Technology Survey Plasma Jet Technology

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Technology Survey Plasma Jet Technology

Transcript Of Technology Survey Plasma Jet Technology

NASA SP-5033
TECHNOLOGY SURVEY

Technology Utilization Division t. V

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PLASMA JET TECHNOLOGY

DISTRIBUTION STATEMENT A Approved for Public Release Distribution Unlimited
20020319 082
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

NASA SP-5033

TECHNOLOGY SURVEY

Technology Utilization
Division

PLASMA JET TECHNOLOGY

Compiled and Edited by:

P. R. DENNIS

D. W. GATES

C. R. SMITH

J. B. BOND

Clyde Williams and Company

Marshall Space Flight Center

Columbus, Ohio

Huntsville, Alabama

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

Washington, D.C.

October 1965

Foreword
The Administration of the National Aeronautics and Space Administration has established a technology utilization program for "the rapid dissemination of information ... on technological developments . . . which appear to be useful for general industrial application." From a variety of sources, including NASA Research Centers and NASA contractors, space-related technology is collected and screened; and that which has potential industrial use is made generally available. Information from the nation's space program is thus made available to American industry, including the latest developments in materials, processes, products, techniques, management systems, analytical, and design procedures.
This publication is part of a series intended to provide such technical information. It emphasizes the industrial potential of plasma generators in materials testing, coating, and spraying, chemical synthesis, and other industrial operations. It includes accounts of NASA contributions to such technology and the instrumentation involved, and lists NASA plasma-arc facilities.
Clyde Williams & Company compiled the information presented in this survey.
THE DIRECTOR, Technology Utilisation Division National Aeronautics and Space Administration

Acknowledgments
This survey of some of the present industrial applications of plasma-arc devices and NASA work in this field was undertaken to stimulate the interest and imagination of readers concerned with teclmological progress. NASA work with such devices has resulted largely from the need to simulate the environments into which space vehicles are sent and from efforts to develop propulsion units for satellite attitude and position control. Equipment manufacturers have been more concerned with welding, cutting, chemical synthesis, particle preparation, melting, and other sucli operations, and their views are presented to indicate ways in which NASA research and development may prove helpful here on earth as well as in space.
NASA work in the plasma-arc field is summarized briefly and a bibliography with selected abstracts is included for readers who wish further information.
Botli arc heater and propulsion work are noted because both are of industrial interest. Work done on small thruster units may prove valuable in cutting, welding, etc., and that done on larger units may be adaptable to chemical and other processes.
The material was collected with the help of the technology utilization officers at NASA centers and many others, some of whom contributed large sections as indicated in footnotes. M. R. Scheckner provided the illustrations and photographs.
IV

Contents

Page

FOREWORD

Mi

ACKNOWLEDGMENTS

iv

INTRODUCTION

1

CHAPTER 1. PLASMA GENERATORS

History

3

The Plasma State

4

Classifications of Plasma Generators

6

Electrode Materials

11

Electrode Configurations

13

Calibration and Operating Efficiency

15

CHAPTER 2. APPLICATIONS OF PLASMA-ARC TECHNOLOGY

Materials Testing

23

Furnaces

28

Radiation Sources

37

Coating and Spraying

41

Spheroidizing and Particle Preparation

64

Chemical Synthesis

74

Glass Industry

105

.Propulsion

. .'.''':

106

CHAPTFR 3. ECONOMICIMPACT OF PLASMA TECHNOLOGY

Research

113

Commercial Market Potential

114

CHAPTER 4. NASA AND PLASMA-ARC TECHNOLOGY

Plasma Jet—Why NASA Is Involved

117

NASA's Contributions

120

CHAPTER 5. NASA DEVELOPED INSTRUMENTATION FOR

MEASUREMENTS IN PARTLY IONIZED GASES

Introduction

137

Pressure Measurement Instrumentation

138

Calorimeters

140

Total Enthalpy—Mass Flow Probe

143

Thrust Measurement

143

Photography

143

V

vi

CONTENTS

CHAPTER 5—Continued

Page

Framing Cameras

'45

Instruments for Velocity Determination

146

Spectroscopy

'"

Schlieren and Interferometer Instruments

1 50

External Measurements

150

Microwaves

1 50

Langmuir Probes

'"

Magnetic Fields

'53

Conductivity Measurement

1 54

i, -

CHAPTER 6. NASA PLASMA-ARC FACILITIES

Ames Research Center

1 56

Langley Research Center

"160

Lewis Research Center

164

Manned Spacecraft Center

166

Army Missile Command

'"°

CHAPTER 7. piRi infiRAPHY OF NASA ARC JET TECHNOLOGY

Bibliography With Selected Abstracts

171

Contracts

190

Cross Index by Author

193

REFERENCES

195

Introduction1
Arcs and arc processes have been used since the turn of the century in a myriad of applications ranging from welding to chemical synthesis. However, no concerted research effort was carried out in this field until the 1950's when first the Department of the Navy and then the Army and Air Force saw fit to fund a number of research endeavors. More recently, NASA has entered the field both in its own laboratories and through contract research support, and the entire arc and plasma field has progressed remarkably since this support became available.
With the advent of the missile and space age, a need became apparent for a method of producing reentry conditions in the laboratory in order to investigate the many phenomena that missiles and spacecraft encounter as they travel back to earth. The effort to produce these conditions has led to the development of large arc heaters and plasma jets which can be controlled precisely to give the exact parameters desired. Small, compact and low power thrustors have also been developed, leading to small cutting and welding torches and high intensity light sources.
From the early beginnings of the plasma jet in Germany, through the work of Finklenburg, this area of physics has progressed to a point where it has become a separate field of investigation and has generated several new theories of arc propagation.
The application of the plasma arc to industrial processes has taken diversified paths. In the metal working industry, new and faster methods of welding and cutting have been developed using plasma jets and arcs. Cutting speeds up to five times that of the oxyacetylene torch have been realized. One of the most useful developments that has come from the more recent research is plasma spraycoating with high-temperature-resistant materials; this was hitherto impossible. Plasma jet devices have also found application as heat sources for high-temperature controlled-atmosphere furnaces.
Studies on the use of plasma devices as radiation sources have led to the vortex-stabilized radiation source where a brightness of 5,000
1 Prepared by Mr. Charles Stokes, Temple University.

