• <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 ?

    Horizontal gas mixing in rectangular fluidized bed:A novel method for gas dispersion coefficients in various conditions and distributor designs

    2017-05-29 01:39:44AsheeshNautiyalChienSongChyangPinWeiLiHsinYungHou

    Asheesh Nautiyal,Chien-Song Chyang*,Pin-Wei Li,Hsin-Yung Hou

    Department of Chemical Engineering,Chung Yuan Christian University,Taoyuan 320,Taiwan,China

    1.Introduction

    A gas- fluidized bed is a system ofrandomly spread macroscopic particles that are suspended by an upward flow of air.In a fluidized bed,widespread gas and solid mixing provide a large active surface area to enhance chemical reactions and heat transfer[1].Fluidized beds are used in industry,particularly for the combustion of various fuels,the bulk drying of materials,and some food processing techniques[2,3].Various studies discussed gas-solid mixing,dispersion in a fluidized bed and fluidized bed design to promote high levels of contact between gases and solids[4-6].

    Numerous studies have been made to estimate only the dispersion coefficient(Dr)for a circularand rectangular fluidized bed,and itis generally constant at all levels in the bed(excluding the level near the bottom).Werther and Molerus[7]reported a detailed experimental study on the bubble behavior of fluidized beds with different diameters,sizes and densities.They suggested that near the distributor,a zone of maximum bubble growth exists in an annulus near the wall.With increasing bed height,this zone approaches the center of the bed.They stated that the presence of the wall prevents attraction to the inner bubbles from the outside;thus,the bubbles tend to coalesce,and the maximum bubble flow position approaches the central axis.If the wall is circular,the effectis circumferentially even,and the peak is atnearly the same radial location at a given height.However,Whitehead and Dent[8]suggested that if the wall is square,then the wall effect is not circumferentially even,and the peak position does not form a circular position but forms several spots arranged in a rectangle.

    Some previous studies observed and discussed the dispersion behavior and dispersion coefficients of the tracer in the lateral and horizontal planes in rectangular and circular fluidized beds.Kunii and Levenspiel[9]reported lateral dispersion of fluidized solids,postulating thatsolid particles are displaced by the rising bubbles,and then the particles are drawn into the wake of the bubbles where they are mixed.Shi and Fan[10]measured the lateral dispersion coefficients of particles(Dsr)in a rectangular gas-solid fluidized bed.They developed an empirical,dimensionless correlation to estimate the lateral dispersion coefficient.Klinkenberget al.[11]presented a study of the concentration distributions caused by diffusion in a fluid moving in a cylindrical tube at uniform velocity.They obtained a solution for a general equation of nonisotropic diffusion using two-sided Laplace integrals with boundary conditions.Brenner[12]provided a method forthe solution ofthe diffusion model of homogeneous fluid displacement in beds of finite length.The results presented in Brenner's paper are given in dimensionless form for the instantaneous concentration of solute leaving the bed and the average solute concentration in the bed at any instant.

    Using the study by Klinkenberget al.[11],Rowe and Evans[13]predicted the tracer dispersion at points within the bed using a singlephase model,primarily depending on the radial dispersion coefficient(Dr).In their study,the radial dispersion coefficient increases rapidly from a value near molecular diffusion with an increase in the excess gas flow(U-Umf.).Atimtay and Cakaloz[14]obtained the two-dimensional diffusion model.They measuredDrof a gas in a 10-cm-diameter fluidized bed charged with resin beads using a new strip staining technique with bromine as the tracer.Lin and Chyang[15]discussed the gas mixing in the radial direction within a cold model circular fluidized bed,which was studied using response surface methodology(RSM).Their results showed that the standard deviation of the time-averaged radial tracer concentration is well correlated with the operational and geometric parameters.?tefanica and Hrdli?ka[16]described the experimental apparatus for measurement ofDr,and the effects of gas velocity at various fluidization values and bed heights were investigated.The maximum value ofDron each level was found either in the center of the bed or at the wall.

    Fuel mixing has a large impact on the overallperformance of a fluidized bed combustor(FBC).As the fuel's horizontal mixing improves,there is a more uniform local stoichiometric ratio in the reactor's cross section,and this lowers the occurrence of sites with unreacted fuel or oxygen.The effects of various operating parameters on the dispersion coefficient have been studied in previous works.Such studies primarily focus on the effects of the operating parameters,such as super ficial gas velocity and particle size,on dispersion behavior[17-19].

    Most studies related to dispersion in the horizontal plane use smallscale circular and rectangular beds.Van Deemter[20]investigated mixing in small and large fluidized beds and demonstrated the importance of the size effect.The author concluded that the differences and similarities between a small and large bed could be attributed to the flow regime.Zhanget al.[21]suggested that the particle concentration is evenly distributed across the bed core but rapidly increases at the boundary layer towards the wall surfaces in circulating fluidized bed boilers.They mentioned that the cross-sectional average solid volume fraction was low,even as low as 0.003.The high particle concentration at the wall in such a dilute phase might be attributed to the membrane-tube wall con figuration and to the small bed aspect ratio,which is an order of magnitude of 10.The effects of various operating parameters on the dispersion coefficient are considered a wellunderstood phenomenon;yet,the effect of the side walls on the dispersion coefficient has not been discussed considerably.Therefore,it is necessary to investigate the effect of the chamber walls on dispersion behavior.

    Using the radial dispersion coefficient(Dr)for a circular fluidized bed is acceptable,but switching to a rectangular bed,Drneeds to be decomposed into Cartesian form,DxandDy,in the horizontal plane.This study uses a new analytic solution to estimateDxandDy.

    Rectangular fluidized-bed combustors have been widely adopted for commercial application.For most of the commercial fluidized beds,tuyere nozzles or bubbling caps are used as the distributor instead of perforated plates.Fora perforated plate,the gas jetfrom the distributoris in the vertical direction.Rather,for a fluidized bed equipped with tuyeretype distributor,the gas jetfromthe nozzle is in the horizontalplane.So,it becomes necessary to develop a method for estimating dispersion coefficients,DxandDy,in a rectangular fluidized bed.Additionally,in a rectangular fluidized bed,with a relatively low length-to-width ratio,back-mixing of solids does not substantially occur.

    In this study,a novel analytical solution,in terms ofDxandDy,was established for a governing equation of the tracer dispersion in the steady state.However,the solutions are valid for specialized situations,such as tracer injection from a point source with the physically relevant boundary conditions[15].Further,a novelsurface fitting ofthe obtained analytical solution to the experimental data is presented in this study.The tracer concentration data points along theXandYaxes at a certain height(Z-axis)were collected using controllable probes with CO2detection tips.In the fluidized bed,the dispersion coefficients are discussed within a Cartesian coordinate system of a three-dimensional dispersion model.In addition,the obtained results were compared with the conventional model[13],which shows that the values ofDxandDyremain in the same range.

    2.Experimental

    All ofthe experiments are conducted in a lab-scale rectangular fluidized bed,fabricated with a transparentacrylic column.The cross section ofthe bed is 0.2 m×0.4 m,and itis 1.5 min height.Aschematic diagram of the apparatus is shown in Fig.1.The experimental setup is similar to thatofour previously published papers[15,17].The fluidizing air is supplied by a 15 hp.Roots blower,and the super ficial gas velocities are set to be multiples of minimum fluidization velocity(Umf),that is,3.5Umf,5Umf,and 6.5Umf.Glass beads with a mean density of 2500 kg·m-3and a mean size of 385 μm are used as the bed material.The minimum fluidizing velocity is 0.115 m·s-1.The static bed height(Hs)is 0.2 m.At the bottom,an acrylic perforated plate with 343 holes of 1.85 mm ID is employed as the gas distributor.In this experiment,carbon dioxide is used as the tracer gas.The glass bead used in this study is smooth and the absorption of CO2by glass beads can be neglected.The injection rate of the tracer gas is 0.20%of the fluidizing air flow rate.The tracer gas was continuously injected from the center while maintaining the same distributor levelviaa 6.4 mm ID stainless-steel tube into the bed.After reaching a steady state of the tracer gas in the bed,using a stainless-steel probe of 6.35 mm I.D,the downstream tracer gas is sampled at 5 and 10 cm(sampling height(Z)is the distance between tracer gas injector and sampling point)above the distributor in a horizontal plane at fixed distances in 2D coordinate geometry,as shown in Fig.2.To observe the effect of the side walls,the tracer position shifted from the center to near the wall of the chamber along the long side,i.e.,theX-axis.To examine the effect of the bed height,two static bed heights of 15 cm and 20 cm were prepared.

    To study the effect of distributor design on the dispersion coefficients,the perforated plate was replaced with a multi-horizontal nozzle distributor.The super ficial gas velocities are 3.5Umfand 5Umf.The bed materials are the same and the static bed height is 25 cm.The height of tracer injection is 10 cm and the sampling height(Z)is 10 cm above the distributor for the multi-horizontal nozzle distributor.

    The concentrations of the tracer gas in the bed are analyzed using a nondispersive infrared gas analyzer(ETG IMA 3000B).The dimensionless ratio,C/Co,represents the concentration of the tracer gas in the study,whereCis the concentration of the tracer gas in the bed where the gas is mixed with the bed particles,andCois the concentration of the tracer gas within the freeboard.The tracer gas and fluidizing air are assumed to be well mixed.In this study,Cois 2350×10-6.Fig.3 shows the con figuration of the 3D lab-scale rectangular fluidized bed with the tracer gas injection and the data sampling locations in the horizontal(X-Y)plane and in the vertical(Z)direction.Our lab scale fluidized bed setup is a small-scale replica of commercially used fluidized bed technology,so the results from this study can be applied more accurately to a large size fluidized bed.

    2.1.Modeling

    In this study,a governing equation for tracer dispersion in a rectangular fluidized bed is formulated.An analytical solution is obtained for the governing equation of tracer dispersion with the physically relevant boundary conditions.

    The governing equation for tracer dispersion in the rectangular bed is as follows:

    whereCis the tracer concentration(kg·cm-3);Vx,Vy,andVzare the super ficial gas velocity vectors(cm·s-1)in the respective directions;andDx,Dy,andDzare the dispersion coefficients(cm2·s-1)in the respective directions.In a fluidized bed, flow through the bed is commonly represented by dispersed plug flow,where the mechanismofmixing involves the effective dispersion coefficients,DyandDr,known as axial and radial dispersion,respectively.Axial dispersion(Dy)can be offset by radial dispersion(Dr),which means that radial dispersion in fluences the plug flow behavior.For a steady state,plug flow,and negligible vertical dispersion(compared with the convective transport)from a point source in the rectangular bed,Eq.(1)can be simplified,as follows:

    The tracer progresses as a thin slab(dZ)in a rectangular bed where a massM(kg)oftracer is released atX=Y=Z=0.Rearranging Eq.(2)in the moving frame of reference with the direction of flow,thenZ/U= τ and ?C/?(Z/U)=?C/?τ and Eq.(2)transforms into the following equation:

    Fig.3.Continuous release of the tracer at mid-width W(X=0),(Y=0)and(Z=0).(a)The lab-scale fluidized bed.(b)Tracer point at mid-width.

    The solution is found by collecting thefandηterms on separate sides of the equation,as follows:

    As assumed in the beginning,τ=Z/U,we return to the stationary frame.Further,the solution transforms into the following equation:

    Dividing Eq.(6)by dZ(the tracer moving as a thin slab of heightdZ),the following equation is obtained:

    whereMis?m·(dZ/U)in which?mis the mass flow rate(kg·s-1,i.e.,Co·U·A),Cois the tracer gas concentration(kg·cm-3)atZ= ∞,andAis the cross-sectional area of theXYplane.Eq.(7)can be written as follows:

    The obtained experimental data are analyzed in OriginPro 8,which includes conversion of the worksheet data into the matrix for the 3D surface plot in theX-Y-Zdimensions.Origin's 3D surface fitting is performed by the nonlinear least squares fitter(NLFit)tool using a “user de fined built-in function”based on the compiled language(Origin C)of Eq.(8)[24,25].The solution,i.e.,Eq.(8),is written in the“Z-Script function form”,whereZis the dependent variable,andXandYare independentvariables.The other parameters in the“Z-Scriptfunction form”for surface fitting of Eq.(8)are de fined as follows:Z0,U1,D1,andD2 are named for the parametersA,U,DxandDy,respectively.Next,the“Z-Script function form”is compiled,and the parameter initialization is performed with constant and initial guess values.The nonlinear fitting always starts with an initial guess of the parameter to ensure greater convergence.Finally,auto-iterations are performed to achieve the best fit of Eq.(8)to the experimental data.

    Previously,Rowe and Evans[13]have discussed the solution and estimation ofDrusing a single-phase modelwith remote boundary conditions,as shown in Eq.(9).The results from Eq.(9)are used for comparison with the proposed model,i.e.,Eq.(8).

    3.Results and Discussion

    3.1.Effect of super ficial gas velocities(U)on the gas dispersion coef ficients(Dx and Dy)

    Fig.4.The experimental 3D surface plot of tracer gas concentrations with various super ficial gas velocities.(H s=20 cm;Z=5 cm).(a)U=3.5U mf;(b)U=5U mf;(c)U=6.5U mf.

    Fig.4(a)-(c)show the 3D surface plot of the tracer gas concentrations at the sampling height of 5 cm with super ficial gas velocities of 3.5Umf,5Umf,and 6.5Umf,respectively.TheXaxis andYaxis represent the length and width,respectively,of the lab-scale fluidized bed as shown in Fig.3.The unit is in centimeter.From Fig.4(a)-(c),it can be observed that as the super ficial gas velocity is increased,the tracer gas concentration spreads farther.

    Subsequently,Fig.5(a)-(c)show the nonlinear least squares surface fitting,based on the analytical solution,on the 3D surface plot ofthe experimental data to estimateDxandDy.The values of Adj.R-square in all surface fittings are greater than 97%,which indicates the quality of the best fit.Table 1 shows the estimated dispersion coefficients,DxandDy,from the nonlinear surface fitting of the experimentaldata under different working conditions.

