US820397A - Centrifugal fan or pump. - Google Patents

Description

in. 320,397. PATBNTED MAY 15, 1906. s. c. mvnssom.

GENTRIPHGAL FAN 0R P'HMP. Ammonium; mum 86124.1904.

6 SHEETS-SHEET 1,

INVENTOR:

WITNESSES 5 PATENTED MAY '15, 1986.

3. G. DAVIDSQN UBNTRIFUGAL PM? GR PUMP.

APPLIGATION FILES 901224. 1984.

QSHEETS-SHEET 2 Win/5 95s.-

R0. 820,397. PATENTED MAY 15, 1906.

S. C. DAVIDSGN.

CENTRIFUGAL FAN UR PUMP.

APPLIGATIOK PELED 03124, 1904.

5 SHEBTS-SHBET 3 v lNl/ENTOR: WITNESSES: I

PATENTED MAY 15, 1906.

. S. 0. DAVIDSON. OBNTRIPUGAL PAN 0R PUMP.

APPLIGATIGH IILEi) 86124, 1904.

5 SHEETS-SHEET 4,

w/mle's $5.9 11v VENTOR No. 820,397. 1 PATENTED MAY 15, 1906. S. G. DAVIDSON.

CENTRIPUGAL FAN 0R PUMP.

APPLICATION IlLgD 001224, 1904.

5 SHBBT$$EBET 5 Ffa' UNITED stares PATENT OFFICE.

SAMUEL oLsLAisn nilvinson, or BELFAST, IRELAND.

CENTRIFUGAL FAN OR PUMP.

Patented m 15, ices.

Application filed October 24, 1904. Serial No. 229,875.

To (tli whom, 131: may concern:

Be it known that I, SAMUEL CLnLAND DA- VwsoN, a subject of the King of Great Britain and Ireland, residing in Belfast, Ireland, have invented certain new and useful Improvements in Centrifugal Fans or Pumps, of which the following is a specification.

This invention aims to improve the efficiency of rotary fans or pumps in which the fluid operated on enters the center of same axially and is discharged circumferentially against a material degree of back pressure or suction resistance. V v

Specifically, my invention relates more es pecially to the multibladed drum form; of centrifugal fan set forth in my Patent o. 662,395, ranted November 27, 1900. This fan has a high volumetric efficiency when th fluid operated on is under little or no bac pressure or suction resistance; but its elliciency diminishes as the back pressure or resistance increases until a point is reached at which the type of fan shown in said patent possesses little advantage over other types of centrifugal fans which are designed for operating under. or against a considerable pressure.

I The .Wor blade shown, for examp In this specification the word Tan is un-' derstood as including a pump. The word axially means 'n a direction coincident with orarallel 'th the axis of rotation. l is used to indicate the art motion to the vanes or wings-w ich irn fluid. The expression 1ntake-chamber is chamber or s ace 1nd illustrating the operation of a fan constructed employed to indicate a closed within the seriesof blades. '1 e wor eye is used to designate the inlet-opening in the c sing or stationary member of the fan, thr ugh which opening the fluid enters the inta e-chamber. of the blades or ports is understood that end which is nearest the e e. The depth of the blades is their wi th'measured radially from the inner to the outer edge, the .length of the blades istheir axial measurement, and the ports are the intervening spaces between the blades.

The fan-wheel is the rotary member or runner as distinguished from the stationary casing.

centrifugal fan-whel of drum form such as that set V le,in Figures 1 and 2 or Flg. where the fan-wheel is inclosed m iii-thereof,

of spiral or snarl-shaped onethe usual form will be better understood By the intake end be seen that 'from a forth in my aforesaid patcnt as' in -that the actidn is materially altered when either the inlet or the discharge is obstructed to cause a back pressure or auction resistance as compared with that when the fan is runnini with a free inlet and free dis-' 7 char e. Sue a fan if unincased discharges the aid radially from its blades and uniformly around its entire circumference in any given plane perpendicular to the axis of rotation. If inclosed in a snail-casing with a free inlet and free discharge, this action is only slightly modified, due to the tangentially-discharged currents being collected by the casing and delivered in one stream through the discharge-outlet. If, however the discharge is obstructed, an ine ualit 0 action around the circumference o the a' wheel is caused, which ine olality reaches its maximum when the disc arge is wholly closed. Under these circumstances instead of the air flowing outwardly through the ports or spaces between the blades around the entire circumfe J-nce of the fan-wheel such outward flow mainly occurs from the one half of the circumference of the fanwheel which approaches the discharge-outlot, while on the opposite half of the circumference, which recedes from-the discharge-outlet, there is a regurgitated or return stream of fiuid flowing first inwardlythroughthe ports and then around inside the blades toward the other half of the circumference, where it finally passes outwardly aizin. This action om Fig.3 of'the accompanying drawings; which is a diagram inaccordance with my invention. In this 'di am A designates the rotary fan-wheel Wit its liladosaa, and B designates the snailcasin The eye or inlet-opening to the fanwhee is indicated by the letter C. Assuming the outlet ii of the casing to be closed and the fan-wheel rotated, the air-currents will be somewhat as indicated by the small arrows. As the precise direction and velocity of these currents varies with different back pressures or suction resistances, different speeds of the fan -wheel and other conditions, only an a prordmate illustration can be given. Taliing, however, the example indicated, it will int indicated approximstely at as around in the direction 0 rota tion) to another point ap roximately indicated at y the air is disc arged outwardly and tangentially from the blades while beyond y to a point adjacent to the nearest IIO , cape of this current through the eye.

