Experimental investigation of pressure effect on ignition delay of monomethylhydrazine, 1,1-dimethylhydrazine, tetramethylethylenediamine and 2-dimethylaminoethylazide with nitric acid

A drop-on-pool impingement setup, coupled with a high-speed camera, was used to investigate the ignition delay of several hydrazine-, amine- and azide-based fuels, including monomethylhydrazine (MMH), 1,1-dimethylhydrazine (UDMH), tetramethylethylenediamine (TMEDA) and 2-dimethylaminoethylazide (DMAZ), with white fuming nitric acid (WFNA) as the oxidizer. The drop-on-pool impingement experiments were conducted in an N₂ purged chamber with pressures ranging from -40 kPa to 600 kPa (gauge). In general, the ignition delay of hydrazines (MMH and UDMH) decreases with increasing pressure, whereas the ignition delay of TMEDA and DMAZ increases with increasing pressure. In addition to the pressure effect, the ignition delay of MMH/WFNA is also significantly affected by the type of droplet-pool interaction. The droplet stays within the pool after impingement at sub-atmospheric pressures (type I), while the droplet is ejected from the pool at elevated pressures (type II). The critical pressure is about 0 kPa (g) at which either interaction type was observed. The ignition delay of type I interaction is much longer than that of type II at that pressure. The ignition delay of a mixture of 33.3% DMAZ and 66.7% TMEDA was also studied. This mixture has a shorter ignition delay than both pure TMEDA and DMAZ. In addition, the pressure effect on the ignition delay of this mixture is not significant.