Sizing device is a kind use extensively at will coming loose cent of account other people is two kinds or the equipment of a variety of size scale. The problem of the development of domestic large sizing device and existence from on 70 time begin the century, home separates the development side of machine in large sieve, did a large number of works, gained very great success. The length of the compass screen surface in screening machinery and width are two important structure parameter, it is design and the problem that when choosing screening engine, encounter above all. According to screening theory, width of compass screen surface and the processing capability that sift extension are relevant, fall with appearance condition namely, compass screen surface is wider, processing capability is bigger. Length of compass screen surface and screening efficiency are relevant, fall with appearance condition namely, proper lengthen compass screen surface can improve screening efficiency, the mechanism that divides by probability screen however is knowable, as the lengthen of compass screen surface, bead diameter is more than the grain of detached bead diameter to sift a quantity to increase fully, and make screening loss of efficiency, from this length of knowable compass screen surface is put in an optimal value to make screening efficiency highest.

With probability statistical the mirrorred grain to grow way along the sieve probability appearing a sieve with build Weibull model better for the foundation, the design that is probability screen provided certain academic basis. Those who derive grain grows way along the sieve can be push to sift efficiency formula fully on the foundation of Weibull model, but this formula is too complex, and the function that did not point out efficiency and sieve are long directly concerns, very disadvantageous on industrial application. Be based on the research that length of compass screen surface affects to screening efficiency, those who put forward length of compass screen surface choose the granuality composition that should consider grain stock, build a sieve to grow to concern with the ration between screening efficiency, the design in probability screen and choose on can provide more direct basis. The article applies probability screen of imitate of law of three-dimensional disperse unit to divide a process, the function that built screening efficiency and length of compass screen surface concerns.

The numeric imitate of 1 screening efficiency and length of compass screen surface

As computer numerical value imitate is in the ceaseless application in industry, 70 time of 20 worlds develop the disperse unit law that rise to was the processing of grain system to offer a kind of new approach. This method is the basic law that collides with grain and Newtonian sports law for the foundation, undertake dogging to the athletic process of every grain in the system, get whole grain thereby group motion curve. Need experience parameter as a result of this method place little, the dimension of OK and convenient set grain distributings with property, because this has extensive adaptability. The article was based on disperse unit law to undertake the three-dimensional imitate of screening.

The three-dimensional model of screening (graph 1) is comprised by box of grain factory, sieve and compass screen surface. Grain factory can lay a track or quality is become

Obedience has some to distributing (normal school, lognormal distribution) grain, grain arrives in the whereabouts of initial velocity action of gravitational Z direction on compass screen surface, the oscillatory parameter of set compass screen surface (amplitude, oscillatory frequency and oscillatory deflection) , happen below grain and action of compass screen surface fully statified sieve and pour out of the screening effect such as compass screen surface, sieve box can collect the content below the content on the sieve and sieve. The coefficient of friction that the collision coefficient that grain and screen mesh of compass screen surface reach between the material property that uses in imitate, grain, grain moves as far as possible set is gotten as actual as the project medium value is adjacent. Detailed and initiative condition sees a table 1.

2 data processing reach conclusion

By simulative result, along statistic of X direction section the sieve unloads grain, and the screening efficiency that gets bead diameter grain grows direction to go up in the sieve differring. By the watch the relation curve between length of 2 medium data scale compass screen surface and screening efficiency, if pursue 2, can see from inside the graph, in the initial phase that screens case, as the addition with long sieve, the screening efficiency of each diameter grain rises quickly, the grain with opposite bead lesser at the same time diameter (0.2, efficiency of 0.4) its screening is fast approach apogee. Grow to increase again as the sieve, the screening efficiency of fine grained begins slow drop, and the grain with opposite bead older way the addition of its screening efficiency also hasten delay. By formula (1) can see, as the addition with long sieve, its sift the grain of some bead diameter fully probability increases, grow when the sieve when increasing to grow indefinitely, its sift probability fully for 100% . Odd grain sifts probability theory to point out fully, probability is sifted fully when relative to bead diameter little grain and compass screen surface are contacted big, because this is small,grain can appear a sieve more quickly. Small-scale diameter grain is in this second imitate inside shorter compass screen surface achieve highest screening efficiency, this also reflected odd grain to because probability screen is a kind of similar sizing device,sift probability theory fully, set the grain besides bead diameter appear a sieve, can reduce the screening efficiency of this diameter grain. If the grain of bead diameter is in some to did not appear a sieve completely to terminal of compass screen surface, the compass screen surface of after this can allow this track besides of grain appear a sieve, the screening efficiency of grain of second bead diameter can be reduced. Because this can conclude, if continue to increase,the sieve in imitate grows, the grain with opposite bead older way (0.6, 0.8) screening efficiency also can drop, it is imitate is restricted by computer hardware only, cannot the screening effect with more lasting imitate just.

3 conclusion: Law of unit of article use disperse (DEM) imitate the screening process of probability screen, put forward screening efficiency to grow the function relation that reachs opposite size to the sieve. Can see from inside function, the sieve grows the concern with screening efficiency is different to different bead way, the grain of small-scale diameter can achieve highest screening efficiency below shorter compass screen surface. And old bead way achieves place of best screening efficiency to need very long sieve to grow. When be being designed accordingly or choosing sizing device, be being comprised by the granuality of sieve stock should be a factor with consideration chief sieve. After integrated consideration affects all sorts of parameter of screening, add the function formula that the article offers, can make the design of sizing device more ideal.

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