Interaction of two burning drops along the stream direction

The interaction of two burning drops along the stream direction was studied experimentally using a free-falling drop apparatus which provided different initial drop diameter (d_i) and initial drop spacing (S_i) for the dodecane fuel. Three initial drop diameter, d_i = 500, 700, 900 μm, and three initial dimensionless drop spacings, S_i = 2.5, 5 and 10, were considered in the experiment. In the combustion chamber, the initial gas velocity of the hot flow was estimated at 2.5m/s and the oxygen concentration (Ω_O2) was controlled at 21%. The temperature of combustion chamber was decreased from about 900 ^oC to 400 ^oC with x = 7 to 85 cm. Results showed burning characteristics of two dodecane drops were affected by thermal expansion of individual drop flame and flow convection of the surrounding gas flow in the combustion chamber. The flame transition could be categorized into four modes. Mode 1 showed both drops with individual wake flame moving downward along the same axis when S_i > 10. In mode 2, two drops similar to mode 1 moved downward out of the same axis. Two drops with a wake flame located at the downstream of the trailing drop moving downward along the same axis was mode 3. In mode 4, two drops similar to mode 3 moved downward out of the same axis. Merging collision was not observed for two dodecane drops in this experiment.