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1 year ago

Fig xA a OH sensitivity analysis SOH part XOH

Fig. 2. (a) OH sensitivity analysis, SOH=(∂XOH/∂ki)/(XOH/ki)SOH=(∂XOH/∂ki)/(XOH/ki). (b) ΔOH sensitivity, SΔOH=(∂ΔXOH/∂ki)/(ΔXOH/ki)SΔOH=(∂ΔXOH/∂ki)/(ΔXOH/ki).Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 3. Uncertainty analysis for the measured rate constant of CH3CHO + OH.Figure optionsDownload full-size imageDownload as PowerPoint slide
4. Summary of results
A total of 61 reflected shock wave experiments were performed to determine the overall rate constants for the reactions of OH with four aldehydes (CH2O, CH3CHO, C2H5CHO and n-C3H7CHO) at near-pseudo-first-order conditions. Experiments were carried out over the temperature range of 950–1400 K at pressures of 1–2 atm using different initial fuel and TBHP concentrations. Results Glimepiride summarized in Table 1.
Table 1.
As expected, the uncertainties in the rate constant measurement were seen to decrease at higher aldehyde/TBHP ratio (Fig. 4). However, though Ordovician extinction was tempting to use even higher aldehyde/TBHP ratio, the increased uncertainties from the thermal decomposition of aldehydes at very high temperatures and from the manometric preparation of very dilute TBHP mixtures eventually limited the measurement accuracy. The current choices of aldehyde/TBHP had already accounted for the tradeoff between these different uncertainty sources. Despite the variations in uncertainty limits, all data points followed the same trend and were seen to be very consistent. Experiments at a higher pressure (∼4 atm) were included, and no pressure dependence was observed, which suggested that the overall OH + aldehydes rates measured in the current study were probably dominated by H-abstraction.

1 year ago

At lower temperatures i e ndash

Measurements of ignition delay times spanning low, intermediate, and high temperatures were carried out in a heated high-pressure shock tube (HPST) at Rensselaer Polytechnic Institute (RPI) using the reflected shock technique. This shock tube has been described by Wang and Oehlschlaeger [19] and references therein, hence, only details relating to the present study PHA-767491 provided here. Ignition delay times were measured for fuel/air mixtures at equivalence ratios of 0.5 and 1.0, temperatures ranging from 714 to 1262 K, and nominal pressures of 20 and 40 bar. Reactant mixtures were prepared by direct injection of fuels into a heated mixing vessel. Following vaporization of the fuel, N2 and O2 were added in emphysema order to the mixing vessel from compressed gas cylinders at a molar ratio of 3.76:1; reactant mixture molar fractions were specified via partial pressure. The ignition event was measured by monitoring the pressure history, and the ignition delay time has the same definition as in the LPST. Following the passage of the reflected shock wave, the pressure was observed to slowly rise due to viscous gas dynamics at a rate of dP/dt = 2–3% per millisecond, which is incorporated into kinetic modeling simulations. The uncertainty in ignition delay is ±20% (95% confidence interval), where the majority of ignition delay uncertainty stems from uncertainty in the reflected shock temperature.

1 year ago

Semtex The C and N variations of

3.4.1.2. Semtex
The δC13 and δN15 variations of seized Semtex, assumed to come from different sources, were evaluated using a likelihood ratio (LR) framework [169]. The authors showed that the misleading evidence rate varied depending on the chosen probability distribution and highlighted the necessity to have large stable isotope ratio databases to use this FK866 approach. Lock obtained similar δC13 and δN15 values on a set of 16 Semtex specimens [168]. Table 7 displays the ranges of bulk isotopic values of Semtex reported in the filaments two studies.
Table 7.
Summary of reported results on the bulk isotopic values of Semtex in literature. * indicates δ values estimated from plots.StudyNumber specimensOriginδC13 (‰)δN15 (‰)δO18 (‰)Pierrini et al. [169]26Unknown−36.53 to −24.76−25.68 to −2.72–Lock [168]16Unknown−38.00 to −26.06−22.43 to −4.57+17.10 to +33.05Full-size tableTable optionsView in workspaceDownload as CSV

1 year ago

In the SF flame Fig upper part it is possible

In the SF flame, Fig. 6 (upper part), it is possible to note that soot starts being detected when surface growth becomes important. Following the streamline, i.e., moving from the flame front toward the stagnation plane (from left to right in the figure), the surface growth becomes even more important, while the GDC-0449 is negligible. This shows that the oxidation cannot affect the final size of the soot particles, which in fact grow reaching a maximum on the stagnation plane. Oxidation is important close to the flame front where soot is present at very low concentration. The model predicts a significant inception rate on the fuel side which suggests that formation of new particles occurs also in this region, in agreement with previous studies [20], [21] and [22].
In the SFO flame, the reaction rate analysis shows a different situation. Particles start being formed very close to the fuel nozzle exit. The small amount of oxygen added in the fuel stream helps to increase the reactivity in this zone and induces a fast growth rate. Oxidation takes place where the formation process is still active. Oxidation by OH is present but it remains quite smaller respect the surface growth. Moving from 2 to 4 mm particle volume fraction rapidly increases. Finally, at the location of the maximum 'GDC-0449' soot concentration the oxidation rate become predominant and soot starts being effectively oxidized. At this point O2 promotes particle and aggregate fragmentation. Fragmentation is probably active even before the maximum soot concentration is reached. In fact, the presence of fragmentation makes the size of particles very small so that the fragmentation rate of particles is even higher than fragmentation rate of aggregates.