The characteristics of volume ozonizer based on the streamer corona discharge have been examined experimentally in model air (N₂ 79%+O₂ 21%) at atomospheric pressure. The streamer corona has a repetitive frequency process (generation, extension, and extinguishment) of fine filamentary discharge across the gap.
The volume ozonizer is composed of coaxial cylindrical electrodes, inner electrode is set with some gear-like electrodes, the outer electrode is stainless steel pipe. The positive DC voltage is impressed to the inner electrode and the streamer corona discharge generate during the gap uniformly, stably and extensively without any dielectrics between the electrodes.
The results show that the ozone is generated through all the area during the discharge gap, and the ozone yield has been progress by increasing the number of gear-electrodes of the volume ozonizer. It is confirmed that the volume of excited nitrogen molecules due to the streamer corona discharge is important for the ozone production process.

View full abstract

The boundary element method (BEM) is useful for analysis of electro-magnetic fields.
In this paper, the BEM is utilized in alalyzing a model of the Fabry-Perot resonator (FPR), the size of which is several times the wavelength and which contains another medium.
We find that the spurious solutions superimpose onto the normal solution as with the usual method of analysis in multimedia problems. The spurious solution is an incomprehensible solution physically and must be separated out of the analysis.
In order to remove the spurious solutions, we propose a new method named the "virtual boundary dividing method". In this paper, we conclude that the cause of spurious solutions in the conventional region dividing method is singularities of the matrixes. These matrixes are made by the counter integrals that are with a parameter in the outer region on the interfece boundary. In order to avoid such integration paths, we divide the outer region into small sub regions by the virtual boundaries that satisfy the continuous conditions.
We can remove the spurious solutions by this method. Furthermore we show the reduction of CPU power cost by this method.

View full abstract

The force-free magnetic field equation ∇×B=αB has been solved analytically in a toroidal coordinates system for the axisymmetric torus which is antisymmetric with respect to equatorial plane without the approximation of large aspect ratios. A set of fundamental solutions are presented each of which asymptotically approaches that for the cylindrical configuration when the aspect ratio goes to infinity. With this set of fundamental solutions, the eigenvalues of the force-free magnetic field are calculated for tori of circular and elliptical cross-section. It has been shown that the antisymmetric eigenvalue increases with decreasing aspect ratio.

View full abstract

We have constructed a prototype of partial discharge (PD) pulse measurement and degradation diagnosis expert system (PDM/ES-I) using a personal computer for insulation degradation diagnosis of materials suffering from PDs. For 0.1 mm-thick low density polyethylene (LDPE) with CIGRE Method II electrode system, temporal change of phase-angle-resolved PD pulse occurrence distribution was measured with PDM/ES- I. We applied the so-called "pattern recognition" of the PD pulse distribution to diagnosis of insulation degradation and assessment of residual life. Experimental results revealed that in spite of large scattering of time to breakdown, i. e. life, from 5 to 43 hours, all the tested samples exhibited similar evolution of the profile of PD pulse occurrence distribution with increasing aging time. The PD pattern measured at a given aging time was compared with five standard normalized PD patterns which had been registered in advance as five representative degradation stages from initial degradation category to final one. The degradation stage determined by the pattern recognition (PR) method proved to vary from the initial degradation category to final one in a correct turn. Consequently, the PR method permitted an exact determination of the degree of degradation at a given aging time. In other words, the PR method was capable of predicting the residual life of LDPE with a CM-II electrode system.

View full abstract