US2408775A

US2408775A - Booster pump

Info

Publication number: US2408775A
Application number: US506165A
Authority: US
Inventors: Robert P Greenwood
Original assignee: PESCO PRODUCTS CO
Current assignee: PESCO PRODUCTS CO
Priority date: 1943-10-14
Filing date: 1943-10-14
Publication date: 1946-10-08
Anticipated expiration: 1963-10-08

Description

Oct. 8, 1946. l `R. P. GREENWOOD v 2,408,775

l BOOSTER PUMP Filed oct. 14, 1945` Hiii- Patented Oct. 8, 1946 eATENT oFPlc-QE f I v Boovscmu PUMP l i l Robert P4 Greenwood; Youngstown, Ohio, assigner Tesco lroductsuCogfa corporationof Ohio v Application october-14, 194s, serial No. 506.165v

centrifugal pumpv .such i as .contemplated herein,

14 claims. (ci. 10s-113) travelina horizontal .planethat is at .a right angle 'to the rotational axis of. the beater and parallel to the plane. of' the impeller element of the pump. The S`shaped curvejof the blades preferably conforms substantially with correspondingcurved recesses or channels between the viins or blades of the .impellerymemben A andlto improve the eiciency and operation of suchpumn i Thi'sinventi'on hasioran object the provision of ,a centrifugal. booster pump structure-that is especially-.designedfior use with high-volatile liquid fuel such .as favored for aircraft engines that arerequired to operate under .the wide. range 4of' barometricpressures yWhiclsi .are encountered betwee'nfthe normal.ground` level. .pressure and r.thepressure of extremelyhi-'gh .altitudes as well rastoi the diierent atmospheric conditions.

i .'Anotherobj'ectof the present invention to provide a novel'. beater for ejecting occludedv air bubbles, the ystructure 'ot' suchbeater being adapt- Aedto reduce the requiredpowermput .and-,thereby decrease the .overall weight aswell. .as consumption of electric. current requiredto operate lthe driving motor.;-`V

. Aiurther o ject gisto provide. afbeater that :is

' of an S-shape having]unpitchedv blades or arms, v.this-shape tending .to,.decreasethetorque load on the'motor.. c

, .A .sti11.further ,Objectis {saprai/ide a .beater l :thatnoperatesfto cause4 the bubbles v:to cling to i the surfaces of .the blades and gradually.y move outwarda-long .the trailing edge orsurface vtowardsth'eutips ofthe blades before they are ejected." therefrom Iata location that is remote to the. rtationalaxisand out of the path of fluid ,discharging from. .the pump :inlet ',gulide.

.Whenpitched bladesare used, thebubbles tend V,toleave the surfaces of the blades a considerable ...distance inwardirom the blade tipsV and thus vming-le directlyin Y.the path of v the fluid moving towards the impeller. Furthermore, when pitched .blades are employed they create'a'region .of confeo siderable-turbulence between. the inlethead 'and andthe inletmouthfrto the impeller increasing the. electric .power consumption; whereasV with ,the novel .beater strueturefherein disclosed the region ofv greatest turbulence is .outside and. be# 'Kyond the path o f .the iiuid. Ilowi-ng. to the inlet mouth so that the bubbles are ejected into'a zone beyondthe discharge .end of 4the .fluidinl'et structure. Thebubbles in the presentstru'etu're"je y y. Additional objects, aims.4 and advantagesv of the present invention will be apparenti-,o persons skilledin the art fatter fthe construction 'and yoperation' 'of 'the booster .purnpfand beater 'are understood v`from theiollowing description, taken. in .connection vwith the accompanying drawing wherein: l, y

l is a vertical axial. section, partly in ele.- vaton. disclosing, the instrumentali'ties for practicing the 'invention contemplated herein in a preferred embodiment thereof.

i Fig.. `'2.is a horizontalsecti-on taken on the plane. oiline 2-2 on Eig... 1 looking in the Ydirec- .tionof 'the.arrowsportions,o'f the adjacent structurev ybeing omitted. for clearness` `.F-ig.,.3' 'isa top plan view on. .an enlarged scale vof.' apreferred form. of lthebeater element shown Lisa transverse section taken substantiallyonline of Fig..3.

