Conditions of steady arc ignition in vacuum and hollow cathode operational life

2016 ◽  
Vol 79 (1) ◽  
pp. 24-30
Author(s):  
N.V. Ferdinandov ◽  
D.D. Gospodinov
Keyword(s):  
Hollow Cathode ◽  
Tantalum Foil ◽  
Hollow Cathodes ◽  
Operating Modes ◽  
Multi Stage ◽  
Operational Life ◽  
Cathode Arc ◽  
Working Parameters ◽  
Parameter Values ◽  
Main Operating

Purpose: The aim of this paper is to determine the conditions of steady arc ignition invacuum and the effect some of the main operating parameters have on the life of tantalumfoilhollow cathodes.Design/methodology/approach: The experiments presented in this paper have beencarried out with equipment for vacuum hollow cathode arc processing similar to whatis used in the industry. In order to find out if steady arc ignition is possible, a two-levelfactorial experiment has been conducted helping to establish the corresponding regressiondependency between the factors examined and the starting parameter values. The evaluationof hollow cathode operational life is based on three criteria: indirectly, considering their erosion[μ]; establishing possible damage on their surface which leads to plasma-forming gas leakageand makes the arc unsteady; taking into account the critical change in the cathode shape.Findings: It has been established that when a multi-stage arc torch is using the necessaryminimum amount of the plasma-forming gas for Ø 3.5-mm-diameter hollow cathodes isQAr=0/3 l/h, and, for Ø 6.0-mm-diameter hollow cathodes, it is QAr=2.4 l/h. It has beenestablished that the operational life of tantalum hollow cathodes can be and even exceed3 hours. Of all the parameters that have been studied, vacuum level has the most negativeeffect. It has been confirmed that tantalum-foil hollow cathodes are suitable mainly forcurrent intensity values of about 120 A.Practical implications: The results of the research allow: guaranteed hollow cathode arcignition regardless of its diameter at the working levels of plasma forming gas; the choiceof operating modes ensures the implementation of processes of varying lengths without theneed for premature replacement of the hollow cathode.Originality/value: This paper presents the results showing the conditions necessary forsteady arc ignition in vacuum with a hollow cathode of the following diameters: Ø 3.5 mmand Ø 6 mm. The effect of some of the main working parameters on the operational life ofhollow cathodes made of tantalum foil is also studied

scholarly journals УЛУЧШЕНИЕ ТОПЛИВНОЙ ЭФФЕКТИВНОСТИ ГАЗОТУРБИННОГО ДВИГАТЕЛЯ УСТАНОВКОЙ В КОМПРЕССОРЕ НАДРОТОРНОГО УСТРОЙСТВА

2018 ◽  
pp. 72-85
Author(s):  
И. И. Редин ◽  
М. А. Шевченко
Keyword(s):  
Fuel Efficiency ◽  
Axial Compressor ◽  
Turbine Engine ◽  
Casing Treatment ◽  
Gas Channel ◽  
Operating Modes ◽  
Compressor Rotor ◽  
Multi Stage ◽  
Hypothetical Mechanism ◽  
Main Operating

The analysis of the influence of annular grooves on the flow in the compressor rotor air gas channel and the axial compressor characteristics as well as on the fuel efficiency of the gas turbine engine is presented. The hypothetical mechanism of the flow effect in the cavity of the annular groove on the main flow in the tip end of the blade air-foil of the axial compressor stage is outlined. The effectiveness of the casing treatment in the form of single annular groove, width is 20% of the axial projection of the chord of the tip end section of the blade is shown experimentally in a single-stage and multi-stage axial compressor system. The increase of the compressor efficiency with ten single annular grooves installed above the leading edges of the blades of each stage, has reduced the specific fuel consumption of the serial GTE in its main operating modes.

