The Effect of Air Pressure on the Technological Process of Grinding in the Grain Hammer Mill

Introduction. The main problem of the grain hammer mill is over-grinding of grain caused by untimely removal of the final product from the grinding chamber. A way to effect the air flow arrangement in the grain hammer mill is to change the air pressure around the grinding chamber. Therefore, the study of the effect of air pressure around the grain hammer mill on the quality and energy indicators of its operation is an urgent task today. Aim of the Study. The study is aimed at determining the effect of air pressure around the grinding chamber on the air flow motion pattern in the grain hammer mill and its energy indicators. Materials and Methods. For a theoretical study of the air flow circulation in the grinding chamber, there was constructed a geometric model of the rotor placed in the grinding chamber. The Reynolds averaged equations of a continuous medium motion was the basis for the mathematical model of air motion. The calculation results were used to construct the velocity fields for the air flow. To conduct experimental studies, there was designed a pressure chamber that allows changing the air pressure in the grain hammer mill. Results. Based on the results of theoretical studies, it has been determined that the pressure decrease in the grinding chamber by 10 times reduces the power consumption by 112 watts. Experimental studies have shown that when the pressure in the grinding chamber decreases, the power consumed by the engine for all types of rotors decreases too. Also, an increase in air pressure in the grinding chamber leads to a change in the amount of grinded grain remains on the sieve to 0 mm: for the blade and hammer rotors, the amount of remains decreases, and for the hammer-blade rotor it increases. Discussion and Conclusions. The results of theoretical and experimental studies have shown that decreasing the air pressure around the grinding chamber can decrease the energy costs for the technological process and air flow motion inside the grinding chamber, and reduce the over-grinding of grain. The study results make it possible to design the grinding chambers for grain hammer mills taking into account the air flow motion.