PatentAn electrogasdynamic spectral anemometer including
a particle injector and a particle collector that are inserted
into a turbulent fluid stream that is under investigation.
The injector includes a hollow cylinder into
which near saturated steam from an outside source is
introduced. The injector also includes a nozzle, a corona
needle and an attractor ring which are oppositely
charged and located within the nozzle. As the steam
passes through the nozzle it supersaturates and condenses
into droplets having a size that is primarily determined
by the condition of the incoming steam. The
droplets are then charged through the corona developed
between the corona needle and the attractor
ring. Then the charged droplets are ejected from the
nozzle and into the stream to be measured where they
follow its rapid fluctuations. These charged particles
move towards the collector which may be placed
downstream of the injector. When a charged particle
passes the collector it becomes neutralized and transmits
an electrical signal into collector circuitry where
it is analyzed to provide information about the intensity
of the turbulence at various frequencies. Different
droplet sizes are used for different turbulent frequencies
of interest depending on the maximum value of
the frequency present in the flow

Biblarz, Oscar

Calhoun, Institutional Archive of the Naval Postgraduate School

Calhoun: The NPS Institutional ArchiveFaculty and Researcher Publications Faculty and Researcher Publications1973-12-11Electrogasdynamic SpectralAnemometerBiblarz, OscarThe United States of America as represented by the Secretary of the Navy, Washington, DC (US)http://hdl.handle.net/10945/7206United States Patent [19] Biblarz [54] ELECTROGASDYNAMIC SPECTRAL ANEMOMETER [751 Inventor: Oscar Biblarz, Monterey, Calif. [73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, D.C. [221 Filed: Dec. 27, 1971 [21 J App1. No.: 212,243 [52J U.S. CI •............................................... 73/194 F [51] Int. CI •......................... GOlf 1/00, G IOn 27/62 [581 Field of Search ....................... 73/194 B, 194 F, 73/147,181; 324/33; 310/5, 6, 7 [56] References Cited 3,417,267 3,184,967 3,359,796 3,638,054 UNITED STA TES PATENTS 12/1968 Marks ..................................... 310/6 5/1965 Rogers ............................... 73/194 F 12/1967 Dimick .............................. 73/194 F 1/1972 Honigsbaum .................. 73/194 F X OTHER PUBLICATIONS Werner et al., "Investigation of a Corona Discharge for Measurements in Air Flow," 1952. Primary Examiner-Charles A. Ruehl Attorney-,-R. S. Sciascia et a1. STEAM (FOR \ AIR " 13 [11 ] 3,777,564 [45] Dec. 11, 1973 [571 ABSTRACT An electrogasdynamic spectral ane:mometer including a particle injector and a particle collector that are in-serted into a turbulent fluid stream that is under inves-tigation. The injector includes a hollow cylinder into which near saturated steam from an outside source is introduced. The injector also includes a nozzle, a co-rona needle and an attractor ring which are oppositely charged and located within the nozzle. As the steam passes through the nozzle it supersaturates and con-denses into droplets having a size that is primarily de-termined by the condition of the incoming steam. The droplets are then charged through the corona devel-oped between the corona needle and the attractor ring. Then the charged droplets are ejected from the nozzle and into the stream to be measured where they follow its rapid fluctuations. These charged particles move towards the collector which may be placed downstream of the injector. Whelli a charged particle passes the collector it becomes neutralized and trans-mits an electrical signal into collector circuitry where it is analyzed to provide information about the inten-sity of the turbulence at various frequencies. Different droplet sizes are used Jor different turbulent frequen-cies of interest depending on the maximum value of the frequency present in the flow. 8 Claims, 9 Drawing Figures ....--10 57 ~~~~+il-rl~~ __ ~] 17 I 63 I ) I I ~~~~~~~~7TTn77TT,~7T~~1 I I I I I I I I 59 I L _____ .J PATENT£OOEC 11 1913 -z o i= <t o ~ N <t Z W 0 ___ ~L--..:..,.' f- -en et: o IJ.. . . 3.777,564 SHEET 1 Df 3 r- --------1 I I , I , :g , ,"-I ' \11 I I ----_______ -.l C\J 10 et: <t -lL. PATENTED DEC 11 1913 3.777,564 SH[ET 2 OF 3 31 38 T 37 29 PATENTEOOEC 11 1913 w U) z o CL U) w a:: 39 >--U N z-W 10. => Q) o.s:. WI a:: ~ u-_ :E ::::> :E SHlET 3 OF 3 1010 _ -.9.91.bLSJQN ... J_R";Q\.LE_N.Qy' £Q~_ AIR MOLECULES ~ CL o 10-9 10-8 10-7 10-6 10-5 3.777,564 PARTICLE RADIUS (R - meters) WATER DROPLETS IN AIR AT STANDARD CONDITION 36 3,777,564 1 ELECTROGASDYNAMIC SPECTRAL ANEMOMETER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anemometer and more particularly to an electrogasdynamic spectral an-emometer for use in measuring the spectral character-istics of unsteady flow covering a frequency spectrum up to about 50,000 hertz. 