Effect of Anode Dielectric Coating on Hall Thruster Operation

An interesting phenomenon observed in the near-anode region of a Hall thruster is that the anode fall changes from positive to negative upon removal of the dielectric coating, which is produced on the anode surface during the normal course of Hall thruster operation. The anode fall might affect the thruster lifetime and acceleration efficiency. The effect of the anode coating on the anode fall is studied experimentally using both biased and emissive probes. Measurements of discharge current oscillations indicate that thruster operation is more stable with the coated anode

Optimization of Plasma Plume Characteristics Based on Multi-anode Coaxial Ablative Pulsed Plasma Thruster

A special surface discharge is proposed based on the multi-anode electrode geometry. Instead of the traditional surface flashover of creepage on the insulator surface between the electrodes, a surface discharge with one of the electrodes being placed far away from the insulator is achieved in this paper. The unique electric field distribution due to the multi-anode electrode geometry has a significant influence on the discharge process of the surface discharge. It changes the generation and propagation process of the plasma, forming a plasma plume contributes to the propulsion performance of the thruster. Through theoretical analysis of the obtained plume data, it is indicated that the ablative pulsed plasma thruster based on multi-anode electrode geometry (short for multi-anode APPT) promotes the internal pressure of the plasma jet during its propagation and significantly increases the density and energy of charged particles. The discharge phenomena manifest that the multi-anode APPT and the helix-coil multi-anode APPT effectively increase the intensity of the plasma plume. Through electron density spatial distribution measurement, it has been found that the helix-coil multi-anode APPT increases the density of plasma in the axial direction to more than 4 times of the conventional coaxial APPT and reduces the electron density in other directions. In the propulsion test, it has been demonstrated that the multi-anode APPT and the helix-coil multi-anode APPT have better performance in terms of the impulse bit and the thrust-to-power ratio. In addition, it is also identified that the pinch effect will be enhanced with the increase of discharge power and the propulsion performance is promoted more distinctly. The multi-anode APPT and the helixcoil multi-anode APPT have been proved to have potential application advantage in the field of micro-satellite propulsion.Comment: 12 pages, 12 figure

Anode power deposition in applied-field MPD thrusters

Anode power deposition is the principal performance limiter of magnetoplasmadynamic (MPD) thrusters. Current thrusters lose between 50 and 70 percent of the input power to the anode. In this work, anode power deposition was studied for three cylindrical applied magnetic field thrusters for a range of argon propellant flow rates, discharge currents, and applied-field strengths. Between 60 and 95 percent of the anode power depositions resulted from electron current conduction into the anode, with cathode radiation depositing between 5 and 35 percent of the anode power, and convective heat transfer from the hot plasma accounting for less than 5 percent. While the fractional anode power loss decreased with increasing applied-field strength and anode size, the magnitude of the anode power increased. The rise in anode power resulted from a linear rise in the anode fall voltage with applied-field strength and anode radius. The anode fall voltage also rose with decreasing propellant flow rate. The trends indicate that the anode fall region is magnetized, and suggest techniques for reducing the anode power loss in MPD thrusters

DEVELOPMENT OF TINB2O7 ANODE FOR LITHIUM ION BATTERY ANODES

I have received 1200 dollars research scholarship.With an increase in gasoline price and greenhouse gas emissions, hybrid electrical vehicles (HEV) and pure electric vehicles (EV) have been commercialized in auto market. Li-ion batteries have become the dominant power source for the EV applications because of many advantages such as high energy densities, less pollution, stable performance and long cycle life. However, the market for HEVs and EVs need to overcome many technical issues. For example, energy densities and cycle life of Li-ion batteries need to be improved at low temperature for electrical vehicle applications. TiNb2O7 (TNO) electrode-based battery can be a good choice in order to improve the energy densities and cycle life. The original anode-based batteries are Li4Ti5O12 (LTO) anode-based batteries. I have made a comparison between TNO anode and LTO anode for Li-ion batteries. The energy densities of TNO anode-based batteries are around 350Wh/L and the energy densities of LTO anode-based batteries are around 177Wh/L. It means that TNO anode-based batteries have a higher energy density than LTO anode-based batteries. In addition, TNO anode batteries have a longer cycle life and shorter charging time than LTO anode batteries. The purpose of this research is to identify whether the TNO anodes-based batteries have the advantage of high energy and power densities for Li-ion batteries application. First, I need to identify whether the TNO anode can be run in normal cycling battery by doing half-cell test. I have done the half-cell test which consist of TNO anode and metallic Li as a counter electrode. The voltage profile obtained from half-cell test fits well with TNO electrode. In addition, cycle life tendency corresponding to high-density TNO composite electrode which indicate the TNO electrode can be used in normal cycling battery. In the future research study, I will identify the important parameters that lead to poor performance in the low-temperature condition and demonstrate the performance of TiNb2O7 anodes-based batteries has been improved in the low temperature condition.College of Engineering Research OfficeNo embargoAcademic Major: Mechanical Engineerin

