EFFECTS OF AIR JET AND MIST INJECTION ON THE COOLING PERFORMANCE OF THE INNER SURFACE OF A GUN BARREL

Abstract

During firing, a significant amount of heat is transferred to the inner surface of the gun barrel, leading to wear and erosion. With prolonged firing, the temperature inside the chamber can reach the cook-off point of the propellant, creating safety hazards for both the operator and the equipment. For large-caliber guns, such as the 52-caliber type, the use of high-energy propellants combined with increased firing rates greatly restricts the weapon's operational capacity. A practical approach to addressing this problem is the implementation of cooling techniques for the barrel. In this study, air and mist cooling methods are applied, and the heat transfer within a 155 mm gun barrel is analyzed through numerical simulations. Numerical simulations were conducted using the commercial computational fluid dynamics software, ANSYS Fluent. For comparison purposes, heat transfer in a naturally cooled barrel was also analyzed as a baseline case. The findings indicate that air and mist cooling are significantly more effective than natural air cooling in dissipating heat from the barrel, primarily due to the higher convection heat transfer coefficient. Air is often readily available and cost-effective. The impingement of a low-temperature air jet on the inner surface of the barrel improves cooling performance. Jet impingement cooling efficiency is influenced by various factors, such as jet diameter, injection velocity, and the distance between the jet and the heated surface. Water's latent heat of vaporization is 2260 J/g, and this property enables mist cooling to offer exceptional heat removal efficiency. This high energy absorption during phase change enhances the cooling performance significantly. ANSYS Fluent supports multiphase modeling through the Eulerian-Lagrangian approach, commonly referred to as the Discrete Phase Model (DPM). For research on mist cooling, the Discrete Phase Model (DPM) was utilized to simulate the behavior of injected mist particles. Mist cooling efficiency is influenced by various factors such as the size of the mist droplets, the velocity of injection, and the temperature of the mist. The numerical findings indicated that the inner surface of the gun barrel experienced a temperature reduction of approximately 5.8°C due to air jet impingement cooling as seen in Figure 1, while mist injection cooling led to a more significant reduction of around 12.2°C as shown in Figure 2. In contrast, natural air cooling only resulted in a temperature drop of about 2°C over the same period. These results demonstrate the high effectiveness of mist cooling as a cooling method.1