• <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.

    久久精品国产亚洲av天美| 尤物成人国产欧美一区二区三区| 亚洲在线自拍视频| 国内精品一区二区在线观看| 亚洲欧美日韩无卡精品| 波多野结衣高清作品| 69av精品久久久久久| 婷婷色av中文字幕| 国产乱人偷精品视频| 九草在线视频观看| 中文欧美无线码| 国产成人精品婷婷| 一本一本综合久久| 美女被艹到高潮喷水动态| 国语自产精品视频在线第100页| 少妇人妻一区二区三区视频| 噜噜噜噜噜久久久久久91| 国产精品久久久久久精品电影小说 | 少妇丰满av| 一级二级三级毛片免费看| 老司机影院成人| 国产亚洲av片在线观看秒播厂 | 午夜精品国产一区二区电影 | 欧美一区二区国产精品久久精品| 精品一区二区三区视频在线| 成人美女网站在线观看视频| 在线观看av片永久免费下载| 乱人视频在线观看| 久久久国产成人精品二区| 日韩欧美在线乱码| 精品人妻视频免费看| 久久久久久国产a免费观看| 日日摸夜夜添夜夜爱| 成人午夜高清在线视频| 日韩欧美国产在线观看| 美女 人体艺术 gogo| 蜜桃亚洲精品一区二区三区| 特大巨黑吊av在线直播| 久久久欧美国产精品| 亚洲人成网站在线播放欧美日韩| 黄片wwwwww| 国产 一区精品| 久久亚洲精品不卡| 美女国产视频在线观看| 成人特级av手机在线观看| av视频在线观看入口| 99riav亚洲国产免费| 精品一区二区三区视频在线| 欧美极品一区二区三区四区| 极品教师在线视频| 国产蜜桃级精品一区二区三区| 中文精品一卡2卡3卡4更新| 成年女人永久免费观看视频| 亚洲欧美日韩卡通动漫| 国产伦精品一区二区三区视频9| 黄片wwwwww| 99久久精品热视频| 波多野结衣高清作品| a级毛片免费高清观看在线播放| av视频在线观看入口| 亚洲精品日韩av片在线观看| 国产精品无大码| 波多野结衣高清作品| 亚洲av免费高清在线观看| 国产成人精品一,二区 | 欧美xxxx黑人xx丫x性爽| 国产久久久一区二区三区| 国产黄片美女视频| 国产精品一区二区三区四区久久| 99热6这里只有精品| 小蜜桃在线观看免费完整版高清| 国产午夜精品久久久久久一区二区三区| 国产一区二区三区在线臀色熟女| 99热6这里只有精品| 18+在线观看网站| 亚洲精品日韩在线中文字幕 | 欧美激情久久久久久爽电影| 午夜激情欧美在线| a级毛色黄片| 国产午夜精品论理片| 村上凉子中文字幕在线| 男女视频在线观看网站免费| 国产成人精品一,二区 | 91精品国产九色| 国产探花极品一区二区| 草草在线视频免费看| 美女内射精品一级片tv| 男女那种视频在线观看| 日韩一本色道免费dvd| 淫秽高清视频在线观看| 一卡2卡三卡四卡精品乱码亚洲| 老熟妇乱子伦视频在线观看| 亚洲av免费在线观看| 男人和女人高潮做爰伦理| 日韩视频在线欧美| 久久99精品国语久久久| 亚洲国产精品成人综合色| 免费黄网站久久成人精品| av天堂中文字幕网| 男女边吃奶边做爰视频| 极品教师在线视频| 成年女人看的毛片在线观看| 狂野欧美激情性xxxx在线观看| 在线免费观看不下载黄p国产| 亚洲人成网站在线观看播放| www日本黄色视频网| 毛片一级片免费看久久久久| 最近最新中文字幕大全电影3| 国产一级毛片七仙女欲春2| 美女黄网站色视频| 久久人人爽人人片av| 国产伦理片在线播放av一区 | 久久人人爽人人片av| 久久久久久久久久成人| 精品国产三级普通话版| 美女cb高潮喷水在线观看| 亚洲三级黄色毛片| 亚洲欧美日韩无卡精品| 