. It is desirable to eliminate these stagnant regions by a proper mixing design[2-5].

    Low viscosity mixing applications can usually be performed with impeller systems consisting of one or more turbines and propellers. The close-clearance impellers are highly recommended for the mixing of highly viscous fluids, especially for shear thinning fluids, in the laminar regime[6]. For instance, in polymerization reactors, it is desirable to ensure efficient mixing to prevent phenomena like hot spots, to control the molecular weight distribution of the final product,and to avoid the dead zones[7].

    Triveni et al.[7]reported that if turbine impellers are used with highly viscous liquids, flow velocities rapidly decay to low values away from the impeller affecting the blending quality. Turbine impellers are therefore not recommended for use in the laminar regime. For such conditions, close-clearance impellers such as anchors are commonly used. Chhabra and Richardson[8]reported that the flow pattern generated by an anchor agitator is tangential and the anchor is suitable for mixing of viscous Newtonian and non-Newtonian fluids. It has been shown that, at higher impeller rotational speeds, an anchor impeller creates secondary axial and radial flows as well[9]. Nagata[10]revealed by experiments that there exists an axial temperature profile within the vessel. Bertrand et al.[11]and Savreux et al.[12]simulated the 2-D laminar mixing of non-Newtonian fluids with an anchor impeller and they confirmed the finding of Nagata that the anchor is inefficient in the laminar regime. Akiti et al.[13]also studied the behavior of an anchor agitated vessel of 2 L and 4 L capacity using CFD and they observedthat the anchor impeller produces little flow and turbulence in the area beneath the impeller irrespective of the reactor configuration. Karray et al.[14]investigated the performance of the anchor for turbulent Newtonian fluid flow. They found that the use of the classical anchor in turbulent flow yields an important deformation of the anchor arm. To solve this problem,they suggested using an anchor blade. Tanguy et al.[15]measured the power consumption of an anchor agitator for the homogenization of non-Newtonian fluids and they showed that the constant Ksdefined by Metzner and Otto[16]do not vary strongly with the power law index(n). Espinosa-Solares et al.[17]studied the combined effect of bottom clearance and wall clearance on the power consumption rate and they proposed a numerical correlation. They have observed that the power consumption decreases as the bottom and wall clearance increase, which is due to the change in the flow pattern.

    By experiments, Triveni et al.[18]studied the mixing of Newtonian and non-Newtonian fluids in an anchor-agitated vessel. They observed an increase in the fraction of the well-mixed region from 0.7 to 0.95 with increase in impeller speed for both Newtonian and non-Newtonian fluids but the increase is small for viscous fluids. Anne-Archard et al.[19]studied numerically the hydrodynamics and power consumption in a stirred vessel by helical and anchor agitators. They discussed the Metzner-Otto correlation for yield stress fluids.

    By CFD simulations, Prajapati and Ein-Mozaffari[6]investigated the mixing of yield stress fluids for an anchor agitator. They found that the optimum values for the impeller width-to-tank diameter and impeller clearance-to tank diameter ratios were 0.102 and 0.079, respectively. The mixing time and the specific power consumption results for different operating conditions showed that a four-blade anchor impeller is more efficient than a two-blade anchor impeller.

    Our search of the literature shows that a little space has been reserved to the prediction of 3-D hydrodynamics of power-law fluids in a tank equipped with an anchor impeller, through CFD modeling. Thus,the purpose of this paper is to simulate the 3-D flow fields generated by an anchor impeller in the agitation of power-law fluids in a cylindrical tank through the CFD technique and to search another design giving better performance.

    The effects of fluid rheology, agitator speed, impeller blade width, number of blades and some other design parameters on the flow pattern, cavern size and power consumption were evaluated. 0.3 m, height:H/ D=1) fitted with an anchor agitator of 0.006 m×0.012 m blade width which is mounted on a shaft of 0.018 m of diameter(ds). The liquid level is kept equal to the vessel height. The impeller is placed at a clearance(c)from the vessel base equal to 0.02 m.

    Fig.1 Simulated system

    The effect of blade diameter(d )is investigated,four geometrical configurations are realized for this purpose, which are:d/ D=0.57, 0.65, 0.73 and 0.82 respectively.

    2. Mathematical modeling

    The fluid simulated has a shear thinning behavior modeled by the Oswald law. Table 1 resumes the fluid properties (fluid density(ρ), power law index(n)and consistency index(m)) according to the measure of Triveni et al.[7].

    Table 1 Properties of the non-Newtonian fluid studied

    For non-Newtonian fluids, the apparent viscosity(η ) is taken as[2,20]

    The average shear rate is

    where Ksis the shear rate constant andNis the impeller rotational speed.

    1. Simulated system

    Details of the simulated system are shown in Fig.1. It consists of a stirred vessel (diameter:D=

    The generalized Reynolds number (Reg)for non-Newtonian fluids is defined as

    Most of the published literature on shear rate constant had considered the dependency of Kson flow behavior n. But Tanguy et al.[15]reported that Ksis independent ofn . Though the variation in term [(3n+1)/ 4n]n(n-1)is from 0.78 to 0.87 for a range innfrom 0.9 to 0.1, the percentage deviation in Ksis 21.8% and 12.3% respectively. So we have considered the dependence ofKsonnin the calculations.

