Improving the burning progressivity is an effective approach to improve the muzzle velocities of projectile of a gun. Composite multi-layered flaky gun propellant is a combination of a fast-burning inner layer and a slow-burning outer layer. It has an obvious burning progressivity which decreases the pressure in bore and increases the muzzle velocity, thus this characteristic is widely concerned by the research of gun propellant. The thermal expansion coefficient of composite multi-layered gun propellant has a significant influence on the combustion performance. Therefore, understanding the thermal expansion properties of the composite multi-layered gun propellant is important. In this study, the thermal expansion coefficients were measured by thermal mechanical analyzer (TMA) for a three-layered flaky gun propellant, and the influence of laminating and coating flaky gun propellant on thermal expansion coefficient was investigated. The results showed that the slow-burning layers had a higher thermal expansion coefficient than the faster-burning layers, the thermal expansion coefficient of slow-burning layers was 4–5 times bigger than that of fast-burning layers, and the order of magnitudes was 1 × 10−5 K−1. The laminating and coating had a great influence on the thermal expansion coefficient of flaky gun propellant, the thermal expansion coefficient of laminate sample was 10 times greater than that of the original sample, and the order of magnitudes for two layers and three layers propellant reached 1 × 10−4 K−1. Furthermore, the theoretical relations between the thermal expansion coefficient of axial and the thermal expansion coefficient of the fast and slow burning layer were derived.

Experimental study on thermal expansion coefficient of composite multi-layered flaky gun propellants

The three-dimensional flow of seven holes variable-burning rate propellant in co-extrusion dies was simulated based on finite element method. The influence of long diameter ratio to interface radius and extrusion swell were analyzed. The result shows that keep the length to diameter ratio L/D0 between 3.5 ~ 13, can control interface radius changes in the process of the extrusion processing co-extrusion processing .And D/D0 reflect the viscoelastic fluid from the shear strain response ability.

Extrusion Swelling on the Co-Extrusion Process of Variable-Burning Rate Propellant by Numerical Simulation

According to the interior ballistic performance of guns, a concept of variable-burning rate propellant was put forward, the fundamental principle of this propellant was discussed and the technologic way to realize the principle was explained.In order to realize the variable-burning rate ,the propellant has two layers ,inner layer's burning rate is higher than the outer layer's. The results show that two-layered variable-burning rate propellant has wishful discharge rule and good properties of progressive combustion.The propellant has the advantages of high energy,universal applicability and high security.

HE Zeng-di

Papers

Principle and Realizable Approach of Variable Burning Rate Propellant