US2625106A

US2625106A - Composite pump for prime mover oil systems

Info

Publication number: US2625106A
Application number: US184481A
Authority: US
Inventors: Herbert N Hoffman
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1950-09-12
Filing date: 1950-09-12
Publication date: 1953-01-13
Anticipated expiration: 1970-01-13

Description

Jan. 13, 1953 H. N. HOFFMAN COMPOSITE PUMP FOR PRIME MOVER on SYSTEMS Filed Sept. 12, 1950 2 SHEETSSHEET l Invenfiorv Herbert N Hoffman.

His After-Hey.

Jan. 13, 1953 H. N. HOFFMAN 2,625,105

COMPOSITE PUMP FOR PRIME MOVER OIL SYSTEMS Filed Sept. 12, 1950 2 SHEETS--SHEET 2 Fig.5. F124.

Inventor": Herbewt NHoFFman,

His At torney.

Patented Jan. 13, 1953 COMPOSITE PUMP FOR PRIME MOVE-R OIL SYSTEMS Herbert N. Hoffman, Wakefield, .Mass assignor to General Electric Company, acorporationfof New York Application September 12, 1 950, SerialiNo.i184,4 81

(cl. 1ll3.4)

,2 Claims. 1

This invention :relates to .a special composite pump :for furnishing hydraulic power and lubrieating liquid in a prime mover, specificallya combination positive displacement and centrifugal pump unit for supplying lubricating :oil to the bearings, hydraulic fluid :to the governing sys- .tem, anda speed-pressure signal for effectingthe governing functionin a steam turbine.

The "pump described herein is specifically intended to be'used :in a hydraulic turbine governing system as described :in :the vcopending :applicationof .StephenJacobs, Serial No. 2277.85, filed April12-3, 1948, now Patent No..2,53.4 ,974 and :assigned to the same assignee as the presentsappli cation. That system incorporated a so-called turbine-type centrifugal "pump further details of which are disclosed in .thecopending application of Stephen Jacobs, Serial No. 116,255, filed September 1 7, 1949, and :my ficopending application Serial No. 129,490,:fi1ed November 25, 1949, now abandoned.

Experience with the turbine-type pumps of these copending applications "has shown that in some turbines his not feasible to obtain all the hydraulic operating liquid, lubricating oil, and other pressure liquid needed in the operation of the prime mover and its governing'system from a single turbine-type impeller. In certain turbines, the .quantity of :hydraulic powerandlubrieating =oi1 required exceeds that which rcanbe obtainedfroma singleimpeller-ofthe turbine type; therefore, a principal purpose of the present invention is to providea composite pump having .apositive displacement pump-element for supplying the lubricating and hydraulic power liquid, while :a comparatively small turbine-type centrifugal pump element serves only to supply the speed-pressure signal for controlling the governingsystem.

Another 'object'is to provide a compositepump of the :type described in which the turbine-type impeller is closely related to the positive displacement rotors so that the whole occupieslittle more space than a conventional positive displacement pumpalone.

A :still further obj eat "is to provide a composite positive displacement-turbine type-pump inwvhi-ch the centrifugal rotor receives its operating liquid from the positive -.displacement pump, with .spe-

cialmeans for insuring 'thatthe pressure signal a 2 of the centrifugal rotor and to insure that it will be self-priming, so that the p p --Can be mounted above the level of the liquid in the system with-which it is connected.

In general, these objects are attained by arranging the small centrifugal turbine-type rotor on'a-shaf-t-common to one of the positive displacement pump rotors and directly :below, 50 that liquid leaking downwardly from the positive -displacement pump provides the supply of liquid needed by the centrifugal turbine-type pump, A reservoir open to the atmosphere is disposed above the centrifugal pump rotor :and communicates with the inlet side thereof so that any "excess liquid supplied from :the positive displacement p mp passes to the :reservoir and overflows, with the'result thatthe static head at the inlet to the centrifugal pump-rotorsismaintained exactlyconstant and the thermal circulation between the centrifugal pump :passages :and the reservoir serves to cool the centrifugalrotor.

