Impact of technological parameters of threshing apparatus on grain damage

L. Špokas, D. Steponavičius and S. Petkevičius

Department of Agricultural Machinery Lithuanian University of Agriculture, Studentu Str.15A,LT 53362 Akademija, Kaunas r., Lithuania; e-mail: Liudas.Spokas@lzuu.lt

Abstract:

The paper describes the impact of the feed rate of cereals to the threshing apparatus, the movement speed of rasp bars and the clearance between the drum and the concave on the grain damage. When the feed rate of the cereals into the threshing apparatus is increased the grain damage decreases. Estimating the crop harvesting conditions the permissible flow of cereal is from 0.70 to 0.96 kg (s m)-1 for one meter of rasp bars length of the combine-harvester with four threshing-separation drums. The rasp bar speed of the threshing drum has the greatest impact on grain damage. When dry crop or cereals grown for seed (with moisture content of 12–14%) were harvested and the permissible limit crop flow was fed into the threshing apparatus the rational speed of drum rasp bars was 25 m s-1; when wet crop (moisture > 18%) was harvested the rational speed of drum rasp bars was from 31 m s-1 to 34 m s-1. Grain separation and their damage rate through all concave length increased when the clearance between the drum rasp bars and concave transverse bars at the beginning and at the end of the threshing apparatus was reduced. When combine-harvesters New Holland were used for the threshing of very dry crops (moisture content < 12%) the optimum clearance between the threshing drum rasp bars and the concave were 12–12 mm, for dry crops (moisture content 12–14%) the optimum clearance was 11–11 mm, and medium (14–16%) or high moisture (moisture content > 16%) the optimum clearance was 10–10 mm. The grain threshing losses were minimized until permissible (0.05%) by increasing the speed of the threshing drum rasp bars.

Key words:

crop flow, grain damage, grain separation, threshing apparatus

The influence of position of the first straw walker´s section on grain separation

D. Steponavičius, L. Špokas and S. Petkevičius

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: