Daniel R. Cohn

Emissions reductions using hydrogen from plasmatron fuel converters

Abstract Improvements in internal combustion engine and aftertreatment technologies are needed to meet future environmental quality goals. Systems using recently developed compact plasmatron fuel converters in conjunction with state-of-the-art engines and aftertreatment catalysts could provide new opportunities for obtaining substantial emissions reductions. Plasmatron fuel converters provide a rapid response, compact means to transform a wide range of hydrocarbon fuels (including gasoline, natural gas and diesel fuel) into hydrogen-rich gas. Hydrogen-rich gas can be used as an additive to provide NOx reductions of more than 80% in spark ignition gasoline engine vehicles by enabling very lean operation or heavy exhaust engine recirculation. It may also be employed for cold start hydrocarbon reduction. If certain requirements are met, it may also be possible to achieve higher spark ignition engine efficiencies (e.g., up to 95% of those of diesel engines). These requirements include the attainment of ultra lean, high compression ratio, open throttle operation using only a modest amount of hydrogen addition. For diesel engines, use of compact plasmatron reformers to produce hydrogen-rich gas for the regeneration of NOx absorber/adsorbers and particulate traps for diesel engine exhaust aftertreatment could provide significant advantages. Recent tests of conversion of diesel fuel to hydrogen-rich gas using a low current plasmatron fuel converter with non-equilibrium plasma features are described.

Modulated submillimeter laser interferometer system for plasma density measurements

A high resolution submillimeter interferometer system for measurement of electron densities in the 10(14)-cm(-3) </= n(e) </= 2 x 10(15)-cm(-3) range has been developed for use in high density tokamaks. Phase modulation at ~1 MH(z) is accomplished by difference frequency mixing of two cavity tuned laser oscillators. The optically pumped CH(3)OH lasers, which operate on the 118.8-microtm line, feature a novel output coupling design that permits good mode quality and low beam divergence. The beat signals are detected using a newly developed Ge:Li photoconductor, and a direct measurement of the phase shift is obtained from the time lag between probe and reference signals. The sensitivity of the resulting phase measurement is independent of the instantaneous phase and unaffected by fluctuations in the amplitude or in the frequency of the modulation.

Compact plasmatron-boosted hydrogen generation technology for vehicular applications

Abstract Onboard hydrogen generation using compact plasmatron devices could provide important new possibilities for reducing pollution from motor vehicles, making use of alternative fuels, and increasing engine efficiency. These improvements would involve the use of the plasmatron as a very small, rugged, rapid response and highly flexible means of electrical heating of gases. Plasmatron heating could be used to facilitate conversion of a wide range of hydrocarbon fuels into hydrogen-rich gas onboard a vehicle. Use of combinations of fuels is possible through potential transformation of a variety of fuels into hydrogen-rich gas. Another advantage of use of onboard plasmatron generation of hydrogen is that it could be used only when required and could be readily turned on and off. Preliminary experimental studies of plasmatron conversion of difficult-to-use alternative fuels (biofuels), iso-octane (representative of gasoline), and diesel fuel are described. Concepts for application to trucks and other heavy duty vehicles, sport utility vehicles and automobiles are discussed.

The ARIES-I Tokamak Reactor Study †

The ARIES research program is a multi-institutional effort to develop several visions of tokamak reactors with enhanced economic, safety, and environmental features. Three ARIES visions are currently planned for the ARIES program. The ARIES-I design is a DT-burning reactor based on modest extrapolation from the present tokamak physics data base; ARIES-II is a DT-burning reactor which will employ potential advances in physics; and ARIES-III is a conceptual D-3He reactor. The first design to be completed is ARIES-I, a 1000 MWe power reactor. The key features of ARIES-I are: (1) a passively safe and low environmental impact design because of choice of low activation material throughout the fusion power core, (2) an acceptable cost of electricity, (3) a plasma with performance as close as possible to present-day experimental achievements, (4) a high performance, low activation, SiC composite blanket cooled by He, and (5) an advanced Rankine power cycle as planned for near term coal-fired plants. The ARIES-I research has also identified key physics and technology areas with the highest leverage for achieving attractive fusion power system.

System optimization and cost analysis of plasma catalytic reforming of natural gas

Abstract Plasma reforming could provide advantages in hydrocarbon reforming especially in small-to-medium-scale plants and in plants with fast transients. The combination of a thermal plasma reformer operating in partial oxidation mode with a catalyst bed will be described. Reduced concentrations of CO (1–3% vol) can be achieved, with high hydrogen yields and minimal plasmatron electrical power requirements. A model for the cost of hydrogen production from natural gas has been developed. The model includes hydrogen cleanup utilizing a conventional pressure swing adsorption unit. The model uses experimentally determined conversion yields and operational parameters. The conditions that result in system optimization and cost minimization have been determined.