Other objects and advantages will he apparent fromthe followin description, taken in connection with the accompanying drawings in which Fig. ;1 is a top view, partly in section, of the composite pump unit; .Fig. .2 is asectional assembly view taken *on the irregular plane .2-2 inFig. :1.; Fig. 3 is an enlarged elevation view .of the :centrifugal turbine-type-impellen; Fig. 4 isa bottom viewin elevationof onerofzthe disk members forming the centrifugal impellerjhousing, taken in .the direction 4-..4 JiniIig. 21; .Fig. 5 is a 1701:) view .in elevation of the disk memberseparating*thecem trifugal rotor housing from .the variable displacement rotor housing, taken in the direction 5-5 in Fig. 2; and Fig. '6 .is a partial sectional view of the complete assembly .taken ontheplane 6-,6 inEig. 1.

Referring :now more particularly to Fig. '2, the assembly comprises 'a 'main housing :member I, an intermediate disk or plate member 12 which, in elfect, forms the bottom of the main housing Land a pair of disk members 3, l which form the housing ;for :the centrifugal element. .As will .be :seen .by comparison of .F'igs. 1 and 2, themain housingcasting I isgenerallyrcylindrical in-shape and has an Leccentrically located upwardly extending portion Ila defining a 'multiple lobed recess 5,*which.houses thetwo intermes'hing gears 6, l constituting the positive displacement pumping units. As maybe seen 'inFig. '2, the pump gear .6 has projecting shaft end portions 6a, 6b, shaft to projecting .upwardly through anopening in .easing Eta andcarryinga spiral gear B-adap'ted to engage :a .mating gear on the turbinesh-aftso as to be driven at a fixed speed ratio relative to turbine shaft speed. Gear 8 may, of course, be locked on a shoulder formed on shaft to by means of a lock nut 8a or other suitable means. The complementary gear 1 also has projecting shaft end portions 1a, 1b. As will be seen in Fig. 2, the lower shaft end portions 62;, lb are supported in holes in the bottom plate 2 forming journal bearings. Shaft lb has a reduced diameter end portion 1c which serves to support and drive the centrifugal turbine-type impeller 9, a described more particularly hereinafter.

Referring again to Fig. 1, it will be seen that the two pump gears 6, 1 occupy diametrically opposed lobes of the recess 5, the other lobes forming the inlet and discharge chambers 50:, b, re-

spectively, for the positive displacement pump. An inlet conduit I8 is cast integral with the housing la and communicates with the inlet chamber 5a. Similarly, a discharge conduit II communicates with the discharge chamber 52).

The offset portion of housing I at the side of the housing portion la defines a liquid reservoir indicated generally at [2 in Figs. 1 and 2. This reservoir is bounded externally by the semi-cylindrical wall l3 and consists of three distinct portions. The first is the comparatively shallow portion indicated at l2a in Figs. 1 and 6. The second is the deeper portion identified at 12b in Figs. 1 and 2. The third portion constitutes a comparatively small sump identified 120 in Figs. 1 and 2.

A top elevation view of the intermediate plate 2 is shown in Fig. 5, and a cross section of this plate is seen in Fig. 2. From these views it will be apparent that plate 2 is secured to the main housing portion l by a plurality of circumferentially spaced threaded fastenings l4 disposed in counterbcred holes I5 in plate 2. Plate 2 is also provided with an axially extending hole It and a smaller hole ll, located at substantially the same radius as hole 16, the purpose of which will appear hereinafter. The centrifugal pump housing plates 3, 4 are secured to the pump body I by a plurality of circumferentially spaced threaded fastenings l8 disposed in holes 18a in the plates 3 and 4 (Fig. 4) and corresponding holes [8b in the intermediate plate 2. Plate 2 is accurately located relative to the pump housing l by a pair of diametrically spaced dowel pins, one of which is indicated in dotted lines at [9 in Fig. 2, which pins project through holes 19a in intermediate plate 2 (Fig. 5).

In order to locate the centrifugal pump housing plate 3 accurately relative to the intermediate plate 2 the latter may be formed with an annular land 2a forming a rabbet fit with the central recess 20 of plate 3, as may be seen in Fig. 2. Similarly, in order to locate accurately the bottom plate 4 relative to the upper plate 3, plate 4 may be provided with a land 4a engaging a rabbet in the adjacent surface of plate 3.

