Ignition Voltage Research Articles

Development and Optimization of the Die-Sinking EDM-Technology for Machining the Nickel-based Alloy MAR-M247 for Turbine Components

In this paper, the results regarding the optimization of the die-sinking EDM-technology for the fabrication of turbine components are presented. The main objective of this work was the reduction of machining time while producing cavities with a depth of 11mm in the alloy MAR-M247, with respect to the requirements for surface roughness and sub-surface damage. The study was conducted using graphite electrodes of three different dimensions, totalizing 12 electrodes and a total electrode area of 89.50 mm2. The machine tool GENIUS 1000 THE CUBE was used in the experiments and IonoPlus IME-MH was used as dielectric fluid. The Design of Experiments Methods (DoE) were applied in the planning and execution of all experiments. Firstly, experiments were conducted to estimate the maximal discharge current that can be applied for fulfilling the quality criteria regarding both surface roughness and thickness of affected sub-surface, since discharge current is known as the main influencing process parameter affecting both factors. In the second stage, the process was optimized by varying following electrical parameters of the machine tool: discharge current (ie), discharge duration (ti), pause duration (t0), ignition voltage (V) and duty factor (τ). Finally, both process parameters as well as machine tool's control parameters were adjusted to achieve optimized results regarding the total machining time and electrode wear with respect to the surface requirements of produced parts. A total machining time reduction of more than 50% in comparison to the technology currently employed by the industry was achieved. Requirements on both arithmetical surface roughness as well as affected sub-surface thickness could be fulfilled. This robust technology was developed for producing the cavities in MAR-M247 and all applied methods, studied parameters as well as the results regarding machining time, electrode wear and the quality of the achieved work piece are presented.

A Novel Dual-Electrode Plug to Achieve Intensive Electric Field for High Performance Ignition

A thorough analysis of electric field is carried out so as to verify that a novel dual-electrode plug can build intensive electric field and can improve the main drawbacks of feeble electric field and low ignition efficiency of the traditional plug. With intensive electric field, the proposed novel plug can achieve high performance ignition, resulting in fuel saving and exhaust reduction. Gauss law is applied for electric field analysis to show that intensive electric field can be built by the novel plug. Then, according to Faraday law a lower-voltage ignition feature accomplished by the plug is discussed. Compared with traditional plug, the novel dual-electrode plug has the following advantages. (1) Much higher energy density is built between the plug electrodes, lowering ignition voltage requirement. (2) Electromagnetic interference (EMI) problem caused by high ignition voltage is readily resolved. (3) Ignition time delay can be improved. (4) The feature to save fuel consuming is achieved. (5) The exhaust of CO and HC is reduced significantly. Practical measurements are fulfilled to validate the electric field analysis and to demonstrate the features of the proposed dual-electrode plug.

Simulation of Gas Discharge in Tube and Paschen’s Law

According to the related theory about gas discharge, the numerical model of a gas discharge tube is established. With the help of particle simulation method, the curve of relationship between gas ignition voltage, gas pressure and electrode distance product is studied through computer simulation on physical process of producing plasma by DC neon discharge, and a complete consistence between the simulation result and the experimental curve is realized.

An investigation into the fabrication and combustion performance of porous silicon nanoenergetic array chips

An investigation into the ignitions and combustions of porous silicon (PS) nanoenergetic material array chips (nECs) at different ignition voltages was performed. The PS nECs were fabricated by integrating PS nanoenergetic material (nEMs) matrices and Cr-microbridges (microigniters) on the surface of silicon substrates. The combustion of PS nECs was in ambient air. Its ignition and combustion were investigated by a testing system and an optical high-speed camera. Experimental results revealed that the combustion delay time of PS nEMs increased from 8.0 × 10−5 s to 1.1 × 10−4 s with the decrement of ignition voltages from 140 to 80 V. The scope of ignition energy ranged from 0.153 to 0.287 mJ by calculations. The reaction type was deflagration, from the analysis of the high-speed video of PS nECs. The comprehensive experimental results indicated that the combustion of PS nECs was ignited by the synergic effect of the heat and the plasma. The ignition experiments suggested that Cr-microbridges were reliable igniters to trigger the self-sustained combustion of PS nECs. The strong plume of flame emitted from the surface of PS nECs indicated that the PS nECs may be applied as micro/nano igniter chips and microthruster chips.