久久国内精品自在自线图片| 亚洲精华国产精华液的使用体验 | 国产大屁股一区二区在线视频| 欧美三级亚洲精品| 成人漫画全彩无遮挡| 一级av片app| 一个人看的www免费观看视频| 高清日韩中文字幕在线| 狂野欧美白嫩少妇大欣赏| 伦精品一区二区三区| 日本色播在线视频| 99久国产av精品国产电影| 免费一级毛片在线播放高清视频| 3wmmmm亚洲av在线观看| 国产片特级美女逼逼视频| 亚洲人成网站在线观看播放| 九九久久精品国产亚洲av麻豆| 禁无遮挡网站| 成人永久免费在线观看视频| 久久精品国产清高在天天线| 麻豆乱淫一区二区| 欧美最新免费一区二区三区| 亚洲内射少妇av| 99热这里只有是精品在线观看| 久久久久国产网址| 欧美精品国产亚洲| 欧美成人精品欧美一级黄| 国产高清不卡午夜福利| 91久久精品国产一区二区三区| 成人二区视频| 国内精品美女久久久久久| 淫秽高清视频在线观看| 又爽又黄a免费视频| 国产精品一区二区性色av| 91久久精品国产一区二区三区| 如何舔出高潮| 三级国产精品欧美在线观看| 精品免费久久久久久久清纯| 国内精品久久久久精免费| 日产精品乱码卡一卡2卡三| 丝袜美腿在线中文| 大又大粗又爽又黄少妇毛片口| 国产av在哪里看| 卡戴珊不雅视频在线播放| 久久久精品大字幕| 在线观看一区二区三区| 51国产日韩欧美| 国产探花极品一区二区| 国产黄a三级三级三级人| 成人鲁丝片一二三区免费| 免费av不卡在线播放| 深夜精品福利| 久久草成人影院| 在线a可以看的网站| 九色成人免费人妻av| 又爽又黄无遮挡网站| 在线观看免费视频日本深夜| 一级毛片电影观看 | 欧美一级a爱片免费观看看| 亚洲精品久久久久久婷婷小说 | 人妻少妇偷人精品九色| 亚洲av二区三区四区| 亚洲精品粉嫩美女一区| 人妻系列 视频| 三级经典国产精品| 亚洲内射少妇av| 亚洲欧美精品综合久久99| 婷婷精品国产亚洲av| 日韩制服骚丝袜av| 男女啪啪激烈高潮av片| 欧美不卡视频在线免费观看| 国产精品久久久久久久电影| 久久精品国产清高在天天线| 国内精品宾馆在线| 国产综合懂色| 搡老妇女老女人老熟妇| 久久99热6这里只有精品| 亚洲第一电影网av| 亚洲av二区三区四区| 久久久午夜欧美精品| 亚州av有码| 麻豆国产av国片精品| 最近最新中文字幕大全电影3| 国产白丝娇喘喷水9色精品| 男女做爰动态图高潮gif福利片| 一区二区三区免费毛片| 精品人妻一区二区三区麻豆| 日本-黄色视频高清免费观看| av免费在线看不卡| 亚洲欧美清纯卡通| 中文在线观看免费www的网站| 小说图片视频综合网站| 色综合亚洲欧美另类图片| 99riav亚洲国产免费| 国产精品麻豆人妻色哟哟久久 | 国产精品精品国产色婷婷| 成人av在线播放网站| 波多野结衣巨乳人妻| 日本免费一区二区三区高清不卡| 国产一区二区在线av高清观看| 亚洲人与动物交配视频| 欧美变态另类bdsm刘玥| 精品不卡国产一区二区三区| 国产精品一及| 久久午夜亚洲精品久久| 精品久久久噜噜| 边亲边吃奶的免费视频| 欧美一区二区国产精品久久精品| 久久久久性生活片| 国产精品99久久久久久久久| 少妇人妻一区二区三区视频| 亚洲国产精品成人综合色| 直男gayav资源| 美女脱内裤让男人舔精品视频 | 国产亚洲精品久久久com| 欧美一级a爱片免费观看看| 亚洲真实伦在线观看| 国产黄色小视频在线观看| 亚洲国产精品久久男人天堂| 亚洲成人久久性| 噜噜噜噜噜久久久久久91| 国产精品蜜桃在线观看 | 国产一区亚洲一区在线观看| 97热精品久久久久久| 