    Power(P)per unit volume(V)is an important approach for scaling up of an agitated vessel as this parameter ensures a constant specific interfacial area. It can be calculated by integration of the viscous dissipation in all the vessel volume

    where Qvis the viscous dissipation.

    The power number(N p)is calculated as

    3. CFD simulations

    A commercial CFD package (CFX 13.0) was employed to solve the momentum and continuity equations using the finite volume method. A pre-processor(ANSYS ICEM CFD 13.0) was used to discretize the flow domain with an unstructured tetrahedral mesh. A mesh test is performed in order to ensure the accuracy of our predicted results. The original 3-D mesh of the stirred system had 130 451 computational cells. Then,this number was increased by a factor of about 2, until to 260 902 cells. The additional cells changed the power number by more than 3%. Thus, the number of cells was increased again until 521 804 cells. The last mesh did not change the power number by more than 2.5%, therefore, the mesh with 260 902 cells was employed in this investigation. For further details, please refer to our previous work[21]. The simulations were considered converged when the scaled residuals for each transport equations were below 10-6. Most simulations required about 2 000 iterations for convergence. The computations were performed on a 3.60 GHz Intel Pentium IV CPU having 2.00 GB of RAM. The computational time was about 5 h-6 h.

    4. Validation of the cfd model

    The performance of the anchor impeller has been evaluated based on cavern size and power consumption. First, we have seen necessary to validate the CFD model. For this purpose, we have referred to the work of Prajapati and Ein-Mozaffari[6]. We note that the same geometrical conditions undertaken by these authors have been considered. The variation of power number versus Reynolds number is presented in Fig.2. The comparison of our predicted results with the experimental data given by Prajapati and his co-worker shows a satisfactory agreement.

    Fig.2 Impeller power number versus Reynolds number

    On the other hand, we remark that the power number data fall along the line with the slope of -1 at Reg<30, indicating that the flow is laminar. At Reg>30, the data start deviating from the line with the slope of -1. This means that the flow within the mixing tank is in the transitional regime.

    5. Results and discussion

    Results of the 3-D hydrodynamics in the whole vessel volume are presented in this section. Figure 3(a)shows the variations of tangential and radial velocities along the dimensionless vessel radiusR?, where R?=2R/ D,Ris the radial coordinate. We note that the dimensionless tangential velocityand thedimensionless radial velocityare defined as:andrespectively.

    Fig.3 For 1 % CMC,,Z?=0.5,D/ d=0.57

    From Fig.3(a), it is observed that both components reach up their maximum at the impeller blade tip,and begin to decay continuously until becoming negligible at the immediate contact with the side vessel wall. In comparison between the two velocity components, the tangential one is the dominant (Fig.3(b)). These results agree well with the finding of Chhabra and Richardson[8].

    Fig.4 Streamlines for 1 % CMC,Z?=0.5,d/ D =0.57

    5.1 Effect of Reynolds number

    The mixing performance is a function of the flow pattern generated by the impeller. Parameters such as impeller geometry, rotational speed and fluid rheology affect the flow pattern generated by the impeller in the mixing tank. In our study, different parameters have been investigated, we begin the test by searching the effects of impeller rotational speed.

    It would be very useful to improve the knowledge of hydrodynamics, particularly the sheared/unsheared region distribution, in order to provide a predictive tool for designers. Figure 4 presents the streamlines for different Reynolds numbers at the middle height of vessel (Z?=Z/ D=0.5,Zis the vertical coordinate). The important remark from these slices is the formation of dead zones at the outside corner of the vertical arm. These dead zones can be eliminated by increasing the impeller rotational speed.

    5.2 Effect of fluid rheology

    The influence of fluid rheology is discussed in this section. We recall that the CMC (sodium carboxymethyl cellulose) solution is simulated in this study which has a shear thinning behavior. Two concentrations of CMC have been used and all the fluid properties are reported in Table 1.

    Streamlines are presented in Fig.5 for the two CMC concentrations at a location upper the horizontal arm of the anchor impeller. For a laminar regime(Reg=20)and due to the insufficient impeller rotational speed, two vortices are formed at the blade tip. These vortices are detached from the blade tip going away to the vessel wall with the increase of CMC percentage.

    Fig.5 Streamlines for the classical anchor,Z?=0.2,d/ D =0.57

    Fig.6 Power number for the classical anchor (Case 1),d/ D= 0.57

    The power number is calculated also for the two cases, as show in Fig.6, this parameter is greater with increase of viscosity. On the other hand, the continuous increase of the impeller rotation speed permits a reduction in the power required. However, for Reg>30(transitional regime), the decrease ofNp is slight when compared with the laminar regime.

    5.3 Effect of blade diameter

    A mixing operation can be defined as an artificial creation of the fluid flow to decrease its heterogeneity,to accelerate its transfer and to achieve a certain degree of homogeneity. These factors are related to the impeller design and the flow behavior. For this purpose, we have taken into account the impeller shape and some design parameters.

