CO2 laser-induced pulsating regression behavior of GAP at sub-atmospheric pressures

• Published in: Combustion and flame Vol. 124; no. 4; pp. 611 - 623
• Main Authors: SAITO, Takeo, SHIMODA, Masataka, TSUYUKI, Tsuyoshi, IWAMA, Akira
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Science 01.03.2001
• Subjects: Applied sciences; Combustion. Flame; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Miscellaneous; Theoretical studies. Data and constants. Metering; Temperature measurement; Pyrolysis; Cyclic ether polymer; laser; Thermal decomposition; Solid propellant; Combustion; Laser irradiation; CO
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/S0010-2180(00)00233-9

Linear pyrolysis of glycidyl azide polymer (GAP) by CO2 laser heating was studied experimentally in argon, nitrogen, or oxygen at subatmospheric pressures with laser heat fluxes of 1 to 20 W/sq cm. Surface temperature variations were measured by fine chromel-alumel thermocouples pressed onto the sample surface, and pulsating regression caused by an abrupt exothermic decomposition was observed. The behavior is very similar to the chuffing phenomenon. The momentary exothermic decomposition reaction was accompanied by the evolution of N2 resulting mainly from breaking of the azide bond. The surface temperature in one cycle is characterized by three critical temperatures: liquefying, abrupt thermal decomposition threshold, and maximum surface temperatures. Maximum surface temperatures are 700 to 800 K, which are equivalent to the surface temperature observed during self-sustained combustion controlled chiefly by exothermic reaction at the decomposition surface. As the surface heat flux increases, the period of the pulsating regression decreases, being only slightly dependent on the ambient gas. If the period becomes shorter than the characteristic time of GAP, then the pulsating regression will transition into steady regression assisted by laser irradiation. (Author)