Technological and structural parameters of a threshing unit must ensure the highest possible quality of its operation under minimum input and cost. The aim of the study was to estimate the variation of speed of threshing cylinder with two different shapes of filler plates (FP-I and FP-II) under various corn ear feed rate into combine harvester. Threshing cylinder speed (frequency of rotation) nb (min-1) was measured simultaneously each 0.075 s using stationary tangential single-cylinder threshing unit located in laboratory-training ground intended for investigation into technological processes of agricultural machinery. Frequency of rotation of non-loaded threshing cylinder speed amounted for 450 min-1. Increase in corn ear feed rate from 6 kg s-1 to 12 kg s-1 caused frequency of rotation of threshing cylinder to decrease from nb=437.82±0.21 min-1 to nb=420.96±0.50 min-1 (using FP-I). Replacing covered spaces between rasp bars with FP-II had no effect on cylinder speed – it has decreased from 438.06±0.23 min-1 to 421.37±0.32 min-1. Results showed that in case of FP-I, the amplitude of speed Anb has increased from Anb=4.07±0.44 min-1 to Anb=8.60±0.88 min-1, whereas in case of FP-II – from Anb=2.67±0.25 min-1 to Anb=4.52±0.62 min-1 in response to increased feed rate from 4 kg s-1 to 12 kg s-1. This means that using the covers FP-II the threshing apparatus will work more evenly. The average threshing cylinder speed, irrespective of the closure of spaces between rasp bars, was found to decrease by approx. 20 min-1 in result of increase in corn ear feed rate from 4 kg s-1 to 12 kg s-1. When threshing corn ears, irrespective of the shape of filler plates, the acceptable feed rate amounted for 10 kg s-1, as it caused to exceed the permissible limit of 5 % allowed for decrease in cylinder speed (nb=427.5 min-1).
Corn ear feed rate variations in the threshing-separation unit of a combine harvester have a significant impact on the dynamic indicators of the threshing process. In this study, we conducted experiments using a stationary tangential threshing device and measured the forces acting on the rear part of the concave as well as the torque of the rotating cylinder during a threshing process. The ThreshLab software was developed for this purpose. We found that increasing the corn ear feed rate made the threshing process more even, due to decreasing the fluctuation of forces acting on the rear part of the concave and torque of the rotating cylinder. The corn ear threshing process may be more stable if the threshing cylinder is fitted with filler plates (FP-II). A comparison of the results obtained for variations in the forces acting on the rear part of the concave with those obtained for variations in the total torque of resistance and the speed of the threshing cylinder revealed a linear correlation between these parameters at varied feed rates. DOI: http://dx.doi.org/10.5755/j01.mech.24.4.20721
Abstract. The main objective of the research was to establish movement of corn ears within the threshing crescent between the cylinder and the concave using high-speed recording method. Tangential threshing unit was used in the experimental trials. Cylinder rotation and linear velocity of rasp bars (11.00 m s ) were determined by using threshing cylinder covered with filler plates having 4 different shapes. During the trials, speed of corn ears within threshing crescent, number of impacts received by the corn ear, rising height of the corn ear after impact of rasp bar and time between two impacts of rasp bar to the corn ear, depending on the shape of filler plates of threshing cylinder were found. Video analysis of corn ear movement showed that the speed of corn ears movement in the threshing crescent highly depends on linear velocity of rasp bars. The average speed of corn ear within threshing crescent and number of impacts received by the corn ear were increased with increase of linear velocity of rasp bars irrespective of cylinder filler plates are used. Moreover, both above-mentioned parameters were larger in the second part of concave length than in the first one. A tendency of increase of the corn ear moving over the surface of the concave and decrease of number of impacts received by the corn ear was observable by reduction in the threshing crescent. Following reduction of linear velocity of rasp bars to 14.14 m s -1 , it would be reasonable to cover the threshing cylinder with filler plates that can reduce the cross-section area between rasp bars and concave (to 94.26 cm 2 in view of one gap between adjacent rasp bar). In this case, filler plates showed a substantial effect on behaviour of corn ears: they restrict a rising height of the corn ear, may be subject to additional rotational motion, deflect the corn ear to the clearance between the rasp bar and the concave bar as well as deflect threshed kernels towards concave grates.
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