    Fig.6(a)and(b)show the 2D form of the concentration profiles of the tracer gas along theXandYaxes with various super ficial gas velocities.The concentration profiles flatten as the super ficial gas velocity is increased,which indicates that the mixing extent at a higher super ficial gas velocity is improved.Fig.6(a)and(b)also show that the tracer gas concentration reaches a steady value,which is equivalent to the CO2concentration in the air(approximately 400×10-6).Because ofthe low sampling height(Z=5 cm),the jet effect is vigorous.Therefore,the maximum vertical tracer gas concentration could be overvalued.The maximum points are distantfrom the peak line.From Table 1,Dxis generally greater thanDy,which may be due to the effect of the side walls.The ratio ofDxtoDyaverages approximately 1.4-1.5,exceptundersome conditions,such aslowersampling height(Z=5 cm)and highersuperficial gas velocity(>3.5Umf)where the jet effect is dominant.

    Table 1Summary of the experimental conditions and results with tracer at center

    Fig.6.Experimental 2D concentration profiles of tracer gas with various super ficial gas velocities(H s=20 cm;Z=5 cm).(a)C/C o vs.Location on X-axis;(b)C/C o vs.Location on Y-axis.

    3.2.Effect of data sampling heights(Z)on the gas dispersion coef ficients(Dx and Dy)

    Fig.7(a)-(c)show the 3D surface plot of the tracer gas concentrations at the sampling height of 10 cm with different super ficial gas velocities of 3.5Umf,5Umf,and 6.5Umf,respectively.It can be observed that as the super ficial gas velocity is increased,the tracer gas concentration spreads farther,and the trends are similar to Fig.4(a)-(c).However,the effectof the side walls on the tracer gas concentration profile in Fig.7(b)and(c)is noticeable.The walleffectatZ=5 cm(Fig.5)is not highly significant.

    Fig.7.The experimental 3D surface plotof concentrations of the tracer gas with various super ficialgas velocities.(H s=20 cm;Z=10 cm).(a)U=3.5U mf;(b)U=5U mf;(c)U=6.5U mf.

    Fig.8(a)-(c)show the nonlinear least squares surface fitting,based on the analytical solution,on the 3D surface plot of the experimental data to estimateDxandDy.The values of Adj.R-square in all surface fittings are greater than 99%,which indicates the quality of the best fit.The estimated dispersion coefficients,DxandDy,are also listed in Table 1.As the sampling height(Z=10 cm)is increased,the jet effect is no longer significant.The side walls along the length of the chamber act as an immediate barrier at a higher super ficial gas velocity;thus,the tracer concentration near the wall is detected as markedly higher.This may affect the estimation of the dispersion coefficients,DxandDy;thus,Dxis not equal toDy.If the bed is sufficiently large throughout its width,then the tracer gas can disperse farther without being blocked by the side walls.In this ideal case,Dxwill be equal toDy.

    Fig.9.Experimental 2D concentration profiles of tracer gas with various super ficial gas velocities.(H s=20 cm;Z=10 cm).(a)C/C o vs.Location on X-axis;(b)C/C o vs.Location on Y-axis.

    Fig.9(a)and(b)show the 2D form of the concentration profiles of the tracer gas along theXandYaxes with various super ficial gas velocities.The concentration profiles flatten as the super ficial gas velocity is increased,and the trends are similar to those in Fig.6(a)and(b).However,the jet effect in Fig.9(a)and(b)is not significant compared with that in Fig.6(a)and(b),demonstrating the significance of the sampling height in estimating the dispersion coefficients.

    Fig.10(a)and(b)show the dispersion behavior in theX-Yplane with various fluidization values at sampling heights of 5 cm and 10 cm,respectively.As can be observed in Fig.10(a)and(b),the dispersion coefficientsDxandDyare increased with the super ficial gas velocity.With no jet effect atZ=10 cm,the dispersion coefficientsDxandDyshow a linear trend.Because of the jet effect atZ=5 cm,when the super ficial gas velocity is greater than 3.5Umf,the dispersion coefficientDxis larger than the value obtained atZ=10 cm.

    3.3.Effect ofwalls on the gas dispersion coef ficients(Dx and Dy)atdifferent tracer positions

    Fig.11(a)shows the 3Dsurface plotofthe concentrations ofthe tracer gas when the tracer's injection position is in the center ofthe bed.The operating conditions areU=5Umf,Hs=20 cm,andZ=10 cm.Subsequently,Fig.11(b)shows the nonlinear least squares surface fitting on the 3D surface plot of the experimental data in Fig.11(a)from whichDxandDyare estimated.The estimated dispersion coefficientsDxandDyare listed in Table 2.

    Compared with Fig.11(a),which has similar operating conditions(U=5Umf;Hs=20 cm;Z=10 cm),Fig.12(a)-(c)shows the 3D surface plot of the tracer gas concentrations when the location of the tracer gas injection point is near the wall.Subsequently,Fig.13(a)-(c)shows the nonlinear least squares surface fitting on the 3D surface plot of the experimental data from Fig.12(a)-(c).The estimated dispersion coefficientsDxandDyare listed in Table 1.

    Under ideal conditions,at the same horizontal plane with similar working conditions and operating parameters,the dispersion coefficientsDxandDyshould notdiffer.Theoretically,by modeling the analytic solution and assuming thatDx=Dy=46.0 cm2·s-1,which is given in Fig.11(b),the simulation of the tracer's concentration profile is presented in Fig.14.By comparing Figs.11(a)and 14,we can see that the tracer gas concentration profiles differ experimentally and theoretically.

    Fig.10.Gas dispersion coefficient with various fluidization numbers at different sampling heights(H s=20 cm).(a)Dx vs.U/U mf;(b)Dy vs.U/U mf.

    Table 2Summary of the experimental conditions and results with different location of the tracer

    However,in Fig.13(a)-(c),as the tracergas injection pointshifted to near the wall from the center,the dispersion coefficients differed.From Table 2,we can see that given similar operating conditions,the value ofDxdecreased,whereasDyremained almostunchanged.The ratio ofDxtoDywas 1.4 in the case when the tracer injection point was at the center.As the tracer injection pointshifted to near the wall,the ratio ofDxtoDywas 1.1.This change could be attributed to the fact that the concentration of the tracer gas(Ca/Co=28.9)was greater near the walls of the chamber.Therefore,the effect of the side walls on both dispersion coefficients in theXandYdirections is similar.Conversely,the tracer that was released at the center can diffuse much farther in theXdirection(Dx=46 cm2·s-1)because the walls are distant compared with theYdirection(Dx=32 cm2·s-1).In other words,if the length to width ratio of the rectangular bed is not appropriate,the mixing in the center area of the bed will not be excellent.

    Painet al.[26]discussed that the particles may slip at the wall or bounce off the wall,which creates complicated boundary conditions.These authors found that the time-averaged distribution of particles demonstrated that bubbles move in the central region of the bed and particles fall down along the bed wall.Liet al.[27]discussed that the solid-phase wall boundary condition needs to be specified with great care when gas mixing is modeled,because free-slip,partial-slip and no-slip wall boundary conditions result in substantial differences in the extent to which gas is transported downwards at the wall.Liet al.[28],in another study,found that both 2D and 3D simulations capture the general flow behavior in bubbling fluidized beds,but the wall effect in an experimental“two-dimensional”column was importantand must be considered when quantitatively comparing numerical simulations and experimental data.

