The influence of position of the first straw walker´s section on grain separation
Department of Agricultural Machinery of Lithuanian University of Agriculture,Studentu St.15A, LT 53362 Akademija, Kaunas r., Lithuania;e-mail: Dainius.Steponavicius@lzuu.lt
Abstract:
The impact of the inclination angle of the first section (screen) of straw walkers on grain separation through the straw layer of various thicknesses has been tested in the laboratory. The straw feed rate on the straw walkers and the Froude number of the straw walkers (rotational speed of the walker crankshafts) was changed during the test. About 20% of the grains threshed and unseparated through the concave of the threshing device remained trapped in the straw layer fed on the straw walkers. It has been defined that the inclination angle of the first section of straw walkers were related to the straw throughput and the rotation speed of the walker crankshafts. The greatest number of grains was separated through the straw layer when it fell from the first section of straw walkers onto the second one. The optimum value of Froude number of the fourth straw walker assembly was 2.58 (the rotational speed of the crankshafts was 215 min-1), the inclination angle of the first straw walkers section was 22º, a step height was 0.28 m, the permissible limit straw feed rate on the straw walkers of dry straw (moisture content 9.8%) was 2.08 kg (s m)-1 on the layer with 0.43 m thickness because then only 3% of unseparated grains reach the fourth section of straw walkers with the straw. The intensity of grain separation can be controlled using the rotational speed of the crankshafts or the inclination angle of the first section of straw walkers.
Key words:
combine harvester, grain separation, straw walker design