Device for simultaneously determining density, velocity, and temperature of streaming ga

Seaton, S. L.

English

NASA Technical Reports Server

REPLY TO 
ATTN OF: G P  
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
MEMORANDUM 
0: KSI/Scientific & Technical Information Division wc 
A t t n :  M i s s  Winnie M. Morgan 
FROM : GP/Office of A s s i s t a n t  General 
Counsel for  Patent Matters 
SUBJECT : Announcement of NASA-Owned 
U . S .  Patents  i n  STAR 
I n  accordance with t h e  procedures contained i n  t h e  Code GP 
t o  Code U S 1  memorandum on t h i s  sub jec t ,  dated June 8, 1970, 
t h e  at tached NASA-owned U . S .  pa ten t  is being forwarded for 
abstracting and announcement i n  NASA STAR. 
The following information is  provided: 
U , S .  Patent  NO. : 3,446,558 
Corporate Source 
Supplementary 
Corporate Source 
NASA Patent  C a s e  No.  : -03375 
Gayle Parker 
Enclosure : 
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May 27,1969 S. L. SEATON 
/ Filed Deo. 8, 1965 Sheet o 
METHOD FOR MEASURING THE CHARACTERISTICS OF A GAS 
FIG. 1 
BY 
' INVENTOR 
STUART L. SEAT 
May 27, 1969 S. L. SEATO 
METHOD FOR MEASURING THE CHARACTERISTICS OF A GAS 
Filed Dec. 8 ,  1965 Sheet o f  3 
FREQUENCY 
FIG. 
60 
STUART 
BY 
May 27, 1969 S. L. SEATON 3, 8 
sheet 3 or 3 
METIiOD FOR MEASURING THE CHARACTERISTICS OF A GAS 
.% 
Filed Dee. 8, 1965 
\\.~. 
\ 
FIG. 3 
BY 
\ 
1 
3,4 4 6,s 5 8 
ETHOD FOR MEASURING THE CHARACTER- 
ISTICS OF A GAS 
Stuart L, Seaton, Hampton, Va., assignor to the United 
States of America as represented by the Administrator 
of the NatZonal Aeronautics and Space Adminisba- 
tiQM -,- -
Filed Dec, 8, 1965, Ser. No. 512,562 
Int. C1. GOln 21 /26 
U.S. Cl. 356-104 1 Claim 
6 
10 
ABSTRACT OF THE DISCLOSURE 
described while referring to FIGS. 1 and 2, then the spe- 
cific embodiments of the invention shown in FIGS. 3, 4, 
and 5 will be described. 
If a narrow beam of light 11 from a light source 
in FIG. 1 is directed into a gas 13, it is well known that 
the light in beam 11 will be 
If a small area 14 of gas 13 
is viewed by a small angle receiv 
receive a beam of light 16 
by the gas particles in gas 13. The magnitude of the light 
in beam 16 received by receiver 15 is proportional to the 
A device to aid in simultaneously determining the den- determined by 
sity, velocity and temperature of a streaming gas. The 15 beam 11, the a 
beams of first and second lasers, having different fre- distance from 
quencies, are directed into a small region of the stream- of gas 13 and 
ing gas. A receiver is aimed at the small region of the 
gas for receiving the difference frequency scattered by frequency of the light in beam 16 is equal to the fre- 
the particles in the gas and producing an electrical signal 20 quency of the light in beam 11. However, if gas 13 has 
therefrom. Means are connected to the output of the re- a streaming velocity in the direction indicated by arrow 
ceiver for recording the magnitude, frequency and spec- 18, beam 16 will have a frequency different from the 
tral distribution of the electrical signal. From these re- frequency of beam 11 by an amount determined by the 
cordings, the recordings of the magnitudes of the beams direction and velocity of flow of the gas. This frequency 
of the first and second lasers, and the calibrations of the 25 difference is due to the Doppler effect and is proportional 
first and second lasers, the density, velocity and tempera- to the velocity Of the gas. 
ture of the streaming gas can be determined. In addition to the streaming velocity of gas 13, each 
particle in the gas will have randomly directed velocities 
caused by the temperature of the gas. As a result of ehe 
and used by or for the Government of the United States be a difference in spectral distribution between 
of America for governmental purposes without the pay- and beam 11. That is, the spectral distribution 
ment of any royalties thereon or therefor. 16 will be broader than the spectral distribution of beam 
The invention relates generally to a method of and 11. This spectral broadening, caused by the randomly d& 
apparatus for measuring the characteristics of a gas and 35 reCted velocities of the gas, is proportional to the absolute 
more specifically concerns a method of and apparatus temperature of the gas. 
for simultaneously measuring the density, velocity, and Tha relation of beam 6 in FIG. 1 to the density, ve- 
temperature of a streaming gas. locity and temperature o gas 13 can best be understood 
An object of the invention is to provide a method of by referring to the intensity versus frequency graph shown 
and apparatus for simultaneously measuring the density, 40 in FIG. 2. Curve 20 is the intensity versus frequency curve 
velocity and temperature of a streaming gas. for beam 11 and curve 21 is the intensity ver 
Another object of this invention is to provide an im- curve for beam 16. The amplitude of curve 
