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To study the form function and combustion characteristics of partially‐cut stick propellants, this paper derived and established the form function of this complex geometry propellant and analyzed the influence of cutting parameters on the form function. The analysis showed that partially‐cut stick propellants retain the high progressive combustion of multi‐aperture granular propellant, which is proportional to the distance between the notch and inversely proportional to the width of the notch. Based on this, partially‐cut stick propellants with different notches were prepared, and closed vessel tests were conducted. The experimental results showed that the notch had a significant effect on the combustion characteristics of the propellant. When there were notches, the wider the notch, the faster the pressure rise. The pressure in the closed vessel for stick propellants without notches rose the fastest. The burning rate of non‐notched or narrow‐notched fluctuated, while the burning rate of wide‐notched was stable. The dynamic vivacity data showed that the wider the notch, the more stable the change of the burning surface, and the combustion characteristic was closer to the granular propellant. Based on the analysis of form function and combustion characteristics, it is recommended that the notch width be 1 mm and the distance between notches on the same side should be the length of a granular propellant for the double‐base homogeneous 19‐perforated propellant studied in this paper. [ABSTRACT FROM AUTHOR]

Mathematical models for the simulation of the operation of various projectile-throwing systems are continuously modified, simultaneously with the development of propellants. For these models, properly determined values of energetic ballistic characteristics of propellants are very important. This paper presents an original test and the results of closed vessel comparative investigations. The study analyses specific combustion characteristics of single-base propellants using conventional black powder ignition, plasma ignition, and gas ignition. The results of the study indicate the need to take into account—in the calculation of the burning rate—not only the dynamics of gas pressure changes but also the real (experimental) form function, which differs from the theoretical one resulting from the assumed geometric burning model. The obtained results allow for a critical analysis of the existing methods used for the determination of values of ballistic characteristics of propellants. Further, it will allow for creating pyrostatic test conditions that would reflect the condition of instantaneous ignition of propellant grains over their entire surface in the most realistic way. [ABSTRACT FROM AUTHOR]

The combustible cartridge case has become an integral part of many modern weapons systems. The energetic and burning characteristics of the combustible case can have a significant impact on shot parameters. This paper describes Closed Vessel Tests (CVTs) performed on combustible cartridge case material and presents a method of determining the physical burning law and the linear burning rate of the tested material. The method was verified on the basis of the results of CVT of the felted combustible cartridge case material of a 120 mm tank round. It is shown that, in the case of porous combustible materials, the standard methods of determining the burning rate fail. The porosity of combustible materials greatly increases the burning surface and heat feedback from the burning zone to the unburned structure. These effects significantly increase the burning rate of porous materials. The results of analysis show the strong dependence of the burning rate on pressure. The results of this study can be applied in the modeling of gun propellant systems that contain combustible case elements. [ABSTRACT FROM AUTHOR]

Mathematical models for the simulation of the operation of various projectile-throwing systems are continuously modified, simultaneously with the development of propellants. For these models, properly determined values of energetic ballistic characteristics of propellants are very important. This paper presents an original test and the results of closed vessel comparative investigations. The study analyses specific combustion characteristics of single-base propellants using conventional black powder ignition, plasma ignition, and gas ignition. The results of the study indicate the need to take into account—in the calculation of the burning rate—not only the dynamics of gas pressure changes but also the real (experimental) form function, which differs from the theoretical one resulting from the assumed geometric burning model. The obtained results allow for a critical analysis of the existing methods used for the determination of values of ballistic characteristics of propellants. Further, it will allow for creating pyrostatic test conditions that would reflect the condition of instantaneous ignition of propellant grains over their entire surface in the most realistic way.

