Stripping mechanism and loss characteristics of a stripping-prior-to-cutting header for rice harvesting based on CFD-DEM simulations and bench experiments

A numerical simulation of the process of stripping-prior-to-cutting in a rice combine header was carried out based on coupled computational fluid dynamics (CFD) and discrete element method (DEM) techniques. A stripping-prior-to-cutting header with increased flow was designed, and a simulation of an upright flexible whole-plant rice cluster was established. The simulations demonstrate that when the rotation speed of the drum is 700 r min−1, the maximum air speed was 37.39 m s−1. Stripping height, forward speed, and stripping drum speed all influence losses during operations. Bench test results suggest that under the same rotational speed, the horizontal distribution and stability of the material thrown by the concave comb are better than those of the flat comb with falling grain loss rate, uncombed loss rate, and total loss rate are all lower compared to a flat comb. The minimum falling grain loss rates for flat and concave comb occurred at 500 r min−1 and 600 r min−1, with an average of 3.16% and 1.95%, respectively. The minimum uncombed loss rates for flat and concave combs occurred at 700 r min−1, with an average of 2.09% and 0.60%, respectively. This study provides a reference for revealing the loss mechanism of stripping-prior-to-cutting operations, promoting the application of stripping-prior-to-cutting harvesting methods, and future research on loss reduction and equipment development of related crops.