Direct numerical simulation (DNS) is used to study chemically reacting, laminar vortex rings. A novel, all–Mach number algorithm developed by Doom, Hou, & Mahesh [1] is used. The chemical mechanism is a nine species, nineteen reaction mechanism for H2/air combustion proposed by Mueller et al. [2]. Diluted H2 at ambient temperature (300 K) is injected into hot air. The simulations study the effe...

Superbursts are very energetic Type I X-ray bursts discovered in recent years by long term monitoring of Xray bursters, believed to be due to unstable ignition of carbon in the deep ocean of the neutron star. A number of intermediate duration bursts have also been observed, probably associated with ignition of a thick helium layer. We investigate the sensitivity of these long X-ray bursts to th...

Experimental and numerical studies are conducted on the thermal, chemical and dilution effects of buffer gas composition on autoignition of dimethyl ether (DME). The buffer gases considered are nitrogen (N2), a mixture of N2 and argon (Ar) at a mole ratio of 50%/50% and a mixture of Ar and carbon dioxide (CO2) at a mole ratio of 61.2%/38.8%. Experiments are performed using a rapid compression m...

On the National Ignition Facility (NIF), hot electrons generated in laser heated Hohlraums are inferred from the >20 keV bremsstrahlung emission measured with the time integrated FFLEX broadband spectrometer. New high energy (>200 keV) time resolved channels were added to infer the generated >170 keV hot electrons that can cause ignition capsule preheat. First hot electron measurements in near ...

Ignition and flame stabilisation have been simulated in a turbulent, bluff body stabilised spray flame. A complete first order Conditional Moment Closure (CMC) model for spray combustion is presented, as well as CMC modelling for spark ignition. The new elements of the two phase model formalism and the spark ignition models are illustrated using a one dimensional spray ignition example. It is s...

The influence of a turbulent spectrum of the temperature field on compression ignition at constant volume under homogeneous charge compression ignition engine conditions is studied by direct numerical simulation with complex chemistry. In particular the dependence of overall ignition progress on initial mixture conditions and turbulence parameters is determined. The propagation speed of ignitio...

Title of Document: PROBING THE IGNITION MECHANISM OF ALUMINUM NANOTHERMITES Snehaunshu Chowdhury, Ph.D., 2012 Directed By: Professor Michael R. Zachariah, Department of Mechanical Engineering, Chemistry and Biochemistry Nanothermites are defined as intimate mixtures of metal and metal oxidizer particles usually below 100 nm in diameter. They belong to a class of energetic materials which have b...

homogeneous charge compression ignition (hcci) combustion is a pioneer method of combustion in which pre-mixed fuel and oxidizer (typically air) are compressed to the point of auto-ignition. hcci engines can operate with most alternative fuels, especially, dimethyl ether (dme) which has been tested as a possible diesel fuel due to its simultaneously low nox and pm emissions. in this paper a sin...

The effects of dimethyl ether (DME) addition on the high temperature ignition and burning properties of methane-air mixtures were studied experimentally and numerically. The results showed that for a homogeneous system, a small amount of DME addition to methane resulted in a significant reduction in the high temperature ignition delay. The ignition enhancement effect by DME addition was found t...