Uneven straw conveying and unstable throwing can reduce the operational performance of rice combine harvesters. To address these problems, an integrated straw conveying and throwing device combining guided conveying with pneumatic throwing was developed. The brachistochrone principle was introduced into the curved-surface design of the diversion plate as a geometry-guided approach to provide a continuous transition between the straw-falling region and the conveying inlet. Based on the motion characteristics of straw in the diversion and throwing regions, a coordinated feeding–acceleration–throwing process was established. The effects of diversion plate angle, blade rotational speed, and blade installation angle on throwing distance and distribution stability were investigated. A computational fluid dynamics model based on the mixture multiphase approach was used to characterize the macroscopic gas–solid flow field and compare airflow organization under different blade installation angles. A Box–Behnken response surface design was subsequently employed to establish regression models for throwing distance and the coefficient of variation in straw distribution, followed by multi-response numerical optimization. The optimal parameter combination consisted of a blade rotational speed of 2500 r/min, a diversion plate angle of 1.25 rad, and a backward blade installation angle of 15°. Under these conditions, the predicted throwing distance and coefficient of variation were 7.89 m and 14.6%, respectively. Validation tests produced throwing distances of 6.94–8.21 m and coefficients of variation of approximately 13%, showing good agreement with the predicted performance. The developed device and optimization results provide a basis for improving the conveying continuity and throwing uniformity of straw-handling systems in combine harvesters.

To address the high kernel breakage rate and incomplete threshing of high-moisture maize ears, a low-damage core-splitting–threshing method was proposed, and a maize-ear core-splitting device based on the internal expansion action of a splitting cone was developed. During operation, the splitting cone was screwed axially into the cob, and a radial splitting load was applied to the cob interior through thread-induced self-feeding and conical wedging, dividing the intact ear into several block-like segments and thereby weakening the kernel–cob connection and the supporting constraints among adjacent kernels. The main structural parameters of the splitting cone and clamping and conveying mechanism were determined through theoretical analysis. The discrete element method was used to investigate the core-splitting process at different splitting-cone rotational speeds, and core-splitting and subsequent threshing tests were conducted at kernel moisture contents of 25–30%. As the splitting-cone rotational speed increased from 150 to 650 r/min, the simulated and measured cob fragmentation degrees increased from 5 to 11 and from 6 to 11, respectively, while the measured kernel damage rate remained below 1.0% under all core-splitting conditions. In the subsequent threshing tests, the mean kernel breakage rate and unthreshed kernel rate of the core-split treatment group were 4.75% and 1.55%, respectively, representing reductions of 44.0% and 15.8% compared with 8.49% and 1.84% for the unsplit control group. Analysis of variance showed that threshing-element type had highly significant effects on both the kernel breakage rate and unthreshed kernel rate, while drum rotational speed and cob fragmentation degree had significant effects on both responses. Type C movable spike teeth exhibited good compatibility with core-splitting pretreatment, with mean kernel breakage and unthreshed kernel rates of 3.52% and 1.30%, respectively, corresponding to reductions of 48.6% and 18.9% relative to the corresponding unsplit controls. Increasing the cob fragmentation degree reduced both response indices, whereas increasing drum rotational speed reduced the unthreshed kernel rate but increased kernel breakage. Multi-objective optimization identified the optimal parameter combination as the Type C threshing element, a drum rotational speed of 1000 r/min, and a cob fragmentation degree of 11. Under these conditions, the predicted kernel breakage rate and unthreshed kernel rate were 3.30% and 1.18%, respectively, with an overall desirability of 0.939. These results provide a reference for pre-threshing core-splitting pretreatment of high-moisture maize ears and for the design and parameter matching of low-damage threshing devices.

High-moisture rice straw processed by whole-feed combine harvesters often exhibits high cutting resistance and uneven particle size distribution after comminution. To address these issues, a straw comminution device integrated with the straw outlet of the threshing and cleaning system was developed, and the shear fracture mechanism and operating parameters were investigated. The geometric characteristics, density, contact properties, and bending properties of rice straw cultivars Yongyou 7301 and Kenuigeng 1 were measured. A hollow flexible straw discrete element model was established using the Hertz–Mindlin with Bonding contact model, and its parameters were calibrated and validated through quasi-static shear cutting tests. The effects of shear cutting angle on maximum cutting force, bond failure evolution, and load transfer behavior were analyzed at shear angles of 30°, 45°, and 60°. Device-scale DEM simulations combined with field experiments were further conducted to optimize the guide plate angle and rotor speed. The results showed that the maximum cutting force under quasi-static single-stalk cutting conditions initially decreased and then increased with increasing shear angle. At a shear angle of 45°, the maximum cutting force was 78 N, representing a 44.8% reduction compared with that at 30°. Meanwhile, the fracture zone expanded along the blade sliding direction and stress concentration was alleviated. The DEM model effectively characterized the fracture behavior of rice straw, with an average relative error of 11.07% between simulated and experimental cutting forces. The optimized operating parameters under the tested conditions were a shear angle of 45°, guide plate angle of 55°, and rotor speed of 2500 r/min, resulting in average chopped lengths of 17.3 mm in simulation and 20.5 mm in field experiments, with a comminution qualification rate of 95.26%. These findings provide theoretical support for improving the fracture characteristics and chopping performance of straw comminution systems.