Influence of Cylinder Design on Its Speed During Corn Ear Threshing

Abstract

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).

Dynamic Indicators of a Corn Ear Threshing Process Influenced by the Threshing-Separation Unit Load

“…The torque of the threshing resistance was measured using a force sensor (Scaime ZFA 2000 N), which was placed between the unit frame and the lever connected to the stator of the electric motor [27]. The rotor shaft rotates in two bearing units attached to the frame of the threshing unit using bolts.…”

“…The output signal of the sensor was amplified using a Scaime CPJ amplifier and subsequently transmitted to the modified converter board (K8055N). The force applied to the rear part of the concave was measured using two Scaime ZFA 5000 N tension-compression force sensors 17 [27] fitted on rods holding the rear part of the concave. These sensors were capable of measuring loads of up to 5000 N. The total error of the sensor and the amplifier was 0.03% of the maximum measurement value.…”

“…The output signal of each sensor was strengthened using a Scaime CPJ amplifier and transmitted to the modified converter (K8055N), which turns the voltage into a 12bit data stream. Then, the signal was transmitted (via USB) from the converter to the computer (20), where it was further processed using the ThreshLab software [27], which calculates the mean value of the force at pre-set time intervals (minimum recommended: 20 ms). For this purpose, while measuring at a 1 kHz frequency, a sample with a pre-established size (5 values) was collected for each sensor.…”

“…The above-mentioned time periods last 1 s. Threshing takes place in period 3 (t2-t3), and its duration is ~5 s. The value of Fg1-2 during the threshing process, even under the well-established operating mode (t2-t3), is variable owing to the different physical-mechanical characteristics of the corn ear flow as well as other random factors. Force variations can be considered using the coefficient of fluctuation and amplitude described in the Methodology section [27]. Force Fg1-2 during process of operation is randomly achieved maximum and minimum numerical values that are different.…”

“…Feeding the threshing unit with a variable (uneven) flow of cereal crops or corn ears causes a significant loss in the quality of operation of combine harvesters. The use of filler plates in the cylinder during corn ear threshing was found to have a substantial effect on the threshing efficiency [26,27].…”