HMX flame structure for combustion in air at a pressure of 1 atm

The chemical structure of HMX flame during combustion in air at a pressure of 1 atm was calculated using molecular beam mass spectrometric sampling. HMX vapor was recorded for the first time near the burning surface. A total of 11 species were identified in the HMX flame (H2, H2O, HCN, N2, CO, CH2O, NO, N2O, CO2, NO2, and HMX vapor), and their concentration profiles were measured. The HMX combustion was unstable. The species concentration profiles exhibit periodic pulsations related to variation in the HMX burning rate. The HMX flame structure at various distances to the burning surface was determined using the average value of the burning rate. Two main zones of chemical reactions in the flame were found. In the first zone ≈0.8 mm wide adjacent to the burning surface, HMX vapor decomposes and NO2, N2O, and CH2O react with each other to form HCN and NO. In the second zone ≈0.8–1.5 mm wide, HCN was oxidized by nitric oxide to form the final combustion products. The composition of the final combustion products was analyzed. The global reaction of HMX gasification at a pressure of 1 atm was established. Heat release values in the condensed phase calculated by the global gasification reaction and by the equation of heat balance on the burning surface (using literature data from microthermocouple measurements) were analyzed and compared.