US839273A - Centrifugal fan or pump and casing therefor. - Google Patents

Description

'NQ- 839,273. I I PATENTED DEC. 25, 1906. s. 0. DAVIDSON. H 'GBNTRIPUGAL PAN 0R PUMP AND CASING THEREFOR.

" APPLICATION FILED JULY 1, 1905.

4. SHEETS-SHEET 1w N5.- 839,273. PATENTBD DEC. 25; 1906.

s. 0. DAVIDSON, CENTRIFUGAL FAN 0R PUMP AND CASING THEREFOR.

APPLIQA TIO N FILED JULYl, 1905.

{SHEETS-SHEET 2.

No. 839,273. PATENT ED DEC. 25, 1906.

S. O. DAVIDSON.

' GEN'TVRIPUGAL FAN 0R PUMP AND CASING THEREFORL APPLICATION FILED JULYI, 1905.

W 4 sums-sum a.

- l 'mmm No; 839,273. V PATBNTEDDEG. 25, 1906. s. 0. DAVIDSON.

GENTRIFUGAL PANOR PUMP AND CASING THEREFOR.

APPLICATION FILED-JULY 1. 1905. H

' 4 8HEI lTS-SKBET 4;

I INVENTOR WITNESSES! By fl #0771 3 operated upon, whether gaseous, like air, or- :5v

UNITED STATES PATENT OFFICE;

SAMUEL OLjELAN-D DAVIDSON, ,oE BELFAST, IRELAND;

GENTRIFUGAL FAN "on PUMP .AND'CATSYING HEREFOR. In

Ho, seaevsg Specification of Letters Patent.

Patented pa. 25,1906.

7 Application filed July 1,1965. SierialNo. 267,989.

To call whom, itma y concern: i Be 1t known that I, SAMUEL 'CLE ND DAVIDSON, merchant, of Sirocco Engineering Works, Belfast, Ireland, have invented cer taln new-andjuseful Improvements in or Re lating to Centrifugal Fans or Pumps and Gasings Therefor, ofwhich the followin'g isa specification. I

This invention relates to centrifugal fans or pumps, (hereinafter referred to as fans,

and more particularly to the inclosing casing therefor, (hereinafter referredtoas casing, 'WllGTGWlllh fluid of any description may be lirpuid, like water, (which fluid is hereinafter re erred to as air. s Some objects, among others, of my hereindescribed invention are to; further improve the mechanical 'efiiciency of said fans, more especially when operating with back p'res-' sure'ag'a st the discharge orsuctionalresisting through the fan from approximately nil up to the full volumetric capacity for which .3 v

ance' against the inflow of the fluid-tothe fan, and also to obtain. when said fan is re- 'volving at a cfonsta'nt speed of revolution a constant indication ofpressu're or suction, as the case maybe, irrespective of any variation which may occur in t evolume of fluid passit is designed. I

In fans as speed and when discharging into (for example) a pressure chamber or reservoir and ifthe outlet therefrom be entirely closed a much higherlpressure will be indicated than ifthej outlet be sufficiently opened toallow of the dischar e of the full'volumetric' capacity of the fan, ut with fans constructed in accordance with my hereinafter described improvements, and assuming the speed toremain constant, the pressure in the chamber will also remain substantially constant, whether the outlet from said pressure-chains. 45

' .of dealing wit ity and importance inconnection with cenher be entirely closed or o ened to the full volumetric capacitfiy-that t e fan isflcapable or numerous reasons this remarkable'feature is of much practical 11til-- trifug'al fans or umps, and the invention is particularly use 1 in combination with a'fan aving a laterally confined cylindrical cran nular zone-space within the inneredges of' the blades, as described in my prior applicathrou hitherto ordinarily constructed and when-same arerotated at'a' constant tions patent, Serial Nos. 204,922 and 209,351, wherein the fan-wheel is mounted by when-operating against a pressure or suceccentrically ina snail-shaped'casing, wheretion there is established a-currentcf fluid v moving inwardly from the further portion (in the'direction of rotation of the fan-wheel) of the space in front of the discharge-openin articillyacross and around the intake-cham-' er of said fan-wheel, that portion of said intake-chamber traversed by said current being practically unobstructed. and having means for op osing the axial flowv of fluid on the intake si e thereof, i v v Figure 1 is a diagrammatic'view illustrating a mrilti-bladed drum type of fan when in- I closed in a snail shaped casing such as is described in a prior patent granted to me, N0.

