STUDIES ON COMBUSTION OF DOUBLE STREAMS OF METHANOL/DODECANOL FUEL DROPLETS NEXT TO A COOLING WALL

Abstract

Combustion characteristics of double droplet streams were experimentally investigated. The streams were injected parallel to a cooling wall in a hot gas environment. The streams were a mixture of methanol and dodecanol. Dodecanol was initially present in mass fractions of 0.0, 0.10, 0.15, 0.30, 0.40, and 0.50 and distances between the nearest droplet stream and the wall were either 0.32 mm or 0.16 mm. Droplets initially about 200 μm in diameter were injected through the center of a flat flame burner at 2.6 m/s. The center-to-center droplet spacing within droplet streams was about 260 μm and the distance between droplet streams was about 360 μm. Results show that droplet size histories for the two streams were very similar and that burning rates increased as the dodecanol mass fraction increased; however burning rates remained constant after the initial dodecanol mass fraction reached 0.30. It was also observed that droplet stream stability depended on the fuel pumping rate and distance between the droplet jet streams and the cooling wall. When the distance between the wall and the droplet streams was small, both burning rates and droplet stream stability decreased. The flame exhibited two different colors and the regions of color also changed with the dodecanol mass fraction. Flame contraction was also observed, resulting from sudden droplet heating when the liquid methanol surface mass fraction became small.

Keywords:

• liquid droplets
• sprays