Evaluation of the combine harvester’s thresher efficiency by grain losses at operating conditions

BACKGROUND: The throughput capacity of the combine harvester’s thresher q_k is determined with permissible grain losses of 1.5% of its total amount collected in the combine bunker. The range of grain mass supply, for example, from a minimum of 0.5–1.0 kg/s to q_k is called the operating characteristic of the thresher (OCT) of a grain harvester. The actual grain loss in the considered supply range is less than 1.5%, but their overall value is unknown. Nevertheless, this is the most important indicator of the combine harvester’s efficiency, since these losses are summed up (for example, at the level of 1–1.2%) and can reach a significant value. Therefore, the assessment of the combine harvester only in terms of throughput is insufficient for efficiency evaluation, since the combine harvester operates at the throughput level rarely, and in the OCT mode, grain losses are summed up every second.

AIM: Development of the criterion for evaluation of operation efficiency of a combine harvester’s thresher by grain losses at operating modes.

METHODS: In the paper, the new method for evaluation of the efficiency of a combine harvester is proposed. Statistical dependences of grain losses change depending on change of grain mass supply to the combine harvester are used. The throughput capacity of the combine harvester’s thresher in kg/s is determined with grain losses behind the thresher at the level of 1.5%.

RESULTS: Numerous laboratory-field tests have revealed a close correlation between the four threshing parameters (engine power and separation area of the concave, straw walker and cleaning, and the dynamics of grain loss growth depending on the grain mass supply with great reliability in the range of the OCT feeds is approximated by a logistic dependence. For practical calculations, the software has been developed. This makes it possible to compare harvesters of different designs with each other faster.

CONCLUSION: For the first time, to evaluate the efficiency of the combine harvester’s thresher, a new criterion named as “average integral operational losses of grain behind the thresher in the operating range of grain mass supply” is introduced. An increase in grain losses behind the thresher was detected with an increase in the throughput of the combine harvester. The optimal harvesting area, during harvesting of which the growth of grain losses per unit of grain mass supply is compensated during the operating mode of highly-productive combine harvesters, is determined. The optimal harvesting area depends largely on the throughput capacity of the combine harvester and the harvesting conditions according to the state of the soil fertility and the zonal sequence coefficient, that is the degree of adaptability of the combine harvesters to the zonal features of the soil fertility and the applied methods of machine use. When calculating the economic efficiency of combines, it is advisable to consider the average integral operational losses of grain for alternative versions of combine harvesters and, on this basis, give them a more comprehensive evaluation. The use of the logistic function of grain losses from the grain mass supply to a combine harvester and, on its basis, the introduction of the criterion of average integral operational losses of grain behind the combine harvester’s thresher represents scientific and practical novelty.