Erosion in vent plugs is studied in a 37 mm. Gun which has been cut off at the end of the chamber. Plugs with vent diameters from 0.04 to 0.63 inches and vent lengths from one to four inches are held in the position normally occupied by the projectile. The weight losses due to erosion are in fair agreement with values calculated from heat transfer theory, assuming melting of the surface, for charges of propellant powder above a minimum value. The weight loss due to melting increases as the weight of charge, the web thickness, the length of the vent, and the gas temperature are increased, and decreases as the vent diameter and the melting point of the metal are increased. The minimum charge to produce melting increases rapidly with increases in vent diameter, but the maximum pressure corresponding to this charge increases only slightly. For charges below this minimum, the erosion is shown to be of a chemical nature by the significant decrease due to the elimination of sulphur from the black powder primer.
Read full abstract