The determination of the Partial Discharges Inception Voltage (PDIV) of the different configurations in electrical motors is essential to ensure the sizing and to choose the right electrical insulation system. For that, the standard IEEE 117-1974 suggests the using of the motorette. Measurements performed on this model show the good reproducibility of the results for non-impregnated and impregnated motorettes. The determinations of the PDIV have also been done using the Paschen's law modified by Dunbar. PDIV resulting from experimental measurements are in good accordance with those obtained by the modeling.

This paper deals with Partial Discharge (PD) detection in Pulse Width Modulation (PWM) inverter fed electric motors. The aim of this work is to detect PD activity in random wound motors, which is the main cause for premature breakdown of insulation system. Detection is performed thanks to a non-intrusive electromagnetic sensor. A high voltage power supply PWM has been built in order to test, offline, electric stators in conditions as close as possible to real electrical conditions. Then, on-line PD measurements have also been successfully carried out, in an engine test bench used to test and control electric vehicle (EV) powertrain.

This study is devoted to an operando study of Pt–Rh/Al2O3–BaO lean-NOx trap catalyst during the regeneration with H2/CO reaction mixture. Particular attention was paid to the influence of CO coexisting with H2 during the regeneration that can simulate the regeneration step by using reformate composed of CO and H2. In rich H2 mixture ammonia predominantly forms. As expected, strongly chemisorbed CO molecules over noble metals lower the efficiency of the trap at 150 °C. Successive hydrogenation of N atoms to ammonia predominates in our conditions. However, the comparison of the outlet gas composition with infrared spectral features also suggests a minor participation of isocyanate species (NCO) as possible intermediates in the production of ammonia especially for long regeneration duration in the absence of water. Interestingly, ammonia formation as reducing agent for the selective reduction of NO can stimulate practical applications for further coupling lean-NOx trap with SCR catalysts.

We present in this paper a MHD modelling of the gliding arc behaviour of a DC plasma torch operating with air under low current and high voltage conditions. The low current leads to instabilities and difficulties to simulate the process because the magnetic field is not sufficient to constrict the arc. The model is 3D, time-dependent and the MHD equations are solved in using CFD software Code_Saturne ® . Although the arc is definitively non-LTE, the LTE assumption is considered as a first approach. The injection of air is tangential. A hot gas channel reattachment model has been used to simulate the restriking process of the arc root. After the description of the model, the most appropriate electrical voltage breakdown parameter has been selected in comparing with experimental results. A typical operating point is then studied in details and shows the helical shape of the arc discharge in the nozzle. Finally, the mass flow rate and the current have been varied in the range 0.16 – 0.5 gs -1 and 100 – 300 mA, respectively, corresponding to typical glidarc operating points of our experimental plasma torch. The model shows good consistency with experimental data in terms of: global behaviour, arc length, mean voltage and glidarc frequency.

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.

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.

The regeneration of Lean NOx Trap catalyst (Pt–Rh/BaO–Al2O3) using H2+CO was followed with operando IR spectroscopy methodology. The role of H2 was investigated from 2 to 20vol.% H2. The increase of H2 partial pressure allowed a subsequent decrease of the regeneration duration. The quantity of NH3 formed during the regeneration was related to H2 quantity which suggests that NH3 formation is governed by the supply of H2. The reactivity of nitrate was found slower than that of nitrite species towards hydrogen at 250°C. CO addition strongly inhibited ammonia production at 150°C due to accumulation of carbonate species at the surface of the catalyst. Above 250°C, two processes coexisted for the reduction of NOx into ammonia in the presence of H2+CO mixture: the successive hydrogenation of N atoms from NO dissociation and the hydrolysis of isocyanate species evidenced by IR.

We present in this paper a magnetohydrodynamic (MHD) modelling of the gliding arc behaviour of a dc plasma torch operating with air under low current and high voltage conditions. The low current leads to instabilities and difficulties with simulating the process because the magnetic field is not sufficient to constrict the arc. The model is 3D, time dependent and the MHD equations are solved using CFD software Code_Saturne ®. Although the arc is definitively non-local thermodynamic equilibrium (LTE), the LTE assumption is considered as a first approach. The injection of air is tangential. A hot gas channel reattachment model has been used to simulate the restriking process of the arc root. After the description of the model, the most appropriate electrical voltage breakdown parameter has been selected in comparing with experimental results. A typical operating point is then studied in detail and shows the helical shape of the arc discharge in the nozzle. Finally, the mass flow rate and the current have been varied in the range 0.16–0.5 g s −1 and 100–300 mA, respectively, corresponding to typical glidarc operating points of our experimental plasma torch. The model shows good consistency with experimental data in terms of global behaviour, arc length, mean voltage and glidarc frequency.

An experimental set-up has been developed to study two typical operating points of Diesel powered vehicle, corresponding to high load and low load points. A sensibility study over O/C ratio, injected electric current and mass flow rate have been carried out. The plasma reformer performances have been evaluated in terms of energy efficiency and conversion rate. At low engine load, an energy efficiency of 40% and a conversion rate of 95% have been reached which correspond to a syngas dry molar fraction of 25%. For the most favorable case, only 12 s are needed to regenerate the NOx trap catalyst. The 1D multistage kinetic model developed has shown good trend correlation with experimental results. It has been demonstrated that the oxygen from CO2 and H2O almost does not intervene in the exhaust gas Diesel fuel reforming. At the contrary, CO2 and H2O decrease temperatures, the kinetic reaction speed and the energy efficiency compared to POx reaction. To higher the temperature, more oxygen is needed but local combustion can happen and promote H2O and CO2 production.

