Volume Ignition Research Articles

Volume ignition of laser driven fusion pellets and double layer effects

The realization of an ideal volume compression of laser-irradiated fusion pellets (by C. Yamanaka) opens the possibility for an alternative to spark ignition proposed for many years for inertial confinement fusion. A re-evaluation of the difficulties of the central spark ignition of laser driven pellets is given. The alternative volume compression theory, together with volume burn and volume ignition (discovered in 1977), have received less attention and are re-evaluated in view of the experimental verification by Yamanaka, generalized fusion gain formulas, and the variation of optimum temperatures derived at self-ignition. Reactor-level DT fusion with MJ-laser pulses and volume compression to 50 times the solid-state density are estimated. Dynamic electric fields and double layers at the surface and in the interior of plasmas result in new phenomena for the acceleration of thermal electrons to suprathermal electrons. Double layers also cause a surface tension which stabilizes against surface wave effects and Rayleigh–Taylor instabilities.

Volume Ignition in Pellet Fusion to Overcome the Difficulties of Central Ignition

Since C. Yamanaka et al. demonstrated that the best fusion gains from laser irradiated pellets result only when central shocks are avoided and an ideal volume compression is achieved, the problems o f the central (spark) ignition with necessary densities of 1000 times the solid state may be overcome. Based on an analytical formula of volume ignition, the new conditions should provide reactor adequate laser fusion with compression to 50 to 100 times solid state.

Origins of Hydrocarbon Emissions from a Multi-Fuel, Torch Ignition Assisted Direct Injection Engine

Unthrottled, direct injection ignition assisted (DI–IA) engines have demonstrated DI diesel efficiencies and multi-fuel capabilities. However, high hydrocarbon (HC) emissions have been a problem with this concept. Torch ignition, provided by a separately fuelled small volume prechamber with spark ignition, was applied as a research tool to define the benefits of large volume ignition for controlling HC emissions. Torch ignition was found to be beneficial for HC control relative to the use of single point spark ignition; however, HC levels were higher than those observed from a DI diesel using low emissions technology. To assist in investigating the cause of the higher HC emissions, tracer experiments were conducted to verify that prechamber combustion characteristics did not contribute significantly to the total exhaust HC emissions. Separate, but similar, fuels were used for the main chamber and prechamber. Through gas chromatographic analysis of the major exhaust HC species, prechamber combustion was found to contribute substantially less than 20 per cent to the overall HC emissions for the engine conditions studied.

Pellet fusion gain calculations modified by electric double layers and by spin polarized nuclei

All preceding hydrodynamic computations of plasmas need correction if the thermal conductivity is used because electronic thermal conductivity is decreased on plasma inhomogeneities due to electrostatic double layers. In the worst case, ionic conductivity remains. We compare this with a possible electronic conductivity by the fast tail of the energy distribution. Using the volume ignition for fusion gain computations, we study the increase of gain by spin-polarization of nuclei for theDTreaction especially in nonlinear ranges. Gain can increase by a factor of 3·1.

Interactions of oxygen with surfaces of cadmium sulfide single crystals

Kerosene combustion in diesel engines is getting more prevalent due to the push for kerosene use in diesel engines by the North Atlantic Treaty Organization military. The study of kerosene combustion in diesel engines has primarily been carried out through engine experiments. Negligible study has been carried out through engine simulations possibly due to the lack of a compact and reliable kerosene reaction mechanism. A compact and well validated kerosene reaction mechanism with embedded soot chemistry for diesel engine simulations is still lacking. In this work, a kerosene–diesel reaction mechanism, containing only 123 species and 586 reactions, is developed. Diesel is represented by C14H28 while kerosene is represented by C12H24. Both C14H28 and C12H24 are assumed to be oxidized via global reaction steps. The kerosene sub-mechanism is well validated for its ignition delay times under different initial shock tube conditions of 20 atm at equivalence ratios of 0.25, 0.5, 1.0, 1.5 and 2.0 for temperatures between 700 and 1400 K. Moreover, constant volume combustion validations were carried out under ambient conditions of 900 K/6.0 MPa and 1000 K/6.7 MPa. It is seen that the newly developed mechanism is able to closely replicate the heat-release rates and flame lift-off lengths under these ambient conditions. In addition, constant volume ignition delay validations were done under ambient densities of 14.8 kg/m3 and 30.0 kg/m3 for temperatures between 800 and 1250 K. The simulated and experimental constant volume ignition delays are very similar. Furthermore, the reaction mechanism is able to predict the combustion characteristics and soot trends of kerosene and diesel well under real engine conditions. In all, this newly developed kerosene–diesel reaction mechanism is suitable to be used for diesel engine simulations.

Stage-wise addition of bromine to propylene at low reaction temperatures

It is generally accepted that knock in a spark-ignition engine is caused by end-gas autoignition. Hu and Keck have recently developed a reduced kinetic model which simulates the kinetic processes involved in autoignition of hydrocarbon-air mixtures. The model was used successfully to correlate measurements of explosion limits in a constant volume bomb and ignition delay times in rapid compression machines. In this paper, the ability of Hu and Keck's model to predict the onset of knock in a spark-ignition engine is evaluatedExperimental data from a large number of individual cycles were generated from a single-cylinder engine over a range of operating conditions where knock occurred. The unburned gas temperature used in the kinetic model was calculated from the measured cylinder pressure data assuming that knock originates in that part of the end-gas region which is compressed adiabatically.The model indicates that autoignition under knocking conditions is a two stage process. The model predictions of when knock occurs generally match well with measured knock angle on a cycle-by-cycle basis for a range of fuel (isooctane, primary reference, and indolene) and engine operating conditions. Agreement is least satisfactory when knock occurs close to the end of the burning process when the end-gas mass fraction is small and its temperature is not known precisely.