US3004495A - High speed hydrodynamic pump - Google Patents

Description

Oct. 17, 1961 s. l.. MAcKLls HIGH SPEED HYDRODYNAMIC PUMP Filed Feb. 11, 1957 3 SheetsfSheet 1 lNVENToR. SnZeyL.MacIZzs BYALu/LQM Oct. 17, 1961 s. l.. MAcKLls 3,004,495

HIGH SPEED HYDRODYNAMIC PUMP Filed Feb. 11, 1957 s sheets-sneer 2 Q u C? "Fig 7 90 A 95 92 52 8 63a. ZJL; 34a Y 41a 95a 96a V g M 95%) 3x23 if y/ w/////////// /////K` /A O LUIL INVENTOR.

Oct. 17, 1961 s. l.. MAcKLls 3,004,495

HGI-I SPEED HYDRODYNAMIC PUMP Filed Feb. ll, 1957 3 Sheets-Sheet 3 zo j 18 52 i 452 4o 40 ,4: Y -24 41o INVENTOR. SinZeyL.Mc/Tli5 BY E A ornega 1United States Patent O 3,004,495- I; HIGH SPEED HYDRODYNAMIC 'PUMP Stanley L. Macklis, Watertown, NY.,` assigner to The :blew York Air Brake Company, a vcorporation f New ersey FiledrFeb. 11, 1957, Ser. No.' 639,297

, 6 Claims. (Cl. 1035-101)l This invention relates to rotary pumps,` and particularly to high pressure pumps capable of operation at speeds of the order of 25,000 and even 45,000 r.p.m., against head pressures of the order of 3,000 p.s.i. and even 4,500 p.s.i.pin special cases. L

Pumps capable of such performance are desirable for use in high performance aircraft and in guided missiles. Such pumps must have a reasonable life, field of' use considered, and should have an eiiiciency of 50% -or better. They would ordinarily be driven by direct-connected turbines, and should vafford a high power-to-weight ratio. Y f v To meet these severe conditions, theinvention proposes a pump of the so-called scoop type whose basic" components are known. 'A dynamically balanced liquid filled cylinder is rotated on a fixed axis which carries a Pitot tube or pairs of Pitot tubes, through which discharge flow occurs under the sum of two heads, namely a pressure head developed by centrifugal force, `and a'pressure head developed by conversion Vo'f the velocity head of the rotating liquid.

. Tosecure high delivery pressure and close approach to perfect dynamic balance, staged operatior'l is adopted. The simplest form has two juxtaposed coaxial rotary chambers, with one Pitot tube in each chamber, spaced 1809.apart around the fixed axis. The flow is in-series through the two units. The' reason for using one Pitot tube per chambervis to minimize whatmight be "called wake effects, eddies and the like. Pumps at least approximating the above basic form have been proposed, but in the crude form'in which they are illustrated in such publications as are -known to applicant, are not suited to the exacting duty here contemplated. Too many factors of controlling importance are ignored. Apparently their controlling importance in high speed operation Was not appreciated. Y One such factor is an inherent tendency for destructive accumulations 'of leakage liquid to occur. The present invention providesV means to dissipate such accumulations at incipience and continuously.

Another such factor is the accumulation of air in the firstfunit. The possibility of air accumulations was known andV manually controlled venting valves were suggested, but `no one seems to have appreciated that the tendency to accumulate air is continuous. The invention provides means continuously effective to purge this air, and what is more difiicult, todo so continuously in ya closed circuit system. r f

Related to the air-purging concept is means to derive the energy needed for such -purgingrfrom the leakage liquid, so that energy otherwise wasted is usefully applied, i

Another factor not heretofore taken'into account is the fact that at the speeds andpressures above suggested, the.pump must operate at high temperatures, s ay 500 F. lAt such temperatures Vavailable liquidsV have low bulk modulus,llow viscosity and increased chemical activity. Thisrequires careful design of bearings to avoid destru'c tive effects. Y Y

At such temperatures, the mechanical strength of materials and particularly their fatigue strength is impaired.