Sampling Theory

2019 ◽  
Author(s):  
David Hankin ◽  
Michael S. Mohr ◽  
Kenneth B. Newman
Keyword(s):  
Natural Resource ◽  
Adaptive Sampling ◽  
Sampling Theory ◽  
Special Importance ◽  
Unequal Probability ◽  
Multi Stage ◽  
R Programming ◽  
Multi Phase ◽  
Systematic Cluster ◽  
Parameter Values

We present a rigorous but understandable introduction to the field of sampling theory for ecologists and natural resource scientists. Sampling theory concerns itself with development of procedures for random selection of a subset of units, a sample, from a larger finite population, and with how to best use sample data to make scientifically and statistically sound inferences about the population as a whole. The inferences fall into two broad categories: (a) estimation of simple descriptive population parameters, such as means, totals, or proportions, for variables of interest, and (b) estimation of uncertainty associated with estimated parameter values. Although the targets of estimation are few and simple, estimates of means, totals, or proportions see important and often controversial uses in management of natural resources and in fundamental ecological research, but few ecologists or natural resource scientists have formal training in sampling theory. We emphasize the classical design-based approach to sampling in which variable values associated with units are regarded as fixed and uncertainty of estimation arises via various randomization strategies that may be used to select samples. In addition to covering standard topics such as simple random, systematic, cluster, unequal probability (stressing the generality of Horvitz–Thompson estimation), multi-stage, and multi-phase sampling, we also consider adaptive sampling, spatially balanced sampling, and sampling through time, three areas of special importance for ecologists and natural resource scientists. The text is directed to undergraduate seniors, graduate students, and practicing professionals. Problems emphasize application of the theory and R programming in ecological and natural resource settings.

Diamond Growth by Dual Hollow Cathode Arc Chemical Vapor Deposition

1997 ◽  
Vol 36 (Part 2, No. 10B) ◽  
pp. L1406-L1409 ◽  
Author(s):  
Gou-Tsau Liang ◽  
Franklin Chau-Nan Hong
Keyword(s):  
Chemical Vapor Deposition ◽  
Hollow Cathode ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Diamond Growth ◽  
Cathode Arc

Flow Assurance and Thermodynamic Challenges of operating CO2 Pipelines for variations in terrains and environments

2021 ◽  
Author(s):  
Terence George Wood ◽  
Scott Campbell ◽  
Nathan Smith
Keyword(s):  
Process Equipment ◽  
Fluid Composition ◽  
Ambient Conditions ◽  
Operating Modes ◽  
Hydrocarbon Reservoir ◽  
Compositional Approach ◽  
Operational Life ◽  
Geographical Distances ◽  
Fluid Behaviour ◽  
The Impact

Abstract The requirement for capturing and storing Carbon Dioxide will continue to grow in the next decade and a fundamental part of this is being able to transport the fluid over large geographical distances in numerous terrains and environments. The evolving nature of the fluid supply and the storage characteristics ensure the operation of the pipeline remains a challenge throughout its operational life. This paper will examine the impact of changes in the fluid composition, storage locations, ambient conditions and the various operating modes the pipeline will see throughout the lifecycle, highlight the technical design and operational challenges and finally give guidance on future developments. The thermodynamic behaviour of CO2 with and without impurities will be demonstrated utilising the fluid characterisation software, MultiflashTM. The fluid behaviour and hydraulic performance will be calculated over the expected operational envelope of the pipeline throughout field life, highlighting the benefits and constraints of using the single component module in OLGATM whilst comparing against a compositional approach when dealing with impurities. The paper will demonstrate through two case studies of varying nature including geographical environment, storage location (aquifer vs. abandoned hydrocarbon reservoir) and ambient conditions, the following issues: The impact of the storage type on the pipeline operations and how this will evolve with time; The environmental conditions and the impact these have on selection of process equipment and operational procedures (i.e. shutdown); and The impact the CO2 composition has on the design of the CO2 pipeline, and The paper will conclude with a set of guidelines for undertaking design analysis of CO2 pipelines for variations in fluid composition, storage locations and ambient conditions as well as some key operational strategies. This paper utilises the current state of the art tools and how these evolving tools are making this technically challenging area more mainstream.

