In-Bore Liquid Injection for Barrel Cooling: Comparison of Liquid and Solid Additives Using Constant Breach Pressure Ideal Gun Calculations

Report No. ARL-TR-1915
Authors: Kotlar, Anthony J.; Birk, Avi
Date/Pages: March 1999; 37 pages
Abstract: A new concept for reducing gun tube wear through the injection of a liquid as a shield in the wall boundary regions of a gun tube is proposed. In this new concept, the liquid is injected and largely remains as a film on the bore surface, thereby acting as a thermal shield in the wall boundary layer region. Ballistic performance is assessed using constant breech pressure (CBP) ideal gun calculations for liquid additives to high-performance solid propellant formulations. These calculations give limiting values for projectile muzzle kinetic energy (KE), assuming complete mixing of the liquid additive and the solid propellant This is a worst-case scenario for the new concept to reduce gun barrel heating. The CBP calculations of representative gun systems provide a comparison of 3 liquids and 10 solid additives, based on increased muzzle velocity and reduced temperature of the combustion products. The CBP calculations demonstrate that, even if total mixing occurs, liquid additives compare favorably with recently studied solid propellant additives. The CBP results, with as little as 4% liquid additive, indicate a potential to attain increased muzzle KE through the use of high flame-temperature and high-impetus solid propellants, without the penalty of increased temperature causing severe barrel erosion. They also indicate a potential for increased rate of firing because of the liquids ability to reduce barrel heating. In either limit (i.e., total mixing or no mixing) the liquids studied, based on the CBP assumptions, emerge as attractive and competitive alternatives to solid propellant additives.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 1999