    In this section, we investigate the influence of impeller blade diameter(d). For the same number of blades(α=2), four geometrical configurations are realized and which are:d/ D=0.57, 0.65, 0.73 and 0.82, respectively. Figure 7 gives an insight about the flow pattern generated by changing the ratiod/ D. For low Reynolds numbers(Reg=20), the formation of recirculation loops is observed at each corner of the blade. Reducing the little space between the impeller blade and vessel wall can participate to eliminate these dead zones. On the other hand, the power required(Table 2) is increased, and this is due to the wall effects and inertial forces.

    Fig.7 Streamlines for, 1% CMC,Z?=0.5,α=2

    Table 2 Power number for Reg=20, 1% CMC,α=2

    5.4 Effect of blade number

    Another parameter which can touch the performance of agitated system is the impeller blade number(α). For this end, three geometrical configurations have been tested, which are:α=2, 4 and 6, respectively.

    For an angular position θ=90o, the variation of mean velocity along the vessel height for different impeller blade numbers is presented in Fig.8. The observation of this figure indicates that there is a great difference between the first case and second one, and just a slight difference between the second and third cases. For the two blades impeller, the fluid motion is less intense which is marked by the formation of a recirculation zone at the blade corner (Fig.9). At the same Reynolds number, these dead zones are eliminated in the second and third cases.

    Fig.8 Mean velocity for Reg=20, 1% CMC,d/ D  =0.57,R?=0.3,θ=90o

    Fig.9 Flow fields for Reg=20, 1% CMC,d/ D =0.57,Case 1

    The agitation of shear thinning fluids results in the formation of zone of intense motion near the impeller (called cavern) with essentially stagnant zone elsewhere. Fig.9 (Line 2) presents the cavern size for the three cases studied, as illustrated: the increase in blade number enlarges the cavern size and enhances the mixing performances. Nevertheless, it is penalizing in terms of power consumption (Table 3). From all of these remarks, and since the dead zones can be elimi-nated by the impeller with four blades, thus α=4can be chosen as a sufficient number.

    Table 3 Power number for Reg=20, 1% CMC,d/ D=

    5.5 Effect of impeller design

    In laminar mixing of highly viscous fluids, the mixing is obtained by a sequence of stretching, folding and breaking mechanisms and not by highly energetic eddies, which makes the design of an optimal mixing device very challenging[22-24].

    Here, we tried to add arm blades at different heights and positions (horizontal and/or vertical), four cases have been investigated and summarized in Fig.10. Values of the power number obtained for all cases studied are summarized in Table 4.

    Fig.10 Cavern size for Reg=20, 1% CMC

    Table 4 Power number for Reg=20, 1% CMC

    The classical anchor is inefficient at low Reynolds numbers (Case 1) and the well stirred region is limited at the tank bottom. Mixing may be enhanced at the upper part of the vessel by adding an horizontal arm in this region (Case 2), and a better enhancement of the axial circulation may be obtained if this arm is placed vertically (Case 3) but with additional power cost.

    6. Conclusion

    In this study, the CFD technique was used to investigate the agitation of CMC solution, which is a shear thinning fluid, with an anchor impeller. The cavern size and the specific power consumption results for different operating conditions showed that the insufficient impeller rotational speed and little blade diameter permit the formation of dead zones at the upper corner of blade. For Reg>20, the decrease of power consumption continues but very slightly. The classical anchor is found inefficient in the laminar regime, thus to eliminate the dead zone, to increase the cavern size and to avoid the deformation of blade we suggest the use of arms (horizontal and vertical). The increase of blade number is also important, based on the comparison made previously we can choose the four bladed as sufficient for obtaining the best performance.

    References

    [1] AMANULLAH A., HJORTH S. A. and NIENOW A. W. Cavern sizes generated in highly shear thinning viscous fluids by Scaba 3SHP1 impeller[J]. Food and Bioproducts Processing, 1997, 75(4): 232-238.

    [2] WOZIWODZKI S., BRONIARZ-PRESS L. and OCHOWIAK M. Transitional mixing of shear-thinning fluids in vessels with multiple impellers[J]. Chemical Engineering and Technology, 2010, 33(7): 1099-1106.

    [3] MAA? S., EPPINGER T. and ALTWASSER S. et al. Flow field analysis of stirred liquid-liquid systems in slim reactors[J]. Chemical Engineering and Technology,2011, 34(8): 1215-1227.

    [4] IRANZO A., BARBERO R. and DOMINGO J. et al. Numerical investigation of the effect of impeller design parameters on the performance of a multiphase bafflestirred reactor[J]. Chemical Engineering and Technology, 2011, 34(8): 1271-1280.

    [5] WOZIWODZKI S. Unsteady mixing characteristics in a vessel with forward-reverse rotating impeller[J]. Chemical Engineering and Technology, 2011, 34(5): 767-774.