Fig. 5 is a plan View offa modified form of the beater.. f l.. Fig,..6 isa. transversesectionon line Y'li-65 on ,IEig.-5 l. y

Fig.. 7 isa gotbeater. n :.Fi'g. 8 isan .enlarged sectional view taken substantially online 8458. ofA Fig.. 2.

rThe. drawing. i'svto be. understood as being more or. less f schematic for the purpose of disclosing typical or preferred forms of. the improvements contemplated herein, and ingthedrawing .like .reference characters identify the same parts in .differentviewsrw- Y Y v i Referring; to. Eigs.` 1 to 4, there is shown apreferred varran'gement of centrifugal pump vincorporating combination my vimproved lvapo-r beater construction. The liquid fuel tank 5 has `an-open-ingin its bottom lwal-l in which the booster `piml'phassembly of the. centrifugal typeis installed. r'I'hepurnp elements are mounted in la housing 6 having-.anaxially disposed concave inlet throat l that converges downwardly from its wide inlet mouth .toa lowerfdischarge opening 9. ,An impellerzl' rcf the rotary centrifugal type is disposed in. close proximity tor-the discharge opening 9,.so I.that .the `sprally extending vanes l l and 'the ntermedate'recesses or channels I2 of the plan viewofanother modified form V impeller are in closely spaced relation to the adjacent housing wall surface I3. The liquid is discharged into a scroll or volute chamber I5 in y,the housing surrounding the impeller Ill, that has an outlet stub I6 projecting laterally to the housing and adapted to be connected in any suitable manner to a fuel feed line leading to the carburetor or other device where the fuel is ,to be used. The impeller I0 is suitably' connected to and supported upon the upper portion of a vertical shaft I'I that is journaled in the housing j v beneath the inlet throat member 'I in axial dis- For cooperation with the above arrangement for effectively accomplishing the ejection of vapor u bubbles, I have provided a particular beater conposition relative thereto, and its upper end is Y* provided with a tapered terminal supportL I8that i is disposed axially Within the inlet throat 1. 4The lower portion of shaft I1 has operative connection struction, a preferred embodiment of which is indicated` generallyat 39, located in the path of the liquid flowing from the guide opening 24 towards the inlet throat 1 and preferably secured to with and is rotated by a small electric motor (not shown) or other suitable prime mover.

termediate recesses or channelsA I2 are Preferably integralwith the diskor body of the impeller l0, the channels l2 having a smooth curved contour in cross-section and are undercut obliquely in the disk as shown in detail in Fig, 8, so that the open portions of the channels closely confront the proximate `face I3 of the housing wall concentric to the discharge opening 9 of theinlet throat member 1. The inner` terminal ends I9 of the vanes ll provide a plurality of sharp blades disposed concentrically around the axis of the impeller and they are slightly inclined. 'Ihe thickness of these blades increases towards the periphery of the impeller disk although the transverse dimensions of the intermediate recesses 'or channels I2 are substantialy uniform in cross-section dimensions from their inner to their outer terminal ends. k A

Viewed in cross-section (Fig. 8) a recess or channel I2 is defined by the faces 20 and 2| Aof the adjacent leading and trailing vanes and these faces are connected by Van inner curved surface 22. Thus, when the impeller travels in the direction of the arrow (Fig. 8) lthe blades I5 of the vanes cut sharply into the body of iiuid adjacent the discharge opening 9 of the inlet throatcaus ing the iiuid, upon entering the channels between the vanes, to turn at a 90 angleto .the general plane of the impeller. j l

The `fluid entering the recesses or channels is at low velocity which will result in a release of any bubbles that may be in the fluid so that these bubbles will move upward' into the inlet throat member. The fluid in the channels is moved centrifugally outward to the periphery ofthe impeller at a constantly increasing velocity, due to centrifugal action and will be, discharged into the volute chamber I5. While centrifugally traversing the channels the fiuid, due to the shape of the channel chamber, will also be whirled in a helical manner around an axis extending along the axis of each channel, and this rotation of the iluidwhile it is being forced centrifugally outward is adapted to impart additional'energy to the iluid therebyincreasing the lefciency of the pump.

