Code 6185 has a long history of fundamental and applied fire science and suppression research. This has included the development and testing of aqueous film forming foam (AFFF) as well as gaseous, water mist/spray, and powder suppression agents. The section’s fire science research has also included the characterization and modeling of blast mitigation, solid combustion and lithium-ion battery fires in efforts to quantify the hazards of the fire products and the propagation behavior.
Code 6185 is involved in fire suppression research that focuses on understanding mechanisms of fire suppression in and outside of a fire environment through foaming and gaseous extinction agents. A key research area is the development of novel environmentally friendly surfactants to replace fluorocarbon surfactants in foaming fire extinction agents (AFFF). We evaluate a potential foam’s ability to suppress a fire by measuring extinction time in a small-scale burning fuel pool, the transient fuel transport through a foam using spectroscopy, and foam properties such as bubble size and liquid drainage rate, relevant for firefighting. Work on recent firefighting foams has been published in Colloids and Surfaces A and presented at the 12th International Symposium on Fire Safety Science.
Experimental work in fire science is supplemented in the section by a robust molecular dynamics modeling effort. This work focuses on surfactant structure and how specific surfactant properties may be optimized to produce foams with improved interfacial properties, necessary for improved fire suppression. Modeling efforts also include Navier-Stokes equations describing foam fire suppression mechanisms characterizing the foam surface cooling effect on liquid pool fires and the diffusion of fuel through fluorinated and fluorine-free foams.
Power & Energy
Efficient fuel consumption extends the U.S. Navy’s tactical and strategic reach. Currently, Code 6185 is conducting research to improve gas turbine efficiency, ignition, and stability. It is also investigating fundamental and applied combustion behavior of solid fuel and catalytic processes to form fuels from seawater.
Our section uses an optically accessible, model gas turbine combustor for basic and applied research. These efforts include proof of concept tests and demonstration of main burner swirlers, fuel injectors, ignition concepts, and igniter placement. Thermocouples and heat flux sensors at the combustor walls and in the exhaust allow time-resolved and in situ measurements. High-speed imaging records and allows ignition, fuel spray, and time-resolved fuel velocimetry measurements.
Air-breathing, solid-fuel propulsion has the potential to be a transformative technology for the U.S. Navy, with up to three times the range of conventional solid rockets that use fuel/oxidizer propellants. To reach this potential, however, solid fuels must achieve faster burn rates (i.e., regression rates), higher combustion efficiencies, and higher energy densities. A promising approach to improve solid-fuel combustion is the inclusion of energetic particle/powder additives, but fundamental understanding of complex composite fuel combustion is lacking. Our objective is to determine the mechanistic details of combustion of composite solid fuels (polymer hydrocarbon fuels containing energetic metal-based additives), including the chemical, fluid mechanic, and thermodynamic processes occurring at the fuel/oxidizer interface. Detailed measurements of combustion behavior for these fuels are necessary to develop and validate theoretical and numerical models. The resulting predictive models can then be used to develop optimal composite solid fuels for hybrid and air-breathing rockets.
A current modeling effort in collaboration with another division at NRL is underway to examine and optimize catalysts to synthesize jet fuel components from carbon dioxide in ocean water. This has required careful model development and validation.
The U.S. Navy has one of the largest supplies of oil spill remediation equipment. To support remediation technology development, Code 6185 is conducting research to examine in situ burning ignition, characterize and predict wellhead burning efficiency, and develop an emulsified crude oil burner. These technologies dispose of spilled crude oil to protect U.S. and foreign coastal ecosystems, trade, and fisheries.
We have designed a crude oil combustor to burn saltwater-crude oil emulsions efficiently. The development is ongoing, with a patent in 2016 and an ongoing development effort to transition it to commercial use.
In the event of oil well blowout, one method to prevent environmental pollution is voluntary ignition of the emerging high-pressure jet of gas and oil. It is crucial, however, to understand the combustion process and burning efficiency of a blown-out wellhead to determine potential impact and response. There are significant knowledge gaps that must be addressed to enable accurate prediction of burning efficiency, namely: (1) the influence of flame size/scaling; (2) the interaction of the liquid droplets with the gas phase combustion, momentum, and heat transfer; and (3) the amount of unburned spray fallout. We seek to address these knowledge gaps via a combination of laboratory- (i.e., small-) scale and larger-scale flame experiments, using laser-based and optical diagnostics and conventional techniques to measure temperature, chemical species, velocity, droplet size, and flow characteristics.