2. Description of Prior Art 2 particle count over a predetermined sampling period at a selected frequency. It has been found that the choice of particle size is very critical and is dependent upon the desired fre-5 quency response of the device. That is, if the turbulent flow has a maximum frequency of about 20,000 hertz, then the particle size must be about 10-7 meters. How-ever, if the frequency is about 3,000 then the size of the particle can be about one micron. It has been found 10 that dielectric liquids and certain solids may be used in place of water droplets. STATEMENT OF THE OBJECTS OF THE INVENTION Many different devices have been used in the past in attempts to accurately measure the spectral character-istics of unsteady flow conditions. A device frequently used for this purpose is generally referred to as a "hot- 15 The primary object of the present invention is to pro-wire anemometer." This device consists of a very small vide an anemometer that is effective for measuring tur-temperature responsive wire that is inserted into an un- bulentflows. steady flow condition. Because of the unsteady flow Another object is to provide an anemometer that is condition the hot wire will convect heat at unsteady accurate, rugged and reliable. rate that corresponds to the unsteady flow. Unsteady 20 Other objects, .advantages, and novel features of the current is applied to the hot wire to maintain the hot present invention will become apparent from the fol-wire at a constant temperature. By measuring the un- lowing detailed description of the i1lJvention when con-steady current it is then possible to indirectly measure sidered in conjuction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS the unsteady flow condition. While this device is quite 25 useful, it has the disadvantage of being quite fragile and breakage is frequently encountered. Moreover, it has FIG. 1 is a schematic drawing of the electrogasdy-serious limitations when used for mesuring high fre- namic sp~ctral anemo~eter ~f the present inv~ntion; quency unsteady flow conditions. This is primarily be- F~G. 2 IS a schematIC drawing of an alter~atlve ~m~ cause, to be responsive to high frequency unsteady flow 30 bodlmen~ of the an~mometer ?f the present In~e?tlon, (for example in the 50 000 hertz range) it is necessary FIG. 31s an end VIew, partly III sectIOn, of the IllJector , , of FIG l' to make the wire exceedingly small and therefore very '!.. .. . . f '1 d d'ff! It t I'b t M 't" d' FIG. 4 IS a Side VIew, partly In sectIOn, of the Injector ragl e an 1 ICU 0 ca 1 ra e. oreover,1 IS an In t- f FIG l' rect measurement requiring calibration for each flow 0 FIG '5 .' t' I' f th I f th . . t d. . IS a sec tona vtew 0 e nozz e 0 e InJec or me tUm. . . . 35 of FIG. 1; The presen~ .mventton overcomes t?ese dtsadvan- FIG. 6 is a side view of the injector of FIG. 2; tages by provtdtng an electr~gasdynamtc anemometer FIG. 7 is an enlarged side view of the injector of that does not employ a hot WIre, but rather, empl9Ys a FIGS 2 and 6' charged particle injector and a charged particle collec- FIG. 8 is a side view of the needle collector of the an-tor to measure the passage of the very small charged 40 emometers of FIGS 1 and 2' and particles that are injected into the unsteady flow media. FIG. 9 is a graph iilustratin~ the optimum water parti-SUMMARY OF THE INVENTION cle size versus frequency response. Briefly, the electrogasdynaniic spectral anemometer DESCRIPTION OF THE PREFERRED EMBODIMENT of the present invention generally comprises an injector 45 and a collector that are inserted into the turbulent stream that is under investigation. In one embodiment the injector includes a hollow cylinder into which steam from an outside steam source is introduced and then ejected from a nozzle into the turbulent stream. The injector also includes a corona needle and an at-tractor ring which are positively charged and located within the nozzle. As the steam passes through the noz-zle it supersaturates and condenses into discrete parti-cles or droplets having varying size depending upon the 55 condition of the incoming steam. The particles are then charged through the corona developed between the co-rona needle and the attractor ring. Then the charged particles are ejected from the nozzle and into the turbu- 60 lent stream where they follow its