Performance Assessment of a Self-propelled Paddy Grain Thresher under Different Threshing Functional Parameters

Highlights This research was aimed at assessing the performance of a self-propelled paddy grain thresher. Increasing cylinder speed increased the threshing percentage and percentage of broken grains of the machine. More broken grains were obtained at a lower concave clearance. The feed rate did not have much significance on the performance parameters that were evaluated. Abstract.This research was conducted to assess the performance of a self-propelled mini combine harvester, model number 4LZ-0.8 under different threshing functional parameters such as cylinder speed, concave clearance, and feed rate. An indoor experiment was conducted using the mini combine with an axial flow threshing cylinder and tangential feeding of material. These functional parameters were set at 5 levels each. The responses were obtained in terms of threshing percentage, percentage of unthreshed grains and percentage of broken grains. Response values were analyzed using the response surface tool (rstool) in MATLAB. Analysis of variance was done to determine the significant effects of the factor variations on the response values. MATLAB was used to present response surface graphs that were used to describe the variations of the responses as the factors changed from one level to the other. Results showed that with an increase in cylinder speed from 697 to 1202 rpm, the percentage of broken grains increased significantly from 0.0384% to 3.4052%, respectively. At cylinder speeds of 697 and 1202 rpm, the percentage of unthreshed grains increased from 0.1515% to 0.2162%, respectively. Furthermore, an increase in feed rate decreased the threshing percentage. The highest threshing percentage was obtained at an average concave clearance of 27 mm. Furthermore, it was realized that increasing the concave clearance from 18 to 35 mm, equally increased the percentage of unthreshed grains from 0.1478% to 0.3177%. The percentage of grain damage decreased from 3.2758% to 0.0268% with an increase in concave clearance from 18 to 35 mm, respectively. From the results obtained, it was tested and suggested that operating the threshing cylinder at a cylinder speed of 1100 rpm, concave clearance of 27 mm and feed rate of 0.9 kg s-1 offered the best machine performance. At these suggested values of the operating parameters, the threshing percentage was 99.9801%, the percentage of broken grains was 0.0134%, and the percentage of unthreshed grains was 0.0199%.