The combustion phenomena of doublet impingements of nitrogen tetroxide and monomethylhydrazine were observed in this research. The total flow rates of the propellants were controlled at&tild;8:00 g/s to simulate the operation of a 5 lbf rocket, and the ratios of the mass flow rates (O/F) of nitrogen tetroxide and monomethylhydrazine were varied from 1.0 to 2.5. With a two-axis translation module, a C-type thermocouple was used to measure the two-dimensional temperature distributions of the flames at 20 mm downstream of their impinging points. The observations showed that induction distances always appeared from the positions of propellants' impingement to ignition, and the ignition was induced by the local concentrations of gaseous monomethylhydrazine. The maximum flame length of&tild;80 mmappeared at the best mixing condition ofO/F=1:2, and diffusion-type flames at higher O/F showed shorter flame lengths for poor mixing after the flames had been ignited. Comparing to the previous cold-flow observations by the planar laser induced fluorescence technique with simulants of water- and chloroform-based solutions to match the densities, viscosities, and surface tensions of monomethylhydrazine and nitrogen tetroxide, the locations of high-temperature zones in hot-fire experiments were adequately described by the calculated two-dimensional temperature distributions from the observed local mixture ratio data at the corresponding ignition positions in the cold-flow experiments. These results inferred that the mixture ratio profile was almost conserved after ignition. That is, by properly analyzing the mass distribution of the cold-flow observation with simulants, the temperature distribution of the impinging combustion of nitrogen tetroxide/ monomethylhydrazine can be predicted.
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