This paper presents the method of determining the burning rate of fine-grained propellants based on the results of closed vessel tests. It is shown that in the case of fine-grained propellants, the standard methods of determining the burning rate fail. There are two reasons for this: imperfections of the grain shapes and the prolonged process of ignition due to a more developed surface than that of coarse grains at the same mass of the propellant. The value of the exponent in the burning law is estimated by the use of the so-called experimental form–function. The upper and lower limits of the value of the coefficient in the burning law are estimated. The accuracy of the proposed method is analyzed. Its validity is assessed by comparing the results of closed vessel tests analysis with accessible literature data. [ABSTRACT FROM AUTHOR]

In theoretical simulations of internal ballistics phenomena, the value of pressure generated by the ignition system is required. Typically, the ignition pressure value is assumed to be 3 - 5 MPa. The work presents a measurement stand using a “micro closed vessel”, designed to determine the ignition pressure for 9 mm pistol ammunition. Pressure measurements were made for two types of ammunition, differing in the construction of the ignition system. The results of measurements indicate that the value of the ignition pressure is twice as high as usually assumed. In addition, the mass of the ignition charge was determined, which is used in selected models of internal ballistics. The mass value was at the level of 0.02 g.

The combustible cartridge case has become an integral part of many modern weapons systems. The energetic and burning characteristics of the combustible case can have a significant impact on shot parameters. This paper describes Closed Vessel Tests (CVTs) performed on combustible cartridge case material and presents a method of determining the physical burning law and the linear burning rate of the tested material. The method was verified on the basis of the results of CVT of the felted combustible cartridge case material of a 120 mm tank round. It is shown that, in the case of porous combustible materials, the standard methods of determining the burning rate fail. The porosity of combustible materials greatly increases the burning surface and heat feedback from the burning zone to the unburned structure. These effects significantly increase the burning rate of porous materials. The results of analysis show the strong dependence of the burning rate on pressure. The results of this study can be applied in the modeling of gun propellant systems that contain combustible case elements.

This paper presents the method of determining the burning rate of fine-grained propellants based on the results of closed vessel tests. It is shown that in the case of fine-grained propellants, the standard methods of determining the burning rate fail. There are two reasons for this: imperfections of the grain shapes and the prolonged process of ignition due to a more developed surface than that of coarse grains at the same mass of the propellant. The value of the exponent in the burning law is estimated by the use of the so-called experimental form–function. The upper and lower limits of the value of the coefficient in the burning law are estimated. The accuracy of the proposed method is analyzed. Its validity is assessed by comparing the results of closed vessel tests analysis with accessible literature data.

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of three types of propellants: a single-base propellant, a double-base propellant and a low vulnerability (LOVA) propellant, as determined via closed vessel tests (CVT). Conventional gunpowder ignition and plasma jet ignition methods were used. The influence of the ignition method on the values of the propellant characteristics obtained in CVT was analysed. It was found that the method of ignition has an influence on the values of propellant characteristics, determined in CVT. An analysis of the experimental form functions showed that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants in which the burning process deviates from the geometric burning law.

Foamed combustible material based on polymer bonded RDX was fabricated using CO2 as foaming agent. The inner structures of felted and foamed combustible materials were presented by SEM. The two materials presented different formulations and inner porous structures. The combustion behaviors of felted and foamed materials were investigated by closed vessel test. Simultaneously, the co-combustion behavior of combustible cartridge case with 7-perf consolidated propellants was also investigated. The results of closed vessel test is applicable to gun system which is made of the foamed combustible material as component.

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of a single-base gun propellant, as determined via closed vessel tests. Conventional gunpowder ignition and plasma jet ignition methods were used, and differences in the ignition time were analysed. The influence of the ignition method on the dynamic vivacity is discussed. It is shown that this influence is significant in the first phase of the combustion process, and with respect to the low values of the loading density. In the second phase of the combustion process, and for large values of the loading density, the dynamic vivacity plots for the two ignition methods converge. Regarding the burning law, close values of the exponent were obtained for the two ignition methods. The dynamic vivacity plots determined for plasma ignition reveal stronger dependence on the loading density than those determined for gunpowder ignition. The conclusion is that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants, which results in deviation of the burning process from the geometric burning law. [ABSTRACT FROM AUTHOR]

Previous published results of closed vessel investigations indicated that classical primers (electric or percussion with black powder bedding) when used with LOVA propellants cause unstable burning, deflagration or even lack of ignition. Capillary Plasma Generator is one of the most reliable ignition sources which make possible a reduction of temperature gradient effect and control combustion process. Comparable tests of black powder and plasma ignition in closed vessel with conventional NC propellant were done. Shorter ignition time while using plasma was achieved.

