Effect of Base Bleed Dimensions on the Ballistic Performance of Artillery Projectiles

Abstract

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.

The Optimization of Base Bleed Grain Parameters for Maximum Ballistic Performance

“…The justification of this could be as follows; in case of low limits, it requires higher value of BR1 to get optimum injection parameter. For the D exit = 48 mm, the accumulation of the pressure inside the base bleed chamber is less than in case of D exit = 40 mm leading to reduction in mass flow rate [9] and consequently higher BR1…”

“…decreases with the increase of Ns as it can be seen in Table 3. The increase of Ns is considered one of the main mechanisms to increases mass flow rate and consequently the optimized value of BR1 is reduced with the increase of Ns for the same exit diameter, D exit [9]. Table 7 shows the optimized design variables at each candidate point and the corresponding range , and the relative difference in range.…”

“…With the increase in the limits from low to medium, injection parameter get closer to the optimum value but when it reaches the upper limits, injection parameter exceeds optimum value leading to reduction in base bleed efficiency. Also, with the increase in the limits of both BR2 and L% more mass flow rate is generated and larger D exit is preferred [9].…”

“…The results of the model [9] and refs. [11,12] Different techniques were implemented to control mass flow rate to achieve these conditions such as the change of burn rate, change the base bleed grain configuration and increase the number of slots.…”

“…al. [9] used a validated mathematical model [8] that has been established based on the model introduced by S. Jaramaz et. al [7] to study the effect of different parameters of projectile 155mm K307 with base bleed.…”