    3.4.The effectof the gas injection rates on the dispersion coef ficients Dx and Dy in a horizontal plane

    To observe the effect of the side walls in the case of different gas injection rates,we changed the tracer gas injection rate from 0.20%to 0.10%of the fluidizing air flow rate.Fig.15(a)shows the 3D surface plot of the tracer gas concentrations when positioned at the center of the bed.The operating conditions were similar tofig.11(a),asU=5Umf,Hs=20 cm,andZ=10 cm,but the gas injection rate was 0.10%.Subsequently,Fig.15(b)shows the nonlinear least squares surface fitting on the 3D surface plot of the experimental data from Fig.15(a).The estimated dispersion coefficientsDxandDyare listed in Table 2.Evidently,we can see thatDychanged slightly from 32 to 29.8 cm2·s-1,butDxchanged from 46 to 26.5 cm2·s-1.At a tracer gas injection rate of 0.10%of the fluidizing air flow rate,the value ofDxwas approximately equal toDy.

    This result may be because the difference between the ambient and referenced carbon dioxide concentration was 1950×10-6(i.e.,2350×10-6-400×10-6)when the gas injection rate was 0.20%of the fluidizing air;the difference was 950×10-6(i.e.,1350×10-6-400×10-6)when the gas injection rate was 0.10%of the fluidizing air.This difference between the ambient and the referenced carbon dioxide concentration in the bed may be significant.The reduction in the ambient carbon dioxide from the background in the case when the gas injection rate was 0.20%ofthe fluidizing air improves the detection sensitivity.Therefore,the value ofDxcan be detected more accurately and is greater thanDy.In contrast,when the gas injection rate was 0.10%ofthe fluidizing air,Dxwas approximately equal toDydue to the lower detection sensitivity.

    3.5.Effect of the static bed heights on the gas dispersion coef ficients(Dx and Dy)

    Figs.16(a)and 11(a)show the 3D surface plot of the tracer gas concentration with a super ficial gas velocity of 5Umfat static bed heights of 15 cm and 20 cm,respectively.Subsequently,the nonlinear least squares surface fitting on the 3D surface plot of the experimental data in Figs.16(a)and 11(a)are shown in Figs.16(b)and 11(b).The estimated dispersion coefficientsDxandDyfor both bed heights(Hs=15 cm and 20 cm)are listed in Table 2.Fig.17(a)and(b)show the 2D representation of the tracer concentration for different bed heights(Hs=15 cm and 20 cm)in theXandYdirections,respectively.Clearly,the effect of static bed height onDxappears to be insignificant.This result is in agreement with our previous study where the effect of different bed heights onDrwas insignificant[29,30].However,the value ofDyincreased from 32 cm2·s-1to 37.3 cm2·s-1as the bed heightdecreased from 20 cm to 15 cm.Overall,the estimation ofthe optimal length to width ratio,bed height,and gas injection rate for good mixing in a rectangular bed is helpful for designing and controlling the fluidized bed reactor.

    3.6.Effect of the super ficial gas velocities on the gas dispersion coef ficients(Dx and Dy)with the multi-horizontal nozzle distributor

    Fig.18(a)and(b)show the 3D surface plot of the tracer gas concentration at super ficial gas velocities of 3.5Umfand 5Umfand static bed heights of 25 cm,respectively.It can be seen clearly that in the case of a multi-horizontal nozzle distributor,the maximum concentration of tracer gas is not at the center of the bed as was observed in the case of perforated plate distributor.The maximum concentration is shifted to the direction of nozzle orientation rather than stable at the center.We would like to validate our dispersion model in the case of a multihorizontal nozzle distributor.For this purpose,we rearranged the scale in theXdirection while inYdirection,the scale remains same.Fig.19(a)and(b)show the nonlinear least squares surface fitting on the 3D surface plot of the experimental data from Fig.18(a)and(b)and the results are listed in Table 2.It can be seen thatDxis considerably larger thanDyfor the multi-horizontal nozzle distributor compared to the perforated plate distributor in Table 2.The ratio ofDxandDyis 1.8.This shows that dispersion in theXdirection is higher for the multi-horizontal distributor than for the perforated plate distributor.

    Fig.12.The experimental 3D surface plot of the tracer gas concentration at 0.20%of the fluidizing air flow rate.The tracer gas injection was near the wall(H s=20 cm;Z=10 cm;U=5U mf).(a)Corner view;(b)side view;(c)front view.

    Fig.13.Nonlinear least squares surface fitting matrix on the experimental 3D surface plot of the tracer gas concentration at 0.20%of the fluidizing air flow rate.The tracer gas injection was near the wall(H s=20 cm;Z=10 cm;U=5U mf).(a)Corner view;(b)side view;(c)front view.

    4.Comparison With the Conventional Method

    Fig.14.The simulated 3D surface plot of the tracer concentrations based on Dx=Dy=46.0 cm2·s-1 where H s=20 cm,Z=10 cm,and U=5U mf.

    Fig.15.(a).The experimental 3D surface plot of the tracer gas concentrations at 0.10%of the fluidizing air flow rate(H s=20 cm;Z=10 cm;U=5U mf).(b).Nonlinear least squares surface fitting matrix on the experimental 3D surface plot of the tracer gas concentration at 0.10%of the fluidizing air flow rate(H s=20 cm;Z=10 cm;U=5U mf).

    Fig.16.(a).The experimental3Dsurface plotofthe tracergas concentration at0.20%ofthe fluidizing air flow rate(H s=15 cm;Z=10 cm;U=5U mf).(b).Nonlinear least squares surface fitting matrix on the experimental 3D surface plot of the tracer gas concentration at 0.20%of the fluidizing air flow rate(H s=15 cm;Z=10 cm;U=5U mf).

    Fig.17.Experimental 2D concentration profile of the tracer gas obtained using various static bed heights at 0.20%of the fluidizing air flow rate(Z=10 cm U=5U mf).(a)C/C o vs.location along the X-axis;(b)C/C o vs.location along the Y-axis.

    Fig.18.(a).The experimental3Dsurface plotofthe tracergas concentration at0.20%ofthe fluidizing air flow rate for a multi-horizontal nozzle distributor(H s=25 cm;Z=10 cm;U=3.5U mf).(b).The experimental3Dsurface plotofthe tracer gas concentration at0.20%of the fluidizing air flow rate for a multi-horizontal nozzle distributor(H s=25 cm;Z=10 cm;U=5U mf).

    Fig.19.(a).Nonlinear least squares surface fitting matrix on the experimental 3D surface plot of the tracer gas concentration at 0.20%of the fluidizing air flow rate for a multihorizontal nozzle distributor(H s=25 cm;Z=10 cm;U=3.5U mf).(b).Nonlinear least squares surface fitting matrix on the experimental 3D surface plot of the tracer gas concentration at 0.20%of the fluidizing air flow rate for a multi-horizontal nozzle distributor(H s=25 cm;Z=10 cm;U=5U mf).