    [6] PRAJAPATI P., EIN-MOZAFFARI F. CFD Investigation of the mixing of yield- pseudoplastic fluids with anchor impellers[J]. Chemical Engineering and Technology,2009, 32(8): 1211-1218.

    [7] TRIVENI B., VISHWANADHAM B. and MADHAVI T. et al. Mixing studies of non-Newtonian fluids in an anchor agitated vessel[J]. Chemical Engineering Research and Design, 2010, 88(7): 809-818.

    [8] CHHABRA R. P., RICHARDSON J. F. Liquid mixing: In non Newtonian flow in process industries[M]. Oxford, UK: Butterworth-Heinemann, 1999, 324-391.

    [9] OHTA M., KURIYAMA M. and ARAI K. et al. A twodimensional model for the secondary flow in an agitated vessel with anchor impeller[J]. Journal of Chemical Engineering of Japan,1985,18(1): 81-84.

    [10] NAGATA S. Heat transfer in agitated vessel. In mixing: Principles and applications[M]. New York, USA: Wiley,1975, 385-387.

    [11] BERTRAND F., TANGAY P. A. and BRITO-DE LA FUENTE E. A new perspective for the mixing of yield stress fluids with anchor impellers[J]. Journal of Chemical Engineering of Japan, 1996, 29(1): 51-58.

    [12] SAVREUX F., JAY P. and ALBERT M. Viscoplastic fluid mixing in a rotating tank[J]. Chemical Engineering Science, 2007, 62(8): 2290-2301.

    [13] AKITI O., YEBOAH A. and BAI G. et al. Hydrodynamic effects on mixing and competitive reactions in laboratoryreactors[J]. Chemical Engineering Science, 2005, 60(8-9): 2341-2354.

    [14] KARRAY S., DRISS Z. and KCHAOU H. et al. Hydromechanics characterization of the turbulent flow generated by anchor impellers[J]. Engineering Applications of Computational Fluid Mechanics, 2011, 5(3): 315-328.

    [15] TANGUY P. A., THIBAULT F. and BRITO DE LA FUENTE E. A new investigation of the Metzner-Otto concept for anchor mixing impellers[J]. Canadian Journal of Chemical Engineering, 1996, 74(2): 222-228.

    [16] METZNER A. B., OTTO R. E. Agitation of non-Newtonian fluids[J]. AIChE Journal, 1957, 3(1): 3-10

    [17] ESPINOSA-SOLARES T., BRITO-DE LA FUENTE E. and THIBAULT F. et al. Power consumption with anchor mixers-effect of bottom clearance[J]. Chemical Engineering Communications, 1997, 157(1): 65-71.

    [18] TRIVENI B., VISHWANADHAM B. and VENKATESHWAR S. Studies on heat transfer to Newtonian and non-Newtonian fluids in agitated vessel[J]. Heat Mass Transfer, 2008, 44: 1281-1288.

    [19] ANNE-ARCHARD D., MAROUCHE M. and BOISSON H. C. Hydrodynamics and Metzner-Otto correlation in stirred vessels for yield stress fluids[J]. Chemical Engineering Journal, 2006, 125(1): 15-24.

    [20] MURTHY S. S., JAYANTI S. Mixing of power-law fluids using anchors: Metzner-Otto concept revisited[J]. AIChE Journal, 2003, 49(1): 30-40.

    [21]AMEUR H., BOUZIT M. and HELMAOUI M. Numerical study of fluid flow and power consumption in a stirred vessel with a Scaba 6SRGT impeller[J]. Chemical and Process Engineering, 2011, 32(4): 351-366.

    [22] IRANSHAHI A., DEVALS C. and HENICHE M. et al. Hydrodynamics characterizations of the Maxblend impeller[J]. Chemical Engineering Science, 2007, 62(14): 3641-3653.

    [23] AMEUR H., BOUZIT M. Mixing in shear thinning fluids[J].Brazilian Journal of Chemical Engineering, 2012,29(2): 349-358.

    [24] AMEUR H., BOUZIT M. and HELMAOUI M. Hydrodynamic study involving a Maxblend impeller with yield stress fluids[J]. Journal of Mechanical Science and Technology 2012, 26(5): 1523-1530.

    10.1016/S1001-6058(16)60671-6

    February 10, 2015, Revised June 13, 2015)

