Regulation of scraper spacing on coal conveying performance under particle viscosity and chain speed coupling

To improve the conveying performance and operational reliability of the on-board short-distance scraper conveyor, different scraper spacings were designed based on the analysis of scraper spacing design parameters and the particle contact theory of the discrete element method (DEM), and a DEM-MBD rigid-discrete coupling model was constructed. The reliability of the dynamic model of the conveying system was validated through a self-developed scaled experimental platform. On this basis, by integrating simulation and experimental methods, the flow behavior of coal bulk material with different particle sizes during conveying was systematically analyzed, and the influence mechanisms of multiple operating parameters—including scraper chain speed, coal bulk material viscosity, and scraper spacing—on conveying efficiency and return coal amount were revealed. The research results indicate that: the simulation and experimental errors of both drive sprocket rotational speed and torque are below 15%; during conveying, the coal bulk material exhibits significant stratification due to the “Brazil nut effect”; scraper spacing shows a nonlinear relationship with conveying efficiency—when the scraper chain speed is 0.9 and 1.5 m/s, a scraper spacing of 303 mm yields superior conveying efficiency, whereas when the scraper chain speed increases to 2.1 m/s, the influence of scraper spacing weakens; an increase in coal bulk material viscosity leads to a decrease in conveying efficiency, and the difference in conveyed coal amount among different scraper spacings is reduced; scraper spacing is negatively correlated with the return coal amount, and with the increase of viscosity, the return coal amount shows a trend of first decreasing and then increasing. This study provides theoretical support for optimizing scraper spacing.