NUMERICAL AND EXPERIMENTAL ANALYSIS OF AIRFLOW IN A MULTI-DUCT CLEANING SYSTEM FOR A RICE COMBINE HARVESTER

Abstract. In order to improve the cleaning quality and efficiency of a rice combine harvester, a cleaning system comprising a cen-trifugal fan and four outlet ducts was developed. Three multi-duct centrifugal fans with the same rotor but different up-per outlet positions and volute walls were studied numerically and experimentally to evaluate the impact of the upper outlet on the inner flow field distribution of the fan. Computational fluid dynamics (CFD) was used to analyze the veloc-ity profiles, flow rate, internal velocity, and pressure of the centrifugal fan. Experiments were performed using hot-wire anemometers to measure the velocity at the four outlets of the fan to validate the simulations. CFD simulations were used to perform detailed flow visualization, velocity profile and flow rate estimation, and internal velocity field and pressure field analysis. Special attention was paid to the effect of the upper outlet on the inner flow field distribution and on achieving a balanced airflow division between the four outlets. It was observed that the internal field distribu-tion and the mass flow rate division between the four outlets can be greatly influenced by the upper outlet position. The optimal structure of the multi-duct centrifugal fan was obtained for the rice combine.