    * Biography: Houari AMEUR (1982-), Male, Ph. D.,Assistant Professor

    2016,28(4):669-675

    国产精品99久久久久久久久| 国产亚洲精品久久久com| 日本色播在线视频| 日本五十路高清| 看免费成人av毛片| 国产精品99久久久久久久久| 久久久久国产网址| 欧美激情久久久久久爽电影| 亚洲精华国产精华液的使用体验 | 性插视频无遮挡在线免费观看| 国产精品日韩av在线免费观看| 精品午夜福利在线看| 草草在线视频免费看| 久久精品国产亚洲av香蕉五月| 丰满的人妻完整版| 国产一区二区在线av高清观看| 天堂√8在线中文| 丰满人妻一区二区三区视频av| 国产亚洲91精品色在线| 久久婷婷人人爽人人干人人爱| 天天躁日日操中文字幕| 欧美zozozo另类| 日本a在线网址| 亚洲18禁久久av| 最近视频中文字幕2019在线8| 一个人免费在线观看电影| 男女之事视频高清在线观看| 久久久久国内视频| 成人av在线播放网站| 毛片女人毛片| 亚洲五月天丁香| 禁无遮挡网站| 日韩 亚洲 欧美在线| 午夜激情福利司机影院| 在线免费观看不下载黄p国产| 老司机影院成人| 一本一本综合久久| 老司机影院成人| 少妇熟女欧美另类| 夜夜夜夜夜久久久久| 日本撒尿小便嘘嘘汇集6| 日韩 亚洲 欧美在线| a级毛色黄片| 桃色一区二区三区在线观看| 亚洲成a人片在线一区二区| 99热6这里只有精品| 欧美中文日本在线观看视频| 午夜久久久久精精品| 精品久久久噜噜| 97超碰精品成人国产| 男女啪啪激烈高潮av片| 校园人妻丝袜中文字幕| 国产久久久一区二区三区| 99久久九九国产精品国产免费| 亚洲精品成人久久久久久| 久久精品综合一区二区三区| 免费av毛片视频| 亚洲成av人片在线播放无| 一个人看的www免费观看视频| 国内少妇人妻偷人精品xxx网站| 婷婷色综合大香蕉| 亚洲精品粉嫩美女一区| 亚洲欧美日韩卡通动漫| 麻豆成人午夜福利视频| 老司机福利观看| 精品久久久久久久久久免费视频| 久久久久久久久中文| 欧美高清成人免费视频www| 熟女电影av网| 无遮挡黄片免费观看| 有码 亚洲区| 美女内射精品一级片tv| 国产亚洲av嫩草精品影院| 精品一区二区三区视频在线| 国产亚洲欧美98| 国产视频内射| 99久国产av精品| 欧美极品一区二区三区四区| 级片在线观看| 亚洲人成网站在线观看播放| 国内精品一区二区在线观看| 精品福利观看| 亚洲欧美精品自产自拍| 男人舔奶头视频| 一级a爱片免费观看的视频| 日日撸夜夜添| 综合色丁香网| 国产淫片久久久久久久久| 老司机午夜福利在线观看视频| av在线亚洲专区| 一级a爱片免费观看的视频| 99国产精品一区二区蜜桃av| 久久久a久久爽久久v久久| 国产午夜福利久久久久久| 欧美精品国产亚洲| 精品人妻熟女av久视频| 亚洲欧美日韩东京热| 黄片wwwwww| 嫩草影院入口| 国产 一区 欧美 日韩| 你懂的网址亚洲精品在线观看 | 国内精品美女久久久久久| 国产亚洲91精品色在线| 国产日本99.免费观看| av在线亚洲专区| 3wmmmm亚洲av在线观看| 午夜免费激情av| 精品久久久久久久久久免费视频| 国产精品福利在线免费观看| 美女内射精品一级片tv| 成人综合一区亚洲| 亚洲成人中文字幕在线播放| 国产黄色小视频在线观看| 日韩 亚洲 欧美在线| 日韩成人伦理影院| 久久久成人免费电影| 午夜免费激情av| 免费人成在线观看视频色| 亚洲专区国产一区二区| 波野结衣二区三区在线| 简卡轻食公司| 国产精品久久久久久久久免| 亚洲精品乱码久久久v下载方式| 尾随美女入室| 两个人的视频大全免费| 高清日韩中文字幕在线| 亚洲av一区综合| 最近中文字幕高清免费大全6| 久久久精品94久久精品| 99热只有精品国产| 99在线人妻在线中文字幕| 亚洲精品一区av在线观看| 最新中文字幕久久久久| 久久久精品欧美日韩精品| 插阴视频在线观看视频| 免费看av在线观看网站| 乱系列少妇在线播放| 精品久久久久久久久av| 久久国产乱子免费精品| 日本成人三级电影网站| 亚洲av五月六月丁香网| 午夜福利18| 深夜精品福利| 婷婷精品国产亚洲av在线| 久久久欧美国产精品| 欧美xxxx性猛交bbbb| 床上黄色一级片| 亚洲欧美精品自产自拍| 男女那种视频在线观看| 国产精品久久视频播放| 