Ignition and Combustion Behavior of Sintered‐B/MgB2 Combined with KNO3. Issue 6 (26th February 2020) - Sun, Yalun
Abstract: To further enhance the performance of B/KNO3 (BPN) igniter, sintered B/MgB2 (s‐B/MgB2 ) powder was proposed to be used as a boron substitute. The amount of heat release was tested by oxygen bomb and thermogravimetry/differential scanning calorimetry (TG/DSC). s‐B/MgB2 /KNO3 (sBPN) igniter could not release as much heat as BPN igniter in the oxygen bomb due to the reduced calorific value of the s‐B/MgB2 . However, calculations show that s‐B/MgB2 reached an over 90 % heat release efficiency in oxygen bomb, compared to that of 53.34 % for boron. At heating rate of 10 K min −1 in TG/DSC experiment, 19.5 % sBPN (sBPN with 19.5 wt. % s‐B/MgB2 powder) has a heat release of 1815 J g −1 and experienced an exothermic span of 2.10 min, whereas it took 24.5 % BPN (BPN with 24.5 wt. % boron powder) 3.45 min to release 1465 J g −1 . The pressure‐time curve (P‐t curve), burning rate and combustion temperature were determined. The P‐t curve indicates that the combustion pressure was more readily established with the sBPN than with the BPN. The maximum pressure rise of sBPN was 362.0 Pa ms −1, whereas the figure for BPN is 77.2 Pa ms −1 . Coupled with infrared radiation (IR) temperature thermometer, the distribution of the flame temperature field during combustion was obtained. It is shown that the combustion temperature of 19.5 % sBPN igniter is approximately 800 K higher than that of 24.5 % BPN. IR images of the combustion process show that the temperature difference of the 19.5 % sBPN flame is smaller than that of the 24.5 % BPN. 19.5 % sBPN also produces more hot residue, which contains KMgF3, resulting in a longer high‐temperature duration. The higher combustion pressure and temperature and more residue may enable the sBPN to readily ignite the following charge. Abstract :