Maxime Makarov

Pulsed low-pressure wire discharge

A pulsed low-pressure wire discharge was studied experimentally. One can clearly distinguish at least three very different phases in the discharge development. During the breakdown lag the ionization takes place principally near the wire anode. The cathode secondary emission under ionic bombardment begins to play a (minor) role throughout the low-current non-steady-state phase since the cathode sheath is not yet formed. Once the sheaths are formed, the hollow-cathode discharge develops. The stability of a hollow-cathode discharge with an immersed small-size wire anode was analyzed. It is shown that the ratio of electrode surfaces Scathode∕Sanode necessary for uniform discharge formation depends on secondary emission yield, the nature of gas, and anode geometry. If the stability condition is violated, a double anode sheath appears and discharge becomes unstable.

Partial discharges monitoring in twisted pair fed with PWM inverter using non-intrusive sensors

This paper deals with partial discharge measurements in twisted pair fed by a PWM inverter. Measurements are carried out using antenna sensors. Both D-Dot sensor and self-made sensors are compared when it comes to detect partial discharge in a PWM environment. High-pass filter performance is tested as well with these sensors. Finally, a innovative noise suppression method is demonstrated using two identical antenna sensors. This method could be a useful and simple mean to improve signal to noise ratio before signal processing.

Plasma-assisted Diesel Oxidation Catalyst: Laboratory and bench scale investigations for CO and HC light-off temperature and nox remediation

Summary form only given. A key feature of Diesel Oxidation Catalyst (DOC) is its ability to efficiently oxidize CO and hydrocarbons (HCs) at the diesel exhaust temperature levels. While the DOC technology has progressed to the point where CO and HCs emissions can be drastically reduced, there remain issues of cost and low temperature activity i.e. cold start engine regime. Recent development researches try to adapt a cost effective integrated solution combining non-thermal plasma (NTP) and DOC technology for diesel applications.

Modelling of pulsed RF corona discharges in high-pressure air

An approach to description of pulsed RF corona discharges in high-pressure air is developed, based on the model of a filamentary discharge sustained by an electromagnetic wave guided along the plasma filament. Results of numerical simulation of spatial-temporal discharge dynamics at the quasi-stationary stage are obtained for various values of gas pressure and wave frequency. Experimental data on the discharge length versus the power absorbed by the discharge are presented. Their comparison with simulation results is given.

Using non-intrusive sensors to detect partial discharges in a PWM inverter environment: A twisted pair example

This paper deals with partial discharge measurements in twisted pair fed by a PWM inverter. Measurements are carried out using antenna sensors. Both D-Dot sensor and self-made sensors are compared when it comes to detect partial discharge in a PWM environment. High-pass filter performance is tested as well with these sensors. Finally, a blind source separation method is presented.

Plasma-to-flame transition at the AC driven filamentary discharge ignition

Non-equilibrium plasmas make a new effective way for plasma-assisted ignition. The mechanisms of transition toward a flame kernel are investigated for the case of ignition initiated by the ac-driven discharge thanks to fast optical techniques. The study is done under 1-10 bars pressure range for air-propane mixtures. At atmospheric pressure, filaments of the discharge present two regions with the hotter one near the electrode. Time-resolved imaging coupled with emission spectroscopy reveals that the inflammation takes place all along the hottest part of the filamentary structure. At higher pressure, the region of inflammation extends over the whole discharge because the more important heating of the gas inside. Thus, the plasma-to-flame transition indicates the energy and so the gas temperature distribution along the filaments. By scanning the spatial expansion of the kernel flame, it can be correlated with the chemical and thermal properties of the discharge. It results that thermal effect presents the governing mechanism of the ignition enhanced by the presences of reactive species created by the discharge. These species could play an important role during the spatial expansion of the kernel flame.

Electrostatic Instability of an AC-Driven Discharge in Dense Air

The results of fast imaging of a streamerlike discharge dynamics around a pin electrode under quasi-continuous ac excitation in air at 1-20 bar are presented. Under a relatively low pressure of 1-3 bar, the discharge filaments show a long smooth and well-branched pattern. As the pressure increases, they get smaller and become twisted. Based on the presented photographs, it was proposed that an electrostatic instability induces secondary radial filaments developing around primary channels, which change the initial straight shape of the discharge.