h the ports between the blades an 662,395. Fig'. 2 is a similar view showing the. same type of fan-wheeland illustrating one form 0 the casing which is provided by my invention, the parts being constructed to form a cylindrical zone-space within the fan,-

with means for opposing the outflow of the fiuidaxially'through the intake end of the fan.

the construction of the-eye. I

@Fig. 1 is intended to illustrate diagram matically the hitherto ordinary construction of casing wherein there is a gradual widenin of the space which exists betweenthesp1ra for snail-shaped contour of same and-the fan wheel'W, beginning. from the top of the dis charge-opening and continuinground the fan-wheel in its direction of rotation-"and back tothe front of said fdischarg-oprimg, and the arrows in this figure indicate approximately the flow -ofv the air-currents within the casing whenthe fan isoperating bythe'letters C C.v 4

. against back pressure or suctional resistance,

the currents within the fan being; indicated i lt will be observed mailing. ,1 the .point' ofclosest proximity of the fan-casing to: the peripheryof the fan-wheel W at E :(heremafter. called the f cut-off is practically at the; point of junction of the circumference ofizthe, 'casin withthez-top of the discharge-o emng A an that from said poin't'E around t e fanwheel (inthe direction of,r otation) 'th e space ment at F in front at A.

I of dischargefrom line marked A A gradually widens out to maximum measureof the discharge-opening To render my description more clear, I have shown in each of the three diagrams 'a which is intended to represent what would be approximately the axis the casing if the outflow of fluid were unobstructed in any way, and parallel tothis line I have shown the line D D,

I drawn parallelto A A through the center of,

' t 'e-fan-wh'eel W, and in addition the line B "'B-"fwhieh' is at right angles to At A and D D periphery of the fancuts same, and it point of closest to the fan-wheel g; I IS substantiallyat the top of the disfrom the cutoff wheel'hnd the "circumference of the casin Y gradually widens out via G. and K to F. The

,1 space marked G, "Dl'Di and the cut-off at E; "will be seen to -2 5 have a wedge likeform with the point of the which lies between the line Iwedge atthe cut-off E and itsbroadest part and therefore farther away from the discharge' Aaround the fan in' the "dirctiorifof'rbtationthan the cut-off at E.

If the fan wheel W in'Fig. 1 be rotated ,the

Tbla'des impel a continuous flow of air into the s 'ace'in front of "the discharge-opening at A, t e force' and velocity of which is strongest on j "the loweror outer side of the line A A from .the fan-wheel I If then 'this current cannot, owing to existing back pressureor resistance, force its'way out through the discharge-opens .ing, it swirls or is deflected upward at A toward the to of the discharge and'then takes a'centripeta jdirection at'the cut-off E, where it passes into the interior'of the fan-wheel W through-the ports between the fan-blades. It be observed} however, that the cur rent atthis-point, as indicated by the arrows,

is very crowded and that its further progress circumferentially is thereby subject to a pronounced check and shock,whereby there 00- curs a loss ,of some ofthe initial velocity at "when a w (in loss of 'power w hiclisame represents. This 1 t'ial velocity will however,- 'bezreacquired on the 'flu'id again passing outward through thefan wheel blades;'but the greater the loss o yelocity due to said'shock the greater will be the power absorbed by the'fan-wheel to rei npart the veloeitylost,

Further, however, with this construction of easing the said regurgitated" fiuidafter again passing out throughthe blades is subject to an eddying action, which I have indicated by arrows pointing in the opposite direction to the genoral flow of. the current, close to the circumference of the casing at J J, which also involves some loss of power. It is thus evi- I being too free, the-result sage of the regurgitated air I I yen; towardthe'dischargeo'penin at'A, an'd consequently the equivalent wheel through rent can pass toward theimterior-thereof' or projectinghthe; current dent that in order to maintain full velocity in the circumferential flow of the air around the fan that this back eddy at J J should be eliminated, and have found that when the circumference of'the casing is concentric with that of the fan-wheel, which consequently means the non-existence therci'nof any cutoff, there-is no regurgitation of the current to the interior of the fan-wheel, and at the same time the back eddies at J J are swe t away by the free circumferential flow of tlie fluid, and-thus disappear; but, on the other hand, a worse-condition develops, owing to the circumferential flow of the an around the casing of which is that with same speed of revolution as whenka spiral casing with cut-off is used the pressure 'then falls, and it becomes necessary m; order to'reinstate the required pressure to materially increase the revolutions of the fan-whee which, however, involves the employment of more power thanis saved by the elimination of the back eddy J J, so that such free circumferentia'l flow of the air. between the-circumferences of the fan-wheel andcasingis disadvantageous. Consequently, in order to produce suitable compression in'front ofthe discharge-opening it is necessar to check-or retard the free circumferentia flow of the air near to the farther side of-the discharge,