少妇丰满av| 看十八女毛片水多多多| 亚洲国产精品久久男人天堂| 国产成人a∨麻豆精品| eeuss影院久久| 99久久九九国产精品国产免费| 欧美极品一区二区三区四区| 亚洲av熟女| 欧美bdsm另类| 国产精品国产高清国产av| 99久国产av精品| 亚洲aⅴ乱码一区二区在线播放| 久久国产乱子免费精品| 日韩国内少妇激情av| 精品午夜福利视频在线观看一区| 日韩欧美免费精品| 久久国产乱子免费精品| 少妇熟女aⅴ在线视频| 亚洲精品456在线播放app| 日本免费a在线| 精品人妻视频免费看| 熟妇人妻久久中文字幕3abv| 干丝袜人妻中文字幕| 日本免费a在线| 黄片wwwwww| .国产精品久久| 亚洲天堂国产精品一区在线| 久久久久国内视频| 日本精品一区二区三区蜜桃| 国产一级毛片七仙女欲春2| 国内精品久久久久精免费| av女优亚洲男人天堂| 女生性感内裤真人,穿戴方法视频| 在线观看av片永久免费下载| 可以在线观看毛片的网站| 久久人人爽人人片av| 成人特级av手机在线观看| 国产av在哪里看| 日韩,欧美,国产一区二区三区 | 日韩大尺度精品在线看网址| 亚洲国产色片| 嫩草影院精品99| 亚洲欧美日韩无卡精品| 亚洲色图av天堂| 久久久久久久亚洲中文字幕| 毛片女人毛片| 亚洲最大成人av| 精品人妻视频免费看| .国产精品久久| 成人综合一区亚洲| 国产日本99.免费观看| av在线播放精品| 日韩欧美一区二区三区在线观看| 免费观看在线日韩| 一级毛片aaaaaa免费看小| 狂野欧美白嫩少妇大欣赏| 俄罗斯特黄特色一大片| av国产免费在线观看| 亚洲中文字幕日韩| 麻豆一二三区av精品| 欧美成人精品欧美一级黄| 亚洲欧美清纯卡通| 国产精品三级大全| 天堂网av新在线| 最后的刺客免费高清国语| 国国产精品蜜臀av免费| 国产真实伦视频高清在线观看| .国产精品久久| av专区在线播放| 免费看日本二区| 美女cb高潮喷水在线观看| 噜噜噜噜噜久久久久久91| 最新中文字幕久久久久| 麻豆久久精品国产亚洲av| 日韩欧美在线乱码| 亚洲精品乱码久久久v下载方式| 99在线视频只有这里精品首页| 俄罗斯特黄特色一大片| 精品一区二区免费观看| 日韩一本色道免费dvd| 免费无遮挡裸体视频| 日韩国内少妇激情av| 精华霜和精华液先用哪个| 国产成年人精品一区二区| 女生性感内裤真人,穿戴方法视频| 俄罗斯特黄特色一大片| 欧美成人a在线观看| 国产精品嫩草影院av在线观看| 乱系列少妇在线播放| 午夜老司机福利剧场| 观看美女的网站| 色哟哟·www| 丰满的人妻完整版| 亚洲乱码一区二区免费版| 午夜福利在线观看免费完整高清在 | 国产高潮美女av| 亚洲色图av天堂| 国产亚洲精品综合一区在线观看| 性欧美人与动物交配| 女的被弄到高潮叫床怎么办| 真实男女啪啪啪动态图| 波多野结衣巨乳人妻| 老熟妇乱子伦视频在线观看| 成人av一区二区三区在线看| 国产高清激情床上av| 亚洲熟妇中文字幕五十中出| 最新中文字幕久久久久| 亚洲精品日韩在线中文字幕 | 波多野结衣巨乳人妻| av在线老鸭窝| 亚洲精品乱码久久久v下载方式| 久久久久性生活片| 美女cb高潮喷水在线观看| 69人妻影院| 色综合站精品国产| 日韩三级伦理在线观看| 成人国产麻豆网| 精品人妻视频免费看| 精品人妻偷拍中文字幕| 全区人妻精品视频| 欧美激情久久久久久爽电影| 亚洲精华国产精华液的使用体验 | 美女 人体艺术 gogo| 春色校园在线视频观看| 99久久无色码亚洲精品果冻| 国产精品爽爽va在线观看网站| 深夜精品福利| 丰满的人妻完整版| 国产一区二区在线观看日韩| av在线观看视频网站免费| 欧美一区二区精品小视频在线| 全区人妻精品视频| 免费av不卡在线播放| 不卡视频在线观看欧美| 亚洲人成网站在线观看播放| 黄色欧美视频在线观看| 国产乱人偷精品视频| 老司机午夜福利在线观看视频| 在线看三级毛片| 狂野欧美白嫩少妇大欣赏| 国产精品嫩草影院av在线观看| 97热精品久久久久久| 欧美在线一区亚洲| 久久综合国产亚洲精品| a级毛片a级免费在线| 国产亚洲91精品色在线| 免费电影在线观看免费观看| 亚洲美女视频黄频| 亚洲精品成人久久久久久| 亚洲乱码一区二区免费版| 神马国产精品三级电影在线观看| 91久久精品电影网| 波野结衣二区三区在线| 在线国产一区二区在线| 中文字幕av在线有码专区| 国产色婷婷99| 免费观看精品视频网站| 