Otimização da geometria do sistema de gases dos fuzis IMBEL IA2 utilizando métodos de delineamento de experimentos aplicados a simulação DFD

Abstract

This work presents a geometric optimization study of the gas system of the IMBEL IA2 rifles using Computational Fluid Dynamics (CFD) combined with Design of Experiments (DOE) methods. The IA2 operating system, responsible for diverting part of the propellant gases from the barrel and converting them into mechanical energy for weapon cycling, was originally dimensioned through empirical procedures. Considering the absence of gas regulation in the current design and the requirement for high reliability under different operational conditions, a detailed understanding of the transient flow phenomena inside the system becomes essential. Experimental tests were conducted by instrumenting the rifle with pressure transducers, enabling the acquisition of real pressure curves inside the barrel and gas cylinder. High-speed camera recordings were also performed to determine the displacement–time curve of the bolt carrier. These experimental data were used to validate a two-dimensional transient numerical model with dynamic mesh and moving wall motion equation implemented in ANSYS Fluent. After validation of the baseline configuration, a factorial design was applied to evaluate the influence of relevant geometric parameters, in this case gas port diameter and initial gas cylinder length, on objective functions related to peak pressure, peak time, and total impulse delivered to the system. An analysis of variance (ANOVA) was performed, and response surfaces were generated for each objective function, enabling the identification of the most influential parameters. Finally, alternative geometries were proposed and assessed, including the addition of a relief orifice and a pressure accumulation chamber. The results indicate that it is possible to delay and smooth the pressure curve inside the gas cylinder, reducing peak pressure without compromising the total impulse required for proper cycling. The study provides technical support for the optimization of the IA2 gas operating system and for the development of future IMBEL firearms, contributing to improved reliability and reduced experimental effort during the design process.