E–H mode transition of a high-power inductively coupled plasma torch at atmospheric pressure with a metallic confinement tube

Inductively coupled plasma torches need high ignition voltages for the E–H mode transition and are therefore difficult to operate. In order to reduce the ignition voltage of an RF plasma torch with a metallic confinement tube the E–H mode transition was studied. A Tesla coil was used to create a spark discharge and the E–H mode transition of the plasma was then filmed using a high-speed camera. The electrical potential of the metallic confinement tube was measured using a high-voltage probe. It was found that an arc between the grounded injector and the metallic confinement tube is maintained by the electric field (E-mode). The transition to H-mode occurred at high magnetic fields when the arc formed a loop. The ignition voltage could be reduced by connecting the metallic confinement tube with a capacitor to the RF generator.

A New Approach to High-Power Pulsed Glow Plasma Generation: Shunting Glow Plasma

Shunting discharge plasmas are metal plasmas that can be generated around a conductive rod at a reduced pressure on the order of 0.1-100 Pa. Even at atmospheric pressure, a plasma can be generated because the rod is heated to emit metal vapor so as to generate gas breakdown around the rod. When the temporally increasing voltage across the rod matches the plasma ignition voltage, a shunting plasma is ignited. The plasma ignition is triggerless and, thus, does not require an external signal. There are two types of shunting plasmas: glow and arc discharges, with sustenance voltages of approximately 100 and 60 V, respectively. The plasma results in an arc discharge via a glow state. When a pulsed-power source with a controlled pulse duration is used to obtain a glow plasma only, a stable steady-state glow can be obtained under a suppressed current with a duration of over 10 s and a consumed power of several tens of kilowatts. A shunting glow plasma can be realized by controlling the pulse duration. In this paper, optical emission spectra from the shunting glow and shunting arc are observed. Singly charged carbon ions were found to be produced by the glow plasma. Carbon emission was significant in a nitrogen gas environment, as compared with an argon environment. In the case of a shunting arc, the optical emission is broad in wavelength, and doubly ionized carbon species also arise. A preliminary test of diamond-like carbon (DLC) film deposition was carried out, where the DLC was deposited on a substrate set near a plasma source. The DLC state was determined using Raman spectroscopy, and no macroparticles were found on the deposited film, which had a clean surface. The rod holder used as an electrode showed no damage. In contrast, in the case of a shunting arc, many macroparticles were found on the deposited films, and serious damage to the electrode also occurred.

Plasmas in saline solutions sustained using rectified ac voltages: polarity and frequency effects on the discharge behaviour

In this work, three major problems, namely severe electrode damage, poor plasma stability and excess power consumption, arising in ac-driven plasmas in saline solutions are solved using a rectified power source. Diagnostic studies on the effects of power source polarity and frequency on the plasma behaviour are performed. Examination of I–V characteristics and temporally resolved light emission shows that the polarity significantly influences the current amplitude when the plasma exists, while the frequency alters the bubble dynamics, which in turn affects the plasma ignition voltage. When the plasma is driven by a rectified ac power source, the electrode erosion is reduced substantially. With a low frequency, moderate applied voltage and positively rectified ac power source (e.g. 100 Hz and 350 V), a stable plasma is ignited in nearly every power cycle.

Microcavity array plasma system for remote chemical processing at atmospheric pressure

A microplasma system designed for chemical processing at atmospheric pressure is fabricated and characterized with flowing He/O2 gas mixtures. At the heart of this microcavity dielectric barrier discharge (MDBD) system are two arrays of half-ellipsoidal microcavities engraved by micropowder blasting into dielectric surfaces facing a flowing, low-temperature plasma. Experiments demonstrate that the ignition voltage is reduced, and the spatially averaged optical emission is doubled, for an MDBD flowing plasma array relative to an equivalent system having no microcavities. As an example of the potential of flowing atmospheric microplasma systems for chemical processing, the decomposition of methylene blue (as evidenced by decoloration at 650.2 nm) is shown to proceed at a rate as much as a factor of two greater than that for a non-microcavity equivalent.

An influence of the electrode emission properties and the gas temperature on the discharge ignition voltage in the mixture of argon with mercury vapor

Kinetics of electrons, ions and metastable excited atoms in the interelectrode gap of a low-current discharge in the argon-mercury mixture is simulated, and the discharge ignition voltage as a function of the temperature and the cathode ion-electron secondary emission rate is calculated. The mixture temperature dependence of the minimum value of the ion-electron secondary emission rate ensuring a given discharge ignition voltage is found.