3,004,495 Patented Oct. 17, 1961V ice dom'lfrom pulsing ows are matters of greater than normal importance. Y

Evaluated against this background, the invention affords substantial advantages. The pump achieves best efficiency withlow viscosityfluids, and is substantially indifferent to`low bulk modulus of iiuid. Flows are continuous, bearing loads are low. T he'pump will ordinarily be operated at inlet pressures between l() and 50 p.s.i.g. This positive inlet'pressure is made effective to bias the rotary element of the pump moderately in an axial direction, and prevent skidding of the balls inthe bearing assembly. When operated at full cut-olf, flow of liquid through the air-purging ejector has a heat dissipating effect and hence limits the temperature rise.

iGenerally stated the pump is characterized by high delivery pressure, 'very high rotary speed and rather low ilow. It can be embodied in forms departing from the preferred form, and some of these modifications will be described.- Y I The general scheme of theV invention having been explained, preferred construction will now be described by way of example, reference being had to the accompanying drawings, in which:

FIG. 1 is an axial section through the pump, as indicated bythe arrows and line 1 1 of FIG. 2.

FIG. 2 is a transverse section through the pump as indicated by the arrows and line 2-2 of FIG. 1.

FIG. 3 is an end view of the pump (the left-hand end in FIG. 1) showing the liquid flow connections.

FIG. 4 is an elevation of the fixed shaft, as it would appear removed from the pump. Two Pitot heads (also visible in FIGS. l and 2) are shown.

Hence dynamic balance, freedomv from vibration and freel.

FIG. 5 shows in elevation one of the Pitot heads removed from the fixed shaft.

FIG. 6 is a view of an alternative form of Pitot head.

FIG. 7 is a sectional view of a liquid-operated air ejector which derives its motive liquid from the interstage passage of the pump. l u FIG. 8 is a view similar to FIG.l 7 but shows how the motive liquid can be derived from interstage leakage, with resultant economy.

In discussing the pump, that end which is to the right in FIG. 1'V will Vbe called the inner end because it is toward the support, andalldesignations of right or lef refer to the pump positioned as in FIG. 1.

The entire pump structure is sustained by an enclosing housing 11 cylindrical in general form and open at its inner end, which end has a mountingface 12 and an annular centering rim 13. The housing 11 is connected to a suitable support by bolts passed through the holes 14 in a mounting flange 15. 'I'he support (not shown) has a seat and centering recess to mate with the parts 12 and 13. Thus a conventional rigid support is afforded.

The outer, otherwise-open, end of housing 11 is closed by la flanged cap 16 whose form is clearly shown in FIGS. 1 and 3. On its outer side cap 16 has a hollow cup-like projection 17, taper-bored to receive and t the tapered end 18 of a xed shaft 19 which sustains all the rotary components of the pump and also the Pitot heads, and other non-rotary componentsof the pumping mechanism.

The shaft 19 is held against rotation by a pin 21 fixed in cap 16 which engages a keyway in the shaft; and penetrationV of portion 18into the taper-bore is limited' by shims 22. A castellarted nut 23 threaded, on a stud formed integrally on the end of `shaft 19 draws the parts into close engagement, and. is pinned to prevent its loosening. v Y

Milled along side portions of shaft 19 are three longitudinal groove passages (see FIGS. l, 2 and 3) namely the inlet passage 24 which leads from inlet connection 25 (FIG. 3) to 'the first stage pumping chamber 26, the inter- 3 stage passage 27 which leads from the Pitot unit (to be described) in the first stage `chamber 26 to second stage pumping chamber 28 and discharge passage 29 which leads from the Pitot unit (hereinafter described) in charnber 28 to discharge connection 31. These three groove passages are covered'and isolated fromone anotherby. an appropriately ported sleeve32 whichseats at its `lefthand end against shoulder 33, is mounted-'witha-shrink iit-and also'brazedto the shaft 1.9.A The result isganv approximately'unitary ported shaft.