久久久a久久爽久久v久久| 男的添女的下面高潮视频| 青青草视频在线视频观看| 直男gayav资源| 边亲边吃奶的免费视频| 激情 狠狠 欧美| 麻豆乱淫一区二区| 久久亚洲国产成人精品v| 精品人妻视频免费看| 18禁在线播放成人免费| 韩国av在线不卡| 国产探花极品一区二区| 亚洲熟妇中文字幕五十中出| 精品人妻一区二区三区麻豆| 久久精品久久久久久噜噜老黄 | 赤兔流量卡办理| 99热网站在线观看| 国产精品久久电影中文字幕| 久久欧美精品欧美久久欧美| 国产片特级美女逼逼视频| 国语自产精品视频在线第100页| 久久久精品欧美日韩精品| av在线老鸭窝| 日韩制服骚丝袜av| 成年av动漫网址| 2022亚洲国产成人精品| 亚洲国产精品成人久久小说 | 国产麻豆成人av免费视频| 免费av不卡在线播放| 国产精品女同一区二区软件| 欧美高清成人免费视频www| 免费不卡的大黄色大毛片视频在线观看 | 一边亲一边摸免费视频| 国产综合懂色| 美女国产视频在线观看| 亚洲国产精品久久男人天堂| 村上凉子中文字幕在线| 久久久久性生活片| 亚洲精品日韩在线中文字幕 | 亚洲欧美精品专区久久| 在线免费观看不下载黄p国产| 免费观看在线日韩| 午夜福利在线观看吧| 欧美+日韩+精品| 日韩三级伦理在线观看| 精品人妻一区二区三区麻豆| 久久婷婷人人爽人人干人人爱| 免费看av在线观看网站| av在线观看视频网站免费| 精品一区二区三区视频在线| 熟女电影av网| 一级毛片我不卡| 久久鲁丝午夜福利片| 成人特级av手机在线观看| 久久久久久久亚洲中文字幕| 高清日韩中文字幕在线| 又爽又黄a免费视频| eeuss影院久久| 久久久久性生活片| 99国产极品粉嫩在线观看| 在现免费观看毛片| 国产极品精品免费视频能看的| 免费搜索国产男女视频| 99久久九九国产精品国产免费| 久久久久久久午夜电影| av专区在线播放| 爱豆传媒免费全集在线观看| 亚洲国产精品久久男人天堂| 久久亚洲精品不卡| 国产久久久一区二区三区| 免费观看a级毛片全部| 精品无人区乱码1区二区| 国产精品一区二区性色av| 日韩欧美精品免费久久| 欧美最新免费一区二区三区| 嫩草影院入口| 国产精品1区2区在线观看.| 69人妻影院| 日韩成人伦理影院| 我要看日韩黄色一级片| 在线播放无遮挡| 亚洲欧洲日产国产| 国产成人精品一,二区 | 亚洲,欧美,日韩| 淫秽高清视频在线观看| 欧美高清成人免费视频www| 精品久久国产蜜桃| 美女被艹到高潮喷水动态| 深夜精品福利| 国内精品久久久久精免费| 美女黄网站色视频| 国产成人a区在线观看| av免费在线看不卡| 男女那种视频在线观看| 亚洲精品色激情综合| 国产乱人偷精品视频| 久久精品夜夜夜夜夜久久蜜豆| 国产精品久久久久久久久免| 日韩中字成人| 欧美成人免费av一区二区三区| 91aial.com中文字幕在线观看| 麻豆乱淫一区二区| 黄片无遮挡物在线观看| 看黄色毛片网站| 国产亚洲91精品色在线| 啦啦啦韩国在线观看视频| 精品午夜福利在线看| 国产亚洲av片在线观看秒播厂 | 高清午夜精品一区二区三区 | 又粗又爽又猛毛片免费看| 精品一区二区三区视频在线| 午夜福利高清视频| 非洲黑人性xxxx精品又粗又长| 中文字幕av成人在线电影| 国产精品久久久久久精品电影小说 | 久久精品人妻少妇| 午夜激情福利司机影院| 最好的美女福利视频网| 国产精品伦人一区二区| 五月伊人婷婷丁香| 亚洲久久久久久中文字幕| 黄片wwwwww| 人妻久久中文字幕网| 亚洲欧美日韩无卡精品| 欧美极品一区二区三区四区| 日韩制服骚丝袜av| 观看免费一级毛片| 