The combustion of zirconium potassium perchlorate (ZPP) in a closed vessel is modelled and validated through a numerical simulation. Because the extremely high pressure oscillation occurs in less than a millisecond, an in-house computational fluid dynamics (CFD) code is used to observe the detailed flow structures and determine the adequate burning characteristics, including the burning rate. A hybrid RANS/LES scheme with a 5th order upwind weighted essentially non-oscillatory (WENO) is implemented to capture complex, strong shock waves in highly turbulent combustion. A two-way coupled Eulerian-Lagrangian scheme tracks the combusting ZPP granules reasonably well. Monodisperse and Rosin-Rammler assumptions are applied to the ZPP granule distribution. The monodisperse assumption reveals that the diameter of the ZPP (17 μm) achieves marginal agreement with the measurements. However, the Rosin-Rammler distribution improves the transient and dynamic combustion characteristics in that the small granules contribute to a faster burning rate and stronger shock waves. These results are more analogous to the closed vessel tests used as validation data. [ABSTRACT FROM AUTHOR]

Microcellular combustible objects for application of combustible case ammunition and caseless ammunition were fabricated by a confined pressure quenching foaming process using supercritical CO2 as foaming agent. The experimental results showed that the force constant ( f) of objects obviously increased with an increasing RDX content and that the force constant of formulation with 55 % RDX is comparable to that of traditional felted case. Pressure histories, dp/ dt- t, and dynamic vivacity curves were investigated and compared by closed vessel tests. The influencing factors such as RDX content, expansion ratio, foaming temperature, sample size, and loading density were analysed. The results revealed that RDX content and expansion ratio significantly affected the burning properties, whereas the foaming temperature did not have obvious influence. Moreover, the burning behavior also changed with sample size and loading density. [ABSTRACT FROM AUTHOR]

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of three types of propellants: a single-base propellant, a double-base propellant and a low vulnerability (LOVA) propellant, as determined via closed vessel tests (CVT). Conventional gunpowder ignition and plasma jet ignition methods were used. The influence of the ignition method on the values of the propellant characteristics obtained in CVT was analysed. It was found that the method of ignition has an influence on the values of propellant characteristics, determined in CVT. An analysis of the experimental form functions showed that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants in which the burning process deviates from the geometric burning law. [ABSTRACT FROM AUTHOR]

• Synthetic sodium azotetrazolate was eco-friendly, hydrogen-free, thermal stable. • NaNO 3 /STZ pyrotechnics could generate 321.04 L/kg vapor-free gaseous product. • The reaction process was: i) decomposed into NaCN; generating ii) N 2 ; iii) CO 2. • NaNO 3 /STZ showed a stable combustion, better ignition delay and burning rate. • The maximum pressure of NaNO 3 /STZ produced was 1.7 times of that of NaN 3 /Fe 2 O 3. Gas-generating pyrotechnics are widely used in airbag inflator, pre-tensioner seat belt, deep-water salvage, fire extinguishing bomb, etc. However, for maintaining prolonged high-pressure, specific gas-generating pyrotechnics are required that are capable of producing water-vapor-free gaseous products to avoid the decrease of pressure caused by the condensation of water vapor. Currently, only sodium azide (NaN 3)-based gas-generating pyrotechnics can meet the demand, but its application is limited due to its toxic effects. In this work, a sodium-azotetrazolate-based (STZ-based) eco-friendly and hydrogen-free gas-generating pyrotechnics was presented. A typical STZ-based gas-generating pyrotechnics was NaNO 3 /STZ gas-generating pyrotechnics, which could generate 321.04 L/kg clean and non-toxic gas composed of N 2 and CO 2 without any water vapor. The burning characteristics, including the ignition delay, maximum pressure and burning time of NaNO 3 /STZ gas-generating pyrotechnics was determined by conducting a closed vessel test. NaNO 3 /STZ gas-generating pyrotechnics showed a stable combustion process, lower ignition delay, higher burning rate, and the maximum pressure produced is 1.7 times of that of NaN 3 /Fe 2 O 3. Thus, STZ exhibited great potential as gas-generating pyrotechnics, which could be applied, especially where a stable pressure is required for a long time. [ABSTRACT FROM AUTHOR]