A bottom view of the upper centrifugal pump housing plate 3 is shown in Fig. 4. By comparison of Figs. 2 and 4, it will be apparent that this plate defines a central recess 22 which cooperates with a recess of the same diameter 2| in the lower plate 4 to form the central portion of the centrifugal impeller chamber. The annular land 22 which surrounds recess 20 is interrupted by a groove 23 which forms the inlet to the centrifugal pumping passage 24 shown in plan view in Fig. 4 and in section in Fig. 2. A hole 16b in plate 3 communicates between the aforementioned hole it in the intermediate plate 2 and a third hole portion in the main housing 1. It will be apparent from Figs. 1 and 2 that the cooperating holes i5, 161), 18c constitute a vertical passage or standpipe communicating with the sump |2c of the reservoir l2.

As will be seen in Fig. 4, the substantially annular groove 24 communicates with an enlarged inlet portion 24a and a smaller enlarged termi-, nal portion 24b, the latter communicating with a discharge port Ila. As may be seen in Fig. 6, port Ila communicates with axial hole I! in intermediate 'plate 2, which in turn communicates with a drilled passage in main housing portion 1, including an axial hole ill), a radially extending hole llc, which continues through an integrally cast extension lb of the main housing l. The plan view of this housing portion lb may be seen in Fig. 1. It will be apparent from Figs. 1 and 6 that the drilled hole lie is closed by a plug 26 and communicates with another drilled hole lld which opens through the flange Illa associated with the main inlet conduit l0.

It will be understood from Fig. 2 that the bottom centrifugal pump housing plate 4 is provided with complementary recesses corresponding to the above-described items identified at 23, 24a, 24, 24b in connection with upper plate 3. To eliminate unnecessary duplication of reference numerals, the whole inlet chamber will be referred to as 24a, the annular pumping passage as 24, and the discharge chamber as 2417.

The centrifugal turbine-type impeller is shown in plan view in Fig, 3 and in section in Fig. 2. As will be apparent from Fig. 3, this consists of a disk having an enlarged hub portion 9a with a bore 25 including axial keyways 25a. adapted to engage a key 26a, as illustrated in Fig. 2. It is to be understood that the impeller hub portion 9a does not fit tightly on the shaft extension 70 but forms a sufficiently free fit therewith, and with the keys 25a, that the impeller is free to shift very slightly relative to the shaft so as to properly center itself between the annular land 22- of the upper housing plate 3 and the similar cooperating land 2'! of the lower plate 4. It will be understood by those familiar with the art pertaining to this type of pump that these lands form small clearance spaces with the sides of the impeller web portion 92), as indicated at 22a, 2112, respectively, in Fig. 2. The hydraulic forces resulting from the liquid in these clearance spaces will tend to center the impeller axially on the shaft exten-- sion 1c so that these clearance spaces are equal. These clearances are shown somewhat exaggerated in size in the drawing, being actually on the order of .003 inch in a pump with a 2 inch diameter impeller.

The blades of the impeller 9 are formed simply by cutting axial slots in the rim of the web portion 9b so as to form the radially projecting blades 90. It will also be seen that the hubportion 9a of the impeller is provided with two diametrically opposed pressure balancing holes 28 which com municate liquid from the top side of the impeller to the bottom side thereof so that there will-be no pressure differential tending to move the impeller axially on its shaft. 1 pi To provide lubrication for the gear rotor-shafts 6a, la, the journal bearing bores in thevuppe'r portion of housing I are provided with axially extending grooves shown at 80. 1e, respectively, between which communicates a transverse groove 29. This groove 29 insures that oil will besup -i plied freely to both axial grooves 60, 1e. These a se -roe ai'iial grooves do not extend all the *way through the'h'ousing but are provided with a sma ll land 'or'dam,'shown at'-lie, l-f-at the exterior 'side'of the housing-to prevent excessivelossoflubricating oil from'the grooves.

For lubricating-the shaft extensions b, lb, the intermediate plate 2 is likewise provided with axially -exte'nding grooves 611, ld connected by 'a transverse groove 30. Unlike the first mentioned axial "grooves 60, lo, these do extend all the way downwardly through the thickness "of intermediate plate '2 so as 'to provide adefin ite leakage path from the positive displacement pump into "the annular recess 20, which llea'kage constitutes the supply-of liquid to "the centrifugal turbinetype impeller 9. To facilitate discharge of oil "from agroove -Bd into recess 20, a groove a, d'isposed parallel to groove 30, may be "formed in "the lower surface of plate 2.

