US1617133A - Centrifugal pump and compressor - Google Patents

Description

' 1,617,133 Feb. 8,1927. SA. Moss ET AL "CENTRIFUGAL PUMP AND COMPRESSOR Filed May 23. 1925 2' Sheets-Sheet 1 Fig.1..

f O O t O O o o S Inventor: Sanford A. M 0 55,

Manuel (5. Robinson,

Their Attovneg.

r 1,617,133 Feb. 8, S. A. M ET AL CENTRIF'UGAL PUMP AND COMPRESSOR Filed May 25, .1925 2 Sheets-Sheet 2 Inventor:

Scinford A. Moss,

Manuel GRobinsoTw,

by Their" Attorneg.

; Patented" 8 ,219,21-

v UNITED r 'ST-ATE-S PATENT ,oFFicE,

-SANIBD A... moss nn MANUEL G. ROBINSON, or LYNN, MASSACHUSETTS, As- .sIGNoRs To GENERAL ELECTRIC COMPANY, A conrona'rron on NEW YORK.

.CE'NTBIFUGAL BUM? AND oomrnnsson.

Application filed May 23, 1925. Serial No. 32,490.

The present invention. relates to. centrif- ,ugal'pumps and compressors of the type comprising an impeller which receives the fluid to be pumped at its central portionand I discharges it at its periphery, and wherein 1913, in a centrifugal compressor for a-com-' lfl pressible fluid, such Ymeansjicomprises a passage which is firstfconvergent I and then" d1- f z'iverg fo ihei e. 0f empamt y ,h

/ 2,0,iinpe1le1: speed and .pressure' I ratio, for a @Lpassagewhich iswholly divergent formore a mal cases.

H Theobject ofcour. invent on 1s to provide ,animprovedmeans, orconstructionan'd are jrangement, for providing the passage in the iforegoing instances, forvconverting, velocity v into pressure, a, high degree-1 of efliciency, and at jtlre sam'e timefmaintaining a construction which is. simple in structure and capable ofybe'ing manufactured I at a .low fjcost, and ,foraiconjsideration of whatiwe be- [lieve to be noveland our-invention, atten .ti0n is directedjto the accompanying, description; and the;claims appendedthereto.

{of a vccntr A I sl cing I a cent fugal compressor) "embodying our invention;illustrating it in its preferred 1 5- form and that 'which it .usiiall-y assumcs in X tratef modifications.

the angle between the direction of a; stream InQthe draw ng; Fig. is j a sectional view gal gjmachine' f( here' '.sh'own as.

ac ual ,prac.tice,-'andj Eigs g, a and fl'illusjlates are, 'broughtltogether 5259, a1id' preferably of the the outer circumference of the j a plates and iw lf maintainfthis constant angle, forming calledffa ,free I vortex. '"By, tl-ie'fiangle" of the fluid inl-s'u'ch a case is meant i line at any point and the ,tangent toa circumference passing through that oint.

In this connection, it ispointe out that since the plates extend radially outward and the angle of the fluid remains constant, there 7 results an area of discharge for the fluid which increases. continuously from the radially inner edge of the passage to its radially outer edge. In. other words, there results a divergent dischargevpassage which functions to convert velocity into pressure.

The area of flow, atany circumference is given by the formula:

Area=21rrWsii1 a where 2=radius of. any circumference. w distance between the plates.

a=the angle of the fluid.

,From this formula it will be clear that if the angle 'a remains constantfthe area increases withth'e 'iadius. I Now, although this property of the formation of a free. vortex has beenknown, so far as we are aware li'ttle practical use of it in centrifugalpumps and compressorshas ever' been made this being due, we now believe, to the fact that because; of the naturally low angle of the'fluid,-thel path of travel of the fluid in "the vortexwasso long "that the friction losses ma'de thefconversion of velocity into pressure exceedingly ineflicient.