Mounted in spaced relation above the iniet throat 1 there is guide 23 having a tapered lower portion that terminates in a discharge opening 24 that is axially aligned with the impeller Il) and serves to direct the fluid into the inlet throat. It will be seen that this discharge opening 24 is of less diameter than the mouth 8 ofthe inlet throat which permits egress of bubbles laterally through the annular space between these elethe' top of theterininal end I8 of the shaft I1 for rotation with the impeller I0. The beater is positioned in a horizontal plane that is immediately above the mOuth 8 of the throat and between said mouth and the discharge opening 24 of the guide 23. Inthe more specific aspecty of my invention, this beater 30 has a substantially S- shapeas Will beseen in Figs. 2 and 3, and the curved portions thereof are disposed inthe same general trailing directions as the vanes andvchannels of the pump impeller l0 above which the `beater is shown in superimposed relation in Fig. 2. The preferred form of beater 30 embodies a flat .piece of metal having a generally rectangular cross-section as shown in Fig. 4, and comprises a central .hubv 3l with ,two opositely disposed flat blades 3 2 extending radially therefrom. It is particularly important to note that blades 32 are unpitched so that the

leadinghand trailing edges

33 and 34 ofeach blade are always in the same horizontal vplane which results invless agitation of the fluid that is moving towards the impeller I Consequently, the cut which the blades make in sweeping through the fluid is no Igreater than the thickness of the flat strip forming the blades. There` `is no axial pumping tendency, and this eliminates a considerable 'portion of the friction which blades' of the pitched type create.

It will be noted that ilat beater 30 is positioned an appreciable axial distance away from the impeller I0 and the discharge opening of the -converging throat for more effectively separating the vapor bubbles before `Athe 'liquid is Vadditionally `acted on'by the converged throat 'L In operation, tarting at or adjacent the inner portions ofthe blades, the bubbles will move close to and across the blade surfaces'and will collect back ofthe trailing vedges 434 of the blades where, and due to centrifugal action, these collectedv bubbles then travel in a radially outward 'path along the trailing edges 34 until they approach the tips of said blades-and they are then ejected radially from the'tps into an annular zonebeyond the edge of the -mouthi24v of the fluid flow guide `23, (passing through the screen Y25) rising upwardly on the outside of the guide and being returned tohthefluid in the tank or reservoir 5. Thespiral curvature of the beater arms forming an S-like shape as a whole con- Itributes definitely to the improved operation.` The explanation for this would appear to be similar to that accounting forfthe improved operation bubbles by virtue of the fact that the same ex- -Atend rearwardly trailing in', the general .direction from which the lsame are moving in being rotated through 'the liquid.-y While the torque for :power :required to `operate v.the :beater is thus frleducedztofa it is :important l.toznote thatgthe vapor bubble'zeliminating capacity/'of this ,'mxpitched'beater .equal to that :of a :pitched propellerltypezbeater.L @From comparative tests of a ;'1'0"1pitchfpropeller y r4type beaterand my unpitched S-shapedebeater, I .have .realized va Vreduction in lcurrent consumpfftfionof Ltheorder :of .one ampere ,and viinincreased pressure .boost ofxtheforder `'of two ipoun'ds per squareinch. -`This .represents :a realradyantage aircraft :installation `Where output 'per unit of YWeight is critical.

A,Thus the inse iof a flat iunpitched beater iila'de uresults an arrangement which :gives `anfinlcreased pressure boost, and a decreased rionsumption of velectric current.` rlliisnrlay be .wat tributed Ilargely v:to the :iac'ttha'tthe only pumpin'g'iactionlresulting from tthe operation of ythis :propeller is Vina `radial )direction and only-bubbles are pumped by this action. vinasmuch :as

there is no axial pumping, the motor Vload is less.

-in some inverse :ratio to the motor .current drawn,

"'thernotor has a' `tendency 'to :speed upfwhile vvbe .seen thatI obtain the fsa-me vapor separating l "action which is obtained 'with -alll pitch k.pro-

/peller Witlimore efficiency. 'lSi-ncethe unpitc'hed blades reduce the torque lfoad on the motor permitting it to operate faster, this results inthe "back elfectrorriotive force being increased @and therefore the current lconsumption through the "series 'eld and armature fis decreased.y

