A nanosecond pulsed discharge circuit model for engine applications

Non-equilibrium plasma discharges in spark gaps have been an increasingly studied method for alleviating cycle to cycle variation in lean and dilute combustion environments. However, ignition models that account for streamer propagation, cathode fall, and transmission line amplification over nanosecond time scales have so far not been developed. The present study develops such a model, with emphasis on the energy delivered from circuit to cylinder. Key pieces of the relevant physics and chemistry are summarized, simplified, and systematically coupled to one another. The set of parameters is limited to a handful of key observables and modeled using Modelica. Results show non-trivial behavior in the energy delivery characteristics of such discharges with important implications for ignition.

A Novel Wastewater Treatment Method Using Electrical Pulsed Discharge Plasma over a Water Surface

Electrical pulsed discharge plasma produces various powerful oxidizing agents, such as hydroxyl radicals and ozone, which have high oxidation potential. These species play an important role in the decomposition of persistent organic compounds in wastewater. Because highly concentrated oxidants are directly produced inside the plasma, plasma realizes high-speed wastewater treatment without pretreatment of samples, such as pH adjustment. The pulsed discharge plasma generated over the water surface and inside bubbles is highlighted as a highly efficient method for plasma generation and radical supply into wastewater. In this paper, the physical and chemical properties of the discharge plasma generated over a water surface are described. The decomposition of persistent organic compounds dissolved in wastewater, such as 1,4-dioxane, formic acid, and dichloromethane, by plasma discharge is demonstrated, and their mechanisms are discussed. These persistent compounds, which have strong toxicity and stability, can be efficiently decomposed and removed quickly from solutions by plasma treatment. Furthermore, the treatment of nutrient solutions used in hydroponic systems for plant cultivation is also introduced as a novel application of plasma, and the effects of bacterial inactivation, decomposition of allelochemicals, and improvement in plant growth by plasma are demonstrated.

Controlling the breakdown delay time in pulsed gas discharge

In experiment and 2D3V PIC MCC simulations, the breakdown development in a pulsed discharge in helium is studied for U=3.2 kV and 10 kV and P=100 Torr. The breakdown process is found to have a stochastic nature, and the electron avalanche develops in different experimental and simulation runs with time delays ranging from 0.3 to 8 μs. Nevertheless our experiments demonstrate that the breakdown delay time distribution can be controlled with a change of the pulse discharge frequency. The simulation results show that the breakdown process can be distinguished in three stages with a) the ionization by seed electrons, b) the ions drift to the cathode and c) the enhanced ionization within the cathode sheath by the electrons emitted from the cathode. The effects of variation of seed electron concentrations, voltage rise times, voltage amplitudes and ion-electron emission coefficients on the breakdown development in the pulsed gas discharge are reported.

Eco-friendly sun lamp for railway facilities

The paper considers the possibility of using a pulsed discharge in cesium as an environmentally friendly high quality light source for lighting industrial premises of railway transport facilities. The use of cesium filling of standard sapphire burners of high-pressure sodium lamps and a pulsed mode of electric power supply of the discharge to create a light source has been substantiated. A mathematical model of a high-pressure pulsed discharge in cesium is formulated on the basis of the radiative gas dynamics equations. The discharge was simulated and it was shown that it is possible to create a plasma with a temperature 4000 -7000 K and a pressure of 0.5 - 1.5 at m with the power supplied to the discharge ∼ 100 W/cm in the steady-state combustion mode. The dependence of the discharge lighting characteristics on the amplitude of the current pulses and the amount of cesium in the gas discharge tube is analyzed. It is shown that in a wide range of currents and plasma densities, the color rendering index of the discharge radiation Ra> 95 with luminous efficacy ηV ∼ 70lm/W and more. The average luminous flux emitted per unit length of the discharge column is ∼ 104 lm/cm. The color temperature of the discharge radiation can vary over a wide range of values Tc∼ 3000÷4500 K. It is shown that the color coordinates Xc,Yc of discharge radiation are close to the values Xc,Yc of a blackbody. The use of such a source in conditions of a short daylight hours will make it possible to create practically solar illumination of large production areas.