Research of operational process of a grain separator with cylindrical screens

Screen separators are widely used in grain-cleaning machines. The separation occurs in the process of movement of grain over the surface of screen. The relative movement of grain is provided by different devices with various modes of motion. The most common is a vibrating sieve pan (screener), in which the grain is moved over screen by inertia. Screener has a high efficiency, but the alternating dynamic loads cause the metal fatigue and reduce machine reliability. The grain-cleaning separators with cylindrical screens operate without dynamic loads and have a simple design. They are less sensitive to grain moisture and impurity. But the separation process uses only 1/4-1/6 of the cylindrical screen surface. This problem reduces the throughput and limits the scope of application of cylindrical screens. The proportion of useful surface area can be increased by simultaneous use of two cylindrical screens. They are located one inside the other and rotate in opposite directions. The grain enters on the inner surface of the inner screen and forms a movable layer that moves in the axial direction. During the movement process, the grain passes through perforations, while the large impurities fall down from the screen. The grain having passed through the perforations of the inner screen reaches the section of the outer screen that is clear of movable grain layer. The rational conditions of simultaneous operation of screens are determined, under them the separation process on the outer screen starts immediately after the grain had passed through the perforations of the inner screen. Due to that the separation area is increased by 34-57%.

separator, grain cleaning, cylindrical screen, screen rotation, separation area, seed trajectory, condition of passing through