Three kinds of propellant grains that have single, 7 and 19 perforations containing triethyleneglycol dinitrate (TEGDN) with a same web thickness were tested in a closed vessel to investigate the effects of the grain geometry and the ignition strength on the combustion characteristics. The web thickness of the three kinds of propellants was intended to be the same to avoid its influence on the combustion performance. The ratio of grain length to outer diameter of three kinds of TEGDN propellants is the same. Therefore, the influence of the ratio of grain length to outer diameter on burning progressivity is minimized as much as possible. The web thickness is twice the inner diameter of the perforations for the 7-perf and 19-perf grains. The inner perforation diameter of the single-perforation grain is large as possible to keep the combustion neutral. Due to the increasing numbers of perforations of TEGDN propellant, the progressivity of the 19-perf grain increases significantly compared with single and 7-perf grain at the same ignition strength.
As the ignition strength increases, the initial gas generated rate increases. However, it does not benefit the burning progressivity. When the number of perforations increases from 7 to 19, increasing the ignition strength may reduce the combustion stability due to gas flow inside the perforations. Meanwhile, the slivering of 19-perf grains begins earlier and lasts for a longer burning time than 7-perf grains. Thus, the burning rate drops gradually after the beginning of slivering. Results show that the burning gas generation rules can be controlled through the grain configuration and ignition conditions during the combustion process.
triethyleneglycol dinitrate (TEGDN) propellants, grain geometry, ignition, burning rate, progressivity