    This approach is compared with the well-known conventional method[13]for estimating dispersion coefficients.In Table 1,by comparingDrwithDxandDy,the values and their order of magnitude generally remain in the same domain.These results show good support for this model.Previously,due to the assumption of uniform tracer concentration in theXandYdirections and the limitation of the solution,i.e.,Eq.(9),itwas only possible to calculateDrby neglecting the effectofthe side walls.With this new solution and using the 3Dsurface fitting method,which further decomposesDrintoDxandDy,it is possible to analyze the nature ofthe dispersion in both directionsas wellas the effect ofthe side walls in the rectangular chamber.It can be considered that there is always disparity between the theoretical and experimental dispersion behaviors due to the design of the chamber.

    5.Conclusions

    In this study,a mathematicalmodel for tracer dispersion in a rectangular fluidized bed is formulated.An analyticalsolution using the Pitheorem of dimensional analysis was obtained for 3D surface fitting of the experimental data.The dispersion coefficients,DxandDy,are estimated and analyzed.The experimental results obtained in this study indicate that the effect of super ficial gas velocity on the extent of gas dispersion is significant.The surface fitting shows that the estimatedDxandDyincrease with the super ficial gas velocity.The results also discussed the domination of the jet effect at a lower sampling height with higher super ficial gas velocity.The jet effect becomes insignificant as the sampling height increases.The estimatedDxandDyare not equal due to the effect of the side walls.The experimental results obtained in this study indicate that the effectof the side walls is significant.With similar working conditions,as the tracer gas injection point shifts near the wall from the center,DxandDychanged.The width to length ratio in a small rectangular fluidized bed affects the mixing in the centerofthe bed.Ata lowertracergas ratio ofthe injected gas to the totalgas flow rate,DxandDyare approximately equal.The results also show that the effect of bed height onDxis insignificant,whereas bed height may have an effect onDy.This model is also able to estimate the dispersion coefficients in the case of a multi-horizontal nozzle distributor.The results from this model are compared with the conventional method,which shows reasonably good agreement.

    Acknowledgements

    The financial support from the Ministry of Science and Technology under Grant MOST 105-3113-E-033-001 is greatly acknowledged.

    [1]K.Daizo,O.Levenspiel,Fluidization Engineering,Butterworth-Heinemann,USA,1991.

    [2]E.J.Anthony,Fluidized bed combustion of alternative solid fuels;status,successes and problems of the technology,Prog.Energy Combust.Sci.21(1995)239-268.

    [3]V.Orsat,V.Raghavan,Radio-frequency processing,in:D.W.Sun(Ed.),Emerging Technologies for Food Processing,Elsevier,USA 2005,pp.445-468.

    [4]D.Bing,L.S.Fan,F.Wei,W.Warsito,Gas and solids mixing in a turbulent fluidized bed,AICHE J.48(2002)1896-1909.

    [5]D.Y.Liu,X.P.Chen,Quantifying lateral solids mixing in a fluidized bed by modeling the thermal tracing method,AICHE J.58(2012)745-755.

    [6]J.J.Derksen,Simulations of scalar dispersion in fluidized solid-liquid suspensions,AICHE J.60(2014)1880-1890.

    [7]J.Werther,O.Molerus,The local structure of gas fluidized beds-II.The spatial distribution of bubbles,Int.J.Multiphase Flow1(1973)123-138.

    [8]A.B.Whitehead,D.C.Dent,Behavior of multiple tuyere assemblies in large fluidized beds,in:A.A.H.Drinkenburg(Ed.),Proceedings of the International Symposium on Fluidization,Netherlands University Press,Amsterdam 1967,pp.802-820.

    [9]D.Kunii,O.Levenspiel,Lateraldispersion ofsolid in fluidized beds,J.Chem.Eng.Jpn2(1969)122-124.

    [10]Y.F.Shi,L.T.Fan,Lateral mixing of solids in batch gas-solids fluidized beds,Ind.Eng.Chem.Process.Des.Dev.23(1984)337-341.

    [11]A.Klinkenberg,H.J.Krajenbrink,H.A.Lauwerier,Diffusion in a fluid moving at uniform velocity in a tube,Ind.Eng.Chem.45(1953)1202-1208.

    [12]H.Brenner,The diffusion model of longitudinal mixing in beds of finite length.Numerical values,Chem.Eng.Sci.17(1962)229-243.

    [13]P.N.Rowe,T.J.Evans,Dispersion of tracer gas supplied at the distributor of freely bubbling fluidised beds,Chem.Eng.Sci.2235-2246(1974).

    [14]A.Atimtay,T.Cakaloz,An investigation on gas mixing in a fluidized bed,Powder Technol.20(1978)1-7.

    [15]Y.C.Lin,C.S.Chyang,Radial gas mixing in a fludized bed using response surface methodology,Powder Technol.131(2003)48-55.

    [16]J.?tefanica,J.Hrdli?ka,Experimental investigation of radial gas dispersion coefficients in a fluidized bed,Acta Polytech.52(2012)97-100.

    [17]C.S.Chyang,Y.L.Han,C.H.Chien,Gas dispersion in a rectangular bubbling fluidized bed,J.Taiwan Inst.Chem.Eng.41(2010)195-202.

    [18]J.Sternéus,F.Johnsson,B.Leckner,Characteristics of gas mixing in a circulating fluidised bed,Powder Technol.126(2002)28-41.

    [19]R.S.Deng,F.Wei,T.F.Liu,Y.Jin,Radial behavior in riser and downer during the FCC process,Chem.Eng.Process.41(2002)259-266.

    [20]J.J.Van Deemter,Mixing patterns in large-scale fluidized beds,in:J.R.Grace,J.M.Matsen(Eds.),Fluidization,Plenum,New York 1991,pp.69-89.

    [21]W.Zhang,F.Johnsson,B.Leckner,Characteristics of the lateral particle distribution in circulating fluidized bed boilers,in:A.A.Avidan(Ed.),Proceedings of the 4th International Conference on Circulating Fluidized Beds,AIChE,USA 1993,pp.314-319.

    [22]W.D.Curtis,J.D.Logan,W.A.Parker,Dimensional analysis and the pi theorem,Linear Algebra Appl.7(1982)117-126.

    [23]L.Brand,The Pi theorem of dimensional analysis,Arch.Ration.Mech.Anal.1(1957)35-45.

    [24]M.L.Oyen,C.C.Ko,Examination of local variations in viscous,elastic,and plastic indentation responses in healing bone,J.Mater.Sci.Mater.Med.18(2007)623-628.

    [25]C.Xu,R.Shamey,Nonlinear modeling of equilibrium sorption of selected anionic adsorbates from aqueous solutions on cellulosic substrates.Part 1:model development,Cellulose19(2012)615-625.

    [26]C.C.Pain,S.Mansoorzadeh,C.R.E.De Oliveira,A study of bubbling and slugging fluidised beds using the two- fluid granular temperature model,Int.J.Multiphase Flow27(2001)527-551.

    [27]T.Li,Y.Zhang,J.R.Grace,X.Bi,Numerical investigation of gas mixing in gas-solid fluidized beds,AICHE J.56(2010)2280-2296.

    [28]T.Li,J.R.Grace,X.Bi,Study of wall boundary condition in numerical simulations of bubbling fluidized bed,Powder Technol.203(2010)447-457.

