The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform

Zhengcai Fu - One of the best experts on this subject based on the ideXlab platform.

  • analysis and experimental investigation of direct lightning protection for floating roof oil tanks
    Electric Power Systems Research, 2013
    Co-Authors: Zhengcai Fu
    Abstract:

    Abstract To improve the lightning protection of large floating roof oil tanks, the process of floating roof tanks stroked by lightning is analyzed, and relevant tests have been developed according to standards. Test results indicate that the major role of conductive film is to release lightning current rapidly, but the presence of conductive films has counter-effects. As long as conductive film is present, it will generate Electric Sparks when the floating roof tanks stroked by lightning. This paper proposes to eliminate the conductive film on the second seal floating roof top edge and instead use a scalable grounding device (SGD) as the lightning protection measure. An empirical formula has been used to calculate the transient voltage drop when the 100,000 m 3 tank is stroked by lightning. The results show that the floating tank is safe when there are 20 SGDs uniformly connecting the floating roof and tank wall.

  • analysis and experimental investigation of direct lightning protection for floating roof oil tanks
    Asia-Pacific International Conference on Lightning, 2011
    Co-Authors: Zhengcai Fu
    Abstract:

    To improve the lightning protection of large floating roof oil tank, the process of floating roof tanks stroked by lightning is analyzed, and relevant tests have been developed according to the standards. Test results indicate that the major role of conductive film is to release lightning current rapidly, but the presence of conductive films has their counter-effect. As long as conductive film exists, it will generate Electric Sparks when the floating roof tanks stroked by lightning. So the paper was proposed to abolish the conductive film on the second seal floating roof top edge and adopt scalable grounding device(SGD) as lightning protection measures. Empirical formula has been used to calculate the transient voltage drop when the 100000 m3 tank was stroked by lightning. The results show that the floating tank is safe when there are 20 SGDs uniformly connected with floating roof and tank wall.

Wu Xiao-song - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Simulation for Shock to Detonation Transition of Pulse Detonation Engine with Different Sub-chamber
    Computer Simulation, 2009
    Co-Authors: Wu Xiao-song
    Abstract:

    The effective producing detonation is an essential technology of pulse detonation engine.The deflagration to detonation transition progress of pulse detonation engine was researched using two-dimensional numerical simulation aimed at detonation engine tube with three different sub-chamber structures.Studies indicate that:(1)the energy of Electric Sparks is too weak to directly trigger a detonation;the detonation is fully established through a series of interactions and impacts of reflected shock waves.(2)Because of different sub-chamber,the deflagration to detonation transition(DDT)is also different;the simulation results of three kinds of situations are contrasted,and the best sub-chamber design is obtained whose SDT time and length is the shortest.

Rolf K. Eckhoff - One of the best experts on this subject based on the ideXlab platform.

  • Ignition of Combustible Dust Clouds by Strong Capacitive Electric Sparks of Short Discharge Times
    Zeitschrift für Physikalische Chemie, 2017
    Co-Authors: Rolf K. Eckhoff
    Abstract:

    Abstract It has been known for more than half a century that the discharge times of capacitive Electric Sparks can influence the minimum ignition energies of dust clouds substantially. Experiments by various workers have shown that net Electric-spark energies for igniting explosive dust clouds in air were reduced by a factor of the order of 100 when spark discharge times were increased from a few μs to 0.1–1 ms. Experiments have also shown that the disturbance of the dust cloud by the shock/blast wave emitted by “short” spark discharges is a likely reason for this. The disturbance increases with increasing spark energy. In this paper a hitherto unpublished comprehensive study of this problem is presented. The work was performed about 50 years ago, using Sparks of comparatively high energies (strong Sparks). Lycopodium was used as test dust. The experiments were conducted in a brass vessel of 1 L volume. A transient dust cloud was generated in the vessel by a blast of compressed air. Synchronization of appearance of dust cloud and spark discharge was obtained by breaking the spark gap down by the dust cloud itself. This may in fact also be one possible synchronization mechanism in accidental industrial dust explosions initiated by electrostatic Sparks. The experimental results for various spark energies were expressed as the probability of ignition, based on 100 replicate experiments, as a function of the nominal dust concentration. All probabilities obtained were 0%<p<100%. A tentative mathematical model could be fitted to all the data, assuming that the life time of the spark channel as an effective ignition source increased with the spark energy, that the minimum time of contact between the spark and the dust cloud for ignition to occur was a function of spark energy and nominal dust concentration, and that the stochastic element was the statistical distribution of the time interval between spark appearance and re-establishment of contact between spark channel and dust cloud, following detachment of the dust cloud from the spark by the shock/blast wave emitted by the spark discharge.

