Soot emissions from spherical droplet flames for mixtures of JP8 and tripropylene glycol monomethyl ether.

The combustion of JP8 (a kerosene-based fuel) mixed with up to 20% (volume) tripropylene glycol monomethyl ether (TPGME, CH3[CH2CH(CH3)O]3OH) is studied to examine the influence of composition on soot dynamics for the configuration of an isolated and stationary droplet burning with nearly spherical symmetry. The spherical droplet flame is characterized by a one-dimensional transport process with a concentric flame and droplet, and a sooting configuration for which the soot aggregates are trapped between the droplet and flame in a "shell" or "cloud". Sooting tendencies are inferred from photographic documentation of the droplet burning process and are found to be in the approximate order JP8 > JP8 + 10% TPGME > JP8 + 20% TPGME. At 20% the soot cloud all but disappears. The maximum soot aggregate diameter is 80 (+/-17) nm, independent of composition. Preferential vaporization is pronounced as evidenced by a plateau in the evolution of the droplet diameter (squared) which indicates a dominant influence of TPGME over other constituents in JP8 that makes JP8/TPGME behave almost like a binary mixture despite the highly multicomponent nature of the JP8/TPGME blend. A scaling relationship for flame, soot cloud, and droplet diameters is shown to consolidate the measurements onto a single curve.