Investigating asymmetric mass and heat transfer in the calendering of modified double-base propellants

Abstract

To improve the plasticization quality and process safety of Modified Double-Base (MDB) propellants during the calendering process. This study, using actual physical parameters of MDB propellant, a three-dimensional thermo-fluid coupled model was developed to investigate the effects of process parameters on the heat and mass transfer behavior of MDB materials during the calendering process. By comparing the effects of different roller speed ratios, roller gaps, and roller speeds on the material's velocity, temperature, and viscosity distribution during the calendering process, it was found that the material forms an asymmetric vortex reflux movement during the calendering process. This unique flow characteristic is the primary reason for the material's asymmetric mass and heat transfer properties. Changes in the rotational speed ratio have a minor impact on the reflux movement but significantly affect process safety. A rotational speed ratio of 1.25 can effectively reduce the temperature of the material at the vortex center, thereby decreasing the risk of combustion. The smaller the roll gap, the higher the starting position of the material reflux. By selecting a roll gap of 0.8 mm, it's possible to effectively reduce the viscosity gradient while simultaneously decreasing the material's residence time. Increasing the rotation speed enhances the intensity of reflux. A speed setting of 20:15 not only reduces heat generated from shearing but also controls the temperature distribution range of the material, thereby enhancing the efficiency of the calendering production process. These adjustments in process parameters enhanced the safety and production efficiency of the MDB propellant calendering process, providing valuable insights for the safe production of MDB propellant calendering technology.