    [29]C.S.Chyang,K.Lieu,S.S.Hong,The effect of distributor design on gas dispersion in a bubbling fluidized bed,J.Chin.Inst.Chem.Eng.39(2008)685-692.

    [30]G.H.Sedahmed,Mass transfer at packed-bed,gas-evolving electrodes,J.Appl.Electrochem.17(1987)746-752.

    国产成人aa在线观看| 国产亚洲精品久久久com| 国产片特级美女逼逼视频| 女人被狂操c到高潮| 精品久久久久久久久久免费视频| 在线天堂最新版资源| 一区福利在线观看| 麻豆国产97在线/欧美| 六月丁香七月| 级片在线观看| 国产精品一区二区在线观看99 | 看非洲黑人一级黄片| 久久久a久久爽久久v久久| 日本撒尿小便嘘嘘汇集6| 菩萨蛮人人尽说江南好唐韦庄 | 国产日韩欧美在线精品| 久久久久久久久久久丰满| 能在线免费观看的黄片| 成年免费大片在线观看| 中文字幕免费在线视频6| 99热这里只有是精品在线观看| 欧美成人免费av一区二区三区| 免费黄网站久久成人精品| 久久草成人影院| 91精品国产九色| 国产一级毛片在线| 中出人妻视频一区二区| 成人亚洲精品av一区二区| 亚洲第一电影网av| 国产欧美日韩精品一区二区| 变态另类成人亚洲欧美熟女| 在线a可以看的网站| 秋霞在线观看毛片| 国产成人91sexporn| 搡女人真爽免费视频火全软件| 国产不卡一卡二| 国产一区二区在线观看日韩| 国产精品福利在线免费观看| 亚洲美女视频黄频| 免费观看人在逋| 午夜激情欧美在线| 蜜桃久久精品国产亚洲av| 日韩一区二区视频免费看| 国产免费一级a男人的天堂| 爱豆传媒免费全集在线观看| 亚洲欧美中文字幕日韩二区| 日韩在线高清观看一区二区三区| 3wmmmm亚洲av在线观看| 女人十人毛片免费观看3o分钟| 99久国产av精品| 国内精品一区二区在线观看| 日本与韩国留学比较| 日韩欧美 国产精品| 国产亚洲精品久久久com| 高清毛片免费观看视频网站| 国产成人a∨麻豆精品| 春色校园在线视频观看| 国产精品美女特级片免费视频播放器| 人妻系列 视频| 成熟少妇高潮喷水视频| 午夜福利成人在线免费观看| 欧美成人a在线观看| 国产一区亚洲一区在线观看| 日韩av不卡免费在线播放| 亚洲av一区综合| 丰满的人妻完整版| 国产一区二区在线观看日韩| 国产一区亚洲一区在线观看| 欧美性猛交╳xxx乱大交人| 男女视频在线观看网站免费| 国产精品美女特级片免费视频播放器| 看片在线看免费视频| 欧美一区二区精品小视频在线| 成年女人永久免费观看视频| 日韩一区二区三区影片| 久久久久久久久久成人| 少妇熟女aⅴ在线视频| 欧美日韩国产亚洲二区| 久久精品综合一区二区三区| 国产成人91sexporn| 99久久中文字幕三级久久日本| 日韩欧美一区二区三区在线观看| 有码 亚洲区| 美女cb高潮喷水在线观看| 欧美色欧美亚洲另类二区| 欧洲精品卡2卡3卡4卡5卡区| 十八禁国产超污无遮挡网站| 欧美日本视频| 夫妻性生交免费视频一级片| 日韩精品青青久久久久久| 婷婷色综合大香蕉| 精品午夜福利在线看| 狂野欧美激情性xxxx在线观看| 午夜激情福利司机影院| 成人高潮视频无遮挡免费网站| 婷婷色综合大香蕉| 男人和女人高潮做爰伦理| 亚洲三级黄色毛片| 久久99精品国语久久久| 国产黄片视频在线免费观看| 午夜精品国产一区二区电影 | 中文字幕av在线有码专区| 国产精品99久久久久久久久| 成年av动漫网址| 亚洲激情五月婷婷啪啪| 亚洲欧美日韩东京热| 国产精品永久免费网站| 美女脱内裤让男人舔精品视频 | 好男人视频免费观看在线| av黄色大香蕉| 成人毛片a级毛片在线播放| 又粗又硬又长又爽又黄的视频 | 亚洲va在线va天堂va国产| av视频在线观看入口| 噜噜噜噜噜久久久久久91| 亚洲婷婷狠狠爱综合网| 成人综合一区亚洲| 精品人妻视频免费看| 69av精品久久久久久| av黄色大香蕉| 99国产极品粉嫩在线观看| 一级毛片久久久久久久久女| 老司机福利观看| 亚洲第一电影网av| 国产在线精品亚洲第一网站| 免费人成在线观看视频色| 亚洲不卡免费看| 麻豆成人午夜福利视频| 国产在视频线在精品| 天堂中文最新版在线下载 | 亚洲一区高清亚洲精品| 在线a可以看的网站| 免费不卡的大黄色大毛片视频在线观看 | 亚洲性久久影院| 免费黄网站久久成人精品| 午夜视频国产福利| 一个人看的www免费观看视频| 国产三级中文精品| 亚洲av成人av| 久久精品夜色国产| 黄色一级大片看看| 99国产极品粉嫩在线观看| 午夜福利高清视频| 日本免费一区二区三区高清不卡| ponron亚洲| 有码 亚洲区| 狂野欧美白嫩少妇大欣赏| 人人妻人人看人人澡| 国产 一区精品| 亚洲国产精品成人综合色| 级片在线观看| 最好的美女福利视频网| 中国国产av一级| 男人的好看免费观看在线视频| 性色avwww在线观看| 精品久久久久久久末码| 毛片一级片免费看久久久久| 可以在线观看的亚洲视频| 天堂影院成人在线观看| 人人妻人人看人人澡| av在线蜜桃| 哪里可以看免费的av片| 亚洲av不卡在线观看| 一个人看视频在线观看www免费| 成人高潮视频无遮挡免费网站| 国产亚洲精品久久久久久毛片| 老熟妇乱子伦视频在线观看| 国产精品三级大全| 成人亚洲精品av一区二区| 99视频精品全部免费 在线| 成人特级av手机在线观看| 可以在线观看的亚洲视频| 亚洲人成网站在线播| 99热这里只有是精品在线观看| 日本欧美国产在线视频| 国产在视频线在精品| 人妻夜夜爽99麻豆av| 色综合亚洲欧美另类图片| 日韩三级伦理在线观看| 男人的好看免费观看在线视频| 亚洲av中文字字幕乱码综合| 国产一区二区三区av在线 | 一本久久中文字幕| 国产精华一区二区三区| 久久精品国产99精品国产亚洲性色| 久久亚洲国产成人精品v| 国产精品av视频在线免费观看| 久久久久网色| 亚洲在线观看片| 伦理电影大哥的女人| 国产一级毛片七仙女欲春2| 亚洲欧美精品专区久久| 久久99热这里只有精品18| 在线观看一区二区三区| 免费av毛片视频| 亚洲aⅴ乱码一区二区在线播放| 亚洲av不卡在线观看| 1000部很黄的大片| 欧美成人一区二区免费高清观看| 尾随美女入室| 国产高清视频在线观看网站| 国产91av在线免费观看| 日韩人妻高清精品专区| 夜夜爽天天搞| 国产精品伦人一区二区| 级片在线观看| 国产av麻豆久久久久久久| 久久精品国产亚洲av涩爱 | 亚洲国产精品国产精品| 黄片无遮挡物在线观看| 亚洲成人久久爱视频| 国内精品一区二区在线观看| 中文字幕熟女人妻在线| 久久精品国产鲁丝片午夜精品| 欧美精品一区二区大全| 国产高清有码在线观看视频| 精品人妻熟女av久视频| 干丝袜人妻中文字幕| av在线老鸭窝| av.