proved method of and apparatus for measuring the density tiOna1 to the density of gas 13. Obviously, the cons 
of a gas. proportionality includes the ampliade of curve 2 
A further object of this invention is to provide a meth- 45 frequency difference 22 between curves 20 and 21 
odL of and apparatus for measuring the-velocity of a Portional to the velocity Of; the gas. The width 23 Of curve 
streaming gas. 21 at its one-half power point or any other convenient 
Still another object of this invention is to provide a point above the frequency axis is proporti 
method of and apparatus for measuring the temperature perature Of the gas* Consequently* if light 
of a gas. duces an output in. accordance with curve 
Other objects and advantages of this invention will fur- l5 receives light in accordance 
ther become apparent hereinafter and in the drawings, and the output of receiver is recorded, the recording can 
in which: be analyzed to simultaneously determine the density, ve- 
FIG. 1 is a schematic diagram for the purpose of ex- 65 locity and temperature Of gas 13. 
plaining the operating principles of this invention; In FIG. 3 there is shown a preferred embodiment o 
FIG. 2 is 27. graph for the purpose of explaining the the invention that operates in accordance with the prin- 
operating principles of this invention; ciples discussed above. The light source consis@ of two 
FIG. 3 is a block diagram of a preferred embodiment ruby lasers, 30 and 31. Lasers 30 and 31 are the pulse 
of this invention; type and are operated in synchronism by means of a 
FIG. 4 is a schematic drawing of an element in an 6o control circuit 32. Control circuit 32 can be a p d s  
alternate embodiment of this invention; and source that applies pulses to lasers 30 and 31 at the same 
FIG. 5 is  a schematic drawing of an element in another times. A heater 33 is connected to laser 30 and a heater 
alternate embodiment of this invention, 34 is connected to laser 31 to apply different ambun@ 
In describing the preferred embodiments of the inven- 65 of heat to the two lasers. As is well known, the frequency 
tion illustrated in the drawings, specific terminology will of a ruby laser can be shifted over a narrow range by 
be resorted to for the sake of clarity. However, it is not adjusting the temperature of the ruby. Consequently, since 
intended to be limited to the specific terms so selected, lasers 30 and 31 are operating at different temperatures, 
and it is to be understood that each specific term includes there will be a small difference in their output frequencies. 
all technical equivalents which operate in a similar man- 70 The differences in the output frequencies of lasers 30 and 
ner to accomplish a similar purpose. 31 are determined in a laboratory *by well-known means 
The operating principles of this invention will first be for different amounts of heat applied to the two 
The invention described herein may be manufactured 30 randomly directed velocities of the gas particles t 
' 
I 
3,446,558 
The output beam 35 from 1 30 passes through a meas- 
uring device 36 and the output beam 37 from laser 31 
passes through a measuring device 38. Measuring devices 
36 and 38 can be any conventional type for measuring the 
magnitude of the power output of a laser and at the same 
time permitting most of the laser energy to pass through 
it. For example, each of the devices could consist of H 
Brewster angle window with means such as a photomdti- 
plier tube for measuring the deflected energy. The output 
from measuring devices 36 and 38 are recorded on re- 
corders 39 and 40, respectively, Laser beams 35 and 37 
are parallel and close to each other, and: are directed 
into a gas 41 whose density, velocity and temperature 
are to be measured. A small angle receiver 42 such as 3 
photomultiplier tube and conventional optics is directed 
into a small region 43 of gas 41 through which beams 35 
and 37 pass. Since the difference frequency between 
beams 35 and 37 is relatively small, it will be in the range 
of receiver 42 and will be seen by receiver 42. The am- 
plitude of the output of receiver 42 is recorded by a re- 
corder 44, The output of receiver 42 is also applied to 
an analyzer 45 which will produce a waveform having 
the frequency characteristics of the curve 21 in FIG. 2. 
alyzers which will perform the function of anal 
are commercially available. The output of analyze 
is applied to a recorder 46 where it is recorded. 
corders 39,4@, 44 and 46 can each be an oscilloscope with 
a Polaroid camera attachment. 
The operation of the preferred embodiment of the in- 
vention shown in FIG. 3 is performed as follows. The 
frequency output and spectral distributions of lasers 30 
and 31 are determined in a laboratory for different tem- 
peratures. Then selected temperatues are applied to lasers 
30 and 31 by heaters 33 and 34 such that the difference 
frequency between the two lasers will be a known value. 
