Yoshiaki Aoki

Hydrogen Evolution by Plasma Electrolysis in Aqueous Solution

Hydrogen has recently attracted attention as a possible solution to environmental and energy problems. If hydrogen should be considered an energy storage medium rather than a natural resource. However, free hydrogen does not exist on earth. Many techniques for obtaining hydrogen have been proposed. It can be reformulated from conventional hydrocarbon fuels, or obtained directly from water by electrolysis or high-temperature pyrolysis with a heat source such as a nuclear reactor. However, the efficiencies of these methods are low. The direct heating of water to sufficiently high temperatures for sustaining pyrolysis is very difficult. Pyrolysis occurs when the temperature exceeds 4000°C. Thus plasma electrolysis may be a better alternative, it is not only easier to achieve than direct heating, but also appears to produce more hydrogen than ordinary electrolysis, as predicted by Faradays laws, which is indirect evidence that it produces very high temperatures. We also observed large amounts of free oxygen generated at the cathode, which is further evidence of direct decomposition, rather than electrolytic decomposition. To achieve the continuous generation of hydrogen with efficiencies exceeding Faraday efficiency, it is necessary to control the surface conditions of the electrode, plasma electrolysis temperature, current density and input voltage. The minimum input voltage required induce the plasma state depends on the density and temperature of the solution, it was estimated as 120 V in this study. The lowest electrolyte temperature at which plasma forms is ~75°C. We have observed as much as 80 times more hydrogen generated by plasma electrolysis than by conventional electrolysis at 300 V.

Maximum entropy spectral analysis of time-series data from combustion MHD plasma

The maximum entropy method (MEM) was applied to the time-series intensity data of the total light radiation from a combustion MHD plasma, and power spectral densities with many characteristic peaks were obtained in the range of a few kHz to ca. 30 kHz. Minimization of FPE, AIC, and CAT was employed to determine the optimum prediction-error filter order required for the MEM spectral analysis. Using the plasma flow velocity of 250 m/s obtained from cross-correlation function analysis, the frequency spectrum of the temperature was transformed to the wave-number-dependent power spectral density, in which a k-5/3-dependence was found in the k-range corresponding to the inertial subrange.

Application of light polarization technique to the generalized line‐reversal method for gaseous temperature measurements

The light polarization technique was applied to the generalized line‐reversal method in order to improve the inherently restricted resolution characteristics found in the conventional method using a chopper or a knife wedge, which discriminate the reference lamp light from the gaseous emission either temporally or spatially, respectively. In the proposed method, each of the lights was linearly and perpendicularly polarized and was detected through the same spatiotemporal optical path. The applicability of this method to measure the hot gaseous temperature was confirmed experimentally in a shock tube MHD power generation system.

ELEMENTAL ANALYSIS OF PALLADIUM ELECTRODES AFTER Pd/Pd LIGHT WATER CRITICAL ELECTROLYSIS

Elemental analyses of palladium electrodes were conducted after a new type of light water electrolysis was performed at optimum conditions in a system designed to induce a nuclear reaction. This process is referred to as Pd/Pd light water critical electrolysis . The conjecture that a nuclear transmutation process is occurring in this experiment is easier to test in this system, because it is easy to determine whether the elements detected on the cathode surface are impurities or transmutation products. We assume that the elements found only on the cathode surface, and nowhere else in the cell as contamination, namely iron, titanium, chromium and so on, must be transmutation products. Furthermore, countless Ohmori-type palladium craters were observed for the first time for this system, and these are evidence that nuclear reactions occurred at the electrode surface.

MHD/GAS TURBINE/STEAM TURBINE TRIPLE COMBINED CYCLE WITH THERMOCHEMICAL HEAT RECOVERY

An MHD/Gas/Steam combined cycle driven by coal gasified gas were studied where the gasification heat was supplied primarily from the MHD exhaust. As the most influential component, the synthetic gasoxygen fired MHD generator was investigated in detail. Without considering heat losses and electrical consumption, a 65 % plant thermal efficienciy was obtained with 25 % MHD enthalpy extraction and 45 % synthetic fuel partition to the MHD cycle. With inclusion of heat losses and power consumption, a 52.1 % efficiency was still demonstrated for a 1000 MWth scale MHD thermal input. The flow in the MHD channel was highly interactive with the magnetic field. The channel length and the volume required for given pressure drop were considerably reduced in comparison with those of the direct coal fired channel. More than 50 MWe/m3 power density could be attained under the wall stresses well below the critical values. We showed that the present cycle surpassed the direct coal fired MHD/ Steam conbination with respect to the efficiency and the C02 emission consuming the same amount of coal.

Maximum entropy spectral analysis of time-series data from combustion MHD plasma. II: The effect of an externally-applied magnetic field on the plasma turbulent flow

The Maximum Entropy Method (MEM), as a high-resolution estimator, was applied to analyse of time-series data from a combustion MHD plasma with an externally-applied magnetic field. Deviation of the k-dependent power spectral densities from Kolmogoroffs k-5/3 -law was found in the inertial subrange (k: wave number): a k-3 -dependent power spectral density due to the effect of the strong magnetic field on the plasma turbulent flow was observed in the higher part of the range.

Measurement of the Time-Dependent Temperature Variation of Combustion MHD Plasma

Using a light-polarization line-reversal method, the temporal temperature fluctuation in a combustion MHD generator accompanied by a transient increase in the Joule heating was clearly observed as a time series over a long period of time of 2~2000 µs. The response time of the method was found to be a few µs, and the method has proved to be an excellent time-resolved method for the direct measurement of time-dependent temperature fluctuations.

Enrichment of 41K isotope in potassium formed on and in a rhenium electrode during plasma electrolysis in K2CO3/H2O and K2CO3/D2O solutions

It was found that potassium forms on rhenium electrodes during plasma electrolysis in K2CO3/H2O and K2CO3/D2O solutions, and the new potassium has unnatural isotopic ratios. The isotope 41K increases from the natural abundance, 6.7%, to as much as 32–37%. The percentage of 41K in the potassium contamination in a rhenium electrode before electrolysis was close to the natural isotopic abundance (6.7%). This result suggests that the 41K was enriched by some unknown process connected with a vigorous discharge of plasma electrolysis.

Consideration of Optimal Magnet Coil Design for 1300 MWth Coal Combustion Magnetohydrodynamic Generator

EVWUDFW The electrical conductivity, Seebeck coefficient, and the thermal conductivity of Fe -doped B4C ceramics with several Fe compositions were investigated experimentally. The ceramics specimens were made by SPS apparatus. The figure of merit for the each specimen were calculated using the above experimental results It was found that the values of the dimensionless figure of merit for the specimens with low concentrations of Fe (less than 15wt%) is much larger compared with one of pure B4C . It was not succeeded to obtain the B4C with higher Fe density(more than 15wt%),by SPS method, because the large part of Fe was precipitated as metal Fe during the sintering process.