'(in'the direction of rotation,')'"wherea-cut-off efiect must be provide'dfor, and I- also find that'the position of said cut-off relative to the discharge-opening and its fonnare importantin effecting said compression with a minimum of detrimental shock and loss of power therefrom and, further, that the pasback to the interior of the fan-wheel should be arranged for in such manner as to avoid a sudden or too great deflection from the line of its concen trio and circumferential path and-"that a wheel should be available for the passage of the regurgitated air through it than indicated in Fig. 1.

According to my im roved construction I emplo with a casing o spiral contour animprove arrangement of cut-off in conjunction with a space leading to-it from the dischar eopening, the shape of which space and its 0- I cation allow the surplusair from the space in front of the discharge 'opening to'be'deflected to the interior of the fan wheel' more gradually and through a lar' erarea of the circumference'df the fan-whe I by the initial fveloeity at which it 'is dr ven into the-space infrontbf the disr aha i-ge -openconstruction exposes a l'argerarea of t e. fanwhich' the re rgitated' "cur,-

without crowdin too far toward t e center of e wheel; as

shown :1; Fig. 1,'and the detrimental eliects :thanhitherto, wherelargerportion of the circumference of the fani i of sudden shock are thereby reduced to the lowest practical minimum, and the effective work (performed is accomplished with im-. prove mechanical efficiency f r; a given ex penditurr of power. v

Figs, 2 and 3 illustrate my improved con struction, and while both represent the same -is"at'E, which is fart .operative principles Fig. 3 illustrates the d velo ment' of same toa further degreethan ig. '2, the location of cut-off or closest proximity of the circumference of the casing to the eripherv of the fan-wheel W being'at E" on t 'e-llne D in Fig. 2, whereas. in -13,3 4.?) it er around thewheel in the direction of rotation. Then. also the clearance-space be ween the casing and the fan-wheeliperiphery is not so large as in Fig. 3; butthe principle involved in both figures is the sameviz., that a wed e-shap'ed or tapering space M isprovided etween the periphery of thefan-wheel and the circumi erence of the casing,'the characteristicfea tures of which are that the -ei1d;; of sar'n'e which adjoins the discharge-openin :fori ls the wide or base end thereof and'that t e apex or narrowi'end thereof is at the cut-off, which is substantially beyond the discharge-opening in the directior f ter of the fanswheel circumference which after rotation and in that quarpasang. the discharge-openin lies 7 a p)roxi matelybetween the tworadia lines 1 and II K,"Whl(3h are at rightanglesto one another.

It will'be apparent from a furthercompari-.

' son of Figs-L land 3 with Fig. 1 that the fact of the ,regurgitated current ntering' the in-.; take-chamber of the fan-w eel within the circular path of the blades with a less de-' fieicted and freer flow than in Fig. 1, and its.

' initial velocitybeing thereby more-fullyre- I ment from the .5

tained, an equivalentpentrifugal force out.-' ward will be set up, tending to press this" current through the bladesto the exclusion of- .any fresh air. entering until reaching where. the teasing is sufficiently. far away from the outer circumference of the fan-- wheel to contain the full volume of the re-' gurgitated, current, and it consequently absorbs. theleas't ossible reinfo. c ng requireh des to bring it up to the original initial velocit at -which it was driven intothe space in ront of the dischargeopening,.and a considerable saving in power is thus effected. i

Itis to beunderstood that my present inof-fan'wheel herein referred to, such 'mere y being taken as a particularly efficient com- 7 bination convenient for illustration, and that the dimensions and shape of the tapering or wedge like spa'ce marked atin Fi 2 and E3 and also the position occupied by t at part -=of the casing which-isin closest proximit tothe periphelriywof the fan-wheel marked in 'F" 2 and in maybe'varied, while 's retaining the hereinbefore -.de s'cr ibed I What charge-opening to said cut-off is pro res- 'sively decreasing like a wedge having i ts l vention-isnotlimited to the particular 'ty 0' characteristic features, even though such variations may mo'difytheoperative effects of same.

