# Predicting Ceramic Wool Diameter by Motor Frequency Using Improved BP Neural Network
## 2 Preparation of the Ceramic Wool  
Raw materials such as bauxite and coal gangue for ceramic wool production were smashed, mixed, and melt together. Then, the homogeneous mixed melted viscous fluid fell on the roller surface. Then, it was sucked into the moving centrifuge disc due to its own viscosity. On the disc surface, a layer of melt film formed gradually and the film was dragged into filaments due to the centrifugal force. The viscosity increased rapidly, and the instability diminished notably as the string increased in length, which allowed the wool to grow. The actual forming process and schematic diagram of the ceramic wool on the rotating wheel is shown in Figure 1.  
Figure 1: (**a**) The actual forming process of the ceramic wool on the rotating wheel; (**b**) The schematic diagram of the process.  
Rotating speed had a great influence on the ceramic wool diameter. However, it was not mature to describe the process by numerical simulation while studying the practical problems of centrifugal wool formation. As the complex fluid resulted from many influencing factors, the simulation results differ greatly from the actual results [20; 21; 22]. In addition, in the real production process, high rotating speed resulted in grossly increased instabilities under the high temperature environment. Moreover, the viscous fluid continued to flow to another spinning disc accompanying the action of collision and centrifugation. In fact, the fiber forming process mostly occurred in the main centrifuge disc. To facilitate the discussion of the centrifugation wool formation mechanism, the fiberization process on the main motor frequency was mainly studied and the secondary motor frequency was fixed in this paper.  
A similar simulation method was used to analyze the ceramic wool formation process. Meanwhile, the following assumptions were made for the particle force analysis of liquid melt in the centrifugal process:  
1. The temperature of the viscous fluid was constant when falling from the directing channel onto the spinning machine;
2. The viscosity of the viscous fluid was not changed in the fiber forming process;
3. The viscous fluid possessed constant density for its incompressibility;
4. The influence of severe temperature and complex physicochemical on the viscous fluid properties was ignored;
5. The ceramic wool fibers were thrown out along the tangent of the separation point of the roll surface.  
Figure 2 illustrates a simplified process of the ceramic wool fiberization. Firstly, the fixed viscous fluid fell downward onto the spinning wheel as shown in the Figure 2a. For an instant, the fluid turned into a thin melt film due to the centrifugal force. The supposed droplets were formed on the wheel as the surface tension increased [23]. The initial speed of the droplet was the same as the roller speed and the droplet velocity direction tended to be parallel to the tangent direction of the roller surface which was also the ideal direction of the droplet elongation. Then, the droplet was stretched into the filament as shown in Figure 2b,c [24]. In a very short time, the elongation process ended and the length of the filament was almost equal to the displacement distance of the droplet. Based on the conservation of mass, the fiber diameter decreased as the length increased. However, the length depended on the initial speed which was related to the main motor frequency. It indicated that the main motor frequency indeed played a decisive role in the fiber diameter [25].