The Pitot unit 34 in first stagechamber 26 and the Pitotunit 35-v in second stage chamber 28 are :identical andare constructed each in one piece as shown in FIG. 5. Each has a sleeve-like hub` 36, lastreamlined radially ported strut 37 and a streamlined head 38 with entrance port 39. The struts havea fineness'ratio of 4and the heads have a iineness ratio of 5. The heads have a form derived from a symmetrical airfoil byimparting a curvature Yappropriatev to the curved` path Yof the liquid as it flows past the head.

The entrance port to each Pitot unit is shown `as circular. This is preferred because it affords the maximum inlet area for a given perimeter and wetted area and alfords the minimum form drag. However, a circle-is simply a special case of the ellipse having equal major and minor axes and, where space requires, it is feasible to use a true ellipse with vits major axisradial or parallel with the axis of rotation, as circumstances may demand. The hub sleeves 36 of the two Pitot units, an Yintervening spacer sleeve 41 and an end sleeve 42 make each a shrink fit with the sleeve 32. Furthermore, recourse is had to lugs 40 each of which engages a notch inthe adjacent pumping chambers. To assure rotation of the liquid in these chambers as the shell 45 rotates, there are provided spiral ribs 64 which projectirom both plane boundary walls of each chamber 26, 28. These ribs are clearly shown in FIG. 2. The` pitch. of the spirals is such that rotation of'the shell 45'tend'stourg'e the. liquid in the chambers 26l and 28-outward.

Seatedagainst the-peripheralportion lof they left-hand face of the member 62 Vis the bearingt support. 65 whose form is clearly'shown in FIG. l.` This is sealed to the shell 45 by an 'O-ring 66. A ring 67 'is threaded to engageinternalfthreads 68 'formedin the left-hand end of the shell. 4/5,1 and. acts .against the-.bearingsupport 65 to force it toward the llange; 46 and thefmembers 59,y 61v and 62.v The periphery of the intermediate member 61 is sealed by an O-rin-g 69. Y In:describingthe.sl,eevef32,. itwas'stated to be suitably ported. As will-be. appreciated from. .an examination of FIG; 1, this sleevev covers a longitudinalgroove 24 which connects inlet-"25y through aport inv sleeve 32 with charnber 26. Insleevew32 there areY also ports connecting passage 27 at one end withrthe passagein the strut- 37 of Pitot member 34 and at the other end with chamber 28. As indicated, in dotted lines'in FIG. l, there'is also cornmunication between .groove passage `29 in the shaft and the passage inthe strut37 of Pitot unit 35.

End4 plate -62- has, on its outer or left-hand face, a lappedplanesurface 71 with which coacts fthe lapped annular bead 72 of-a running seal'structure 73. Thisis of commercialformand. hence'is merely indicated in diagram. The seal *73 is.-designed-to inhibit leakage leftward from chamber 26. Thebearing support 65 has an internal conical surface. 74 which Vflares towardthe left.

It is convenient to state at thispoint, that it is practicable p and advantageous under certainV conditions, to replace each Pitot unit 34, 35 with a disc-like unit of the form shown in FIG6. In these the entrance 39a to thePitot passage is formed in a projection 38a in theperiphery of the disc 36a.' The projection is streamlined asindicated by shading. The form shown in FIG. 5 is preferred, as a general rule.

