Autoignition of diesel/oxygen/nitrogen mixture under elevated temperature in a heated shock tube

Isopropanol has potential as a future bio-derived fuel and is a promising substitute for ethanol in gasoline blends. Even so, little has been done in terms of high-temperature chemical kinetic speciation studies of this molecule. To this end, experiments were conducted in a shock tube using simultaneous CO and H2O laser absorption measurements. Water and CO formation during isopropanol pyrolysis was also examined at temperatures between 1127 and 2162 K at an average pressure of 1.42 atm. Species profiles were collected at temperatures between 1332 and 1728 K and at an average pressure of 1.26 atm for equivalence ratios of 0.5, 1.0, and 2.0 in highly diluted mixtures of 20% helium and 79.5% argon. Species profiles were also compared to four modern C3 alcohol mechanisms, including the impact of recent rate constant measurements. The Li et al. (2019) and Saggese et al. (2021) models both best predict CO and water production under pyrolysis conditions, while the AramcoMech 3.0 and Capriolo and Konnov models better predict the oxidation experimental profiles. Additionally, previous studies have collected ignition delay time (τign) data for isopropanol but are limited to low pressures in highly dilute mixtures. Therefore, real fuel–air experiments were conducted in a heated shock tube with isopropanol for stoichiometric and lean conditions at 10 and 25 atm between 942 and 1428 K. Comparisons to previous experimental results highlight the need for real fuel–air experiments and proper interpretation of shock-tube data. The AramcoMech 3.0 model over predicts τign values, while the Li et al. model severely under predicts τign. The models by Capriolo and Konnov and Saggese et al. show good agreement with experimental τign values. A sensitivity analysis using these two models highlights the underlying chemistry for isopropanol combustion at 25 atm. Additionally, modifying the Li et al. model with a recently measured reaction rate shows improvement in the model’s ability to predict CO and water profiles during dilute oxidation. Finally, a regression analysis was performed to quantify τign results from this study.

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Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010011043x ◽

1978 ◽

Vol 36 (1) ◽

pp. 658-659

Author(s):

G.J.C. Carpenter

Keyword(s):

Elevated Temperature ◽

Strain Field ◽

Zirconium Hydride ◽

Zirconium Atom ◽

Atom Diffusion ◽

Solvus Temperature ◽

Hexagonal Close Packed ◽

Partial Dislocations ◽

The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

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Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104819 ◽

1988 ◽

Vol 46 ◽

pp. 550-551

Author(s):

R. E. Franck ◽

J. A. Hawk ◽

G. J. Shiflet

Keyword(s):

High Temperature ◽

Elevated Temperature ◽

Grain Growth ◽

Volume Fraction ◽

Microstructural Characterization ◽

Second Phase ◽

Microstructural Stability ◽

Elevated Temperature Strength ◽

Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

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Using a shock tube to predict the response of polymeric foam to a blast loading

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2006134121 ◽

2006 ◽

Vol 134 ◽

pp. 783-787 ◽

Cited By ~ 2

Author(s):

S. Ouellet ◽

D. Frost ◽

A. Bouamoul

Keyword(s):

Shock Tube ◽

Blast Loading ◽

Polymeric Foam

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