"While I vliavendisclosed the preferredorrn of impeller to be `used co'rnlbination -witli my `unv'pitched 'beater because of 'heimproved'results obtained, it Will beunfelers'toodfthat'lin the broader aspects of my invention I also contemplatevother available fforrns -of impellers. K

vTn lieu of 'the at blade-beater "above --described, the beater may `embody a wire 'element vsuch `as Villustrated 'in Figs. -5 and 7., which llas anarcuate or cylindrical contour "morose-'section 'as shotvn in Fig 6. n the*structure illustrated lin Fig. 5, the wire S5 is preferably of suiiicien't Ygauge and stiiness to be 'formed into a perrnanent VS-slriape and suitably mounted upon kthe terminal end vI 8 .of theactuator or `s'haitjlfl. lIhe wire iiV shown` in Fig. 'l is oa flexible character .and isstraight .trom end .toend .When not being rotated. When this latter type vof vbea/ter is rotated throughthe fluid itxWi-ll bend backwardin 4a'trailing manner nand assur-ne an St-shape as .shown in -dottedlines onliig, 7.. -ln both of-these v.tsfpesfof fWireJeea-ter the bubbles Willicollect 'back of the trailing surfaces of .the AS-*s'haped blades and .they'will be .ejectedjiradially outward 'from the tips Vdof said blades. The results attained-toy f these Seshaped wire beaterszare suhstantiallythe Asame as With'the :use :ofthe :flat unpitehed blades .previously explained. K

.Itisimportantto note that while I have gshown A`aninstallation in the :bottom lofa -fuel tank by `way of example, :my invention .isequall-y TYapplica- -ble -to yother .arrangements including y.booste-r v pumpinstallatons introduced sthroughithe :roof v :of v:the tank as :Well as lside wall installations.

While thisinwention has vbeen described indetail in itslpresent :preferred form or embodiment, .it lwill be .apparent to personsskilled in :the art, after :understandingthe improvements, athat uvarious 'chan-ges 'and `modifications .may :be :made 'therein without departing from the spirit or scope thereof. It is 'intended that the appended :claims cover all such changes and modiiications.

el. 1n a centrifugal pump, ahousing having. van impeller chamber; 5a centrifugal impellerirotatable `rin said hamber., a' fluid V1inletrthroat yconfimunicatm'g :with 'said 'chamber fforwardiy .of :said iimpel-ler; Yfa :fluid-:guide 'nn' directing fluid-itof said inlet; :and a beater ,interposed between said inlet throat and said '-.iiuid guide, .said lbeater being arranged lacoaxi'ally with isa'd ,'-i'mpeller Afor rotation in a iplane `:normal to the axis lof rotation` ithe impellerand consisting :of :an 'impitchedimem- `ber Zhaving `leading :edges 'fandrtrailing edges :conformed and arranged to operate.` so Vthat.rotation -vof the-beaterabout said axis vwill" cause bubbles .of vapor'rto be generated vtrono fluid ',directed'ioy `saidguide tofsaid throat Without directly `Aaccelerating the .speed o'f rthe'ifljui'd in the 'direction :of the said axis, the trailing edges of said fbeater beingadapted to collect 'vapor bubbles along the same andznove ther-'bubbles .radially 5to 'the ltips offy Athe "beater to "be ejected-therefrom into a 'ZoneV outside the influence fof the ilud `guide.

2. ln a 'centrifugal fpinnpV adapted for pumping .volatile .liquid :containing vapor, :a housing having `anirnpeller chamber; a centrifugalimpeller .rotatable `said chamber, said iimpell'er fiorr'ned with spirally 'cunvedv impelling vanos.; an inlet throat communicating"withsaid chamber Labove said rimpellerj -a lnid `guide for ydirecting u'id 'tozsafidinlet throat; and la beaterinterposed between said. inlet Ethroat and said iluid fgui'd-e, said beaterrbefing arranged .oo-axially with said Jimpeller tor 4'rotation lina plane .normal to ith-e Saxis oi' rotation'rot the `impeller and 4consisting of radially opposite blades :disposed insa-id plane,

each-blade having `a Yportion curvle'd in the fgenferal direction of the 'impeller ymemloers andsaid blades "together fioirinin'g an JS-sh'apeg the sa'icl blades 'being conformed and arranged to operate 'so'tha't rotation .of lthe saidb'eater'will cause bublo'les 'of 'Vapor to 'Ibo-generated -iromfuid directed byfsaid fguide to 'saidthroat Without directly =ac `cel'ereting the flow of iuidin the direction' of the said axis, :and substantially fal-l `the blib-bles to 'be lcolilected :along lthe A*trailing edges, the said -collcted`bubbles bei-ng moved A'cent'rifffugaflly along the' blades .and vejected :from the tips 'thereof into a zone radially outward ofthe discharge terminal Loi said il'uid guide.

