Heat release rate of enhanced large-scale open oil slick fires with Outdoor Gas Emission Sampling (OGES) system.

The Outdoor Gas Emission Sampling (OGES) system was developed to serve as an economical alternative to expensive industrial gas monitoring equipment. By establishing a sampling plane with four discrete sampling points along the radial direction of the smoke plume, the heat release rate (HRR) was measured for large-scale open oil slick fires. This newfound technique was particularly noteworthy during enhanced burns involving Flame Refluxer™ technology, where it is believed that partial premixing of the fuel and air by the apparatus resulted in a higher HRR than existing flame height correlations would suggest, evident by the HRR calculated using mass burning rate and gas analysis methods, which were in good agreement. Results from OGES show the potential of using point sampling within the plume regime to measure the HRR of fires that exceed the capabilities of conventional hood-based calorimeters, especially when it pertains to large-scale open burns.

A study of thin fuel slick combustion on wavy water.

In-situ burning is a fast, cheap, and effective means for cleaning up spilled fuel in the environment. As in-situ burning grows in popularity as a viable way to clean up oil spills, it is increasingly important to study the combustion of liquid fuels floating on wavy water. This study analyzes the burning behavior of a liquid fuel floating on water with the interaction of waves. Nine wave profiles are evaluated with thin layers of kerosene poured into a circular, floating test pan in a rectangular freshwater-filled wave tank. Wave generation and wave absorbing equipment ensure linear wave composition for interaction with the burning pool. Water sublayer and fuel/water interface temperatures are measured for incorporation into a model. It is observed that waves reduce the burning rate and flame height. The burning rate is directly proportional to the steepness of the wave and decreases as steepness increases.

Effects of Natural and Forced Entrainment on PM Emissions from Fire Whirls.

The influence of different air entrainment conditions on the emissions of particulate matter from fire whirls was investigated by igniting a diesel fuel pool, 0.7 m in diameter, within a four-walled enclosure. Four different natural entrainment conditions resulted when gap sizes in the walls were varied between 0.35 and 0.65 m. In addition, three forced-entrainment conditions were created by holding the gap width constant and varying the air-entrainment velocity using fans positioned at each of the four gaps. The concentration of particulates was measured for these seven conditions, and one pool fire condition for comparison. For fire whirls under natural entrainment, the emission factor of total particulate matter, EFPM, was lower than that for pool fires, and decreased with increasing gap size. Fire whirls under mild levels of forced entrainment showed the lowest values of EFPM, but as the level of forced entrainment was increased, EFPM increased steadily to a value higher than that of pool fires. The reduction in EFPM is attributed to a combination of leaner stoichiometry and the interaction between the entrainment and the instantaneous burning rate. Thus, for a given pool diameter, an optimum value of entrainment velocity exists where the EFPM is lowest. Considerations for utilizing whirling flames to reduce airborne particulate emissions from in situ burning are discussed.

Ignitability of crude oil and its oil-in-water products at arctic temperature.

A novel platform and procedure were developed to characterize the ignitability of Alaska North Slope (ANS) crude oil and its water-in-oil products with water content up to 60% at low temperatures (-20-0°C). Time to ignition, critical heat flux, in-depth temperature profiles were investigated. It was observed that a cold boundary and consequent low oil temperature increased the thermal inertia of the oil/mixture and consequently the time to sustained ignition also increased. As the water content in the ANS water-in-oil mixture increased, the critical heat flux for ignition was found to increase. This is mainly because of an increase in the thermal conductivity of the mixture with the addition of saltwater. The results of the study can be used towards design of ignition strategies and technologies for in situ burning of oil spills in cold climates such as the Arctic.

An active role for the ribosome in determining the fate of oxidized mRNA.

Chemical damage to RNA affects its functional properties and thus may pose a significant hurdle to the translational apparatus; however, the effects of damaged mRNA on the speed and accuracy of the decoding process and their interplay with quality-control processes are not known. Here, we systematically explore the effects of oxidative damage on the decoding process using a well-defined bacterial in vitro translation system. We find that the oxidative lesion 8-oxoguanosine (8-oxoG) reduces the rate of peptide-bond formation by more than three orders of magnitude independent of its position within the codon. Interestingly, 8-oxoG had little effect on the fidelity of the selection process, suggesting that the modification stalls the translational machinery. Consistent with these findings, 8-oxoG mRNAs were observed to accumulate and associate with polyribosomes in yeast strains in which no-go decay is compromised. Our data provide compelling evidence that mRNA-surveillance mechanisms have evolved to cope with damaged mRNA.

A means to estimate thermal and kinetic parameters of coal dust layer from hot surface ignition tests.

A method to estimate thermal and kinetic parameters of Pittsburgh seam coal subject to thermal runaway is presented using the standard ASTM E 2021 hot surface ignition test apparatus. Parameters include thermal conductivity (k), activation energy (E), coupled term (QA) of heat of reaction (Q) and pre-exponential factor (A) which are required, but rarely known input values to determine the thermal runaway propensity of a dust material. Four different dust layer thicknesses: 6.4, 12.7, 19.1 and 25.4mm, are tested, and among them, a single steady state dust layer temperature profile of 12.7 mm thick dust layer is used to estimate k, E and QA. k is calculated by equating heat flux from the hot surface layer and heat loss rate on the boundary assuming negligible heat generation in the coal dust layer at a low hot surface temperature. E and QA are calculated by optimizing a numerically estimated steady state dust layer temperature distribution to the experimentally obtained temperature profile of a 12.7 mm thick dust layer. Two unknowns, E and QA, are reduced to one from the correlation of E and QA obtained at criticality of thermal runaway. The estimated k is 0.1 W/mK matching the previously reported value. E ranges from 61.7 to 83.1 kJ/mol, and the corresponding QA ranges from 1.7 x 10(9) to 4.8 x 10(11)J/kg s. The mean values of E (72.4 kJ/mol) and QA (2.8 x 10(10)J/kg s) are used to predict the critical hot surface temperatures for other thicknesses, and good agreement is observed between measured and experimental values. Also, the estimated E and QA ranges match the corresponding ranges calculated from the multiple tests method and values reported in previous research.