Numerical simulation on a nanosecond-pulse surface dielectric barrier discharge actuator in near space

Lift-enhancement–drag-reduction technology is strongly required by near-space vehicles with low Reynolds number. It is known that a flow control method by a surface dielectric barrier discharge (SDBD) plasma can play an important role in this field. In order to obtain the discharge characteristics and evaluate the flow control effect of a SDBD actuator, the nanosecond-pulse discharge and induced flow field by the SDBD plasma are simulated at various altitudes using discharge-aerodynamics models. The results show that the ignition voltage decreases with altitude and it is very easy to discharge in near space. Compared with a SDBD at ground level, the plasma is produced on both sides of the exposed electrode and distributes more uniformly in near space. Although the body force generated by the SDBD actuator is less effective in inducing a jet with nanosecond-pulse excitation than that with alternating voltage excitation, the induced jet by body force is with longer extent, thicker profile and higher velocity in near space than at ground level. The plasma bulk heating should be taken into account for nanosecond-pulse excitation. The Joule heating of electrons is the main source of plasma bulk heating which acts as a micro-explosion and mainly induces pressure perturbation. The discharge at ground level is like a ‘point explosion’, but a ‘region explosion’ in near space, which indicates a diffuse distribution of energy, should be responsible for the fact that the effect of bulk heating is reduced in near space.

阴极氧化对逸出功的影响

To explore how the degree of cathode oxidation influences the ignites characteristics of ring He-Ne laser,photoelectric retarding potential method is used to investigate the variation of the work function with the cathode oxidation.As the cold cathode of discharge device,aluminum′s work function and the work function variation before and after oxidation are measured under the high vacuum conditions by Лукирский spherical photo electronic measure equipment and parallel electrodes optic-electronic discharge device.The experimental results show that work function of aluminum cathode in the natural oxidation is 2.60±0.2 eV.The mass percent of oxygen on aluminum cathode surface is 3.2%.At different times of oxidation process,the work function of aluminum cathode decreases with the growth of the oxidation time.The reasons that work function measurements of aluminum cathode may be in 2.5～4.3 eV are explained.The conclusion from the experimental results is the oxidation time is longer,the smaller the work function of the material,the more conducive to the ignition of the ring He-Ne laser within a certain range.Cathode oxidation also affect the ignition voltage and the cathode potential drop of gas discharge process.So the choice of the optimal oxidation time ought to consider these two factors.

Effect of Chemistry on the Performance of Calcium Disilicide Primers

ABSTRACTRotary atomization was used to synthesize spheres of CaSi2-based compositions in order to understand issues relative to primer performance for military applications. Elemental silicon and calcium were used to synthesize the line compound CaSi2or the eutectic composition between CaSi2and Si. Fe was added to form FeSi2as a secondary phase in selected compositions. Rietveld analysis showed that CaSi2polytypes in the synthesized materials consisted primarily of 6R, with less 3R and some hexagonal material. Synthesized materials had low surface areas (≈0.1 m2/g), but short milling times increased the surface area by an order of magnitude. Peak pressures, pressure rise time, and ignition voltage showed no significant differences between experimentally prepared samples and existing commercial samples. Stoichiometric CaSi2performed as well as CaSi2-Si or CaSi2-FeSi2-Si mixtures. The military specification for calcium disilicide should be changed to reflect the broad chemistry which can be used for primer performance.

The Effect of an Antenna on the Breakdown Process in an HID Lamp

Antenna structures are not often used as a way to influence the breakdown process in gases. However, they do show great potential for lowering the ignition voltage of high-intensity discharge (HID) lamps. We used HID lamp burners filled with pure argon to test the effects that a simple active antenna can have on the breakdown process. We show the photographs of the process and explain why it is different from the case without antenna structures.

Ignition and Warm-Up of High-Pressure Plasma Lamps

Investigation of the breakdown and early warm-up of high-intensity-discharge (HID) lamps demands appropriate imaging techniques due to short time scales of the ignition processes and initially poor optical conditions. High-speed cameras are able to access these phases and give additional information needed for theoretical modeling and HID design, which is focused on instant light and reduced ignition voltage. This work presents optical measurements on a 200-W HID mercury lamp ranging from ignition to steady-state operation, showing typical evolution stages of the warm-up process.