在线天堂| 国产一区二区激情短视频| 晚上一个人看的免费电影| 寂寞人妻少妇视频99o| 少妇裸体淫交视频免费看高清| 99久久成人亚洲精品观看| 亚洲精品日韩在线中文字幕 | 精品熟女少妇av免费看| 久久久久久久久大av| 亚洲av男天堂| 国产成人精品婷婷| 99久国产av精品国产电影| 亚洲欧美成人精品一区二区| 色综合亚洲欧美另类图片| 国产视频内射| 男的添女的下面高潮视频| 校园人妻丝袜中文字幕| av在线老鸭窝| 黄片wwwwww| 国产精品一区www在线观看| 99久久精品一区二区三区| 亚洲在久久综合| 人人妻人人澡人人爽人人夜夜 | 亚洲人成网站在线观看播放| 久久精品国产亚洲av香蕉五月| 成人性生交大片免费视频hd| h日本视频在线播放| 丰满乱子伦码专区| 成人美女网站在线观看视频| 亚洲国产精品sss在线观看| 在线观看午夜福利视频| 国产老妇伦熟女老妇高清| 国产日本99.免费观看| 精品人妻一区二区三区麻豆| 22中文网久久字幕| 国产亚洲av嫩草精品影院| www.av在线官网国产| 丰满乱子伦码专区| 午夜精品一区二区三区免费看| 国产三级在线视频| 亚洲人与动物交配视频| 色哟哟哟哟哟哟| 亚洲国产精品成人综合色| 大又大粗又爽又黄少妇毛片口| 国产精品1区2区在线观看.| 一个人看的www免费观看视频| 久久精品91蜜桃| 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 | 国产精品.久久久| 九九热线精品视视频播放| 国产精品永久免费网站| 成人三级黄色视频| 日韩成人av中文字幕在线观看| 欧美xxxx黑人xx丫x性爽| 亚洲自拍偷在线| 国产真实伦视频高清在线观看| 欧美精品国产亚洲| 午夜福利视频1000在线观看| 亚洲欧美精品综合久久99| 日本三级黄在线观看| 国产免费一级a男人的天堂| 狂野欧美激情性xxxx在线观看| 国产精品精品国产色婷婷| 99久久九九国产精品国产免费| 欧美日韩一区二区视频在线观看视频在线 | 国产成人91sexporn| 最近手机中文字幕大全| 成人亚洲欧美一区二区av| 午夜亚洲福利在线播放| 免费av观看视频| 亚州av有码| 天天躁日日操中文字幕| 麻豆乱淫一区二区| 真实男女啪啪啪动态图| kizo精华| 搡女人真爽免费视频火全软件| 国产精品一二三区在线看| 午夜福利在线观看免费完整高清在 | 亚洲国产精品国产精品| 久久亚洲精品不卡| 亚洲人成网站在线播| 99国产极品粉嫩在线观看| 在现免费观看毛片| 日本黄色视频三级网站网址| 美女内射精品一级片tv| 老熟妇乱子伦视频在线观看| 亚洲七黄色美女视频| 18+在线观看网站| 哪里可以看免费的av片| 亚洲在线自拍视频| 在线免费观看的www视频| 欧美极品一区二区三区四区| 3wmmmm亚洲av在线观看| 一级av片app| 91午夜精品亚洲一区二区三区| 男人和女人高潮做爰伦理| 国产精品一区二区在线观看99 | 亚洲欧美日韩无卡精品| 少妇熟女欧美另类| 成人毛片a级毛片在线播放| 插阴视频在线观看视频| 免费av不卡在线播放| av在线播放精品| 国产伦在线观看视频一区| 床上黄色一级片| 中文在线观看免费www的网站| 黄片wwwwww| 免费看av在线观看网站| 国产精品福利在线免费观看| 精品无人区乱码1区二区| 欧美日韩综合久久久久久| 狠狠狠狠99中文字幕| 成人永久免费在线观看视频| 中国国产av一级| 欧美潮喷喷水| 男女边吃奶边做爰视频| 午夜视频国产福利| 99在线人妻在线中文字幕| 老女人水多毛片| eeuss影院久久| 麻豆精品久久久久久蜜桃| 两个人的视频大全免费| 国产精品嫩草影院av在线观看| 小说图片视频综合网站| 国模一区二区三区四区视频| 日本熟妇午夜| 美女xxoo啪啪120秒动态图| kizo精华| 18禁在线播放成人免费| 国产午夜精品论理片| 国产一区二区三区在线臀色熟女| 日韩欧美在线乱码| 亚洲最大成人av| 午夜视频国产福利| 欧美一区二区国产精品久久精品| 亚洲av中文字字幕乱码综合| 久久精品综合一区二区三区| 午夜免费男女啪啪视频观看| 我要看日韩黄色一级片| 午夜免费男女啪啪视频观看| 欧美性猛交╳xxx乱大交人| 亚洲av中文字字幕乱码综合| a级毛片免费高清观看在线播放| 亚洲在线自拍视频| 少妇丰满av| 插阴视频在线观看视频| 久久久精品大字幕| 婷婷亚洲欧美| 婷婷色综合大香蕉| 97热精品久久久久久| 亚洲av成人精品一区久久| 亚洲精品亚洲一区二区| 精品久久久久久久末码| 老师上课跳d突然被开到最大视频| 免费看a级黄色片| 非洲黑人性xxxx精品又粗又长| 悠悠久久av| 麻豆国产av国片精品| 亚洲成人久久性| 亚洲四区av| 在线观看免费视频日本深夜| 午夜老司机福利剧场| 亚洲成人av在线免费| 91久久精品国产一区二区成人| 人妻制服诱惑在线中文字幕| 日韩av在线大香蕉| 在线观看免费视频日本深夜| 男人的好看免费观看在线视频| 插逼视频在线观看| 久久久国产成人免费| 99久久久亚洲精品蜜臀av| 老司机影院成人| 亚洲中文字幕日韩| 国产老妇伦熟女老妇高清| 国产精品一区二区性色av| 国产亚洲精品久久久com| 天堂中文最新版在线下载 | 国产精品人妻久久久久久| 成人特级av手机在线观看| 看片在线看免费视频| 久久久久久国产a免费观看| 日韩一区二区视频免费看| 国产一区二区在线av高清观看| 国产欧美日韩精品一区二区| 淫秽高清视频在线观看| 搞女人的毛片| 少妇猛男粗大的猛烈进出视频 | 日韩 亚洲 欧美在线| 大型黄色视频在线免费观看| 少妇熟女欧美另类| 18禁黄网站禁片免费观看直播| 嘟嘟电影网在线观看| av免费观看日本| 精品日产1卡2卡| 看非洲黑人一级黄片| 中文字幕免费在线视频6| 久久精品久久久久久噜噜老黄 | .