  • Gas and Vapor Cloud Explosions
    Explosion Hazards in the Process Industries, 2016
    Co-Authors: Rolf K. Eckhoff
    Abstract:

    The chapter first discusses combustion of gases/vapors. The distinction between “diffusion” combustion and “premixed” combustion is made. The concepts of laminar burning in premixed combustion and flammable fuel concentration ranges are presented. Then the concept of maximum pressures in constant-volume adiabatic combustion of premixed gas/vapor and air is discussed and that of “expansion ratio” presented. Then, turbulent combustion and detonation are discussed, followed by ignition of premixed gas/vapor and air. The question “what is ignition?” is posed and the basic idea of “thermal runaway” is presented. Then a review of ignition by hot surfaces, Electric Sparks/electrostatic discharges, and some other sources follows. The subsequent section is a review of a number of case histories of accidental gas/vapor cloud explosions, from 200 years ago until recently. The final section is a discussion of various means of preventing and mitigating gas/vapor explosions in the process industries.

  • Chapter Seven – Dust Explosions
    Explosion Hazards in the Process Industries, 2016
    Co-Authors: Rolf K. Eckhoff
    Abstract:

    The chapter starts with the question: What is a dust explosion? Materials that can give dust explosions are then presented together with factors influencing the ignitability and explosibility of dust clouds. Flame propagation processes and explosive dust-concentration ranges of dust clouds in air are discussed. This includes close-to-laminar flame propagation and maximum pressure generated from constant-volume adiabatic combustion of dust clouds. Turbulent flame propagation and detonation in dust clouds are also discussed. The important distinction between primary and secondary dust explosions is made. The discussion of potential ignition sources includes open flames, hot surfaces, heat from mechanical impacts, Electric Sparks and arcs and electrostatic discharges, jets of hot combustion products, shock waves and light radiation. Then a discussion of case histories of dust explosions from before 1800 till recent years follows. Means of preventing and mitigating dust explosions in the process industries are discussed in the final part of the chapter.

S. K. Jha - One of the best experts on this subject based on the ideXlab platform.

  • Assessment of Surface Integrity in Diamond Grinding – Based Hybrid Machining of Tungsten Free Carbide based Hard Metal
    Journal of Physics: Conference Series, 2019
    Co-Authors: Jayant Kumar Jha, S. K. Jha
    Abstract:

    Hybrid machining process comprises of applying at least two process components all the while or successively in synergistic way to improve the machining performance. One such machining process is diamond grinding in presence of high frequency Electric Sparks. This process is all about making trade-off between surface finish and process efficiency. This paper attempts to model the surface roughness using artificial neural network with supervised learning in which back propagation algorithm is used for minimizing error and estimation of adaptive weights. Experimental data for machining of TN20 Russian grade cermet is used for development of neural network.

  • Assessment of Surface Integrity in Diamond Grinding - Based Hybrid Machining of Tungsten Free Carbide based Hard Metal
    Journal of Physics: Conference Series, 2019
    Co-Authors: Jayant Kumar Jha, S. K. Jha
    Abstract:

    Hybrid machining process comprises of applying at least two process components all the while or successively in synergistic way to improve the machining performance. One such machining process is diamond grinding in presence of high frequency Electric Sparks. This process is all about making trade-off between surface finish and process efficiency. This paper attempts to model the surface roughness using artificial neural network with supervised learning in which back propagation algorithm is used for minimizing error and estimation of adaptive weights. Experimental data for machining of TN20 Russian grade cermet is used for development of neural network.

T. Riedel - One of the best experts on this subject based on the ideXlab platform.

  • Sparking at cathode tools during electrochemical machining in flow-through cells
    Journal of Applied Electrochemistry, 1994
    Co-Authors: I. Roušar, T. Riedel
    Abstract:

    The current density used in electrochemical machining can be increased only up to a certain value, above which the formation of Electric Sparks on the cathode (tool) is observed, whereby the latter is damaged and the anode surface becomes rough. The present work is devoted to the measurement of this critical density for small metal cathodes placed on the wall of a flow-through channel for Reynolds numbers from 1265 up to 5902 and static pressures ranging from 0.1 up to 1.0 MPa. The results are correlated by criterion equations which gave values of critical (sparking) cathodic current density,j s, with an average error of 7.1 % for laminar flow and 4.1 % for turbulent flow. The equations can be used for the calculation of the sparking current density for industrial flow-through cells for electrochemical machining.