Validation of Fire Simulations and Aerosol Formation in Fires
Research at ICSE includes extensive experimental work to validate the simulations of jet fuel fires being developed under the C-Safe program and to enhance our understanding of aerosol formation in fires. Our work focuses on the following areas:
- Fuel combustion and decomposition and the development of a surrogate fuel for performing experiments.
- Gas-phase reactions and the formation of soot precursors
- PAH formation and particle inception
- Chemical transformations and surface reactions on soot particles
- Soot agglomeration and oxidation
- Soot deposition
- Heat transfer
Development of a surrogate for jet (JP8) fuel
In order to perform reproducible fire validation experiments and simulations, ICSE has been developing a surrogate for jet fuel. Ideally, the surrogate fuel:
- Will contain only components that have known detailed kinetic mechanisms.
- Contain a limited number of components to facilitate computation.
- Match the chemical and physical properties of jet fuel in terms of volatility, sooting tendency, and combustion properties.
- Be cost effective.
In order to evaluate the surrogates, we are evaluating the fuel properties in our smoke lamp, laminar and inverse diffusion flames, premixed flames, drop-tube furnace, and fire facility. The initial surrogates contained components that represented the four major hydrocarbon classes: normal paraffins, branched paraffins, cyclo-paraffins, and aromatics. Initial testing showed that the surrogate produce similar chemistry and similar products during experiments on soot formation. We are now focusing on improving our surrogates by focusing on chemical structure.
Gas-phase mechanisms for soot precursors
ICSE has been performing experiments and collecting literature data for the development of a web-based validation where mechanisms can be easily compared with experimental data sets.
Chemical transformations and surface reactions on soot particles
Research at ICSE is focusing on identifying mechanistic pathways for hydrocarbon growth, condensation, and transformation into carbonaceous aerosol particles. Experiments performed in our laminar, premixed, and inverse-diffusion flames as well as our drop-tube furnace will help elucidate the chemical and physical processes in the initial stages of soot formation.
Soot agglomeration and oxidation
ICSE has been developing descriptive models using aerosol dynamics for soot particle growth, agglomeration, and oxidation using results from our two-stage burner and the literature. The two-stage burner work is providing information on soot oxidation rates. Thus far, we have generated initial particle size distributions for a range of stoichiometries.
Soot deposition
ICSE is studying the rate of soot deposition for objects contained in fires with an aim toward identifying key mechanisms effecting deposition. Our experimental work focuses on developing a densitometry technique for identifying soot deposition rates in laminar-diffusion flames and in our fire facility. The densitometry technique works well in a laminar diffusion flame, but the non-uniform deposition behavior in the turbulent environment of a jet-fuel fire is more challenging. Related studies also include determining the effect of soot deposition on heat transfer.
Heat transfer
ICSE is determining the rate-limiting aspects of heat transfer into a container of explosive material. Our experimental work focuses on experiments performed in our fire facility and larger scale experiments performed at a Thiokol's propulsion test facilities.
Our preliminary results show a significant variability in the violence of explosion depending upon heat flux experienced by the explosive material, corresponding to engulfed and adjacent flame conditions. One primary limitation to heat transfer into a container of explosive material is the air gap formed due to differential expansion of steel and explosive material under flame-heating conditions. We are currently working on including the effect of circumferentially variable ullage and exploring the need for more sophisticated gas phase chemistry in our simulation work.
