CFD analysis of flow-field characteristics and operating-parameter optimization of a dual-shaft straw biomass shredding and spreading machine

Straw biomass is an important agricultural renewable resource, and its shredding and field spreading are essential for sustainable agricultural development. This study investigates how internal airflow characteristics, airflow uniformity, and shaft-speed matching affect spreading-related flow-field conditions and field spreading performance in a dual-shaft straw biomass shredding and spreading machine. CFD simulations were used to characterize internal airflow structures and identify airflow-favorable shaft configurations. The CFD model was validated by comparing simulated airflow velocities with static airflow measurements at 26 points on three cross-sections. Across the 26 validation points, with a maximum absolute percentage error of 4.16%, indicating satisfactory agreement between the simulation and measurement results. Field experiments were then conducted to evaluate the practical relevance of the CFD findings through spreading performance and to optimize the operating parameters. A quadratic regression model of the uneven distribution rate was established, and the optimal operating parameter combination was identified as PTO Speed Setting 2, working height 6 cm, and forward speed 5 km/h. Under this operating condition, the measured uneven distribution rate of straw biomass spreading was reduced to 8.45%. This study provides a flow-field-based basis for improving internal airflow uniformity and straw biomass spreading performance in dual-shaft straw shredding and spreading machines, and offers useful support for the efficient recycling of agricultural biomass resources and sustainable agricultural development. • Airflow distribution patterns in dual-shaft straw shredding and spreading machine. • CFD analysis shows the influence of dual-axis steer and speed on airflow patterns. • Predicting uneven distribution models using response surface methodology. • The uneven distribution rate was reduced to 8.74% after field validation. • Providing a theoretical basis for the design of straw biomass return equipment.