We present, in this paper, the MHD modeling of a dc plasma torch operating with air under very peculiar high-voltage low-current conditions. The model developed is 3-D, is time dependent, and assumes local thermodynamic equilibrium (LTE). The study has been carried out considering an axial injection of air with flow rates varying in the range of 0.16-0.5 g/s and currents varying in the range of 300-600 mA. The numerical modeling has been developed using Code_Saturne, a computational fluid dynamics software developed by EDF R&D which is based on colocated finite volume. After a detailed description of the model, the results are presented, analyzed, and discussed. The influence of current and that of air flow rate over the arc characteristics are studied in terms of temperature, velocity, electrical potential, Joule heating, and arc root motion. Regarding numerical issues, the MHD modeling of low-current high-voltage arc discharge is particularly tricky since, below 1 A, the self-induced magnetic field becomes negligible and the convection effects induce a highly irregular and unstable motion of the arc column. However, despite these difficulties, the numerical model has been successfully implemented. Numerical results have shown good correlation and good trends with experimental ones despite a discrepancy which is probably due to the LTE assumption. The model gave fruitful and significant information on parameters that could hardly be obtained experimentally. This preliminary work is likely to open the way toward a better understanding of low-current arc discharges, which technologies are currently encountering an important development in many application fields.

The present study is dedicated to the reforming of diesel fuel with diesel engine exhaust gas (i.e., air, CO2, and H2O mixture) using a nonthermal plasma torch for a NOx trap regeneration application. The plasma technology developed is based on a high voltage/low current nonthermal plasma torch. In the first part of the paper, experimental results on synthesis gas production from exhaust gas fuel reforming of diesel fuel are reported. In the second part of the paper, these experimental results are compared with a 1D multistage model using n-heptane as a surrogate molecule for diesel fuel. Two compositions of synthetic diesel engine exhaust gas, corresponding to high and low engine loads, have been studied. It has been demonstrated that the oxygen from CO2 and H2O hardly ever intervenes in the reforming reactions. In the most favorable condition corresponding to a higher O2 rate, a production of 7 × 10−3 mol·s−1 of syngas has been reached, corresponding to an energy efficiency and a conversion rate of 40% ...

The aim of this work was to study the formation of ammonia during the regeneration step of a commercial lean NO x Trap catalyst in real conditions. Experiments were carried out on an engine test bench equipped with 2.2 L common rail diesel engine. The after-treatment system was composed of a commercial NSR monolith catalyst with a volume of 2.2 L. This material was composed of platinum, palladium and rhodium, as active components, with barium oxide and alumina as storage component and support, respectively. Catalytic measurements were carried out at 280 °C. Particular attention has been paid to formation of ammonia during the purge using hydrogen and CO as reducing agents. The time dependency of the extent of ammonia formation and the influence of hydrogen concentration were carefully examined. It was observed that the temperature rose in the first step of the regeneration process, after the switch in rich conditions, due to the occurrence of exothermic oxidation (H2/O2, CO/O2) accompanied with the releasing of available vacant noble metal sites which may provide a route for H2 and NO dissociation and/or subsequent surface reactions leading to the ultimate formation of ammonia. It was found that ammonia formation strongly depends on the purge duration and on the concentration of the reducing agent available during the purge.

Kinetic mechanisms of NO removal are studied in N2/NO and N2/H2O/NO gas mixtures. A very short duration (60 ns) photo-triggered discharge is used to create a homogeneous plasma at a total pressure between 230 and 460 mbar. Measurements of the NO density are performed in the afterglow by time-resolved laser-induced fluorescence, for a time scale between 2 and 200 µs after the current pulse excitation. Plasma homogeneity allows effective comparison between experimental results and predictions of a fully self-consistent discharge and kinetic modelling. It is shown that the NO removal efficiency is mainly determined through loss mechanisms balance for nitrogen metastable singlet states. In the absence of H2O, NO is in great part dissociated owing to collisions with singlet states. When water vapour is added, these states are destroyed through collisions with H2O with a rate constant k = (3.0±1.5)×10-10 cm3 s-1, and it leads to the decrease of the NO removal efficiency. This reaction is invoked for the first time.

The breakdown delay time and temporal evolutions of the current and voltage for homogeneous photo-triggered discharges were studied in mixtures of neon with C2H4 or C3H6 at 1 bar total pressure. Experimental results were compared to predictions of a fully self-consistent modelling of C the discharge. Over the whole range of initial reduced electric fields (5 < EIN < 35 Td) and hydrocarbon concentrations (0.1-10%), a very good agreement was obtained between measurements and computation. This provides an overall validation of the data used in the model and particularly of the electron-molecule collision cross-sections for which a complete set is proposed for the first time in the case of propene. Moreover, a detailed analysis of the ionization processes is given, which provides insights into the dependence of the breakdown delay times with respect to the hydrocarbon concentration and the initial reduced electric field values.