Investigation of Fire Safety Characteristics of Alternative Aviation Fuels
Abstract
Due to the depletion of fossil fuel reserves and emission challenges associated with its usage, there is a need for alternative aviation fuels for future propulsion. The alternative fuels with handling, storage and combustion characteristics similar to conventional fuels can be used as “drop-in” fuels without significant changes to the existing aviation infrastructure. Fire safety characteristics of alternative aviation fuels have not been studied intensively and therefore research is needed to understand these characteristics. In this study, fire safety characteristics namely hot surface ignition (HSI) and flame spread phenomena are investigated for alternative aviation fuels. HSI is defined as the process of a flammable liquid coming in contact with a hot surface and evaporating, mixing and reacting with the surrounding oxidizer with self-supporting heat release (combustion). If all the conditions are adequate, the fuel may completely turn into combustion products following the ignition process. This work presents results from more than 5000 ignition tests using a newly developed reproducible test apparatus. A uniform surface temperature stainless steel plate simulating the wall of a typical exhaust manifold of an aircraft engine is used as the hot surface. Ignition tests confirmed that the ignition event is transient and initiates at randomly distributed locations on the hot surface. The results show many significant differences and some similarities in the ignition characteristics and temperatures of the different fuels. In this work, hot surface ignition temperatures (HSITs) are measured for nine hydrocarbon liquids. Five of these fuels are piston engine based, three fuels are turbine-engine based and one fuel is a pure liquid, heptane. The piston engine based fuels are given by FAA and are confidential and hence labeled as test fuels A, B, C, D for this study. The HSITs of these fuels are measured and compared against a baseline fuel 100 LL aviation gasoline (100LL Avgas). HSITs of conventional turbine engine based fuels namely Jet-A, JP-8, and JP-5 are also measured. Flame spread along liquid fuel has been one of the important combustion phenomena that still requires more in-depth research and analysis for the deep understanding of the chemical processes involved. Flame spread rate determines how fast the flame spreads along the fuel surface and it is an important parameter to study for fire safety purposes. For the flame spread rates study, a novel experimental apparatus is designed and fabricated. The experimental apparatus consists of a rectangular pan, a fuel heating system, an autonomous lid actuation system, a CO2 fire extinguisher system, and a laser ignition system. The flame spread phenomenon is studied for a conventional aviation fuel namely, Jet-A and three alternative aviation fuels namely, hydro-processed ester fatty acids (HEFA-50), Fischer-Tropsch – IPK (FT-IPK) and synthetic iso-paraffin (SIP). The experiments are conducted for a wide range of initial fuel temperatures ranging from 25°-100°C for Jet-A, HEFA-50, FT-IPK and from 80-140°C for SIP as the flash-point of SIP is 110°C and is ~3 times higher than that of other three fuels.
Degree
Ph.D.
Advisors
Gore, Purdue University.
Subject Area
Design|Materials science|Optics|Thermodynamics
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