An Analysis of Bore Surface Temperatures in Electrothermal-Chemical Guns
Final rept. Jan-Dec 90,
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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Electrothermal-chemical ETC guns use working fluidelectrical energy combinations which may produce gas temperatures in excess of 3,500 K. The high potential for gas temperatures is of concern due to increased possibility of barrel erosion. However, it is speculated that the fluid propellants form a thermal insulating layer for the gun tube, and thus, the barrel is protected against excessive erosion. This paper is a theoretical investigation of the reduction of bore surface temperature due to a liquid insulating layer. The analysis considers unsteady heat conduction through a multi-layered hollow cylinder with time-varying convective boundary conditions. The model is used to estimate the thickness of an insulating layer near shot start, based on gas temperature, required to maintain the bore temperature at an acceptable maximum determined from a conventional hot propellant. The required mass of fluid in the tube is used to suggest the feasibility of the liquid protecting the bore.