The spectral distribution of this difference frequency is 
also determined. The magnitudes of the outputs of the 
two lasers is then determined from the recordings made 
by recorders 39 and 40. From the information obtained, 
a curve similar to curve 20 in FIG. 2 can be drawn. The 
sc ht in region 43 of gas 41 is then received by 
re and recorded on recorder 44. This will give 
th de of the curve 21 shown in PIG. 2. Conse 
quently, since the magnitudes of curves 20 and 21 are 
known, the density of gas 41 can be determined. The out- 
m receiver 42 which is applied through analyzer 
recorded on recorder 46 will supply the frequency 
ation for curve 21. Since the frequency of curve 
been determined in the laboratory and the f r e  
quency of curve 21 can be determined from the record- 
ing made by recorder 46, the difference between these 
two frequencies can be determined which will be propor- 
tional to the velocity of gas 41. Also since the dimen- 
sion 23 of CUNe 21 can be determined from the record- 
ing made by recorder 46 and a similar dimension is de- 
termined by the laboratory calibrations run on lasers 30 
the temperature of gas 41 can be determined. 
other embodiment of this invention the modified 
s laser shown in FIG. 4 is used in place of the lasers 
and 31 in FIG. 3, Otherwise, this embodiment of the 
ention is the same as the one shown in FIG. 3. The 
embodiment of the invention shown in FIG. 4 consists of 
an He-Ne or other type gas laser 50. An electromagnetic 
helix 51 is wrapped around laser 50 and connected across 
an adjustable regulated D.C. power supply 52. Helix 51 
develops a uniform longitudinal magnetic flux throughout 
the gas in laser 50 which causes Zeeman splitting of the 
output frequencies from laser 50. The resulting output 
frequencies 53 from laser 50 to take the place of the f r e  
ced by lasers 30 and 31 in FIG. 3. The 
produced by laser 50 can be varied by 
means of the adjustable power supply 52. 
n still another embodiment of this invention, the 
laser beam modulator shown in FIG. 5, is used in place of 
and 31 in FIG. 3. Otherwise, this embodiment 
6 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
00 
65 
70 
of crystal 57 is connected across the electrical axh of 
crystal 57. As is well known in the 
57 will oscillate at the frequency f,. 
in refraction of crystal 
fLrfc. The frequencies in eith 
can take the place of the frequ 
30 and 31 in FIG, 3. 
caused by its oscillations 
and due to the 
ferred embodiment. Various changes may be made in the 
shape, size and arrangement of parts. For example, equiv- 
alent elements may be substituted for those illustrated and 
described herein (neodymium doped glass lasers could ‘be 
used in place of ruby lasers 3 and 31); parts may be 
reversed; and certain features of the invention may 
utilized independently of the use of other features, 
without departing from the spirit or scope of the hven- 
tion. 
W a t  is claimed is: 
3. A device to aid in simultaneuasly dele 
density, velocity and temperature of la str 
comprising: 
first and second lasers, calibrated for frequency 
spectral distribation, with their energies directed 
the same small region of said streaming gas; 
means for adjusting the frequency of said first Bwr 
to a frequency fl; 
means for adjusting the frequency of said 
to a frequency fi different from fi; 
means for measuring and recording t&e  ma^^ 
the energy from said first and second lasem; 
receiving means, aimed at said small region of s 
gas, for receiving the fi-fa laser energy in said 8 
region scattered by the particIes in said 
verting the received scattered energy into a first el* 
trical signal; 
analyzer means connected to said receiving means for 
streaming gas can be determined from the calibra- 
tions of said lasers and said recordings. 
3,277,396 10/1966 Statz et al. ______I___ 
3,329,821 711967 Eesage ________..-___ 
3,339,073 8/1967 ------------ 
3,353,114 11/1967 ---..--”---- 
“Measurement of Free Air 
of a Laser Beam,” Nudell 4 al., IEEE Internat. 
Electronics Symp, Rec. 2-E-1 to 2-E-7 (1964). 
76 (Other references (P 
3,446,558 
“He-Ne Laser source for light scattering measure- 
ments,” D. H. Woodward, Appl. Opt., Vol. 2, NO 11, 
November 1963, pp. 1205-1207. 
RONALD L. WIBERT, Primary Examiner. 
5 
“A New Method for the Determination of Plasma 
Electron Temperature and Density from Thompson Scat- 
tering of an Optical Maser Beam,” T. P. Hughes, Nature, 
vol. 194, Apr. 21, 1962, pp. 268-269. 
“Localized Fluid Flow Measurements with an He-Ne 
Laser Spectrometer,” Yeh et al., Appl. Phys. Let’rs, vol. 
4, No. 10, May, 1964 p.p. 176-8. 
“Measurement of Localized Flow Velocities in Gases 
with a Laser Doppler Flowmeter,” Foreman et al., Appl. 
Phys. Letters, vol. 7, No, 4, August 15, 1965, pp. 77-78. 
J. 
U.S. C1. X.R. 
250-43.5,219; 331-94.5; 356-28 


Method for measuring the characteristics of a gas Patent

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