,As -acresult, it has'been thefpractice, in con.

structing suchlcentrifugal machines, to 'pro vid'e Idischarge vanes with a divergent pas sage; for directing the flow ofth e fluid'radially outward, the velocity of ,the ifi uid being at the same time converted into pressure;

In connectionflwithl a diffuser i-n'lthe ivyform "of two spaced annular plates, we have found that, other things being 1 equal, the, jclose'rjhc y ,7 -plates are broughfltogethenflthejh'ighei"the -Whenanjii1peller is: running,l.the fluid being handled xis;discharged from itsperi' hr]; rjy atla constant angle,"anditliskriownlt at. if; thelclischarge ;jt akesliplace' {into fa .difl'use'r formed-:- of' two-Icircular, parallehplate's', the

angle of the flfuid'lwill be, andhat thatfthe -angle of the fluid ei' results normaljfload on thes compres a .cdnstructlonrwhrein the path oftravel of the fluid becomes short enough tomake prac tical the use of afdilfuser'comprising'spaced annular plates ieven Ithou ghfthe radial jde th inorder to providefor the i'diifnsion necessary to effect conversion of the velocity into pressure. p

In other words, we have discovered that if the plates defining the diffusers are brought close enough together to effect an initial directioning of the fluid discharged from-the impeller at an angle of the fluid greater than 25, and then are made of a radial depth to provide a final discharge area sufliciently great to effect the required conversion of velocity into pressure, that efficient operation of the machine is obtained. The correct relative positioning of the plates to give the desired angle of the fluid can be determined experimentally by positioning the plates, and then measuring the angle of flow by inserting a freely moving vane in the stream and reading the angle which it assumes. Or, it may be determined by calculation from the quantity of flow, speed of'the machine, and its dimensions. The required 7 radial depth for the plates forming the diffuser can be determined also by experiment and measurements.

In connectionwith the foregoing, it is pointedout that the angle of the fluid varies with the quantity of the fluid delivered by the impeller which means that, in any construction embodying our invention, if the,

quantity of the fluid being handled increases. the angle of the fluid increases, and that if such quantity decreases the angle decreases. In carrying out our invention we provide an arrangement such that for the loads which the machine will be required to carry ordinarily under normal operating conditions,

the angle of the fluid will not fall below 25 for the least value of such load. Preferably We construct the machine so that at normal rated load the angle of the fluid will be of the order of 35, which means that at normal load the highest efficiency will-be obtained. Under thesecircumstances, the angle of'the fluid will remain greater than 25, and so give eiiicient operation of the machine at loags of the order of one-half normal rated loa I i If the tip of the impeller is sufliciently narrow in width, the plates of the diffuser may be'par'allel throughout their length, but ordinarily such a condition is not met with,

so that in carrying out our invention we provide plates which approach each other and then are parallel, or substantially parallel, the ap roaching portion being such that the desire high angle of the fluid is obtained. However, the arrangement is always such 1 that the discharge area is always increasing so as to at all times form a divergent passage, unless conditions are such as to require a preliminary converging portion to effect the conversion of velocity into ressure.

Where the plates are paralie and close enough together to give the desired angle of flow, the result may obtain that, in order to provide the necessary discharge'at the periphery of the diffuser, it assumes .a circumference too large for practical purposes, and to avoid this, the parallel portion may be followed by, a final portion wherein the plates recede from each other. In the preferred and usual form of our invention, therefore, we have a diffuser structure where in the plates first approach each other, then are parallel, and finally recede from each other. This providesa passage of a length such as to give small friction losses and at the same time provide the desired final discharge area without undue outer diameter of the diffuser.

Referring to the drawing, 1 indicates the casing of a centrifugal compressor attached to which are bearings 2 in which a shaft 3 is mounted. On shaft 3 is an impeller which receives fluid at its central portion through the inlets 5 and discharge it at its periphery to a discharge ring 6 from whence the fluid passes to a discharge scroll 7. The compressor illustrated is shown only by Way of example and is not described in "detail, since its specific structure forms no part of our present invention, our invention relating particularly to the discharge ring 6.

Referring now particularly to the discharge ring, it is shown as comprising walls formed in continuation of the side walls 8 for the impeller, and as comprising a section 9 wherein the walls approach each other, then a section 10 wherein the walls are parallel or substantially parallel, and finally a section 11 wherein the walls recede from each other.

In constructing the section 9 it is desirable to make the slope of the walls quite steep so as torapidlyincrease-the angle of the fluid, which may be termed the vortex angle. Ordinarily, however, the should not be so steep that the walls approach each other with a rapidit such that the decrease in width reduces t e efi'ective discharge area faster than the increase in diameter increases it. If such were the case, there would result a converging passa e which under operating conditions usualTy met with would effect aconversion of pres sure into velocity which would have to be reconverted into pressure whereby a double energy conversion would take place. However, if the conditions are such as to require a preliminary converging portion for conversion of velocity into pressure, then a slope so steep as to give this preliminary converging passage is necessarily used. The sloping walls are extended radially to a point where they come close enough together to give the desired vortex angle or angle of the fluid, (i. e., an angle of the fluid of at least 25.) and then they merge into the parallel or substantially parallel walls which form the section 10; The angle ofthe fluid is slope than 25.

