No abstract

No abstract

A series of small and large-scale tests were performed to measure the radiant transmission of energy and the window breakage characteristics of seven different multi-plane glazing samples. The samples tested included both double and triple-pane glazing specimens with a laminate interlayer between panes for additional strength. These test series were designed to provide the information necessary to assess the hazard from radiant energy to building occupants and contents due to a large fire in close proximity to a structure with a large amount of exterior windows. For incident heat fluxes 30 kW/m 2 or lower, the triple-pane glazing samples had a total transmittance less than 10% of the incident heat flux, back-side surface temperatures did not exceed 100 • C, and the back-side heat flux did not exceed 4 kW/m 2 . For double-pane laminates, the total transmittance was less than 25% of the incident heat flux, the back-side temperature did not exceed 220 • C, and the back-side heat flux did not exceed 5 kW/m 2 . For incident heat fluxes greater than 30 kW/m 2 , the glazing samples degraded very quickly, generally buckling and losing integrity. The time for the first pane to crack decreased with increasing incident flux level. A number of tests included a water deluge system, which served to maintain sample integrity for extended exposures. In these cases, the total transmittance was less than 6% of the incident heat flux, back-side surface temperatures did not exceed 45 • C, and the back-side heat flux did not exceed 1 kW/m 2 .

Experimental and kinetic modeling of kerosene-type fuels is reported in the present work with special emphasis on the low-temperature oxidation phenomenon relevant to gas turbine premixing conditions. Experiments were performed in an atmospheric pressure, tubular flow reactor to measure ignition delay time of kerosene (fuel–oil No. 1) in order to study the premature autoignition of liquid fuels at gas turbine premixing conditions. The experimental results indicate that the ignition delay time decreases exponentially with the equivalence ratio at fuel-lean conditions. However, for very high equivalence ratios (>2), the ignition delay time approaches an asymptotic value. Equivalence ratio fluctuations in the premixer can create conditions conducive for autoignition of fuel in the premixer, as the gas turbines generally operate under lean conditions during premixed prevaporized combustion. Ignition delay time measurements of stoichiometric fuel–oil No. 1∕air mixture at 1 atm were comparable with that of kerosene type Jet-A fuel available in the literature. A detailed kerosene mechanism with approximately 1400 reactions of 550 species is developed using a surrogate mixture of n-decane, n-propylcyclohexane, n-propylbenzene, and decene to represent the major chemical constituents of kerosene, namely n-alkanes, cyclo-alkanes, aromatics, and olefins, respectively. As the major portion of kerosene-type fuels consists of alkanes, which are relatively more reactive at low temperatures, a detailed kinetic mechanism is developed for n-decane oxidation including low temperature reaction kinetics. With the objective of achieving a more comprehensive kinetic model for n-decane, the mechanism is validated against target data for a wide range of experimental conditions available in the literature. The data include shock tube ignition delay time measurements, jet-stirred reactor reactivity profiles, and plug-flow reactor species time–history profiles. The kerosene model predictions agree fairly well with the ignition delay time measurements obtained in the present work as well as the data available in the literature for Jet A. The kerosene model was able to reproduce the low-temperature preignition reactivity profile of JP-8 obtained in a flow reactor at 12 atm. Also, the kerosene mechanism predicts the species reactivity profiles of Jet A-1 obtained in a jet-stirred reactor fairly well.

ABSTRACf-We have obtained quantitative LIF measurements of NO concentration in the postllame zone of a series of lIat, laminar, premixed CH./O,(N, lIames (0.5:s ",:S 1.6) at pressures ranging from 1-14.6 atm. The temperatures of the lIames were 1660-1960 K, indicating that prompt NO was the primary pathway for NO formation in the majority of these flames. In addition, we have modeled many of the experimentaillames using the chemical reaction mechanism ofGlarborg-MiJler-Kee as modified by Drake and Blint (GMK-DB). This model accurately predicts the behavior of NO with increasing pressure and shows reasonable quantitative agreement for many of the lIames at pressures :s 6.1 atm. At pressures greater than 6.1 atm, inaccuracies in the predicted temperature field preclude good quantitative agreement between the modeled and measured NO concentrations. Detailed NO measurements in ultra-lean ('" = 0.55-0.8) flames showed higher NO emissions with increasing pressure, a result consistent with kinetic modeling of these lean lIames via the GMK-DB mechanism.

