Numerical simulation of multi-gasbag propulsion system and attitude control of release unit based on two-phase flow method

• A novel multi-gasbag propulsion system that balances high thrust and low overload is proposed to enable technical collaboration with the large-scale deployment of overload-sensitive drone swarms. • Adequate experiments and two-phase flow numerical simulations are employed to effectively capture the pressure fluctuation and spatiotemporal distribution of flow field parameters within the system. • The study also investigated the separation attitude of the release unit in the multi-gasbag propulsion system and explored the governing control law of its separation attitude. Collaborative technology for the remote, large-scale deployment of drones using dispersal systems holds significant potential in applications such as post-disaster rescue, which must balance low overload with high thrust, in addition to precisely controlling the separation attitude. To address these issues, this paper introduces a multi-gasbag propulsion system with a high aspect ratio that coordinates multiple gasbags to generate sufficient thrust. By adjusting the inlet size of the gasbag, the separation behavior of the release unit can be accurately controlled. A multidimensional two-phase flow model is established, accompanied by both combustion and flow experiments and a double-gasbag propulsion experiment. The results demonstrate that the proposed mathematical model is accurate, effectively captures the pressure fluctuations and spatiotemporal distribution of flow field parameters, and determines the separation attitude of the release unit. For the cases studied in this paper, the pressure at the gasbag inlet ( z = 650 mm) is the dominant factor during the gasbag propulsion response, causing the release unit to rotate counterclockwise when the gasbag inlet sizes are identical. Increasing the inlet size at z = 50 mm compensates for the adverse effects of uneven axial pressure distribution, thereby achieving a neutral separation for the release unit. When the radii r ₁ and r ₂ vary between 2 and 12 mm, the angular velocity and attitude angle of the release unit are found to range from −15.50 to 15.20 rad/s and from −0.109 to 0.106 rad, respectively.