An analysis has been performed to investigate the ballistic performance of the 155mm K307 extended range projectile provided with base bleed unit. Different tools were used to perform this analysis; including analytical modeling and available computational resources. Drag reduction modeling has been used to study the effect of different parameters on base bleed performance such as burning rate, number of base bleed grain parts and the grain dimensions. The study has showed that a better ballistic performance could be obtained when the exit mass flow rate of the burnt gases is relatively large at the first few seconds of the projectile flight. To change this mass flow rate along the trajectory, a newly developed technique has been introduced. The technique depends on filling the base bleed unit with a grain subjected to burning by two rates resulting in extending the projectile range.
Base bleed unit is one of the active methods to increase the range of artillery projectiles. Ballistic performance of base bleed unit has been experimentally assessed using firing tests and wind tunnel experiments. Meanwhile, analytical and numerical studies have been carried out. In some of these studies, solid propellant is used as the source of the burnt gases ejected into the wake behind the projectile base. But, in other studies, different types of gases such as air, argon, hydrogen, and helium are ejected at different temperatures. In this paper, the effects of the main dimensions of 2-parts tubular base bleed grain unit on its ballistic performance are studied analytically. These dimensions are base bleed grain maximum radius, length, inner diameter of the grain, and exit diameter of base bleed unit. The study is applied to the base bleed unit which is installed to K307 155mm projectile. The study leads to a new method to control the ejected mass flow rate. This method is based on changing the exit diameter of base bleed unit in order to get higher injection parameter in the first few seconds of projectile flight and lower values in the remaining time of base bleed grain burning. Therefore, the base bleed projectile range is increased by 1.7 % when comparing with its counterpart which is supplied with base bleed unit having constant exit diameter and the same base bleed grain.
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