Spatiotemporal inhibition and concealed migration mechanism of high-temperature zones by air-inlet side air curtains in coal spontaneous combustion

The installation of an air curtain at the intake side of a working face alters the goaf temperature field, yet the specific evolutionary patterns remain largely unclear. To address this knowledge gap, a three-dimensional physical similarity simulation platform was established. A room-temperature self-heating similarity material was developed, and a macro-scale synchronous testing system was designed. An oxygen-heat kinetic equivalence model for goaf spontaneous combustion was subsequently constructed. The reconstruction characteristics of the goaf temperature field under air-curtain control and the thermodynamic mechanisms driving the hidden migration of high-temperature points were quantitatively revealed in this study. Experimental results demonstrate that local aerodynamic resistance was increased by the intake-side air curtain, restructuring the dynamic competition between oxygen supply and heat dissipation within the goaf. The high-temperature core zone was forced to migrate significantly from the shallow intake area observed under natural leakage conditions (strike 0.5∼0.6 m, transverse 0.1∼0.3 m) to the mid-deep region (strike 0.8∼0.9 m, transverse 0.3∼0.4 m), culminating in the formation of a new deep heat-storage zone. Under air-curtain regulation, the coal spontaneous combustion induction period was extended by 4.17 times, the peak area of the effective high-temperature zone was reduced by 54%, and the low-temperature safety zone near the working face was broadened from 0.2 m to 0.4 m. Mechanism analysis indicates that the shallow oxygen supply channel is effectively severed by the air curtain, achieving a spatiotemporal dual suppression of the original high-temperature zones. Simultaneously, the reconstructed air-leakage flow field induces the formation of a novel heat-storage zone in the deep goaf, driving the deep coal mass into a protracted, low-temperature slow oxidation stage. Long-term monitoring and precise intervention mechanisms must be established for these mid-deep high-temperature zones following the implementation of intake-side airflow control.