Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
COOK-OFF EVALUATION IN GUN BARRELS THROUGH A TRANSIENT HEAT TRANSFER ANALYSIS
Submission Author:
Bruna Loiola , RJ , Brazil
Co-Authors:
Rodrigo Telles, Francesco Scofano Neto, Rodrigo Otávio de Castro Guedes, Bruna Loiola
Presenter: Rodrigo Telles
doi://10.26678/ABCM.COBEM2021.COB2021-1314
Abstract
Gun designers have long realized that during repeated firing situations, a great amount of heat is transferred to the inner surface of the barrel due to the burning of the propellant. As the firing sequence continues, the thermal load increases despite the natural heat loss through the outer wall of the gun barrel and consequently, the bore of the weapon experiences an acute temperature elevation as the ballistic cycle takes place. In gun operations at moderate and high rates, the time between rounds is probably insufficient for the dissipation of the thermal load to the environment and therefore a management of firearms involving passive or active cooling methods is commonly utilized. However, even when such strategies are employed, a critical event is expected to arise where the safety of the operating crew, the accuracy of the projectile and the life span of the gun barrel are seriously compromised. This undesirable outcome is known as the “thermally induced firing” or the “cook-off condition”. In this circumstance, an uncontrolled and unexpected detonation of the ammunition is achieved due to the elevated temperatures in the gun chamber caused by previous firing rounds. Therefore, the main purpose of this contribution is to perform a numerical analysis of the transient temperature distribution in gun barrels when operating in burst mode. An effective model based on the heat diffusion equation in cylindrical coordinates is advanced where an imposed heat flux boundary condition in the inner wall accounts for various types of charges and manufacturing arrangements On the other hand, the outer boundary condition deals with heat dissipation by means of a simultaneous convection and linearized radiation process. The mathematical formulation of the problem is addressed by the finite volume method and care was taken to verify this solution against analytical results published in the open literature for both a single and multiple rounds. The results obtained so far indicate that the number of safe rounds of firing before the attainment of the cook-off condition is significantly dependent of the inner flux boundary condition associated to the ammunition.
Keywords
transient thermal analysis, gun barrels, “cook-off” condition, Finite volume method
