NON-STATIONARY BEHAVIOR OF A SOLID PROPELLANT CHARGE FOR NOZZLELESS SOLID ROCKET MOTORS UNDER GAS-DYNAMIC LOAD

The numerical solution to a conjugate problem of an unsteady flow of combustion products in a flow path of the nozzleless solid rocket motor (SRM) and the oscillation of a solid propellant charge under the action of the forces directed from combustion products is considered. The Navier-Stokes equations for a compressible viscous gas are used to mathematically describe the flow of the combustion products. To model the charge oscillations, the equations of solid mechanics are applied, which take into account the propellant hyperelasticity. Pressure distributions and the propellant burning rate along the charge channel are presented for different models of the propellant burning rate. It is revealed that at the stage of SRM design, the use of the burning rate law, determined by pressure in the head of the combustion chamber, is more preferable in order to assess the internal ballistic characteristics. The solution to the conjugate problem shows that in the nozzleless SRM with the propellant having low Young's modulus, resonance can occur, which causes uncontrolled charge oscillations.

INFLUENCE OF THE INITIAL PROPELLANT TEMPERATURE AND IGNITION METHOD ON BALLISTIC CHARACTERISTICS OF A SHOT IN THE SETTING OF A 120 MM CALIBER MODEL BALLISTIC INSTALLATION

In this paper, the effect of the initial temperature of a propellant charge and ignition method on ballistic characteristics of a shot from a model installation with a caliber of 120 mm is theoretically studied. Two types of charge ignition are considered: ignition by means of an electric primer-igniter and by a "flute"-type plasma torch. The developed numerical technique is described, which serves to simulate an artillery shot in an axisymmetric setting in conditions of the indicated ignition types. Three values of the initial temperature of the propellant charge are considered: –40, 0, and +40 °C. Configurations of computational domains for the given ignition methods are shown, and some calculated shot ballistic characteristics for six different calculation options, differing in the ignition type and initial temperature, are presented. It is revealed that in the specified range, the initial temperature of the propellant charge significantly affects the ballistic characteristics of the shot, such as a throwing speed and a maximum pressure in the chamber, while the type of ignition does not significantly affect these characteristics. It is noted that the ignition type has a great impact on temporal characteristics of the shot: the ignition time of a propellant charge and the time of the shot as a whole.

A STUDY OF THE COMBUSTION OF HIGH-DENSITY PROPELLANTS IN A MODEL BALLISTIC INSTALLATION

In internal ballistics of barrel systems, a promising trend is related to the increasing of projectile muzzle velocity by means of high-energy propellants utilized as a traveling charge. The use of a loading scheme with a traveling charge allows one to increase the loading density and to redistribute the energy of powder gases in the space behind the projectile, which leads to a significant increase in the muzzle velocity of the projectile. To attain the listed advantages, it is necessary to know the laws of dispersion and combustion of the propellants used as traveling charges, providing non-digressive gas entry into the charge space. In this work, a comprehensive experimental and theoretical study of the laws of dispersion and combustion of high-density propellants under dynamic pressures, provided in a model ballistic installation, is carried out. The main ballistic characteristics of shots are obtained, which use a classic scheme of loading with a propellant charge made of pyroxylin powder and a scheme with a traveling charge, where, in addition to the propellant charge, a high-density propellant is included. All the experiments are simulated in a software package, taking into account the presence of the high-density propellants in the propellant charge, dispersing into individual particles that burn out while moving along the barrel. As a result of comparing the calculated and experimental data, plausible patterns of the distribution of gas-dynamic parameters are obtained using the classic loading scheme and the loading scheme with a travelling high-density propellant charge.

ALLOWANCE FOR THE EFFECT OF CONDENSED PARTICLES ON BALLISTIC PARAMETERS OF A SHOT

A mathematical model of the shot fired from a powder propellant setup is developed. An arbitrary number of powder particles of various types are supposed to be in a propellant charge, which are different in size, shape, energy characteristics, and layer-by-layer burning velocity. The products of their combustion represent a mixture of non-viscous non-heat conductive gases with known equations of state. These gases are generated during combustion of the powder particle of a corresponding type. Some condensed particles may occur in the mixture of combustion products during the burning of powder particles. The motion of the polydispersed mixture of combustion products along a varying-cross-section channel is described by the laws of conservation of mass, momentum, and energy. When formulating these laws, the mass, momentum, and energy exchange between gas and condensed phases is taken into account. The formulation is universal and allows one to use the laws for modelling a wide range of internal ballistic phenomena. In this paper, a theoretical parametric research is shown as an example, which is aimed at estimating the effect of quantity of the occurring condensed particles on basic ballistic characteristics of a shot.

MEASUREMENT OF NEGATIVE POWDER GAS PRESSURE DURING SHOOTING WITH 120 MM TANK AMMUNITIONIN ACCORDANCE TO STANAG 4493

The article introduces an issue of measuring a negative pressure of powder gases in accordance with STANAG 4493. The negative pressure is obtained from measurements of the maximum pressure of powder gases at the front and the end of cartridge chamber during firing with 120 mm tank ammunition. In connection with the above, a simultaneous use of two piezoelectric sensors, placed in special sockets, is needed on a ballistic stand equipped with 120 mm L44 cannon of Leopard 2A4 tank. The purpose of the measurement is to record the values and curves of pressure allowing a detection of any dangerous phenomena occurring in the cannon's chamber during the shot and determination of the level of negative pressure of powder gases for tested ammunition. Defining the negative pressure value facilitates the construction of the propellant charge and helps to analyze the condition of the cannon cartridge chamber over

Analytical Method for the Estimated Calculation of the Required Amount of Propellant Charge for the Reusable Training-Practice Mortar Round for Small Distance Firing

The paper presents an analytical method for determining the estimated amount of propellant charge for the reusable training-practice mortar round intended for short distance firing, as a part of simulator for mortar crews. For verification of the analytical method an experimental research was conducted where the 82mm training-practice mortar round was fired at a distance of 100 meters. The experimental research and the verification of the statistical hypothesis confirm that the formula can be used to practically determine the required amount of propellant charge.

STUDY OF THE PASTE-LIKE PROPELLANT COMBUSTION AT VARIOUS LOADING SCHEMES

The experimental and theoretical studies of the paste-like propellant combustion in a model ballistic installation are implemented. The research is carried out using three masses of projectile assemblies and three types of the propellant charge. The paper presents two versions of the law of dispersion for paste-like propellants which allow accounting for the pressure on the front and acceleration of the projectile assembly with a traveling charge. The coefficients in the laws of dispersion are obtained. Using the mathematical model presented in this work, the gas-dynamic pictures of the shots when the propellants are applied as traveling charges are obtained for each dispersion law. Based on the results, a detailed study of the processes occurring with the traveling charge consisting of a model paste-like propellant is implemented for various shot arrangements. The discrepancy between theoretical results and the results obtained in the set of experiments is no more than 2% for the maximum pressure and no more than 1% for the muzzle velocity. The dispersion law accounting for the projectile assembly acceleration and traveling charge makes it possible to describe accurately the processes in the space behind the projectile for projectile assemblies of various masses and different types of granulated powder charge in terms of the model ballistic installation in the considered pressure range.