a centrifugal pump adapted for pumping l volatile liquid containing Lvapor, avhous'in'g having an impeller chamber; a centri gal "impell'er roita-table in saltiv chamber, s'aid LlllnpellerA formed with spirally eur-ved impe-lling vvvaries? `aninlet throat communicating with said :lcliamber'ifor- Ward'lyV of said impeller'.; a fluid guide forfdirecting rfluid to'said inlet throat; ,and an S-'sihape `rotatable beat-er interposedfabetween said inlet thro-at and said fluid guide, esaid 'beater .consisting Yof radially vopposite flat :unpitehed blades dis- "ilosedina planezat'a right-angle tofth'e rotational axis of the beat-er :and 'in spaced relation zwith v.said throat, :each .Je-lade .having a :spirally *curved 'of the impeller vanes and the leading edges of the beater blades respectively being conformed and arranged to operate so as to generate bubbles of vapor from fluid directed to said throat, and the trailing edges of the curved flat blades adapted to collect vapor bubbles back of the same and to mo-ve the said collected bubbles centrifugally to their tips and eject the bubbles radially into'a zone outside the inuence of the liquid being discharged by said guide.

4. A beater for a centrifugal booster pump, consisting of a plurality of thin, radially opposite blades having closely spaced opposite flat surfaces and arranged for rotation about a central axis normal to the flat surfaces/said blades hav- "ing leading edges and trailing edges so conformed and arranged that the radially outer vportion of each Vblade curves backwardly and the leading edge of one blade and the trailing edge of an opposite blade form generally an S-curve and that rotation of the beater about said axis in a stream of fluid flowing to the pump and Within a. body of the fluid will cause bubbles of Vapor to be generated from the iiuid without directly accelerating the ow of uid in the direction of the axis and substantially all the bubbles to be collected along the trailing edges and translated therealong to the outer extremities of the beater whence they will be ejected from the stream in a generally radial direction in relation to the axis.

5. A beater for generating bubbles of vapor from a stream -of fluid flowing to a centrifugal pump and consisting of a thin blade having opposide at surfaces of generally S-shape arranged Afor rotation about a central axis normal to the at surfaces, said blade having a leading edge, the radially outer portion of Which curves backwardly, and the edges of said blade being so conformed and arranged that rotation of the beater in a predetermined direction about said axis in a stream of fluid flowing to the pump and Within a body of the fluid will cause bubbles of vapor to be generated from the fluid without directly accelerating the flow of fluid in the direction of the axis and substantially all the bubbles will be collected along the trailing edges and translated therealong to the outer extremities of the beater whence they will be ejected from the stream in a generally radial direction in relation to the axis.

6. A beater for a centrifugal booster pump consisting of a flat strip providing oppositely disposed blades arranged for rotation about a central axis, the said blades being generally of S-shape and having opposite flat surfaces normal to said axis, the radially outer portion of the leading edge of each blade being curved backwardly and the leading and trailing edges of each blade being so conformed and arranged to operate upon rotation in a predetermined direction of said beater in a body of fluid as to generate bubbles of Vapor therein and to cause the bubbles so generated to collect .along the trailing edges and to be translated -therealo'ng tothe outer extremities of the blades and thence ejected in a generally radial direction in relation to said axis.

7. In a centrifugal pump assembly, a housing having an impeller chamber, a centrifugal impeller arranged in said chamber for rotation about a Vertical axis, a fluid inlet throat arranged in co-axial, spaced relation with said impeller and communicating with said chamber above said impeller, a uid guide for directing fluid to said inlet throat and arranged in co-axial, spaced relation with said inlet throat, and a beater ar- ,ranged co-axially with said impeller and intermediately of said inlet throat and said fluid guide `for rotation in a plane normal to said axis, said beater consisting of an unpitched member having leading edges and trailing edges conformed and arranged to operate so that rotation of said beater will cause bubbles of vapor to be generated from uid directed by said guide to said throat without directly accelerating the speed of the uid in the direction of the said axis and substantially all the bubbles of vapor generated from said uid to be collected along the trailing edges and translated therealong to the outer extremities of the beater whence they will be ejected in a generally radial direction in relation to the said axis to a Zone outside the zone of influence of the fluid guide.