亚洲在线观看片| 亚洲在线自拍视频| 十八禁国产超污无遮挡网站| 日本在线视频免费播放| 午夜精品国产一区二区电影 | 国产精品一二三区在线看| 亚洲成人久久爱视频| 久99久视频精品免费| 国产人妻一区二区三区在| 别揉我奶头~嗯~啊~动态视频| 麻豆国产av国片精品| 给我免费播放毛片高清在线观看| 午夜福利视频1000在线观看| videossex国产| 中国美女看黄片| 男女视频在线观看网站免费| 国产成人a∨麻豆精品| 久久天躁狠狠躁夜夜2o2o| 天天躁日日操中文字幕| 性插视频无遮挡在线免费观看| 美女内射精品一级片tv| 午夜老司机福利剧场| 春色校园在线视频观看| 久久午夜亚洲精品久久| 亚洲国产精品成人久久小说 | 免费观看人在逋| 天美传媒精品一区二区| av视频在线观看入口| 69av精品久久久久久| 色播亚洲综合网| 国模一区二区三区四区视频| 午夜福利视频1000在线观看| 在现免费观看毛片| 狂野欧美白嫩少妇大欣赏| 亚洲成a人片在线一区二区| 成人二区视频| 国产精品久久电影中文字幕| 99久久成人亚洲精品观看| av在线老鸭窝| 日日摸夜夜添夜夜添小说| 久久久久久久久中文| 一个人看视频在线观看www免费| 色综合色国产| 在线观看免费视频日本深夜| 日本黄色视频三级网站网址| 国产免费一级a男人的天堂| 男女边吃奶边做爰视频| 男女视频在线观看网站免费| 欧美成人免费av一区二区三区| 搡老熟女国产l中国老女人| 国产三级中文精品| 国产精品日韩av在线免费观看| 亚洲四区av| 一卡2卡三卡四卡精品乱码亚洲| 淫妇啪啪啪对白视频| 久久亚洲国产成人精品v| 白带黄色成豆腐渣| 悠悠久久av| 国产真实伦视频高清在线观看| 国产成人91sexporn| 国产精品三级大全| 少妇裸体淫交视频免费看高清| 久久午夜福利片| 久99久视频精品免费| 亚洲精品456在线播放app| 亚洲天堂国产精品一区在线| a级一级毛片免费在线观看| 不卡视频在线观看欧美| 精品一区二区免费观看| aaaaa片日本免费| 精品少妇黑人巨大在线播放 | 欧美丝袜亚洲另类| 变态另类成人亚洲欧美熟女| 久久久精品94久久精品| 在线播放国产精品三级| 久久久午夜欧美精品| 午夜免费激情av| 国产综合懂色| 亚洲专区国产一区二区| 高清日韩中文字幕在线| 国产美女午夜福利| 国产成人a区在线观看| 亚洲欧美日韩东京热| 国产免费一级a男人的天堂| 看非洲黑人一级黄片| 精品久久久久久久久av| av卡一久久| 99热全是精品| 丝袜喷水一区| 久久鲁丝午夜福利片| 国产高清视频在线播放一区| 男女下面进入的视频免费午夜| 有码 亚洲区| 亚洲婷婷狠狠爱综合网| 精品无人区乱码1区二区| 天堂影院成人在线观看| 色5月婷婷丁香| av在线蜜桃| 久久亚洲精品不卡| 久久精品久久久久久噜噜老黄 | 国产私拍福利视频在线观看| 国产精品日韩av在线免费观看| 丰满人妻一区二区三区视频av| 免费大片18禁| 1024手机看黄色片| 中文字幕免费在线视频6| 中文字幕av在线有码专区| 国产熟女欧美一区二区| 美女大奶头视频| 麻豆国产97在线/欧美| 亚洲婷婷狠狠爱综合网| 久久99热6这里只有精品| 国内精品久久久久精免费| 成年版毛片免费区| 日本五十路高清| 波多野结衣高清作品| 美女内射精品一级片tv| 干丝袜人妻中文字幕| 日日摸夜夜添夜夜添小说| 九九在线视频观看精品| www日本黄色视频网| 综合色av麻豆| 亚洲四区av| 亚洲第一电影网av| 熟妇人妻久久中文字幕3abv| 国产一级毛片七仙女欲春2| 久久精品久久久久久噜噜老黄 | 免费看日本二区| 日韩欧美在线乱码| av在线蜜桃| 国产精品,欧美在线| 欧美zozozo另类| 国产69精品久久久久777片| 美女被艹到高潮喷水动态| 你懂的网址亚洲精品在线观看 | 日韩欧美精品免费久久| 老司机福利观看| 国产伦在线观看视频一区| 天天躁夜夜躁狠狠久久av| 深夜精品福利| 亚洲精品久久国产高清桃花| 亚洲久久久久久中文字幕| 特级一级黄色大片| 亚洲激情五月婷婷啪啪| 国产亚洲91精品色在线| 最近手机中文字幕大全| 国产精品永久免费网站| 欧美激情久久久久久爽电影| 久久人人精品亚洲av| 噜噜噜噜噜久久久久久91| 精品人妻熟女av久视频| 亚洲三级黄色毛片| 国产成人精品久久久久久| 一进一出好大好爽视频| 国产成人a∨麻豆精品| 精品午夜福利视频在线观看一区| 