Atomization of gel propellants using a Hartmann whistle injector

Abstract

Gel propellants, which combine the benefits of solid and liquid propellants, suffer from poor atomization quality due to their high viscosity. Sonic atomization technology has demonstrated potential in atomizing high-viscosity non-Newtonian fluids. This study designed a Hartmann whistle injector comprising a central gas path, an annular slit liquid path, and a resonant cavity. Schlieren imaging and the microphone measurements revealed that the sound waves originate at the leading edge of the resonant cavity, with an optimal gas path pressure identified for generating the strongest acoustic field. A water-based simulant with rheological properties similar to gel propellants was employed for atomization experiments. High-speed imaging demonstrated that the Hartmann whistle injector significantly enhanced gel liquid breakup, reducing the Sauter Mean Diameter (SMD) by up to 37 % compared to the conventional gas-liquid coaxial injector. Orthogonal experiments investigated the effects of liquid annular slit width, central rod diameter, resonant cavity distance, and gas pressure on atomization performance, revealing optimal parameter combinations. These findings highlight the potential of Hartmann whistle injectors for advancing gel propulsion technologies.