Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 10 December 2019; accepted for publication 20 February 2020)
Abstract. When unloading grain harvester hoppers at standstill the time of emptying the hopper has a significant effect on the harvester productivity. The paper is about a conducted survey in 15 agricultural farms with 15 harvesters monitored including 14 models of 6 different brands during wheat harvesting. The time for emptying the grain hopper of the harvesters was defined by measuring the time. It was found that the actual time for emptying the hoppers of the studied harvesters was 134.85 s, and the actual flow rate of unloading of the screw in them being 69.63 L/s on average. A multivariate regression analysis was performed on the effect of the harvester grain hopper volume and the actual flow rate of the unloading screw on the time from switching on the unloading screw till its switching off in various grain harvesters. An adequate mathematical model of the effect of the hopper volume and the flow rate of the unloading screw of grain harvesters on the time for emptying the grain hopper under real production conditions has also been created. These results can also be used for minimizing costs in the technological process at harvesting.