Resistive MHD modes in hollow cathodes external plasma

2021 ◽  
Author(s):  
Giulia Becatti ◽  
Francesco Burgalassi ◽  
Fabrizio Paganucci ◽  
Matteo Zuin ◽  
Dan M Goebel
Keyword(s):  
Magnetic Field ◽  
Hollow Cathode ◽  
Electric Propulsion ◽  
Axial Magnetic Field ◽  
Mhd Equations ◽  
Linear Perturbation ◽  
Plasma Parameters ◽  
Hollow Cathodes ◽  
Plume Region ◽  
Helical Mode

Abstract A significant number of plasma instabilities occur in the region just outside of hollow cathodes, depending on the injected gas flow, the current level and the application of an external magnetic field. In particular, the presence of an axial magnetic field induces a helical mode, affecting all the plasma parameters and the total current transported by the plasma. To explore the onset and behavior of this helical mode, the fluctuations in the plasma parameters in the current-carrying plume outside of a hollow cathode discharge have been investigated. The hollow cathode was operated at a current of 25 A, and at variable levels of propellant flow rate and applied magnetic fields. Electromagnetic probes were used to measure the electromagnetic fluctuations, and correlation analysis between each of the probe signals provided spatial-temporal characterization of the generated waves. Time-averaged plasma parameters, such as plasma potential and ion energy distribution function, were also collected in the near-cathode plume region by means of scanning emissive probe and retarding potential analyzer. The results show that the helical mode exists in the cathode plume at sufficiently high applied magnetic field, and is characterized by the presence of a finite electromagnetic component in the axial direction, detectable at discharge currents $\geq$ 25 A. A theoretical analysis of this mode reveals that one possible explanation is consistent with the hypotheses of resistive magnetohydrodynamics, which predicts the presence of helical modes in the forms of resistive kink. The analysis has been carried out by linear perturbation of the resistive MHD equations, from which it is possible to obtain the dispersion relation of the mode and find the $k-\omega$ unstable branch associated with the instability. These findings provided the basis for more detailed investigation of resistive MHD modes and their effect in the plume of hollow cathodes developed for electric propulsion application.

scholarly journals Optimal Power and Efficiency of Multi-Stage Endoreversible Quantum Carnot Heat Engine with Harmonic Oscillators at the Classical Limit

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 457 ◽  
Author(s):  
Zewei Meng ◽  
Lingen Chen ◽  
Feng Wu
Keyword(s):  
Classical Limit ◽  
Heat Engine ◽  
Combined Cycle ◽  
Harmonic Oscillators ◽  
Total Power ◽  
Cycle Period ◽  
Carnot Cycle ◽  
Heat Current ◽  
Operating Modes ◽  
Multi Stage

At the classical limit, a multi-stage, endoreversible Carnot cycle model of quantum heat engine (QHE) working with non-interacting harmonic oscillators systems is established in this paper. A simplified combined cycle, where all sub-cycles work at maximum power output (MPO), is analyzed under two types of combined form: constraint of cycle period or constraint of interstage heat current. The expressions of power and the corresponding efficiency under two types of combined constrains are derived. A general combined cycle, in which all sub-cycles run at arbitrary state, is further investigated under two types of combined constrains. By introducing the Lagrangian function, the MPO of two-stage combined QHE with different intermediate temperatures is obtained, utilizing numerical calculation. The results show that, for the simplified combined cycle, the total power decreases and heat exchange from hot reservoir increases under two types of constrains with the increasing number (N) of stages. The efficiency of the combined cycle decreases under the constraints of the cycle period, but keeps constant under the constraint of interstage heat current. For the general combined cycle, three operating modes, including single heat engine mode at low “temperature” (SM1), double heat engine mode (DM) and single heat engine mode at high “temperature” (SM2), appear as intermediate temperature varies. For the constraint of cycle period, the MPO is obtained at the junction of DM mode and SM2 mode. For the constraint of interstage heat current, the MPO keeps constant during DM mode, in which the two sub-cycles compensate each other.

Operating modes of a hydrogen ion source based on a hollow-cathode pulsed Penning discharge

2016 ◽  
Vol 87 (2) ◽  
pp. 02B703 ◽  
Author(s):  
E. M. Oks ◽  
M. V. Shandrikov ◽  
A. V. Vizir
Keyword(s):  
Hollow Cathode ◽  
Ion Source ◽  
Hydrogen Ion ◽  
Operating Modes
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