Parameter optimisation of a centrifugal fan for rice combine harvesters based on airflow resistance coefficients and CFD simulations

In this work, both experimental and numerical simulations were employed to identify optimal fan parameter settings for achieving efficient cleaning performance during high-yield rice harvesting. First, field experiments were conducted to analyse the distribution of threshed outputs within the cleaning shoe, and then airflow resistance coefficients created by the fluidised grain and cleaning sieves in each zone were calculated. Subsequently, perforated plates were designed based on the calculated airflow resistance coefficients in different sieve zones to represent the cleaning load. The computational fluid dynamics (CFD) simulation results were validated by using measured airflow velocity at multiple points beneath the perforated plates. After validation, additional CFD simulations were performed under various fan parameter settings, incorporating porous media to simulate the fan's working load. The results indicated that a sieve opening of 26 mm, guide plate angles (I) of 38° and (II) of 36°, and a fan speed of 1300 rpm significantly improved airflow and pressure distribution within the fan. Finally, a field experiment validated the cleaning performance using the selected parameter combinations, achieving a grain sieve loss ratio of 0.78 % and a grain impurity ratio of 1.15 % at a feed rate of 6 kg s⁻¹. This innovative approach not only provides an accurate method for determining the fan's working load but also enables the evaluation of fan performance under varying load conditions through CFD simulations, ultimately enhancing the cleaning performance of rice combine harvesters through optimised parameter selection.