A Two-Dimensional, Two-Phase Flow Simulation of Ignition, Flamespread, and Pressure-Wave Phenomena in the 155-mm Howitzer

摘要

Past attempts to simulate two-phase flow phenomena in high-performance, bagged-charge artillery using available one-dimensional, Two-phase flow interior ballistic codes have met with only limited success, presumably because of the inability of these models to capture configural complexities associated with the charge/chamber interface. Previous work with a quasi-two-dimensional version of one such code (NOVA), in which the charge and unoccupied regions in the gun chamber were treated as disjoint but coupled regions of one-dimensional flow, revealed that early flow external to the charge can alter the flame path and equilibrate pressures throughout the gun chamber. Moreover, characteristics of the bag material itself - strength and permeability, affecting both communication of gases between the charge and external regions and persistence of circumferential ullage - can have significant impact on the development of longitudinal pressure waves in the tube. Yet these calculations recognized only an axial thermal stimulus in the propellant bed and ignored entirely the structure of the radial flow field in the two-phase medium. Current work addresses application of a fully two-dimensional, axisymmetric, two-phase flow mode (TDNOVA) to the bagged-charge problem, providing for the first time an explicit treatment of two-dimensional flamespread in this configurally complex environment. Functioning of the basepad/centercore igniter is included within the physical scope of the model, as is the presence of reactive parasitic charge components which exhibit exothermic or endothermic properties in addition to resistance to gas and solid phase flows.