High frequency gyrotrons and their application to tokamak plasma heating

Abstract High frequency (⩾ 200 GHz) gyrotrons are potentially useful for several important applications, including plasma heating and radar. For electron cyclotron resonance heating of a moderate-size, high power density tokamak power reactor to ignition temperatures, a gyrotron frequency around 200 GHz appears to be necessary. The design of high frequency gyrotrons is discussed. Analysis of overall gyrotron efficiency indicates that high efficiency may be obtained in fundamental electron cyclotron frequency (ω c ) emission at high frequencies. The linear theory of a gyrotron operating at the fundamental frequency is derived for the TE mpq modes of a right circular cylinder cavity. An analytic expression is given for the oscillator threshold or starting current versus magnetic field.

Plasma reformer-fuel cell system for decentralized power applications☆

A plasma-driven process is described for the reforming of hydrocarbon fuels into hydrogen-rich gases for use in fuel cells. High temperature non-catalytic reforming offers many advantages over thermal catalytic reforming. The high gas temperatures obtained via plasmas reduce the volume and weight of the reformer, due to the fast kinetic rates. In addition, it allows fast response to changing fuel requirements, a characteristic needed in mobile applications. A plasma reformer-fuel cell system could provide a means to increase fuel flexibility and cost reduction of systems for both stationary and mobile fuel cell systems, over a wide range of operating modes. In addition to steam reforming and partial oxidation, thermal decomposition could be used to provide hydrogen-rich gas with greatly reduced production of carbon dioxide. Plasma reformer-fuel cell systems could utilize a wide range of hydrocarbon fuels including diesel, gasoline, biomass, natural gas and alcohols.

Near-term possibilities for extremely low emission vehicles using onboard plasmatron generation of hydrogen

Abstract A concept has been developed for use of onboard plasmatron generation of hydrogen-rich gas to provide a major decrease in air pollution from internal combustion engine vehicles. Compact plasmatron devices would provide highly controllable electrical heating of ionized gasoline-air mixtures facilitating production of hydrogenrich gas by partial oxidation. Hydrogen-rich gas/gasoline mixtures would then be combusted in present spark ignition internal combustion engines operated with very lean amounts of fuel. The electricity required by the plasmatron would be produced by a generator driven by the engine. The increased engine efficiency provided by the use of the hydrogen-rich gas would compensate for the power loss resulting from the plasma-boosted partial oxidation process. In conjunction with improved three-way catalytic convertor operation, overall emissions levels could be extremely low relative to present vehicles with present three-way catalytic converters. NOx levels could be reduced by factors of more than 20. This type of gasoline-fueled extremely low emission vehicle could provide a near-term alternative to the battery-powered electric car. Onboard plasmatron generation of hydrogen-rich gas could also be used in natural gas-powered vehicles resulting in even lower overall pollutant emission levels. Key feasibility issues that must be investigated include plasmatron energy requirements, purity of plasmatron-generated hydrogen-rich gas, and the lifetime of plasmatron electrodes.

Electron beam atmospheric pressure cold plasma decomposition of carbon tetrachloride and trichloroethylene

The cold plasma decomposition of carbon tetrachloride (CCl 4 ) and trichloroethylene (C 2 HCl 3 ) at dilute concentrations in dry and wet air of atmospheric pressure was investigated. The cold plasma was generated in a tunable plasma reactor, where the electron concentration is controlled by an electron beam and the average electron energy is controlled by a superimposed sub-breakdown electric field. The energy expense for decomposition, i.e., the electron beam energy per molecule decomposed, as well as the intermediate and final decomposition products were determined. Moreover, likely reaction mechanisms for the decomposition of CCl 4 and C 2 HCl 3 are presented. These mechanisms are based on bimolecular dissociative electron attachment for both CCl 4 and C 2 -HCl 3 and additionally a chlorine chain reaction for C 2 HCl 3 . The present work provides a reference for the development of an advanced oxidation process on the basis of a tunable plasma reactor. Such a process would be especially suitable for the treatment of air contaminated with chemical compounds that dissociatively attach electrons.

Compact plasmatron-boosted hydrogen generation technology for vehicular applicationsfn2

Abstract Onboard hydrogen generation using compact plasmatron devices could provide important new possibilities for reducing pollution from motor vehicles, making use of alternative fuels, and increasing engine efficiency. These improvements would involve the use of the plasmatron as a very small, rugged, rapid response and highly flexible means of electrical heating of gases. Plasmatron heating could be used to facilitate conversion of a wide range of hydrocarbon fuels into hydrogen-rich gas onboard a vehicle. Use of combinations of fuels is possible through potential transformation of a variety of fuels into hydrogen-rich gas. Another advantage of use of onboard plasmatron generation of hydrogen is that it could be used only when required and could be readily turned on and off. Preliminary experimental studies of plasmatron conversion of difficult-to-use alternative fuels (biofuels), iso-octane (representative of gasoline), and diesel fuel are described. Concepts for application to trucks and other heavy duty vehicles, sport utility vehicles and automobiles are discussed.