Abstract: This article conducted pottery jar fire tests at different liquid level heights, elucidating the evolution of flame morphology from the initial blue bimodal shape to a yellow conical flame, and distinguishing its combustion stages based on the rate of mass loss. The leakage combustion phenomenon observed during the stable combustion stage of the pottery jar fire was found, and the typical location where the external flame appeared was at the maximum belly width. The fracture time of ceramic jars with different liquid levels was calculated, revealing the development pattern of cracks on the jar wall. Cracks first appeared at the jar mouth and then flowed down along the jar wall. The research results indicate that as the liquid level increases, the probability of cracks appearing on the ceramic jar wall decreases. Among them, when cracks appear on the wall of the ceramic jar at a liquid level of 26, 27 cm, the tensile stress at the mouth of the jar is 8~17 MPa; When cracks appear on the walls of ceramic jars with liquid levels of 28, 29, 30 cm, the tensile stress at the mouth of the jar reaches over 30 MPa; The large pottery jar test broke for the first time at a temperature difference of 18.8 ℃ at the mouth, with a tensile stress of 5.1 MPa.

Key words: pottery jar, fracture combustion, liquid level, fracture stress