Reducing the pressure in the vicinity of the arc attachment point by allowing the gas to flow through a supersonic nozzle minimizes local heating rates, prevents ablation, and increases the efficiency of coaxial gas-flow arcs

Lenn, P. D.

Richter, R.

English

NASA Technical Reports Server

August 1970	 Brief 70-10329 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U .S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Low Pressure Arc Electrode 
.
Low
- Pressure 
Arc
	
-	 Region 
High	 /_ 161 
Electrode Pressure	
( " ' 
­­­ 
:^ 
Region	 W7^1 Gas 
Flow 	 Bow Shock 
The problem: 
To minimize local heating rates, prevent ablation, 
and increase the efficiency of coaxial gas-flow arcs. 
The solution: 
Reduce the pressure in the vicinity of the arc 
attachment point by allowing the gas to flow through 
a supersonic nozzle. 
How it's done: 
The electrode is placed behind an electrically floating 
orifice which is shaped in the form of a supersonic 
nozzle. Gas from the high pressure region in which 
the main arc is operating flows through the nozzle 
into a low pressure region. The expanding gas flow 
creates a region of very low pressure; an electrode 
of blunt shape is positioned in the flow so that the 
bow shock produces a significant decrease in stag-
nation pressure at the arc attachment point. The re-
duction of pressure in the vicinity of the arc 
attachment point reduces local heating rates and ab-
lation; because lower power inputs are possible, the 
overall efficiency of the element as a radiation source 
is improved. Typical values for argon gas with such an 
element are arc operating pressure, 25 atm: static 
pressure in the low pressure region, 1.5 atm; ratio of 
area in the plane of the blunt electrode to the nozzle 
throat area, 2.14; Mach number, 2.5; and stagnation 
pressure at the blunt electrode, 14.4 atm. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B70-10329 
Patent status: 
No patent action is contemplated by NASA. 
Source: P.D. Lenn and R. Richter of 
Electro-Optical Systems, Inc. 
under contract to 
Ames Research Center 
(ARC-10012) 
Category 01 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned
- rights.
https://ntrs.nasa.gov/search.jsp?R=19700000317 2020-03-17T00:20:17+00:00Z


Low pressure arc electrode

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