Investigation of kerosene combustion characteristics with pilot hydrogen in model supersonic combustors

Experimental investigations on the ignition and combustion stabilization of kerosene with pilot hydrogen in Mach 2.5 airflows were conducted using two test combustors, with cross sections of 30.5 x 30 and 51 x 70 mm, respecti vely. Various integrated modules, including the combinations of different p ilot injection schemes and recessed cavity flameholders with different geom etries, were designed and tested. The stagnation pressure of vitiated air v aried within the range of 1.1-1.8 NiPa, while the stagnation temperature va ried from 1500 to 1900 K. Specifically, effects of the pilot hydrogen injec tion scheme, cavity geometry, and combustor scaling on the minimally requir ed pilot hydrogen equivalence ratio were systematically examined. Results i ndicated that the cavity depth and length had significant effects on the ig nition and flameholding, whereas the slanted angle of the aft wall was rela tively less important. Two cavities in tandem were shown to be a more effec tive flameholding mechanism than that with a single cavity. The minimally r equired pilot hydrogen equivalence ratio for kerosene ignition and stable c ombustion was found to be as low as 0.02. Furthermore, combustion efficienc y of 80% was demonstrated to be achievable for kerosene with the simultaneo us use of pilot hydrogen and a recessed cavity to promote the ignition and global burning.