Electrothermal-Chemical (ETC) Closed-Chamber Interrupted-Burning Tests With JA2 and M30 Solid Propellants

摘要

Interrupted- and noninterrupted-burning tests were conducted with cylindrical perforated grains of JA2 and M30 in a closed bomb with a loading density of approximately 0.2 g/cu cm. Both conventional black-powder and plasma igniters were used. The plasma igniter was an ablating capillary, and the electrical energy density was about 0.7 kJ/g of propellant. The diameters of the collected grains yielded the actual burn distance at the time of the interrupted burning. The experimental pressure traces and the conventional burn-rate coefficients of the propellants were used to calculate the theoretical depth burned assuming no plasma-induced burn-rate modifications. Overlapping pressure traces at several interrupted pressures and from comparison to the calculated- versus-measured burn distances indicated that there is burn-rate enhancement during the plasma pulse, but not much once the pulse has ended. In contrast to the JA2 burn rates, both ambient and cold (-20 deg C) M30 burn rates, deduced from the noninterrupted tests using the BRLCB code, were enhanced even after the plasma turn-off, thus contradicting the interrupted test results. However, vivacity analysis of the noninterrupted tests indicated that the M30 grains exhibited increased surface area (possible fragmentation) because of the plasma interaction, an effect that would cause erroneous results from the BRLCB. Indeed, simulating the noninterrupted M30 tests using the XNOVAKTC code and assuming partial fragmentation of the propellant charge yielded vivacities that mimicked the experimental ones.