Сoncept of corn threshing by a rotary threshing-and-separating unit with an air curtain of the discharge port

Abstract

To increase the efficiency of harvesting corn for grain, some improvement is necessary in the design of the rotary threshing-and-separating unit, which has a massive rotor and an increased length of the path of active separation of grain mass during threshing. Reducing the size of rotary threshing units is possible by stopping the free grain flow into the discharge port at the output of the threshing chamber. This can be achieved by using an air curtain of the discharge port. At the same time, the free grain flow will be within regulated rates with a reduced rotor length and, accordingly, a shortened path length of the active separation of the grain mass. The stopping effect on the free-flowing grain in the discharge port should ensure its movement to the lower part of the threshing zone, where it is advisable to install a vibrating section of the deck that intensifies separation. Controlling the air curtain operation requires determining the shape of the grain profile common to the main botanical groups of corn and its effective area of contact with the air flow. The authors constructed the approximation of frontal and profile projections of dent and flint corn grains, taken from the lump, middle and toe of the cob, in the Compas‑3D environment. The values of generalized coefficients in polynomials determining the averaged geometry for the corn grain profile and the effective area of grain contact with the air flow were established. At the same time, the average value of the effective area of contact with the air flow is within 76 to 82 mm2 . The obtained coefficient values are necessary to calculate the parameters of the air curtain of the discharge port of a rotary threshing and separating unit for corn with a rotor length reduced by 10 to 15%. The authors propose to test an improved rotary threshing and separating unit in conditions of threshing corn cobs with a moisture content of more than 14% and without previous husk removing