Initial Gas Fraction Research Articles

Spark ignition of combustible gas mixtures

A mathematical model is presented to simulate the evolution with time of a spark channel into a combustion wave. The model considers the phenomena associated with electrical breakdown and arc phases, the plasma conductivity and realistic transport coefficients at high temperatures, and a detailed chemical reaction scheme. The growth of the initial flame radius is calculated by a numerical integration of the model equations and compared with the experimental observation of Tagalian and Heywood. The time needed for the establishment of a flame propagation in the “like-laminar” regime was found to be strongly dependent on the breakdown energy and on the spark duration, and to a small extent on the initial pressure, temperature, and residual gas fraction. The model was used also to examine quantitatively the effect of some relevant parameters on the cycle-to-cycle variation in the steady-state burning velocity and it was concluded that the cycle-to-cycle variation is attributed mainly either to the inhomogeneity of the trapped mixture and/or to the cycle-to-cycle variation in trapped conditions; a variation of 5% of the volumetric efficiency affects the burning velocity by some ±13 %.

The effects of induced star formation on the evolution of the galaxy. II - The galactic ecosystem

view Abstract Citations (42) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The effects of induced star formation on the evolution of the galaxy. II - The galactic ecosystem Shore, S. N. Abstract The deterministic dynamical systems approach of Paper I is here generalized to the case of a disk galaxy with star-induced star formation. It is shown that the cases of a rigidly rotating axisymmetric and nonaxisymmetric, and a differentially rotating galaxy model can be solved explicitly. The results are compared with stochastic simulations. A wave of star formation, propagating outward from the central portion of an active region, is found. The velocity and properties of this star formation front are examined. A two-phase model with time delays is also presented, which can be used for modeling sequential star formation. In this case, critical initial gas and star fractions are presented. Finally, a brief discussion is presented of the stochastic generalization of the one-zone model for a two-phase galaxy with and without infall. Publication: The Astrophysical Journal Pub Date: February 1983 DOI: 10.1086/160664 Bibcode: 1983ApJ...265..202S Keywords: Astronomical Models; Disk Galaxies; Galactic Evolution; Galactic Rotation; Star Distribution; Star Formation; Dwarf Galaxies; Dynamic Models; Galactic Structure; Spiral Galaxies; Stochastic Processes; Time Lag; Astrophysics full text sources ADS |

An 40Ar/ 39Ar age spectrum for a cordierite-bearing rock: Isolating the effects of excess radiogenic 40Ar

Cordierite-bearing rocks commonly contain excess radiogenic 40Ar and therefore yield anomalously old conventional K-Ar dates. Mechanical separation of cordierite cannot always be used to circumvent this problem. The 40Ar/ 39Ar incremental release technique was successfully used to isolate the effects of excess radiogenic 40Ar in a cordierite-bearing rock. An 40Ar/ 39Ar age spectrum was obtained for a cordierite-bearing rock whose true cooling age could be presumed by dating equivalent cordierite-free rocks. The initial gas fraction in the age spectrum exhibits an extremely high apparent age. Each successive step shows a decrease in apparent age. The apparent age of the last increment yielding a significant quantity of gas is in reasonable agreement with the presumed cooling age. The release pattern obtained suggests that radiogenic 40Ar associated with cordierite is released primarily at low temperatures. At higher temperatures the 40Ar released is primarily that derived from in-situ decay of 40K in the other minerals present. The 40Ar/ 39Ar incremental release technique may therefore be useful in isolating the effects of excess radiogenic 40Ar in cordierite-bearing rocks. This would enable the determination of true cooling ages for this rocks.