Tomoyuki Nakano

Central Research Institute of Electric Power Industry | CRIEPI

By using the conventional Shack-Hartmann sensors, it has been impossible to measure the two-dimensional electron density distributions over the SF6-gas-blast decaying arcs exposed to the strong turbulent flow with high spatial frequency variations in the gas density. In order to remove the high spatial frequency components, spatial filters were imp...

This paper focuses on a fundamental experimental approach to thermal arc re-ignition processes in a variety of gas flows in a nozzle. Using power semiconductor switches in the experimental system, the arc current and the voltage applied to the arc were controlled with precise timing. With this system, residual arcs were created in decaying phase un...

This paper presents the arc quenching abilities of various gases studied using a power semiconductor switching technique. The technique uses an insulated gate bi-polar transistor (IGBT) to inject current and apply voltage to the plasma arc. Using this technique, arcs in free recovery condition after a 50 A steady state condition were investigated i...

Shack-Hartmann type laser wavefront sensors were applied to gas-blasted arc discharges under current-zero phases, generated in a 50 mm-long interelectrode gap confined by a gas flow nozzle, in order to conduct a systematic comparison of electron density decaying processes for two kinds of arc-quenching gas media: air and CO2. The experimental resul...

The present paper describes numerical thermofluid simulation results of SF6, Ar, and Ar/SF6 arcs in a nozzle space at atmospheric pressure on the assumption of local thermodynamic equilibrium (LTE) condition. It is crucial to investigate fundamentals on arc extinction phenomena by numerical simulation approach as well as experimental approach. Two-...

This paper first describes the effect of water absorption in polyamide material irradiated by thermal plasmas on the occurrence of spallation phenomena. The interaction between polyamide materials and arc plasmas occurs particularly in the low voltage circuit breaker and aerospace fields. Spallation phenomena are those in which polymer particles ar...

Modeling of spallation polymer particles in polymer ablated arcs was conducted to numerically simulate its dynamics and thermal decomposition. We had found that spallation particles ejected from the polyamide materials contacting thermal plasmas experimentally. For the modeling of the particle dynamics, the temperature and gas flow fields in polyme...

This paper has proposed a new fundamental investigation technique on arc behaviors in decaying and re-ignition processes under gas flow condition. This technique utilizes power semiconductors like insulated-gate bipolar transistors (IGBTs) to control the arc current and voltage with a high accuracy in time domain. The free recovery condition was cr...

This paper reports a new simple test technique to evaluate current interruption ability of arc quenching gases. In the test, current and voltage applied to the arc was controlled using a insulated gate bipolar transistor (IGBT). Switching the IGBT enables us to produce free recovery conditions for a fundamental arc decay in nozzles. In addition to...

This paper describes the influence of initial conditions for spallation particles flying in polymer ablation arcs on dynamics and evaporation of the polymer spallation particles using the numerical model. Through our previous experiments, we had found micro-sized ‘spallation particles’ ejected from polyamide materials by thermal plasma contact. To...

Collective Thomson scattering has been applied to gas-blasted arcs confined by a nozzle to measure their decay processes with respect to electron density (n e). Pure SF6 gas, an Ar/SF6 gas mixture (SF6 was 20, 40, 60, and 80% of the mixture), and pure Ar gas were used as arc-quenching media at atmospheric pressure. Copper–tungsten (40% copper) elec...

This paper reports enhancement effect of N2/O2 gas addition in thermal plasma irradiation on the spallation phenomena from polyamide-66 (PA66) specimens with water absorption. The polyamide materials are widely used, for example, in low-voltage circuit breakers and arcing horns as ablation material. In such devices, the polymer is often contacted w...