Having inow described all the passages constituting the various paths for the liquid through the .pump, the operation will *be seen to be as *follows: Since the positive --'displacement pump '6, 1 is capable of priming itself, 'the in'let conduit 1-0 may communicate with a source of oil which is either above or below "the level of the "pump. Ordinarily, when used in a steam turbine governing-system, the entire pump assembly will be supported within an enclosing sumpor tank-adjacent the turbine "shaft, as disclosed in the above-mentioned application of Stephen Jacobs, Serial No. 22,785. This enclosing tank or sump may :constitute the "liquid reservoir for the hydraulic system, or a separate external-tankm'ay he-provided from which oil is supplied'to the conduit H1. Rotation of the gear-pump impellers 6, 1 (gear 6 rotating counterclockwise-as indicated by the arrow in Fig. *1) draws "liquid from the inlet chamber 5a and delivers it under pressure to the discharge chamber 5b. The main discharge from "the pump is through "the conduit I i which "supplies the bearing lubrication system, hydraulic motor :for positioning 'the turbine inlet valve, and other "devices about the turbine which requireoil'underpressure.

.The sole function :of the centrifugal turbinetype impeller 9 :is togprovide a (liquid signal "pressure hearing :a preselected relation to turbine shaft speed. This pressure is communicated -.to a suitable pressure responsive element (not shown), such as a closed flexible bellows associated with the turbine governor. -As will be appreciated by those tamilia-r with turbine governing systems of this type, the-only .flow required from the centrifugal pressure signal generator is that small amount required to make up for any small leaks which may occur in the pressure sensing device of the turbine governor. For all practical purposes :it may be assumed that there is zero flow from the centrifugal pump element. In other words, the impeller 9 is a static pressure generator, rather than a flow supplier? It will be understood from the above 'clescription of the structure that rotation of the impeller 9 causes liquid to be drawn in from the central recess 20, which is kept full of oil by the abovedescribed leakage through the lubricating grooves 6d, 1d. The dimensions of these oil grooves 6d, 1d, etc., are so selected that the rate of oil supply to the recess 20 is at all times greater than the comparatively small flow discharged from the centrifugal pump through outlet ll. It will be understood that the discharge pressure of the positive displacement pump will insure that there will be a positive flow through the oil grooves 6d,

'ld *lnto the recess 20. Oil from iiile't -:chaniber '20 communicates by way of the inlet groove 23 in the upper plate 3, and the corresponding :groove in the lower plate 4, with the pump inlet chamber 24a, whence the centrifugal action of the impeller blades BC causesithe fluid lto becarrie'd around through the pumping passage 24 to the discharge port -l'la. The pressure thus generated at port I la-causes oil to flow through the related passages ill, 'l 11), =l lc,-fld-'(Fig.'6). The pressure signal from conduit lTd is-eommunicated to the turbine governor by a suitable conduit (not shown).

0fcou-rse, this how will take place principally when the system is started up, and will continue only-unt'il all the passages are full, after which the only flow taken "from the centrifugal rotor will be that required to make up for leakage.

Thus in normal operation the fluid in the discharge passages communicating with the centrifugal rotor is substantially stagnant, which means 'lth'at hydraulic friction and other energy losses in the centrifugal pump passages generate .asubstantial amount of heat, which must be dissipated in order to prevent excessive changes in LVQllfiS always .kept rumor liquid,twith the further result that the istatic head of the liquid at the inlet 121411110 thepumping passage .25 is maintained exactly constant. This is important if the discharge pressure generated by the-centrifugal rotor is :to be :a "truefunction of turbine shaft speed. It will be "apparent that with this arrangement any variationsin discharge pressure of the positivezdisplacementpum'p 6, J have-no "effect on the discharge pressure "of the centrifugal elem'en't, since variations in positive displacement pump pressure :merely change the rate at which excess .oil overflows from the :reservoir .12.