Numerical Study of Heterogeneous Reactions in an SOFC Anode with Oxygen Addition

Previous experimental studies have shown that addition of small amounts of oxygen to a hydrocarbon fuel stream can control coking in the anode, while relatively large amounts of oxygen are present in the fuel stream in single-chamber solid oxide fuel cells (SOFCs). In order to rationally design an anode for such use, it is important to understand the coupled catalytic oxidation/reforming chemistry and diffusion within the anode under SOFC operating conditions. In this study, the heterogeneous catalytic reactions in the anode of an anode-supported SOFC running on methane fuel with added oxygen are numerically investigated using a model that accounts for catalytic chemistry, porous media transport, and electrochemistry at the anode/electrolyte interface. Using an experimentally validated heterogeneous reaction mechanism for methane partial oxidation and reforming on nickel, we identify three distinct reaction zones at different depths within the anode: a thin outer layer in which oxygen is nearly fully consumed in oxidizing methane and hydrogen, followed by a reforming region, and then a water–gas shift region deep within the anode. Both single-chamber and dual-chamber SOFC anodes are explored

Nitrogen front evolution in purged polymer electrolyte membrane fuel cell with dead-ended anode

In this paper, we model and experimentally verify the evolution of liquid water and nitrogen fronts along the length of the anode channel in a proton exchange membrane fuel cell operating with a dead-ended anode that is fed by dry hydrogen. The accumulation of inert nitrogen and liquid water in the anode causes a voltage drop, which is recoverable by purging the anode. Experiments were designed to clarify the effect of N-2 blanketing, water plugging of the channels, and flooding of the gas diffusion layer. The observation of each phenomenon is facilitated by simultaneous gas chromatography measurements on samples extracted from the anode channel to measure the nitrogen content and neutron imaging to measure the liquid water distribution. A model of the accumulation is presented, which describes the dynamic evolution of a N-2 blanketing front in the anode channel leading to the development of a hydrogen starved region. The prediction of the voltage drop between purge cycles during nonwater plugging channel conditions is shown. The model is capable of describing both the two-sloped behavior of the voltage decay and the time at which the steeper slope begins by capturing the effect of H-2 concentration loss and the area of the H-2 starved region along the anode channel

Coaxial anode improves sensitivity of gas radiation counters

Anode wire itself is enclosed by three segments. Two on ends are rejector segments, and middle one is primary charge-detecting segment. Anode wire is made from tungsten and is surrounded by enamel insulation. Enamel is covered by segments of vapor-deposited gold. At one point in center segment, gold layer makes direct contact with anode wire

Investigation of low current gas tungsten arc welding using split anode calorimetry

Most previous split anode calorimetry research has applied high weld currents which exhibit pseudo Gaussian distributions of arc current and power density. In this paper we investigate low current arcs and show that both the current and power distributions have minima in the centre – varying significantly from the expected Gaussian profile. This was postulated due to the formation of the arc with the copper anode and the tungsten cathode. Furthermore, a number of parameters were varied including the step size between measurements, anode thickness and anode surface condition as well as cathode type and tip geometry. The step size between measurements significantly influenced the distribution profile and the anode thickness needed to be above 7 mm to obtain consistent results

Coaxial anode wire for gas radiation counters

The design and characteristics of a gas radiation counter are discussed. The coaxial anode consists of an elongated central wire covered with an electrically insulating sleeve. Several longitudinally discontinuous segments of an electrically conductive coating are disposed about the insulating sleeve in a coaxial pattern along the length of the central wire. The conductive coating segments form a veto or rejection anode at each end of the central wire and a main or primary charge detecting anode between the ends. The segments are coupled together so that the primary charge detecting anode is connected to detection circuitry in anti-coincidence with the veto anodes. Background radiation detected by either of the veto anodes and the primary charge detecting anode is rejected and the sensitivity of the radiation counter device is increased