INTRODUCTION
candles per sq. millimeter and a luminous efficiency of 60 lumens per watt may be achieved.
In chemical synthesis the impact of the plasma arc device is just beginning to be felt. Because of the high temperature within the plasma stream (10,000 to 30,000° F.), chemical elements and compounds are fragmented into radicals and atoms when introduced into it. These radicals and atoms, when cooled rapidly, can and do react to produce compounds other than those initially introduced. For example, methane yields acetylene when passed through a plasma arc of helium, argon or hydrogen. Acetylene is presently manufactured by an arc process, and the plasma jet has been employed in the preparation of many refractory-metal compounds.
Research in plasma technology and devices has tremendous potential for producing new and varied industrial processes which will add to our economic growth and development. Results of these efforts are already being felt in the national economy. It has been estimated that, in addition to die benefits in defense and space, approximately $100,000,000 has been added to the gross national product by a government expenditure of $30,000,000.
In the last ten years, plasma technology has made great strides due mainly to the support of the Army, Navy, Air Force, and National Aeronautics and Space Administration. But some of the greatest gains are yet to come through the use of plasma-arc devices. If the level of effort increases at the present rate, the next ten years will bring new theories, methods, equipment and processes which will revolutionize this field. Industrial application of many of these research developments will undoubtedly be feasible within a few years.

Plasma Generators

CHAPTER 1

HISTORY
The phenomenon of a heat source which comes into existence at the upper limit of chemical flames has intrigued research scientists since the turn of the century. Since the introduction of early arc devices, engineering researchers have continually sought better and more efficient ways of obtaining temperatures which would allow both the research scientist and industrial manager the greatest latitude in working with materials. Today several techniques are capable of producing temperatures beyond which metals and liquids as such cease to exist. Table 1-1 compares a number of these sources. On a comparative basis, the plasma jet is potentially a source of controllable intense heat and, as such, warrants consideration as a commercial device for industrial use.

TABLE 1-1.—High Temperature Heat Sources

Heat Source

Approximate Tempoeprature

Gas

Maximum

Velocity Gas Enthalpy

fps

Btu/lb.

Open flames, air and oxygen. Enclosed flames, air and oxygen Open arc, low intensity Open arc, high intensity Plasma jet, arc contained within
device.

3, 000-7, 500 . 3, 000-7, 500
6, 000-8, 500 .. 6, 000-10, 000
5, 000-30, 000

Plasma jet, arc transferred to object receiving heat.
Solar and arc image furnace

6, 000-60, 000 6,500

1-600 1-9, 000 1-30 1-100 1-30, 000
1-40, 000 0

4,700 02 1,300 Air 4,700 02 1,300 Air 25,000 N2 1,000 Air 30,000 N2 8,000 Air 130,000 H2 100,000 N2 33,000 Air
200,000 H2 30,000 N2

PLASHA JET TECHNOLOGY
Historically, the illuminating arcs and electric furnace arcs were the forerunners of the plasma generators of interest in this work. In Norway, starting about 1910, nitrogen fixation was accomplished on a commercial scale (at 2 to 4 percent conversion efficiency) for a number of years using arc techniques. Yet, despite the vintage of very basic knowledge, practical industrial data are only now becoming available. For the most part, the modern aspects of plasma technology must be linked closely to two important factors: economics and equipment development. Despite obvious technological advantages, various designs of plasma generating devices have only recently made sufficent gains in these areas so that broad-scale application may be
realized.
THE PLASMA STATE
Because of the high quality and ready availability of information elsewhere on plasma physics, this work is concentrated on the technology and applications of the plasma jet.
There are a variety of techniques for producing plasma or nearplasma conditions. Some of these techniques do not really produce plasma in accordance with the accepted definitions, viz., that the gases generated be of an energy state which involves complete dissociation and ionization. A more accurate definition of "plasma" generators which may potentially benefit industry would include heat sources capable of producing temperatures in excess of 3,000° F. which are attained without exothermic reactions within the gas itself. Plasma generators can be operated at fairly low temperatures, 3,000 or 4,000° F. at a pressure of 1 atmosphere.
Actual ionization of part of the gas takes place within the heating region, i.e., where the arc strikes or where the high frequency field couples to the gas. From an applications standpoint, however, the principal interest lies in the average properties of the gas leaving the device. Considerable mixing of the products occurs after exit from the arc-heated region and average gas temperatures are well below the ionization level of the gas. In many cases, some residual ionization may remain in the plasma as it leaves the device, but again this is more related to relaxation phenomena than to equilibrium conditions.
Figures 1.1 through 1.6 show schematically the various methods of heating to "plasma" temperatures. Several of these designs have been developed to a greater state of commercialization than others, and in the following sections they are considered individually and then compared graphically with various devices.
Basically, the following sections describe plasma generators of two designs: in the first the plasma is generated by an arc between two
PlasmaArcFieldTemperaturesApplication