【正文】 result tested by the autogenous grinder was pared with extremely high specific area were obtained. The feasibility lf the developed newtype artogenous grinder in the view of fluid motion of bulk material was proved.Key words: motion of bulk material。 selfgrinding mechanism。 new developed mill1 IntroductionComminution except coarse grinding in most mintors or crushing machines is performed in the course of motion of bulk materials. Only in a few minting equipments such as rollermill and extruding milll, the vomminuted materials are stationary or fluid motion was provided through grasping the characteristic of fluid motion in the course of minuting.2 Fluid Motion of Bulk Materials of bulk materialsIn unconsolidated media mechanics, bulk material is also named loose body, it is the aggregate of interrelated solid particles, where a single particle presents the characteristic of solid and is the skeleton of the loose body. However, in macroscopic view, it also presents fluidity and some characteristics of liquid: (a) being the same with liquid, bulk material can not keep a certain shape。 (b) both bulk material and liquid can not bear a tension force but bear a pressure force. The difference between bulk material and liquid is that there exists an inner friction (inner friction angle) in the bulk material. This is to say, if an external condition is exerted on bulk material to alleviate or eliminate the inner friction angle, the bulk material will be fluidized. For example, adding some media such as water and colloid materials to bulk material or exerting special external forces (resonant force etc.) on bulk material, the bulk material can be fluidized. Affecting facters of bulk material motionAs stated above, the most predominant factor affecting the motion of bulk material is the existence of inner friction angle. The smaller the inner friction angle is, the easier the motion of bulk material bees. In the conctrte, the factors can be: (a) the lumpiness of single particle in bulk material, the lumpier the particle is, the more difficult the motion of bulk material will be。(b) the unit weight of bulk material, the beavier the rnit weight is, the more difficult the motion will be。(c) the looseness (porosity) of bulk material, the looser the bulk material is, the easier the motion will be。(d) the humidity of bulk material, bulk material starts to flow when the humidity exceeds a critical, whereas, for some bulk materials, the increment in humidity conversely brings about the increment of inner friction angle and leads it difficult to flow。(e) the morphology and surface roughness of single particle, the inner friction angle is colsely related to the morphology and roughness of particle of bulk material。(f) it is more difficult for momideal bulk material to flow than for ideal bulk material to. Classification of fluid motion of bulk materialThe fluid motion of bulk material can be classified according to whether there is energycarrier medium or not:(Ⅰ) Singlephase flow. When there is not energycarrier medium in the bulk material, or there are media, for example, air and water, but the media do not play the role of energycarrying, the flow is all regarded as singlephase flow.(Ⅱ) Biphase flow, when there are quantities of energycarrier media in the bulk material, the particles of bulk material are suspending or near to suspending, the flow is biphase flow.The flow velocity of bulk material is an impoetant parameter for selfgrinding. According to the velocity, the fluid motion can be classified:(ⅰ) ultimate low velocity (ν9m/s)。 (ⅱ) low velocity (9ν100m/s)。(ⅲ) medium velocity (20ν100m/s)。(ⅳ)high velocity (100ν200m/s)。 (ⅴ) ultrahigh velocity (250ν1000m/s). The efficiency of selfgrinding is very low when the flow velocity is in the ultimate low velocity range, the velocity is hardly chosen as a parameter in autogenous grinder. The low velocity is often chosen as a parameter in horizontal cylindrical autogenous grinders. The medium velocity is usually chosen as a parameter in vertial shaft centrifugal minutors, and high velocity and ultrahigh velocity are adopted in ultrafine minution.3 Analysis of Fluid Motion Mechanisn Classification of selfgrinding modesThe selfgrinding modes of fluid motion can be classified into:(a) impact selfgrinding. In this mode, particles collide each other and reduction takes place。(b) delaminating selfgrinding. Particles impact and shear each other, the particles are delaminated and reduction take place。(c) fatigue rupture selfgrinding. Materials are fatigued to rupture under the condition of highfrequency altenating pulse stresses. The fatigue rupture selfgrinding can make tough mateials to be minuted in the way in which brittle materials are minuted. Analysis of selfgrinding mechanismThe flowing forms of every kinds of bulk materials are posed of two basic flowing forms:linear flow and rotational flow. In practice, an independent flowing form is usually present in grinding machine, in a very few case, two flowing forms are positely present in centrfugal autogenous grinder. Hence, respectively studying the selfgrinding mechanism of the two basic flowing forms is the basis for investigating the selfgrinding mechanism of bulk material. Moreover, difference in phase and state of flowing bulk material must also be considered. linear flow(a) Singlephase linear flow. The forms of selfgrinding are impacting and delaminating of particles. For example, he principle of vertical shaft impact minutor is that a strong centrifugal force field caused by a highspeed rotating centrifugal disk brings about a highspeed linear jet of bulk material, the jet collides and impacts the particles remained the wall of cylinder. Meantime, the difference in velocity of jet particles caused by different sizes and morphologies also brings about impacting and delaminating of particles, but the degree of wearing and delaminaing is limited.(b