Increasing the Stability of the Active-Reactive Projectile Movement Due to Special Ribbing of the Inner Surface of the Nozzle

The paper presents the results of a study into the possibility of increasing the stability of a jet-propelled projectile during operation of a jet engine. The stability of a jet-propelled projectile on its trajectory is determined by the gyroscopic stability coefficient, which depends on the gyroscopic and aerodynamic moment coefficients. To increase the stability of the projectile, a nozzle with special ribbing of the inner surface of the outlet section is considered, due to which some of the thrust will be directed to increasing the rotation of the projectile. A mathematical model of the internal ballistics problem of a solid-propellant jet engine is presented. The model makes some assumptions: the area of the fuel combustion surface and the pressure in the combustion chamber are constant, the fuel combustion rate obeys a power law. The parameters in the outlet section of the nozzle were determined using gas-dynamic functions. Analytical dependencies are proposed for calculating the thrust and torque of a jet engine depending on the rib parameters: height, angle of inclination and number of ribs. To verify the analytical dependencies, numerical simulation of gas flow in a nozzle with ribs was performed in Ansys Fluent. Based on a 3D model of a jet engine nozzle with special ribbing of the inner surface of the nozzle, a finite-volume computational grid was constructed. Based on the results of numerical simulation, the thrust force, combustion product flow rate through the nozzle, and the thrust share per torque were determined at different heights, angles of inclination, and numbers of ribs. The flight stability of a 152-mm high-explosive fragmentation projectile, a rocket-propelled projectile, and a rocket-propelled projectile with special ribbing of the inner surface of the nozzle was investigated. The rib parameters were determined at which the 152-mm rocket-propelled projectile is stable along the entire trajectory.