Research on spatiotemporal evolution patterns of dust and dynamic spraying strategy in fully mechanized mining face

To characterize the spatiotemporal evolution of dust concentration in a fully mechanized mining face and achieve precise dynamic spray dust suppression, eight dust concentration sensors installed at intervals along the face were used to continuously and synchronously monitor dust concentrations at different locations during shearer movement. The spatiotemporal evolution characteristics of dust concentration were analyzed under two operating conditions, namely downwind cutting and upwind cutting. The results showed that, under both conditions, the peak dust concentration was always located at the shearer cutting position, and dust concentration on the downwind side decreased exponentially with increasing distance from the shearer. Under upwind cutting, continuous dust accumulation resulted in a significantly higher background concentration than under downwind cutting. Exponential decay models of dust concentration were established for the two cutting conditions. The fitting and analysis results indicate that the coefficient of determination (R²) was 0.96 for both models, the mean absolute percentage errors were 9.8% and 10.2%, respectively, and the residuals were normally distributed, confirming good fitting performance and prediction accuracy. Based on the exponential decay pattern of dust concentration, a dust suppression strategy was designed to dynamically activate the spray devices on the hydraulic support corresponding to the real-time shearer position and on consecutive downwind supports. An index of dust suppression efficiency per unit water consumption was introduced to comprehensively evaluate the effects of activating different numbers of spray-device groups. Field tests identified six groups of support-mounted spray devices on the downwind side as the optimal configuration (dust suppression efficiency per unit water consumption: 2.22). The practical performance of the strategy was verified using the gravimetric filter method. The results showed that dust suppression efficiency reached 63.8% at the shearer operator position and ranged from 56.1% to 64.4% at the support measurement points on the downwind side. These results demonstrate that the strategy achieves balanced dust suppression across the entire face.