New ignition methods for droplet combustion studies

ABSTRACT

Two new methods for igniting suspended droplets, namely Plasma Arc Ignition (PAI) and Photoignition (PI), were developed which offer relatively short ignition initiation times within 65–110 ms range for all fuels except hexadecane that is about 260 ms. The fuels included ethanol, methanol, n-heptane, n-dodecane, toluene, RP-2, JP-8, Fischer-Tropsch (FT), diesel #2, and hexadecane. The resulting average droplet ignition delays were up to an order of magnitude smaller than other methods for ignition of fuel droplets reported in the literature such as heated furnaces and ignition coils. The significant reduction in the ignition delay is most likely due to the substantially hotter ignition temperatures (≥2000 K) of these methods, which makes them more suitable for relatively well-defined ignition events and capable of igniting less volatile fuels such as diesel and hexadecane. To the best of our knowledge, this is the first report on the use of these techniques for the ignition of suspended fuel droplets.

KEYWORDS:

• Plasma Arc Ignition
• Droplet Ignition
• Photoignition
• Suspended Droplets
• Flash Ignition
• Ignition Delay
• Hydrocarbon Fuel Droplets

Acknowledgment

We gratefully thank Dr. Rosa Padilla for help with thin-filament pyrometry and Dr. Mario Roa for assistance with the diagnostic imaging of the plasma arc ignition source.

Additional information

Funding

This work was funded by the Air Force Office of Scientific Research (AFOSR), under Dr. Mitat Birkan, Project Officer.