Determination of the Reserved Gap Between the Obturator Ring and the Breechblock in the Metallic Obturation Mechanism of a Large Caliber Gun Howitzer

Abstract

A reserved gap between the obturator ring and the breechblock in the obturation mechanism of a large-caliber gun is required in the locked state of the gun, which is the main cause of gas leakage. In this study, the finite element analysis of the dynamic contact between the obturator ring and the breechblock and the computational fluid dynamics (CFD) analysis of the high-pressure gas flow through the gap between the obturator ring and the breechblock are conducted. The results show that the smaller the reserved gap is, the shorter the time period during which the contact pressure is zero after the obturator ring contacts with the breechblock will be under a low-bore pressure condition. The results also demonstrate that the leakage flow at the outlet of the gap and the gas flow in the external domain increase with the reserved gap size, and the gas flow in the external domain decays rapidly if the reserved gap is less than or equal to 0.02 mm under a high bore pressure condition. Based on the simulation results, the appropriate reserved gap value is determined and adopted in the studied gun, and good results are achieved in the firing tests.