The above-described"circulation10f excess oil past the impeller hubfportionfiaiand out through the standpipe servesto cool the impeller-rand thus limitthe'temperatureirise produced .by the churning of the :oil .in the centrifugalpump.

:Still another function of the :reservoir 12 "and standpipe 16;, :etc., lies .in the :fact that when the machine stops, the reservoir "will keep the posi- .tive displacement and centrifugal pump chambers and related passages filled with oil so that, when :operation begins again, the centrifugal pump will be-completelyfiooded and thus is selfpriming. his is an important feature, since the rate of flow through the centrifugal :pump element is so small that without this self-primmg feature the pump may not be able to clear itself of air when starting, with the result that discharge pressure would not accurately represent pump speed.

Thus it will be seen that the invention provides a simple and extremely compact composite pump, the positive displacement portion of which may be made of any desired capacity to supply the lubricating and governing all requirements of a turbine, while the pressure signal required for the governing system is supplied by a comparatively small centrifugal impeller, the pressure sigbe made, As suggested, the positive displacement pump may be made of greater capacity simply by making the, gear impellers 6 I of greater axial length, without changing the construction or characteristics of the centrifugal pressure generating element. Likewise centrifugal rotors of slightly different construction may be employed, for instance those shown in my above-mentioned application Serial No. 129,490 or the application of Stephen Jacobs, Serial No. 22,785. Also, other types of positive displacement pump may be employed. It will also be obvious that the arrangement of the casing elements and the passages therein may be greatly modified, as long as they perform the same functions in substantially the manner described above. For instance, the grooves (id, id may be omitted and the normal leakage from the bearings relied upon to supply the centrifugal rotor. It is, of course, intended to cover by the appended claims all such modifications and changes as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a composite positive displacement-centrifugal pump, the combination of a positive displacement pump having at least one driven rotor member, first housing walls enclosing the rotor and defining inlet and discharge chambers associated with the rotor and journal means supporting the rotor, second centrifugal pump housing walls immediately adjacent the positive displacement pump and defining a central circular recess surrounded by an annular turbine-type pumping passage extending less than 360 degrees circumferentially, a turbine-type centrifugal pump rotor with a central hub portion disposed in said recess and a bladed rim portion projecting into said annular pumping passage, the positive displacement pump rotor having a shaft extension supporting and driving the centrifugal rotor, said first and second housing walls defining-passages adapted to supply liquid under pressure from the positive displacement pump.

sphere and having a passage connecting the lowermost portion thereof with the inlet end of the annular pumping passage, whereby when the rate of discharge from the centrifugal pump rotor is less than the rate of supply of liquid from the positive displacement pump to the centrifugal pump, the excess liquid fills the reservoir and overflows so as to maintain a constant static head at the inlet end of the centrifugal pumping passage and the circulation of excess liquid past the centrifugal rotor effects cooling thereof.

2. In a composite pump, the combination of a positive displacement pump having at least one driven rotor member, first housing walls enclosing the rotor and defining inlet and discharge chambers associated with the rotor and journal means supporting the rotor, second housing walls adjacent said first wallsand defining a central circular recess surrounded by an annular turbine-type pumping passage extending less than 360 around the central recess, a turbine-type centrifugal pump rotor with a central hub portion'disposed in said recess and a bladed rim portion projecting into the annular pumping passage, the positive displacement pump rotor having a shaft extension supporting and driving the centrifugal rotor, said first and second housing walls defining passages for supplying liquid under pressure from the positive displacement pump to the central recess in the centrifugal pump, said second housing walls defining an inlet passage communicating between the central recess and the inlet end of the annular pumping passage, said seoond housing walls defining also a discharge, port at the end of the annular pumping passage remote from said inlet the first housin walls forming a reservoir above the level of the centrifugal pump and open to the atmosphere, said first and second housing walls having passages cooperating to define a standpipe com,- municating between said reservoir and the inlet end of the annular pumping passage, whereby excess liquid supplied from the positive displacement pump to the centrifugal pump fills the reservoir and overflows so as to maintain a constant static head at the inlet endof the annular centrifugal pumping passage while the circulation of excess liquid past the centrifugal rotor effects cooling thereof. HERBERT N. HOFFMAN.

REFERENCES CITED The following references are of record in the file of this patent:

Great Britain 1921