of the casing which is referred'to as the cutoff ma extendfor a suitable distance par- In the improved construction that point allel wit the fan-wheel, or nearly so, and is not necessarily limited to a point or veryshort'portion of the oirculnferencelof the casdn Figs. 2, 3, and 4. I haveshown the fan as constructed with means for o )posinithe out flow of fluid-axially throu h t 'e'inta eend of the fan. The [means s own comprises a plate Z Z',fixe1d'; to the casing N i Fig. 4,.and,

aving aneye or opening through which the sult may be-substituted therefor. j 1

tion have obtainedthe following resultsconstant the pressure or'suction'set'upby the fans in a reservoir attached to e ther. the

let from or inlet to said reservoirJbe completely closed or o ened out to a sufficient fluid enters the Yan'whichis smaller than the intakeopeningof the fan. o ther .con-;-.; 1 struction effecting substantially-the same re- I, In Y tactical operation of the above-invenjw viz.', that provided the number of-revolutions per minute of the fan-wheel employed be discharge or the inlet opening will als'o'remain substantially constant whether the outextent to permit 0 the discharge (or inflow, I as the case may be) ofthe full volume of fluid that the fan can efficiently deal with, and at 7 same time. these duties are performed with .aqelnarkably hi'lgh ratio of mechanical effici'ency.

ters Patent,is- 1. Acentrifugal circumference of the casing to the circumfer ence ofithe fan-wheel is situate sufficiently I claim, and desireato secure by Let fan or pump comprisin a fan-wheels. shad-shaped casingwherein t e position of cut-off or closest proximity of the farther round the-fan-wheel in the direction i of rotation than the discharge-opening, to provide an intervening space between the an wheel and casing which from said disthereof, that portion of said intake chamber traversed by said current .being practically unobstructed, andsaid fan orpump having means for opposing the outflow of fluid axially through the intake end, the position of cut-off between the fan-wheel and the inclosing casing being situate sufficientlyfarther round the fan-wheel in the direction of rotation than the discharge-opening to provide structed, an'd said'fan or pump having means. for opposing the outflow of fluid axially vide an intervenin tELbllShBd a currentof fluid moving inwardly from the space between the circumferences of the fan-wheel and casing'and in front of the discharge-opening through the ports between the blades of said fan-wheel and partially across and around the intake-chamber thereof, that portion of said intake-chamber traversed by said current being practically unobthroug the intake end, said means comprising a plate having an eye which is smaller than the intake-opening of said chamber the position of cut-off between the fan-wheel and the inclosing casing being situate sufficiently farther round the fan-wheel in. the direction of rotation than the discharge-opening to pros ace between the fanwheel and casing w 'c 1- from said dischargeopening to said cut-off is progressively de-' creasing like a Wedge having its base or broad end toward and leading from said dischargeopening and its point or narrow end toward said cut-ofl.

4. A centrifugal fan or pump, comprising a snail-shaped casing and a fan-wheel mounted eccentrlcally therein whereby when operfrom the s ace between the circumferences of 7 ating against a pressure or suctlon'there is establlshed a current of fluid moving inwardly the faneel and casing and in front of the discharge-opening through the ports between the blades of said fanwheel and partially across and around the intake-chamber thereof, that portion of said intake-chamber traversed by said current being practically unobstructed; and'said fan or pump having means for opposing the outflow of fluid axialliy throug the intake end, said means comprising a plate fixed or forming part of said casing and having an eye concentric to the axis of said fan-wheel and smaller than the intake-opening of said intake-chamber the position of cut-off between the fan-wheel and the inclosing casi being situate sufiiciently farther round the an-wheel in the direction of rotation than the discharge-opening to provide an intervening space between the fan-wheel and casing, which from said discharge-opening to said cut-off is progressively decreasing like a wedge having its base or broad end toward and leading from said discharge-opening and its point or narrower end toward said cut-ofi.

5. A centrifu al fan or pump comprising a fan-wheel a small-shaped casing wherein the position of cut-off or closest proximity of the circumference of the casing to the circumference of the fan-wheel is situate at a farther round the fan-wheel in the lrection of rotation than the discharge-opening and within that quarter of the fan-wheel circumference which lies next beyond the dischargeopening between a line drawn through the fan-wheel axis and parallelto the axis of the discharge-opening and a line drawn perpendicular thereto through said fan-wheel axis, and the fan-wheel being located so as to provide an intervening s ace between the fanwheel and casing whic from said dischar eopening to said cut-oif is progressively ecreasing like a wedge having its broad end or base toward and leading from said dischargeopening and its narrow end or point toward said cut-off.

' In witness whereof I have hereunto si ned my name in the presence of two subscri ing witnesses.

SAMUEL OLELAND DAVIDSON.

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