CONCEPTION OF A “SILENT” MORTAR PROJECTILE. PART II – CALCULATIONS OF INTERNAL BALLISTIC PARAMETERS

The paper presents a theoretical description of computer codes for solution of the major question of internal ballistics for a “silent” mortar projectile. The computer codes proved their usefulness by providing the characteristics of a shot for each correct configuration of the projectile and eliminat-ing automatically the solutions not complying with the accepted specifications. Additionally, the structure of the code facilitates the modifications of a system of equations and parameters of the model to assisting a designing process of other systems of firearms.

Development of the model and the method for determining the influence of the temperature of gunpowder gases in the gun barrel for explaining visualize of free carbon at shot

A phenomenon that is present in almost every shot is highlighted. It manifests itself in the muzzle discharge as a certain amount of free carbon. The thermochemical reaction of Boudouard-Bell (disproportionation of carbon monoxide) was determined, which explains the formation of free carbon in the gunpowder gases during the firing process. A feature of this reaction is the formation of a condensed phase of carbon during the firing process after the gasification of the gunpowder charge. The reason is revealed that does not allow describing the formation of free carbon during firing on the basis of existing models of internal ballistics processes. It is the lack of taking into account the temperature distribution of the gunpowder gases along the length of the gun barrel and its change. A mathematical model is proposed that makes it possible to estimate the temperature distribution during the shot. A method has been developed for solving the problem of internal ballistics with the ability to determine the temperature of gunpowder gases along the length of the gun barrel at different times and at different positions of the projectile in the barrel. The original model is built using generally accepted assumptions. Modeling results can only be estimated. For this reason, the method is based on simple calculations, which makes it possible not to involve high-power computing equipment. The modeling of the temperature distribution of gunpowder gases in the space of the gun barrel between the charging ball and the moving projectile in the model system is carried out. The possibility of changing the length of the zone of the Boudouard-Bell reaction (the zone of formation of free carbon) depending on the initial data is shown. The use of a fresh gunpowder charge and a degraded one is simulated. Full and reduced charges are considered. The simulation results showed the reason for the possibility of initiating a secondary muzzle discharge flash both from the front side and from the side of the muzzle brake.

Numerical Simulations of the Internal Ballistics of Paraffin–Oxygen Hybrid Rockets at Different Scales

Hybrid rockets are considered a promising future propulsion alternative for specific applications to solid or liquid rockets. In order to raise their technology readiness level, it is important to perform predictive numerical simulations of their internal ballistics. The objective of this work is to describe and validate a numerical approach based on Reynolds-averaged Navier–Stokes simulations with sub-models for fluid–surface interaction, radiation, chemistry, and turbulence. Particular attention is given to scale effects by considering two different paraffin–oxygen hybrid rocket engines and a simplified grain evolution approach from the initial to the final port diameter. Moreover, a mild sensitivity of the computed regression rate to paraffin’s melting temperature, surface radiation emissivity, and Schmidt numbers is observed. Results highlight the increasing importance of radiation effects at larger scales and pressures. A numerical rebuilding of regression rate and pressure is obtained with simulations at the time-space-averaged port diameter, producing a reasonable agreement with the available experimental data, but a noticeable improvement is obtained by considering the grain evolution in time.

Scale Effects on Quasi-Steady Solid Rocket Internal Ballistic Behaviour

The ability to predict with some accuracy a given solid rocket motor’s performance before undertaking one or several costly experimental test firings is important. On the numerical prediction side, as various component models evolve, their incorporation into an overall internal ballistics simulation program allows for new motor firing simulations to take place, which in turn allows for updated comparisons to experimental firing data. In the present investigation, utilizing an updated simulation program, the focus is on quasi-steady performance analysis and scale effects (influence of motor size). The predicted effects of negative/positive erosive burning and propellant/casing deflection, as tied to motor size, on a reference cylindrical-grain motor’s internal ballistics, are included in this evaluation. Propellant deflection has only a minor influence on the reference motor’s internal ballistics, regardless of motor size. Erosive burning, on the other hand, is distinctly affected by motor scale.

Scale Effects on Quasi-Steady Solid Rocket Internal Ballistic Behaviour

The ability to predict with some accuracy a given solid rocket motor’s performance before undertaking one or several costly experimental test firings is important. On the numerical prediction side, as various component models evolve, their incorporation into an overall internal ballistics simulation program allows for new motor firing simulations to take place, which in turn allows for updated comparisons to experimental firing data. In the present investigation, utilizing an updated simulation program, the focus is on quasi-steady performance analysis and scale effects (influence of motor size). The predicted effects of negative/positive erosive burning and propellant/casing deflection, as tied to motor size, on a reference cylindrical-grain motor’s internal ballistics, are included in this evaluation. Propellant deflection has only a minor influence on the reference motor’s internal ballistics, regardless of motor size. Erosive burning, on the other hand, is distinctly affected by motor scale.

Internal ballistics of polygonal and grooved barrels: A comparative study

As a parameter important ballistic, the research about polygonal and grooved barrels’ behavior has not been widely carried out. The pressures, velocities, stresses, deformations, and strains generated by the firing of 9 mm × 19 mm ammunition in weapons with polygonal barrels are analyzed numerically and experimentally, compared with those generated in pistols with grooved barrels. The Finite Element Method with equal boundary and loading conditions was used in both types of guns, specifying the actual materials of the projectile and the barrels. Subsequently, experimental tests were carried out on various weapons with 9 mm ammunitions of 115, 122, and 124 gr. The results show that the 9 mm bullet fired in a polygonal barrel undergoes a maximum deformation towards its exterior of 0.178 mm and interior of 0.158 mm, with stress up to 295.85 MPa. Compared with 0.025 mm maximum external deformation and 0.112 mm internal deformation of 9 mm projectiles fired in a grooved barrel, with stress up to 269.79 MPa. The deformation in the polygonal barrel is in a greater area, but the rifling impression left is less deep, making its identification more difficult. Although there are differences in the stresses and strains obtained, similar velocity and pressure parameters are achieved in the two types of barrels. This has application in the development and standardization of new kinds of barrels and weapons.