rapid fluctuations. These charged particles move towards the needle col-lector which may be placed downstream of the injector. When a charged particle passes the needle of the col-lector it becomes neutralized and transmits a signal into 65 collector circuitry where it is analyzed to provide infor-mation about the intensity of the turbulence at various frequencies. The intensity is determined by the total In FIG. 1 is illustrated a schematic drawing of the electrogasdynamic spectral anemometer 10 of the pres-ent invention. From a source, not shown, air flow 11 is introduced into test section 13. Included within test 50 section 13 are injector cylinder 15 and needle collector 17 of the anemometer 10 of the present invention. The arrangement shown in FIG. 1 may be used to determine the turbulence generated by the configuration of the injector cylinder itself. It is to be understood that the injector cylinder could be made into many different configurations depending upon the particular shape de-sired for testing. Alternatively, a test fixture 16 having a different shape could be attached to and enclose the injector cylinder, as illustrated by dotted lines. If this were done then the turbulence measured by the needle collector 17 would be that of test fixture 16 and not the injector cylinder. In FlG. 2 is illustrated another embodiment of the electrogasdynamic spectral anemometer 18 of the pres-ent invention. In this embodiment the injector cylinder 19 and needle collector 21 are held in rigid and fixed spaced relationship by means of insulator brackets 23. 3,777,564 3 It is to be understood that the FIG. 2 embodiment may be put into any fluid stream to measure its unsteady flow characteristics. For example, an air stream may flow perpendicular to the plane of the paper and the needle collector would measure the charged particles 5 issuing from nozzle 41 thereby indicating the turbu-lence in the plane of the paper, as illustrated by lines 25. Referring to FIGS. 1,3,4 and 5, injector cylinder 15 includes corona needle 27, attractor ring 29 and cylin- 10 der 31. The cylinder 31 is preferably made of Teflon, but it may be made of other dielectric materials. Co-rona needle 27 includes an enlarged metal section 33 which threads into cylinder 31 and includes a sharp-ened end 35 which is spaced from and centrally posi- 15 tioned with respect to attractor ring 29. Nozzle 37 may be formed integral with the cylinder or it may be sepa-rately made, as illustrated in FIG. 5, and attached to the cylinder by threads or the like. Lead wire 36 connects attractor ring 29 to potential source 53 and lead wire 20 38 connects corona needle 27 to ammeter 54. In FIGS. 6 and 7 is shown an alternative technique for making injector cylinder 19 which may be used in the FIG. 2 embodiment, for example. In this embodi-ment cylinder 39 is made of Teflon and the nozzle 41 25 is formed from the Teflon cylinder itself. In certain situ-ations it maybe desirable to offset the opening 43, as shown, so that more threads will be available to hold corona needle 4S and also provide better insulation of the steam from the cooling effect of the fluid. Section 30 47 of the needle is reduced in size to minimize the cool-ing of the steam. The attractor ring 29 is positioned flush with the outside surface of cylinder 39. In FIG. 8 is illustrated the details of needle collector 17 used in the FIG. 1 and the FIG. 2 embodiments. 35 Needle collector 17 includes body 49, needle 51, and lead wire 52. The body 49 surrounds part of needle 51 and wire 52 and is machined from Plexiglass, or similar dielectric material. The exposed length of the needle is not critical, but the overaJl needle collector 17 should 40 be streamlined with respect to air flow. Electrical sig-nals from needle 51 are transmitted by lead wire 52 to the electrical equipment, shown in FIG. 1. The operation of the electrogasdynamic spectral ane-mometer of the present invention is as follows: From an 45 outside source, not shown, steam is introduced in injec-tion cylinder 15. This steam may be saturated at a pres-sure of about 8psig and a temperature of about 235 0 F, for example. As the steam issues out of the nozzle it su-persaturates and condenses into droplets having vary- 50 ing size depending upon the condition of the incoming steam. The droplets are then charged through the co-rona, developed between the corona needle 27 and the attractor ring 29. The amount of charge is determined 55 by the level of the potential provided by variable poten-tial source 53 and the size of the water droplets. The choice of droplet size depends upon the desired fre-quency response of the