日韩强制内射视频| 国产人妻一区二区三区在| 成人综合一区亚洲| 国产极品精品免费视频能看的| 91麻豆精品激情在线观看国产| 亚洲精品影视一区二区三区av| 91精品国产九色| 国产精品乱码一区二三区的特点| 久久人人精品亚洲av| 美女xxoo啪啪120秒动态图| 在线看三级毛片| 亚洲国产日韩欧美精品在线观看| 欧美又色又爽又黄视频| 亚洲最大成人av| 国产视频内射| 特级一级黄色大片| 少妇人妻一区二区三区视频| 天美传媒精品一区二区| 成年女人毛片免费观看观看9| 久久鲁丝午夜福利片| 一a级毛片在线观看| 欧美在线一区亚洲| 亚洲美女搞黄在线观看 | a级毛片免费高清观看在线播放| 国产麻豆成人av免费视频| 99久久九九国产精品国产免费| 国产真实伦视频高清在线观看| 免费看美女性在线毛片视频| 久久草成人影院| 日韩人妻高清精品专区| 麻豆国产av国片精品| 午夜福利高清视频| 嫩草影院入口| 中国美白少妇内射xxxbb| 97超视频在线观看视频| 蜜桃亚洲精品一区二区三区| 亚洲成人久久性| 丝袜美腿在线中文| 精品久久久久久久人妻蜜臀av| 在线免费观看的www视频| 国产高清视频在线观看网站| 国产精品一区www在线观看| 午夜免费男女啪啪视频观看 | 亚洲最大成人手机在线| 精品国内亚洲2022精品成人| 人人妻,人人澡人人爽秒播| 久久综合国产亚洲精品| 高清毛片免费看| 日本黄色视频三级网站网址| 麻豆国产97在线/欧美| 美女高潮的动态| h日本视频在线播放| 国产高清视频在线观看网站| 热99re8久久精品国产| 国产成人freesex在线 | 99热这里只有是精品在线观看| 黄色配什么色好看| 变态另类丝袜制服| 精品一区二区三区av网在线观看| 男女做爰动态图高潮gif福利片| 女人被狂操c到高潮| 又粗又爽又猛毛片免费看| 男插女下体视频免费在线播放| 亚洲国产精品合色在线| 噜噜噜噜噜久久久久久91| 精品久久久噜噜| 国产成人91sexporn| 极品教师在线视频| 日韩欧美精品v在线| 午夜激情福利司机影院| 亚洲无线观看免费| 国产精品免费一区二区三区在线| 国产中年淑女户外野战色| 国产黄片美女视频| 精品久久久久久久久av| 欧美成人免费av一区二区三区| 精品一区二区三区视频在线观看免费| 国产一区二区三区在线臀色熟女| 九九爱精品视频在线观看| 欧美一区二区精品小视频在线| 狠狠狠狠99中文字幕| 久久久精品大字幕| 欧美日韩在线观看h| 性色avwww在线观看| 免费av观看视频| 久久久久久伊人网av| 韩国av在线不卡| 国产视频一区二区在线看| 久久久精品欧美日韩精品| 99久久成人亚洲精品观看| 亚洲av中文av极速乱| 性插视频无遮挡在线免费观看| 成人欧美大片| 久久精品国产自在天天线| 成人av在线播放网站| 亚洲色图av天堂| 91久久精品国产一区二区三区| 亚洲第一电影网av| 婷婷精品国产亚洲av在线| 插阴视频在线观看视频| 国产精品99久久久久久久久| 国产高清视频在线观看网站| 精品午夜福利视频在线观看一区| 99久久久亚洲精品蜜臀av| 色播亚洲综合网| 日韩在线高清观看一区二区三区| 国产精品免费一区二区三区在线| 性欧美人与动物交配| 我的老师免费观看完整版| 99久久无色码亚洲精品果冻| 18+在线观看网站| 黑人高潮一二区| 亚洲人成网站在线播| 国产av在哪里看| 亚洲最大成人手机在线| 国产精品国产高清国产av| 欧美性猛交黑人性爽| 中文在线观看免费www的网站| 精品人妻视频免费看| 国产成人aa在线观看| 夜夜看夜夜爽夜夜摸| 免费人成视频x8x8入口观看| 国产精品不卡视频一区二区| 天堂动漫精品| 国产av一区在线观看免费| 深夜a级毛片| 51国产日韩欧美| 国产一级毛片七仙女欲春2| 一个人观看的视频www高清免费观看| 在线播放无遮挡| 麻豆国产97在线/欧美| 天堂影院成人在线观看| 久久精品国产自在天天线| 99热全是精品| ponron亚洲| 给我免费播放毛片高清在线观看| 白带黄色成豆腐渣| 欧美日韩乱码在线| 欧美高清成人免费视频www| 免费高清视频大片| 久久久a久久爽久久v久久| 国产高清激情床上av| 国产v大片淫在线免费观看| 免费看a级黄色片| 午夜爱爱视频在线播放| 亚洲第一区二区三区不卡| 一区二区三区免费毛片| 欧美不卡视频在线免费观看| 国产精品女同一区二区软件| 看黄色毛片网站| 国产一区二区激情短视频| 免费观看精品视频网站|