国产一区亚洲一区在线观看| 欧美最黄视频在线播放免费| 国国产精品蜜臀av免费| kizo精华| 国产黄色小视频在线观看| 搞女人的毛片| 岛国在线免费视频观看| 久久久久久久久久久免费av| 亚洲高清免费不卡视频| 在线观看免费视频日本深夜| 综合色丁香网| 婷婷亚洲欧美| 最后的刺客免费高清国语| 美女脱内裤让男人舔精品视频 | 亚洲人成网站在线观看播放| 免费电影在线观看免费观看| 久久人人爽人人片av| 亚洲经典国产精华液单| 成人特级av手机在线观看| 男女那种视频在线观看| 久久精品国产自在天天线| 欧美丝袜亚洲另类| 波多野结衣巨乳人妻| 最新中文字幕久久久久| 国产片特级美女逼逼视频| 亚洲欧美日韩东京热| 深夜精品福利| 别揉我奶头 嗯啊视频| 波多野结衣高清无吗| 春色校园在线视频观看| 老熟妇乱子伦视频在线观看| 亚洲国产欧美人成| 日韩欧美国产在线观看| www日本黄色视频网| 99热全是精品| 两个人的视频大全免费| 国产成人影院久久av| 日韩,欧美,国产一区二区三区 | 国产精品日韩av在线免费观看| 晚上一个人看的免费电影| 久久99蜜桃精品久久| 国产美女午夜福利| 中文亚洲av片在线观看爽| 国产黄色小视频在线观看| 久久久精品大字幕| 亚洲国产精品sss在线观看| 亚洲人与动物交配视频| 欧美三级亚洲精品| 欧美成人一区二区免费高清观看| 国产精品国产高清国产av| 久久综合国产亚洲精品| 中文字幕av在线有码专区| 日韩欧美精品v在线| 国产亚洲精品久久久com| 国产伦一二天堂av在线观看| 中文精品一卡2卡3卡4更新| 国产又黄又爽又无遮挡在线| 97人妻精品一区二区三区麻豆| 久99久视频精品免费| 成人亚洲欧美一区二区av| 一级毛片久久久久久久久女| av在线老鸭窝| 亚洲美女视频黄频| 国产一级毛片在线| 午夜a级毛片| 久久久久久久久久久丰满| 免费电影在线观看免费观看| av专区在线播放| 青春草亚洲视频在线观看| 我要看日韩黄色一级片| 中国美白少妇内射xxxbb| 久久久精品94久久精品| 十八禁国产超污无遮挡网站| 亚洲欧美清纯卡通| 中国美白少妇内射xxxbb| 国产精品日韩av在线免费观看| 国产av一区在线观看免费| 欧美bdsm另类| 91精品国产九色| 日韩欧美精品v在线| 国产69精品久久久久777片| 日韩精品青青久久久久久| 精品一区二区三区视频在线| 亚洲电影在线观看av| 卡戴珊不雅视频在线播放| 亚洲性久久影院| 青春草亚洲视频在线观看| 天堂av国产一区二区熟女人妻| 亚洲av.av天堂| 99久久成人亚洲精品观看| eeuss影院久久| 特大巨黑吊av在线直播| 村上凉子中文字幕在线| 少妇熟女欧美另类| 麻豆久久精品国产亚洲av| 日本一二三区视频观看| 亚洲色图av天堂| 亚洲最大成人av| 免费观看精品视频网站| 免费不卡的大黄色大毛片视频在线观看 | 又爽又黄a免费视频| 亚洲欧洲国产日韩| 国产精品一二三区在线看| 在线天堂最新版资源| videossex国产| 人妻制服诱惑在线中文字幕| 在线观看美女被高潮喷水网站| 欧美日韩国产亚洲二区| 成人漫画全彩无遮挡| 18+在线观看网站| 国产国拍精品亚洲av在线观看| 国产亚洲av片在线观看秒播厂 | 美女高潮的动态| 日本熟妇午夜| 最近视频中文字幕2019在线8| 中国美白少妇内射xxxbb| 免费大片18禁| 国产精品99久久久久久久久| 欧美一区二区亚洲| 97超碰精品成人国产| 欧美性猛交╳xxx乱大交人| 欧美高清成人免费视频www| 亚洲欧美成人精品一区二区| 久久精品久久久久久噜噜老黄 | 