The rotary components ofthe pump 'are enclosed in a cylindrical shell 45.which 'hasfan annular inward-extending headange 46 terminating ina hub portion 47 bored A to a shoulder to receiveandposition a bushing 48.A This ange 54 which seats against the end of hub 47. Machine Y screws 55 with thread-locking sleeves56 (whose form. is not here material) fixA the ilange 54 tothe. end of hub 47. The disc 57, which closestheinnerend .of connector 52, is -brazed in .place so as to be leak-proof, and flange 54-isfsealed to bushing 48 and the bore of hub 47 by the O-ring 58. v v f Fitting into the bore of the cylindrical housingv 45 and seated against the head ange 46- is athree-part assembly which encloses the two pump chambers A26 and: 28. This assembly comprises a cup-shaped right-hand-end member 59, an intermediate member 61 and a left-handendplate 62. The member 59 encircles the vbushing 48. The web of the member 61 which separates chambers 26 and 28 carries, fixed at its center, aring internally formed as a 1abyrinth763; Y'Ihela'byrinth surface 'encircles'y and coacts with the member 41`carried by the sleeve 32, topro# vide a labyrinth seal between the two chambers `26am 28; Thus the members 59, 61-and 62 denne the two Whenthe rotary; partsiare in motion, leakage escaping pastfseal 73 'will` beurged centrifugally Valong the surface 74 and out-through. ports-75 and75 into the space in housing 11 betweenthe housingantl the rotary shell 45. Such leakage. escapes throughthe dra1rr76.l An insert l0-'resists entrance, intothe space between the parts- 11 and 45.

Thefseal unit-173 -is sustained.at its lett-hand end by a iiangedycollar.4 77 which-engages va shoulder 78 on .the sleeve 32,(see l1116,51); soithatits position is fixed The hub ofthiscol1ar77fserves as; the support forthe inner race 79 of. afballibearingwhoseouter racev 81 lis positionedby'theybearing support 65.?

The outer race 8,1.-.isnmountedrbetweerrtvvo4 grease baiiies 82; and 83 .which are annular inform. The outer margin ofthe baflie 82. seats against an annular .shoulder on the bearing support y65. and the left-handbale 83 is confined between ythe outerY race and a threaded. ring. 84 which engages threads atv the outer end of the .bearing support 65. Thebatlles 82 and 83 aredesigned to retain inthe bearinga delinite'amount of grease and to exclude from nthe bearing'otherwise possible accessions of leakage oil. At the speeds contemplated, Vtheentrance of excessive oil -wouldlbe-destrucrive to the bearing.

The' bearing, whoseraces'appearl atA 79 and 81,-.is a combined; radial; 'and-"thrust ball-.bearing which: resists motion of the rotary components of the purnpto the right? and also defines-the. axis of .rotation `of these components. Motor..means.are incorporated in .the pump,v to

' developtheaxial-.thrust so' resistedand these means'corni prise a port which leads from the inlet passage 24 -to theend of the shaft19 so.that.inlet pressure, which is above atmospheric as ,alreadyY stated, is admitted .to the interval between closure disc 57 and the end of theV shaft 19. The effectY is toA urge the rotary element to theright Yantllto establish sutlicient' axial load on the bearing balls to assnrethat they will neverskid. The operation of the Ipumpdoes notV develop unbalanced axial `thrust on the rotary element, so that the axiall biasing is`A simply a function ofthe inlet pressure which is'reasonably constarrt. I

The member vindicated M85 isaA sheet metal nut lock designed to prevent the ring S4 from `backing olf. Similarly, the member 86 is a wire ring which functions as a a nut lock and servesto prevent the member .67 vfrom backing out. No noveltyis here claimed* for either nut lock, and various commercial units could be substituted. Hence, detaileddescription is unnecessary. 'i

1 In. pumps of this (type, accumulations `of air in the pumping chambers, such as 26, must be prevented. yPractically all oils, or other hydraulic liquids carry gases either occluded or dissolved therein. Under the`centrifugal forces developed in the pump, these gases separate out. IIn a two-stage pump such as illustrated,V such separation occurs in the first stage chamber 26. One ofthe important features of the invention is provision of means to remove such gases continuously. t t

FIG. 7 shows a construction in whichthe gas is drawn oif by an ejector whose motive fluid'is liquid drawn from the interstage passage 27. This liquidis at the discharge pressure ofthe firs'tstage.u As shownin FIG. Tand also in FIG. 2, a cross-drilled nozzle unit 91 is mounted in a bore 92 in the shaft member 1'9 and receives liquid through the port 93 leading from the interstage passage 27. The nozzle 91 delivers oil into the throatfof a venturi 94 also formed in an insert. The nozzle 91 and the venturi member 94 are clamped bya threaded plug v95. The venturi throat discharges into a passage 96 which leads to connection 97 (see FIG. 3`). The connection 97 would be connected to discharge in-to the oil reservoir of the system. v