8. In a centrifugal pump assembly, a housing having an impeller chamber, a centrifugal impeller arranged in said chamber for rotation about a vertical axis, a fluid inlet throat arranged in co-axial spaced relation with said impeller and communicating with said chamber above said impeller, a fluid guide for directing iluid to said inlet throat and arranged in co-axial, spaced relation with said throat, and an unpitched beater arranged co-axially with said impeller and intermediately of said throat and said fluid guide for rotation in a plane normal to said axis and in spaced relation with said throat, said beater consisting of radially opposite blades disposed in a horizontal plane and with leading edges and trailing edges arranged and conformed so that the leading edge of one blade and the trailing edge of the opposite blade form generally an S-curve and that rotation of said beater in a predetermined direction will cause bubbles of vapor to be generated from fluid directed by said guide to said throat without directly accelerating the speed of the fluid in the direction of the said axis and substantially all the bubbles of vapor generated from said fluid to be collected along the trailing edges and translated therealong to the outer extremities of the beater whence they will be ejected in a generally radial direction in relation to the said axis to a zone outside the zone of influence of the fluid guide.

9. In a centrifugal pump assembly, a housing having an impeller chamber, a centrifugal impeller arranged in the chamber for rotation about a vertical axis, the impeller being formed with spirally extending impelling vanes arranged in radially spaced relation with the axis, a iluid inlet throat arranged in co-axial, spaced relation with the Yimpeller and communicating with the chamber above the impeller, a fluid guide adapted to be mounted in a body of fluid for directing fluid from the body to the throat and arranged in coaxial, spaced relation with the throat, the vanes being arranged whereby upon rotation of the impeller in a predetermined direction radially inner portions of the vanes will generate bubbles of vapor from fluid directed to the throat and the bubbles will be caused to flow upwardly in the throat and into the body of fluid, and an unpitched beater arranged co-axially with the impeller and within the body of fluid intermediately of the throat and the fluid guide for rotation in a plane normal to the axis and in spaced relation with the throat, the beater consisting of radially opposite, flat unpitched blades disposed in a horizontal plane normal to the axis and having leading edges and trailing edges arranged and conformed so thatthe leading edge of one blade and the trailing edge of the opposite blade form generally an S-curve and that upon rotation of Y the beaterin a predeterln eddirection bubbles ,of vaporwill regenerate f 'd direetedhy Mittelerdirection. ,0f the the guide. to the throa "thembulobles .OIiNaPOr a housing having an impeller chamber, a centrifugal; impeller, arranged, said chamber for rotation about a vertical axis, a fluid inlet throat arranged in co-axial, spaced relation with said impeller and communicating with said chamber above said impeller, and a fluid guide for directing fluid to said throat and arranged in co-axial, spaced relation with said throat, a beater arranged co-axially with said impeller and intermediately of said throat and said fluid guide for *housing having 'an-impeller chamber, a 'spirallyy varied impeller. arranged insaid chamber for rotarotation in a plane normal to said axis, said beater having thin, radially opposite blades with closely spaced opposite flat surfaces disposed in parallel relation to the plane of rotation and leading edges and trailing edges so arranged and conformed that the leading edge of one blade and the trailing edge of the opposite blade form generally an S-curve and that rotation of said beatervv in a predetermined direction will cause bubbles of vapor to be generated from fluid directed by said guide to said throat without directly accelerating the speed of the fluid in the direction of the said axis and substantially all the bubbles of vapor generated from said fluid to be collected along the trailing edges and'translated therealong to the outer extremities of the beater whence they will be ejected in a generally radial direction in relation to the said axis to a zone outside the zonel of influence of the fluid guide.v