亚洲天堂国产精品一区在线| 全区人妻精品视频| 国国产精品蜜臀av免费| 久久人人爽人人片av| 国产成人精品久久久久久| 99在线视频只有这里精品首页| 午夜福利在线观看免费完整高清在 | 午夜福利成人在线免费观看| 国产精品久久久久久久电影| 在线观看午夜福利视频| 免费无遮挡裸体视频| or卡值多少钱| 国产精品麻豆人妻色哟哟久久 | 久久久久免费精品人妻一区二区| 久久久久久国产a免费观看| 国产精品电影一区二区三区| 精品午夜福利在线看| 中文字幕久久专区| 哪里可以看免费的av片| 免费人成在线观看视频色| 有码 亚洲区| 国产大屁股一区二区在线视频| 在线免费观看的www视频| 十八禁国产超污无遮挡网站| 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 | 晚上一个人看的免费电影| 男人舔女人下体高潮全视频| 欧美另类亚洲清纯唯美| 一区福利在线观看| 国产av一区在线观看免费| 丰满人妻一区二区三区视频av| 国产色爽女视频免费观看| 天堂√8在线中文| 国产激情偷乱视频一区二区| 久久久久久久午夜电影| 久久亚洲国产成人精品v| 偷拍熟女少妇极品色| av在线亚洲专区| 国产黄片视频在线免费观看| www.av在线官网国产| 亚洲七黄色美女视频| 亚洲国产精品合色在线| 91在线精品国自产拍蜜月| 亚洲最大成人中文| av在线播放精品| 日韩,欧美,国产一区二区三区 | 18禁在线无遮挡免费观看视频| av天堂中文字幕网| 午夜精品在线福利| 精品一区二区三区人妻视频| 成人av在线播放网站| 亚洲精品乱码久久久久久按摩| 美女 人体艺术 gogo| 日产精品乱码卡一卡2卡三| 成人二区视频| 国产高清激情床上av| 色尼玛亚洲综合影院| 久久久久久久久大av| 国产在视频线在精品| 91麻豆精品激情在线观看国产| 老女人水多毛片| 中文精品一卡2卡3卡4更新| 乱码一卡2卡4卡精品| 99热网站在线观看| 亚洲人成网站高清观看| 我的女老师完整版在线观看| 中文在线观看免费www的网站| 色综合亚洲欧美另类图片| 欧美最黄视频在线播放免费| 色综合站精品国产| 国产探花极品一区二区| 色播亚洲综合网| 看免费成人av毛片| 中国美女看黄片| 成人毛片60女人毛片免费| 美女 人体艺术 gogo| 日韩欧美精品v在线| 精品久久久久久成人av| 国产高清激情床上av| 又黄又爽又刺激的免费视频.| 久久精品综合一区二区三区| 亚洲国产日韩欧美精品在线观看| 舔av片在线| 成人高潮视频无遮挡免费网站| 91久久精品国产一区二区成人| 全区人妻精品视频| 久久久久网色| 99久久久亚洲精品蜜臀av| 成年免费大片在线观看| av免费观看日本| av黄色大香蕉| 国产亚洲91精品色在线| 亚洲在线观看片| 亚洲国产欧美人成| 欧美激情国产日韩精品一区| 色播亚洲综合网| 国产极品精品免费视频能看的| 亚洲人与动物交配视频| 国产精品福利在线免费观看| 成年av动漫网址| 日韩三级伦理在线观看| 国产欧美日韩精品一区二区| 我要看日韩黄色一级片| 欧美最新免费一区二区三区| 99在线视频只有这里精品首页| 神马国产精品三级电影在线观看| 久久草成人影院| 国产私拍福利视频在线观看| 大又大粗又爽又黄少妇毛片口| 久久久精品94久久精品| 亚洲,欧美,日韩| 国模一区二区三区四区视频| 两个人的视频大全免费| 桃色一区二区三区在线观看| 久久亚洲精品不卡| 日韩一区二区视频免费看| 日韩成人av中文字幕在线观看| 黄色日韩在线| 欧美色视频一区免费| 久久欧美精品欧美久久欧美| 人妻久久中文字幕网| 色吧在线观看|