The nozzle 91 discharges into the venturi throat continuously and whenever air is present in the chamber 26, it will be drawn out through passage 90, but the ejector is virtually ineiiective to withdraw oil from the chamber 26. Thus, air is removed automatically by an ejector mechanism having no moving parts and ineffective' to remove any considerable quantity of oil from the pump.

The construction shown in FIG. 8 is differently proportioned from that shown Vin FIG. 7, but has the same functional elements. The reference numerals applied in FIG. 8 are the same as those applied in FIG. 7 but with the distinguishing letter a.

The distinguishing characteristic of the structure shown in FIG. 8 is the fact that the liquid-supplying port 93a leads, not from interstage port 27a, but from a'point in the labyrinth 63a. In this way, leakage oil is tapped olf and usefully applied.

The leakage oil in FIG. 8 is under the pressure developed in chamber 26, so that functionally, the two schemes are basically similar, even as to the selective removal of air as contradistinguished from oil.

One of the conspicuous features of the structure above described is the fact that the running seals (except for the seal 73) are of the labyrinth type. Static seals are of the familiar O-ring type. The labyrinth 63 prevents liquid from chamber 218, which is at high pressure, from flowing into chamber 26. The labyrinth seal 51 develops back pressure on the hydrodynamic bearing 49. As this is considered a very important detail, it is desirable to reinforce the labyrinth' seal 51, and reinforement is had by two simple labyrinth seals which have been worked in between the sleeve 32 and the driving member 52. The iirst of these appears at 97 where the end of the sleeve 32 enters a shallow groove turned on the inner face of the ange 4. The second occurs at 98 where a ange on the left-hand end of the driving member 52 enters the shallow annular groove. fIhe clearance here, as well as at 97, is small enough to give a reasonable labyrinth seal effect.

The fact that the air ejector acts continuously and ejects air whenever air is present is a matter of extreme importance, because in any ordinary case, air will be disengaged from the oil almost continuously. This circumstance is of even greater importance where the pump is used yin. a closed circuit. In such a case, positive ejection 6 by the jet and venturi throat is the thing that makes the scheme practicable. Y

t The scheme of forming all the ow passages in the shaft leads. to compact and light-weight construction, and the use of thesleeve 32V gives an inexpensive construction with all the, advantages of unitary construction. Incidentally, it affords some choice in the selection of material.

. The tendency of any pump, Operating under the conditions suggested, to run hot is a source of considerable difficulty. Advantage hasb'een taken of the oilcirculation' used primarily to remove air, to afford effective means for' dissipating at least some of the generated heat. More be knowni on this -head whenthe experimental workhas progressed fur-ther. At the temperaturescontemplated, it is necessary to afford some compensation in thebearings. This is had by theuse of metals charac-Y terized by different coeiicients of thermal expansion. Fortunately, the pump is characterized by very moderate bearing loads and serious difficulty with theV bearings is not anticipated. Y A

Streamlining of the Pitot Vstrut and the Pitot head is a matter of considerable importance. The entrance rim at 39 (FIGS. 2 and 5) must, be roundedV and ther-trailingend which overhangs the strut is important as means Vfor reducing wake effects and minimizing the degeneration of mechanical energy into heat.

Applicant recognizes that staged operation is important and that more than tw'o stages can b e devised. Two stages are a plurality, and 'will support the use of that term in the claims. It would obviously be simple to elaborate the structure by adding pumping chambers each with its own Pitot strut and head. Applicant believes that it is unwise to use more than one Pitot unit per chamber, and the present belief is that satisfactory balance can be had if these units are angularly spaced at uniform intervals.