.to-its radially outer edge, as already explained. This results in a divergent'passage, and the fluid in flowing through this divergent passage has its velocity converted into pressure, as is well understood.- Theparallel portion of the plates of the diffuser may be made of a radial depth to give a final efiective area such as to eflect the desired conversion of velocity into pressure. However, in actual practice, this may result in" a structure of-tdo" great diameter, and to avoid this we preferably construct the final portion of the diffuser with diverging walls so as to provide the section 11 wherein the conversion of velocity into pressure takes place at a more rapid rate. Of course, the angle of the fluid or vortex angle is less in this section, but as such section is of small radial depth, the increase in friction loss over what it would otherwise be is not great.

. In 'Fig. 2 is illustrated a form of the invention wherein the tip of the impeller 12 is narrow and wherein the two plates 13 which form the diffuser are parallel throughout their radial depth, and are so close to-. gether that the angle of the fluid is eater This forms-an eflicient diffuser,

but as already stated, leads ordinarily to a-' constructionwherein the difi'user is of considerable radial depth.

Fig. 3 showsa modification of the Fig. 2 arrangement wherein the radial-depth of the diffuser is shortened by providing at its periph'ery a section 14 wherein the walls recede from each other. In this figure, 15 is the impeller'and 16 the difl'user.

Fig. 4 illustrates an arrangement similar to Fig. 1, except that the receding walls at.

of the diffuser are omitted the periphery and the requlred discharge area is obtained by increasing further the diameter of the diffuser. In this figure. 17 is the impeller and 18 the diffuser, and as will 'be noted, the diffuser comprises, first a portion 19 wherein the walls approach each other, and

A then a portion 20 wherein the are parallel.

\Vhat we claim as new an desire to'seci're by Letters Patent of the United States,

l. A centrifugal machine having a dif tuser comprising two spaced walls between which the fluid flows radially outward, said walls being so close together that the angle.

of the fluid at normal load is greater than 25 throughout the major portion of its:-

travel.

p 2.'A' centrifugal machine having a dif fuser comprising two spaced walls between tween which the fluid flows outward, said walls being so shaped that the first approach each other, then extend su stantially parallel to each other, and then recede from each other.

3. A centrifugal. machine having a dif- 25, and then extending substantially paral- .lel to maintain such angle of the fluid.

4. A centrifugal machine having adif- "fuser'comprising two spaced walls whichprovide a discharge. passage of continuously increasing effective area, said walls first approaching each other to an extent such as to provide at normal load an angle of the fluid greater than 25, and then extending substantialy parallel to maintain such angle of the fluid. f

5. A centrifugal machine having a diffuser comprisin two spaced wallsbetween which the fluid ows radially-outward, said walls being so close together that the an le of the fluid at normal load on the machine is of the order of.35 throughout the major portion of its travel.

--6.. A centrifugal machine having a diffuser comprising two spaced walls between which the-fluid flows radially outward, said walls bein' so close together that the angle oftheflui at normal load is greater than 25 throu bout the major portion of its travel, an the peripheral ortion of said walls receding. from each 0t er.

7. A centrifugal machine having a diffuser comprising two spaced walls which provide a discharge passage which continu ously converts velocity into pressure, said walls first approaching each other to an extent such as to provide an angle of the fluld at normal load greater than 25, then extending substantially parallel to maintain such angle of the fluid, and. finally receding from each. other.

8. A centrifugal machine havin a dif fuser'comprising two spaced walls tween which the fluid flows outward, said walls first extending substantially parallel to. each other and then receding from each other at their peripheral portions. O

9. A centrifugal machine having a difprovide a dischar e passage which continuously converts v e oclty into pressure, said walls approaching each other to an extent such asto provide'at normal load anangle of the fluid of the order of 35 and then extending substantially parallel to maintain such angle of the fluid throughout the major portion of its travel. 1

10. A centrifugal machine having a dif? Z-fuse'r comprising two spaced walls which I fuser comprising two spaced walls which provide a discharge passage which continuously converts velocity: into pressure, said walls first approaching each other to an extent such as to provide at normal load an angle of the fluid of the order of 35, then extending substantially parallel to, each other to maintain such angle of the fluid, and finally at their eripheral portions'receding from each ot er. 7 T 4 In witness whereof, we have hereunto set our hands; this 21st day of May 1925.

SANFORD A. MOSS. MANUEL G. ROBINSON.

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