1l. In a liquid fuel system, a liquid fuel tank having an outlet in the bottom thereof, a centrifugal pump secured to the outside of the tank adjacent said outlet and comprising a housing having, an impeller chamber, a spirally-vaned impeller arranged in said chamber .for rotationr about a vertical axis, an inlet throat arranged in co-axial, spaced relation with said impeller and communicating with said outlet and said chamber above said impeller, a guide mounted in the tank and arranged inco-axial, spaced relation with said inlet throat for directing fuel to said throat, and rotatable beater means disposed intermediately of and in spaced relation with the guide and the throat and in open communication with a body of fuel in said tank, said beater consisting of a thin blade having opposite flat surfaces of generally S-shape arranged for rotation about a central axis normal to the at surfaces and co-extensive with the said vertical axis, the blade having edges conformed and arranged to operate so that rotation of said beater inv a predetermined direction will cause bubbles of vapor to be generated from fuel directed by said guide to said throat without directly accelerating the flow of the fuel in the direction of the said axis and substantially all the bubbles to be collected along the trailing edges and translated therealong to theV outer extremities of the beater whence they will be ejected from the fuel directed to the throat in a generally radial direction in relation to the axis;

12. In a liquid fuel system including a liquid fuel tank having an outlet in the lower portion tion abouta vertical axis, an inlet throat arranged in .co-axial,y spaced relation with said impeller and communicatingv 'witlil said outlet and said chamber above said impeller, and aguide mounted intheY tank and arranged in ctn-axial, spaced rela- Y .tion w` ithsaidY inlet jthroa"r,`forf directing fuel to Said-throat, a beaterarranged in open communication witha body of fuel inthe tank and co- .axiallyvwith said .impeller andintfermediatelyof said throat'and `said guide for rotation ina plane .normal to said axis, said beater consisting ofan unpitched memberhaving thin, radially opposed blades with closely spaced opposite flat surfaces disposed in parallel relation to the plane of rotation and so conformed and arranged to operate that the leading edge of one blade and the trailing edge of the opposite blade form generally an S-curve and that rotation of said beater in a predetermined direction will cause bubbles vof vapor to be generated from fuel directed by said guide to said throat Without directly accelerating the flow of the fuel in the direction of the said axis andV substantially all the bubbles'will be collected along the trailing edges and translated therealong to the outer extremities of the blades whence they will be ejected in a generally radial direction in relation'to the said axis to a zone of said body of fuel beyond the Zone of influence of the guide.

13. In a centrifugal pump assembly, a housing having an impeller chamber, a centrifugal impeller arranged in the chamber for rotation about a vertical axis, the impeller being formed with spirally extending impelling vanes arranged in radially spaced relation with the axis, a fluid inlet throat'arranged in co-axial, spacedl relation with 'the impeller and communicating with the chamber above the impeller, a fluid guide adapted to be mounted in a body of fluid for directing fluid from the body to the throat and arranged in co-axial, spaced relation with the throat, the vanes being arranged whereby upon rotation of the impeller in a predetermined direction radially inner portions of the vanes will` generate bubbles of vapor from fluid directed to the throat and the bubbles will be'caused to flow upwardly in the l throat and into the body of iluid, a baille arranged transversely of the throatto equalize the flow of fluid therein in the direction of the axis whereby to enable substantially uniform generation of bubbles by the impeller vanes and to direct the upward flow of bubbles generated by the impeller vanes to the zone ofloperation of the beater, and an unpitched beater arranged co-axially rwith the impeller and Within the body of fluid intermediately of the throat and the fluid guide for rotation in a plane normal to the axis and in spaced relation with the throat, the beater consisting of radially opposite, flat unpitched blades disposed in a horizontal plane normal to the axis and having leading edges and trailing edges arranged and conformed so that the leading edge of one blade and the trailing edge of the opposite blade form generally an S-curve and that upon rotation 'of the beaterin a predetermined direcalong the trailing edges and translated therel1 along to the outer extremities of the beater whence they will be ejected in a generally radial direction in relation to the axis to a zone of the body of fluid outside the zone of influence of the fluid guide.

14. In a centrifugal pump, a housing having an impeller chamber, a centrifugal impeller rotatable insaid chamber, a fluid inlet throat communicating with said chamber forwardly of said impeller, a guide for directing fluid to said throat, and a beater consisting of a member having opposite, unpitched surfaces, interposed between said throat and said guide, said beater being arranged coaxially with said impeller for rotation in a vplane normalto the axis-of rotation-of theinil- ROBERT P. GREENWOOD.