Applicant has endeavored to describe in careful detail a satisfactory embodiment of the invention but by doing so, he does not imply that the illustrated structure is the only one which might be used within the scope of his invention. That scope is defined solely by the claims.

What is claimed is:

l. In a scoop pump, the combination of a fixed shaft provided with a plurality of liow ports, different ones of which serve as a supply port and a discharge port, and

one serves as a loading port; -a rotor enclosing a generally Y cylindrical pumping chamber provided with liquid impelling vanes, said rotor being mounted on said shaft to turn about the shaft axis as the rotor turns; radial and thrust bearing means supporting said rotor on said shaft and having anti-friction rolling components; a scoop unit Y fixed on said shaft and comprising a ported strut land a Pitot orilice, said strut port communicating with the Pitot orifice and with the inlet port in said sha-ft; a pressure motor operable -by iluid pressure derived from said loading port in said shaft and serving to develop an axial thrust resisted by said bearing means; and a connection for rotating said rotor.

2. The combination defined yin claim 1 in which the inlet port is capable of being operated at a superatmospheric pressure and serves as the loading port, whereby the pressure motor is energized by pressure fluid from said inlet port.

3. In a multistage scoop pump, the combination of a fixed shaft provided with a plurality of flow ports, different ones of which serve as a supply port, an interstage port, -a high pressure discharge port, and a low pressure drain connection; a rotor enclosing a plurality of generally cylindrical coaxial pumping chambers which encircle said shaft and turn -about their common axis as the rotor turns; liquid impelling vanes in said chambers; -a plurality of scoop units, one enclosed by each of said chambers, each scoop unit comprising a ported strut and a P-itot orifice carried by said strut and communicating t 7 i Wththe' port in its strut, said'scoopunits being individu ally mounted in successive corresponding pumping cham-v bers andangu'larlyspaced uniformly 'about the' shaft'l axis, the: supply port, the'interstageiport, and the'discharge port in {said'shaft 'serv-ing'to complete `a continuous Vpath from s'n'pplyoethe' interioriof vthe first chamber, andthence by way of its enclosed scoop unit andfan'interstage port tothe next Ypumping chamber, and soV on, the last scoop unit'delivering to the discharge'port insaidjfixed shaft; `an'ejector]'comprisin'g `a combining tube and "aejet nozzle, said combining tube opening into-and connected tor draw gaseous mediurn'from therst pumping chamber atV a point adiacent the surface ofi said shaft; conduit means insaid shaft to receive liquid 'under pressure from a point in said continuous path between the first scoop unit and the end ofthe discharge portland deliver` said liquidto said nozzle, said ejector delivering mixeduid and vgas tosaid l-oW pressure drain' connection;A and a mechanical connection for rotating said rotor.

-4. A pump -as defined in cla-im 3 in which said point in the continuous .path from which the nozzle receives liquid is in the interstage' port between the first stage and the second stage.

5. The pump vas defined in claim 1 and a hydrodynamic 8 f-'The pnrnp' asideiined inclaim `5 andan anti-friction bearing between' 'said rotor and.j shaft at lthe' end opposite saidhyd'rodynamic `zbe'a-ring; shields', mountedV on 'the rotor juxtaposition" to'iopposite' sides of said anti-friction -References'Cited'in'the'iile ofthis patent vUNITED STATES PATENTS OstenbrergVj July 30, 1918 1,504,738 y, Brown' Allg. 12, 1924 1,756,958` Schmidt.; May 6, 1930 '2,124,681 Jauch" etalj July 26, 1938 2,648,491 Wood Aug. 11, 1953 2,690,130 Boeckeler Sept; 28, 1954 2,775,208' Mueller` Dec. 25, 1956 i 2,798,438 Greathouse Iuly 9, 1957 FOREIGN PATENTS 492,854- Great'Britain Sept. 28, 1938 693,871-` Great Britain July 8, 1953 Y 735,279 Germany May 11, 1943 919,449 Germany Oct. 21, 1954

Images