Ignition delay times of a “real” synthetic jet fuel (S8) were measured using an atmospheric pressure flow reactor facility. Experiments were performed between 900 K and 1200 K at equivalence ratios from 0.5 to 1.5. Ignition delay time measurements were also performed with JP8 fuel for comparison. Liquid fuel was prevaporized to gaseous form in a preheated nitrogen environment before mixing with air in the premixing section, located at the entrance to the test section of the flow reactor. The experimental data show shorter ignition delay times for S8 fuel than for JP8 due to the absence of aromatic components in S8 fuel. However, the ignition delay time measurements indicate higher overall activation energy for S8 fuel than for JP8. A detailed surrogate kinetic model for S8 was developed by validating against the ignition delay times obtained in the present work. The chemical composition of S8 used in the experiments consisted of 99.7 vol% paraffins of which approximately 80 vol% was iso-paraffins and 20% n-paraffins. The detailed kinetic mechanism developed in the current work included n-decane and iso-octane as the surrogate components to model ignition characteristics of synthetic jet fuels. The detailed surrogate kinetic model has approximately 700 species and 2000 reactions. This kinetic mechanism represents a five-component surrogate mixture to model generic kerosene-type jets fuels, namely, n-decane (for n-paraffins), iso-octane (for iso-paraffins), n-propylcyclohexane (for naphthenes), n-propylbenzene (for aromatics) and decene (for olefins). The sensitivity of iso-paraffins on jet fuel ignition delay times was investigated using the detailed kinetic model. The amount of iso-paraffins present in the jet fuel has little effect on the ignition delay times in the high temperature oxidation regime. However, the presence of iso-paraffins in synthetic jet fuels can increase the ignition delay times by two orders of magnitude in the negative temperature (NTC) region between 700 K and 900 K, typical gas turbine conditions. This feature can have a favorable impact on preventing flashback caused by the premature autoignition of liquid fuels in lean premixed prevaporized (LPP) combustion systems.

Coefficients for the interdiffusion of Sn in Pb-rich alloys and Pb in Sn-rich alloys were established using 1.5-mm-diameter capillaries and the semi-infinite rod technique. Interdiffusion coefficients are presented for the entire concentration range from pure Pb to pure Sn, for temperatures from 668 to 1031 K. The concentration dependence of the interdiffusion coefficients was determined by establishing the concentration along the length of the capillaries and calculating the coefficients using a finitedifference technique. The interdiffusion of Sn in Pb, extrapolated to 0 at. pct Sn, is given by D ϭ 8.8 ϫ 10 Ϫ8 exp Ϫ (22,600/RT ) m 2 /s and that for Pb in Sn, extrapolated to 0 at. pct Pb, by D ϭ 2.4 ϫ 10 Ϫ8 exp Ϫ (19,300/RT ) m 2 /s The "average" value for the interdiffusion of Sn in Pb, for the concentration range from 0 to 74 at. pct Sn, is given by D ϭ 1.1 ϫ 10 Ϫ7 exp Ϫ (25,200/RT ) m 2 /s and the average value for the interdiffusion of Pb in Sn, for the concentration range from 0 to 26 at. pct Pb, is given by D ϭ 1.3 ϫ 10 Ϫ8 exp Ϫ (22,600/RT ) m 2 /sThe values obtained for the coefficients agree reasonably well with previous results for the diffusion of Sn in Pb-rich alloys and are consistent with solvent self-diffusion coefficients for pure Pb and pure Sn. However, while the diffusion coefficients obtained from these Arrhenius equations are likely of the right order of magnitude, it is concluded that the results are affected by fluid flow in the capillaries, resulting in higher than actual activation energies. It is suggested that, for the capillary-reservoir technique, convective flow in the reservoir across the open end of the capillaries induces "lid-driven" flow in the upper portions of the capillaries, resulting in higher than actual diffusion coefficients, particularly for the Sn-rich alloys, since the Sn-rich end of the capillaries was open to the reservoir. Because of fluid motion induced in the capillaries, all of the results for solute and self-diffusion in Pb, both present and previous, are likely erroneous because they were obtained using the capillaryreservoir technique. Some previous results for solvent self-diffusion in liquid Sn were obtained using either the thin disk or the semi-infinite rod technique and, since these results agree with results obtained in microgravity, it is concluded that the nonreservoir methods may provide a means of obtaining more accurate liquid diffusion data.

No abstract