Date of Award

Spring 1986

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

S. G. Cupschalk

Committee Member

G. M. Molen

Committee Member

S. N. Tiwari

Call Number for Print

Special Collections; LD4331.E56R42

Abstract

Erosion rates of yellow brass and type 304 stainless steel electrodes were studied in air under pulse discharge conditions at a voltage of 100 kV, a current of 20 kA, and pulse durations of 70 ns. Anodes and cathodes, configured vertically, were fitted with removable hemispherical tips having a diameter of 0.95 cm and a mass of 3 gm. Tests were conducted inside a low speed, high pressure wind tunnel at pressures of 30 and 50 psig and air velocities ranging from 0 to 36 nm/s.

Erosion was studied gravimetrically for several flow velocities. As many as 60,000 discharges were recorded at a given velocity for a set of tips. Surface topology was monitored using the scanning electron microscope (SEM). A rather surprising result was that increasing the velocity of the air flow consistently led to a decrease in the rate of erosion. It was also noted that increasing the pressure increased the erosion rate, and that brass and stainless steel electrodes eroded at approximately the sarne rate when tested under the same conditions. Results for brass indicate that for all conditions studied, at the relatively small charge transfers considered (approximately 3 mC per shot), the top electrode, which was initially the anode, eroded at about twice the rate of the bottom one. A method was developed for measuring the depth of cracks produced on electrode surfaces as the result of spark gap operation, and it was applied to the case of the stainless steel electrodes. In addition, the early stages of electrode deterioration were observed for brass using the SEM. These results were interpreted by a theory which explains the formation of surface boundaries which consist of craters and cracks on the eroded electrode tips.

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DOI

10.25777/1r1x-zw19

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