Development and Performance Studies of Pyrotechnic Composition for Pressure-Generated and Delay Cartridges

Abstract

The work presented in this thesis is focused on the development and performance studies of different types of pyrotechnic compositions for pressure-generated and delay cartridges. A lot of work has been carried out in the field of pyrotechnic compositions; however, there is not much data available on the development and selection of the suitable igniter and booster pyrotechnic compositions for pressure-generated cartridges, coupled with lack of understanding of detailed parametric studies on pyrotechnic delay compositions to improve their burning performance. The published work in the field of pyrotechnic delay compositions presents individual studies of one or two parameters affecting burning performance. The present work is a concerted effort to provide an insight into the detailed studies of a number of parameters to investigate and improve the performance of particular delay compositions. For this purpose B, Zr and Pb(SCN)2 were used as fuels and KNO3, KClO4, KClO3 as oxidizers for the development of igniter and booster pyrotechnic compositions, whereas B and Si were used as fuels while BaCrO4, PbO and Pb3O4 as oxidizers while FG, CMC, Dextrin as binders for the development of different types of pyrotechnic delay compositions. The first part of this research work pertains to develop different types of high energy igniter and booster pyrotechnic compositions: B/KNO3, Zr/KClO4 and Pb(SCN)2/KClO3 as igniter compositions while B/Mg/KClO4/Bi2O3 and B/Mg/KClO4 as booster pyrotechnic compositions. The study shows that the best combination for igniter and booster compositions in terms of safety, calorific values and cartridge functionality are Zr/KClO4 (40/60) and B/Mg/KClO4 (30/10/60), respectively. Further, the development and parametric studies of different types of pyrotechnic delay compositions comprising B/BaCrO4/Binder, Si/Pb3O4/Binder, Si/PbO/Binder and Si/Pb3O4/PbO/Binder was conducted. Effect of fuel contents, binders, temperature variation, loading pressure, ingredients mixing and body material on the burring time and burning rate/mass consumption of these delay compositions were experimentally investigated and Calorific values were determined. These studies revealed that burning performance of a pyrotechnic delay composition could be modified by altering these parameters through an indepth study of these parameters to enable the end-user to develop and optimize the burning performance of pyrotechnic compositions as done in this work.Variation in the burning time has been significantly reduced in these delay compositions through homogenous mixing as being a problem in delay mixtures. The burning rate and mass consumption of these compositions increased with increase in fuel contents until maximum value was achieved. These values then decreased on further increase in fuel contents until misfire condition was recorded. It was also revealed during this study that binders also play an important role in modifying the burning rate of delay compositions. Variation in loading pressure did not significantly affect the burning performance. Burning rate of these delay compositions increased with the decrease in ambient temperature and vice versa. By replacing the stainless steel body material with brass and controlling the laboratory operating conditions further reduced the variation in the burning time. In the last part of the thesis, studies were undertaken for the measurement of minimum pressure together with ejection velocity, required for the release of the external stores from military aircraft on powerful pressure generating cartridge. Pressure generating cartridge converts chemical energy into mechanical energy. Mission effectiveness and sustainability for military aircrafts are highly dependent on ability to separate the external stores with required velocity to minimize risk during mission flight. The prediction of ejection velocity for the separation of external stores from the military aircrafts is an important task in the aerodynamic design area. It not only requires to separate the stores safety from the aircraft but also requires a relatively smooth release for good delivery accuracy. The experimental data shows that minimum pressure required to separate the external store from Ejection Release Unit (ERU) must be more than 70 bars depending on the mass of store. The ejection velocity with single cartridge is between 3.59~4.5 m s-1 The upshot of this work is that it provides new insight in the function and performance of pyrotechnic delay compositions and pressure generated-cartridges to enable the end-user to optimize the performance of these compositions, as per requirement.