anemometer. That is, if the tur-bulent flow has a maximum frequency of about 20,000 60 hertz, then the droplet size must be very small, for ex-ample, about 10-7 meters. This is because larger parti-cles have too much inertia and would not foJlow the turbulence. However, if the turbulence is about 3,000 hertz, then the droplets could be about one micron. In 65 FIG. 9 is illustrated curves that bracket the desired droplet sizes which optimaJly match the highest fre-quency response of the interest. It should be noted that 4 matching the highest frequency automatical1y matches all others. Also, it is preferable to match the droplet size with the highest frequency response because small droplets are generally more difficult and expensive to produce than larger droplets. It should also be noted that other materials may be substituted for water. That is, most dielectric liquids may be used. Moreover, it has been found that solid particles may be also used. For example, submicron polystyrene latex spheres are available on the open market and have been found to be satisfactory. Hollow spheres are preferably used be-cause they are lighter and have a frequency response that is higher than solid spheres of the same size. When the charged particles are injected into the tur-bulent stream, they follow the rapid fluctuations be-cause of the matching of the particle size to the fre-quency. These charged particles move with the flow towards the needle col\ector and when a charged parti-cle passes the needle of the collector it becomes neu-tralized and transmits a signal into the collector cir-cuitry shown in FIG. 1. Capacitor 55 of this circuitry functions to isolate frequency analyzer 57 from the D.C. component of generated signals. Ammeter 59 functions to measure the D.C. component of generated signals. Diode 61 functions to prevent reversal of cur-rent and resistors 63 and 65 provide a voltage divider network for use with an oscilloscope or the like for ana-lyzing the characteristics of the signals. Typically, the frequency analyzer will provide information about the intensity of the turbulence at the various frequency of interest. The intensity is determined by the total count over a predetermined sampling period at a particular frequency. It should be noted that a complete position measurement spectrum may be obtained by moving the needle collector into a plurality of different positions. What is claimed is: !. A device for measuring the dynamic characteris-tics of a fluid comprising: a. an injector for injecting particles into said fluid; b. a collector for collecting particles injected into said fluid; c. a source of particle material operatively connected to said injector; d. said injector including charging means for electri-cally charging said particles; and e. means for measuring the charge and frequency of the particles collected by said collector. 2. The device of claim 1 wherein: a. said particles have a size range from about 10-6 meters to about 10-8 meters in radius. 3. The device of claim 2 wherein: a. said particles having a linearly decreasing size range of from about 10-5 to about 10-9 meters in radius with a linearly increasing turbulent fre-quency of said fluid of from about 1 to about 1010 hertz per second. 4. The device of claim 3 wherein: a. said source of particle material is steam near the saturation point. 5. The device of claim 1 wherein: a. said injector includes a wall forming a cavity; b. a first opening in said wall for introducing said par-ticle material into said cavity; c. a second opening in said wall for introducing parti-cles into said fluid; d. a corona needle positioned within said cavity and spaced from said second opening; and 3,777,564 5 e. an attractor ring surrounding and forming part of said second opening. 6. The device of claim 5 wherein: a. said second opening is formed by a nozzle opera-tively connected to said wall and extending out- 5 wardly from the outside surface of said wall. 7. The device of claim 6 wherein: a. said collector is operatively connected to one side of a capacitor; and b. the other side of said capacitor is operatively con- 10 15 20 25 30 35 40 45 50 55 60 65 6 nected to a device for measlJlring the number of particles contacting said col\ector at a predeterined frequency. 8. The device of claim 5 wherein: a. said second opening is formed by a nozzle formed in said wall; and b. said attractor being positioned flush with the out-side surface of said wall. * * * * * 

Electrogasdynamic Spectral
Anemometer

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Electrogasdynamic Spectral Anemometer

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