国产精品久久| 日韩高清综合在线| 国产精品一区二区性色av| 成人av在线播放网站| 日韩精品青青久久久久久| 色视频www国产| 少妇人妻一区二区三区视频| 精品久久久久久成人av| 免费不卡的大黄色大毛片视频在线观看 | 夜夜爽天天搞| 美女脱内裤让男人舔精品视频 | .国产精品久久| 最后的刺客免费高清国语| 日本黄色视频三级网站网址| 乱系列少妇在线播放| 精品人妻偷拍中文字幕| 日本黄色片子视频| 3wmmmm亚洲av在线观看| 国产又黄又爽又无遮挡在线| 村上凉子中文字幕在线| 国产精品久久久久久av不卡| 最近最新中文字幕大全电影3| av在线亚洲专区| 成人三级黄色视频| 人妻少妇偷人精品九色| 在线观看66精品国产| 国产黄片视频在线免费观看| 波多野结衣巨乳人妻| 我要看日韩黄色一级片| 九草在线视频观看| 日本-黄色视频高清免费观看| 99久国产av精品国产电影| 国产爱豆传媒在线观看| 又爽又黄无遮挡网站| 免费观看a级毛片全部| 一卡2卡三卡四卡精品乱码亚洲| 免费av毛片视频| 青春草视频在线免费观看| 哪里可以看免费的av片| 国产亚洲精品av在线| 日日摸夜夜添夜夜爱| 国产精品1区2区在线观看.| 久久久久九九精品影院| 男女啪啪激烈高潮av片| 国产精品久久久久久久久免| 99久久精品热视频| 美女被艹到高潮喷水动态| 淫秽高清视频在线观看| 黄色一级大片看看| 国产亚洲精品久久久com| 国产三级中文精品| 极品教师在线视频| 国产精品,欧美在线| 一级毛片aaaaaa免费看小| 久久久久久大精品| 不卡视频在线观看欧美| 最近手机中文字幕大全| 日韩av不卡免费在线播放| 又爽又黄无遮挡网站| 国产蜜桃级精品一区二区三区| 真实男女啪啪啪动态图| 我要看日韩黄色一级片| 国产黄片美女视频| 麻豆国产av国片精品| 亚洲乱码一区二区免费版| 亚洲精品乱码久久久v下载方式| 日韩欧美三级三区| 日韩欧美在线乱码| 亚洲高清免费不卡视频| 日韩欧美 国产精品| 色视频www国产| 日本色播在线视频| 国产精品伦人一区二区| av.在线天堂| 国产精品一区二区性色av| 丰满乱子伦码专区| 黄色欧美视频在线观看| 只有这里有精品99| 亚洲欧美清纯卡通| av福利片在线观看| 欧美性猛交╳xxx乱大交人| 国产在线男女| 国产精品三级大全| 中文字幕久久专区| 国产成人精品婷婷| 日韩视频在线欧美| 波多野结衣高清作品| 久久久精品大字幕| av又黄又爽大尺度在线免费看 | 卡戴珊不雅视频在线播放| kizo精华| a级毛片免费高清观看在线播放| 欧美最黄视频在线播放免费| 国产蜜桃级精品一区二区三区| 特大巨黑吊av在线直播| 亚洲欧美精品专区久久| 久久精品国产亚洲网站| 波多野结衣高清无吗| 99热6这里只有精品| 91午夜精品亚洲一区二区三区| 一进一出抽搐动态| 日本免费一区二区三区高清不卡| 亚洲国产色片| 欧美精品一区二区大全| 美女 人体艺术 gogo| 18禁黄网站禁片免费观看直播| 精品久久久久久成人av| 午夜a级毛片| 内地一区二区视频在线| www日本黄色视频网| 久久精品久久久久久久性| 日韩av不卡免费在线播放| 成人性生交大片免费视频hd| 永久网站在线| 一本一本综合久久| 麻豆久久精品国产亚洲av| 午夜精品在线福利| 日本黄大片高清| 国产亚洲av嫩草精品影院| 不卡一级毛片| 国产真实乱freesex| 日韩av不卡免费在线播放| 人妻系列 视频| 日韩欧美一区二区三区在线观看| kizo精华| 国产一区二区三区在线臀色熟女| 日日摸夜夜添夜夜添av毛片| 嫩草影院精品99| 中文字幕av在线有码专区| 亚洲精品色激情综合| 国产大屁股一区二区在线视频| 色综合亚洲欧美另类图片| 亚洲天堂国产精品一区在线| 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 | 中文字幕制服av| 亚洲国产欧美在线一区| 免费av观看视频| 性色avwww在线观看| 日韩精品青青久久久久久| 极品教师在线视频| 精品国产三级普通话版| 亚洲美女搞黄在线观看| 91av网一区二区| 亚洲一区高清亚洲精品| 亚洲激情五月婷婷啪啪| 国产淫片久久久久久久久| 精品一区二区三区人妻视频| 男人和女人高潮做爰伦理| 在线天堂最新版资源| 午夜福利视频1000在线观看| 国产免费一级a男人的天堂| 成人性生交大片免费视频hd| 久久精品人妻少妇| 中文字幕精品亚洲无线码一区| 欧美bdsm另类| 欧美最黄视频在线播放免费| 男女视频在线观看网站免费| 欧美又色又爽又黄视频| 久久久国产成人精品二区| 欧美日韩精品成人综合77777| 久久久国产成人精品二区| 黄片无遮挡物在线观看| 干丝袜人妻中文字幕| 亚洲真实伦在线观看| 三级毛片av免费| 色哟哟哟哟哟哟| 午夜爱爱视频在线播放| 亚洲精品乱码久久久久久按摩| 美女 人体艺术 gogo| 欧美日本亚洲视频在线播放| 女的被弄到高潮叫床怎么办| www.色视频.com| 小蜜桃在线观看免费完整版高清| 好男人视频免费观看在线| 国产亚洲5aaaaa淫片| 精品久久久久久久久久免费视频| 国产黄片视频在线免费观看| 大型黄色视频在线免费观看| 夜夜夜夜夜久久久久| 亚洲精品成人久久久久久| 日本在线视频免费播放| 亚洲av.av天堂| 欧美高清性xxxxhd video| 久久久久久伊人网av| 国产日韩欧美在线精品| 成年女人永久免费观看视频| 国产在线男女| 一级二级三级毛片免费看| 国产亚洲精品av在线| 一区二区三区四区激情视频 | av卡一久久| 国产女主播在线喷水免费视频网站 | 精品少妇黑人巨大在线播放 | 一级毛片我不卡| 少妇高潮的动态图| 国产一区二区激情短视频| 欧美高清成人免费视频www| 我要搜黄色片| 一个人看的www免费观看视频|