GALLIUM NITRIDE NANOWIRES ENHANCED HIGH-EFFICIENCY COLD CATHODE FLUORESCENT LAMP

We demonstrated a cold cathode fluorescent lamp that contains gallium nitride ( GaN ) nanowires at the electrode surfaces in a gas discharge light source to enhance the power efficiency of this luminance system. GaN in the nanowire structure has a high geometric aspect ratio, which makes it an ideal plasma ignition enhancer. The nanostructure enhancer not only improves a lower ignition voltage but also eliminates the use of mercury in the conventional cold cathode fluorescent lamp system. Due to high temperature of plasma, the GaN nanowires are partially dissociated to release the Ga ions into the lamp. Because the Ga ion has a large capture cross-section of electrons, it helps the lamp electrodes to maintain a high electric resistance. This could enhance the power efficiency and prevent the sputtering effect on the electrode to improve the lifetime of the lamp. This mercury-free approach also makes such cold cathode fluorescent lamp as an environment-friendly device.

Effect of a floating electrode on an atmospheric-pressure non-thermal arc discharge

Characteristics of the atmospheric non-thermal ac arc air plasmas produced by a plasma generator with a floating electrode are investigated. The measurements show that, with the help of the surface dielectric barrier discharges between the main electrodes and the floating electrode, the ignition voltage of the non-thermal arc discharges can be reduced significantly, and an arc discharge mode can be stabilized at high gas flow rates. The measured temperatures of the non-thermal arcs are at the level of 2000–3000 K under different operating conditions.

Medium Voltage Power Supply with Enhanced Ignition Characteristics for Plasma Torches

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torches. A series resonant half-bridge topology is presented as a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. A plasma torch rated at 3㎿, 2㎄ and having a physical size of 1m is selected to be the high enthalpy source for a waste disposal system. The steady-state and transient operations of a plasma torch are simulated. The parameters of a Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. The circuit simulation waveform shows that the ripple of the arc current can be maintained within ±10% of its rated value under the presence of a load disturbance. This power conversion configuration provides a high enough ignition voltage, around 5KA, during the ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.

Transition from dielectric barrier discharge to microhollow discharge in parallel-plate electrodes with intercavity microholes

Parallel-plate electrodes with microholes were used to study microhollow discharges (MHDs) triggered by dielectric barrier discharge (DBD) generated by applying a low-frequency high ac voltage under atmospheric conditions. The results obtained reveal that MHD is ignited simultaneously with spiky DBD signals generated by applying two cycles of time-truncated sinusoidal waves. The discharge ignition voltage of MHD was about 1 kV lower for electrodes with intercavity holes than for electrodes with conventional straight holes. This reduction is due to the triggering effect of self-generated DBD.

The effect of hydrogen iodide on the ignition of Hg-free metal–halide lamps

Trace amounts of moisture (e.g. adsorbed on metal–halide salt pellets during lamp fabrication) may react with the salts during initial lamp light-up to form volatile hydrogen iodide (HI). Hg-free lamps are particularly prone to HI formation since the elemental mercury is not included. The Hg-free lamps can develop high ignition voltages due to the HI, which adversely affects lamp operation especially ignition. This work discusses the thermochemistry and spectroscopic measurements which predict and demonstrate that HI is indeed formed in the reaction of salts and moisture. Experimental confirmation of increased breakdown voltage with increasing concentration of HI (at the ppm level) was obtained in discharge cell experiments. Computer simulations of xenon and HI gas mixtures show qualitative agreement with experiments.

Cold Plasma Jets Made of a Syringe Needle Covered With a Glass Tube

A syringe needle assembled with a glass tube has been used as a plasma jet device for biomedical applications. According to the various types of ground electrode installed at the glass tube, argon plasma from an atmospheric pressure discharge has been investigated with a dc-ac inverter of several tens of kilohertz. When the ground electrode is absent or floated, the length of the plasma jet is about 10 mm at an ignition voltage of about 3 kV, and it extends further to a few tens of millimeters as the voltage increases to 5 kV. If the ground electrode is inserted inside the end of the glass tube, all plasma current is sunk directly to the ground electrode so that the plasma plume cannot emit out of the glass tube. For the case of an external ground electrode which is similar to a dielectric barrier discharge, the ignition voltage is as low as 1 kV, and the plume length is easily adjustable to be 1-10 mm in the voltage range of 1-3 kV.