point z of the cas ng inn-o is an inflow of air through the ports and thence a current or stream r c wit hin thifan-wl'ieel, which stream passes outwardly 11,111111 between the blades as it a proa" lies the point 01:.

By measuring or in icatin the [low of this current or stream 0 at different points within the fanwheel (which may be done with a thread on the end of a wire) a line may be plotted indicating what I may call the inner" margin of be taken as the inner limit of the inwardlyregurgitated or return current from the latter ortion of the discharge-outlet which the bla es pass. If ,this stream of air were within the circumference of the e eC, an outflow of air would occur through t e same on the side coincident with the stream 0 0, so that if the eye'were subdivided with a flat plate. in a plane coincident with the axis extended approximately in a line between a; and y an outflow would be found to occur on the left side of this plateand an inflow on the ri ht side thereof. Throughout the intake 0 amber orspace inclosed within the blades to the right of the line as y the air is found to be undera condition of partial vacuum, which is most marked near the inner edges of the blades on the sides most remote from said line as g.

It is a remarkable fact thatthe air-current c c if unobstructed in its course travels at a higher velocity than the blades. Repeated tests have shown itsvelocity to be nearly or quite double that of the inner edges of the blades when the back pressure or suction resistance is hi h relatively to the speed of rotation of-the an-wheel.

My present invention is based upon a recognition of the phenomena above stated. I have found by experiment that anything which obstructs the current a 0 within the fan-wheel at once lowers the efficiency of the fan and defeats its objects. Those fans in which occasional blades have been extended inwardly farther than their fellows (whether this extension be for a part only or for the whole width of the blades) have had this result and are found by test to be notably inefiicient under back pressures or suction resistances. Accordingly I avoid placing anything within the fan-wheel which will materially resist the current 0 c or retard it, and I permit it freely to flow with its wonted ve ocity-that is to say, considerably faster than the movement of the blades. also provide means for preventing the axial es- In my application 'for United States Patent filed May 23, 1904, Serial No. 209,351, I have set forth certain iniprovements based also upon the phenomena already stated. According to the invention claimed in my said application. I have altered the relative size and proportions of the revolving fan and the inclosing casing, so that the eye or inlet-opening, which, as in Patent No. 662,395, is concentrio with the axis of rotation and is of about the same area relatively to the size of the casing, is by reason of the relative enlargement of the revolving fan-wheel of materially smaller size than the interior of the circle described by the inner edges of the fan-blades.

Accordin to my present invention instead of ma ing the e' e or inlet-opening concentric, or substantia 1y so, to the axis of rotation I so form the inlet area that the boundary thereof extends more to one side of the circle of the fan-blades than the other,or I make the eye eccentric to the axis of rotation, whereby its position is more nearly concentric to the outline of the casing than formerly. All these forms are intended to be included in the term eccentric e e, which is hereinafter used for the sake o simplicity and clearness. By preference I make the (Eye of non-circular shape, as illustrated in ig. 1, conforming it on its side adjacent to the internal current or stream 0 c to the form taken by such stream, and on the opposite or suction side of the fan-wheel carry the eye outward, preferably, to an outline corresponding more or less closely with the path of the fan-blades. Thus the eye assumes a shape rough] approximating to an ellipse somewhat attened on its side nearest the return or internal current and a shape which I will hereinafter refer to as approximately of D form.

I will proceed to describe the principle of my invention and its preferred embodlment with reference to the accompanying drawin s, wherein 1g. 1 is a diagram illustrating the currents which are set up in fans constructed in accordance with my invention when,operating against back ressure or suction resistances, as already escribed. Fig. 2 is 9. diagram corresponding to a section on the line 2 2 in Fig. 1. Fi 3 is a diagrammatic or outline elevation o the casing of the fan, illustrating one form of my invention Fig. 4 is a front elevation of a fan, illustratm a urther modified form of construction. 1g. 5 1s a sectional elevation of a fan, illustrating the preferred contruction embodying my invention. Fig. 6 is a horizontal section thereof in a plane intersecting the axis Figs. 7 and 8 are respectively sideelevation and vert cal section illustrating a modified construction. Figs. 9 and 10 are similar views in the same planes as Figs. 5 and 6, showing a modified construction. 1

My present invention in its preferred embodiment follows the general princi les of construction of a drum-shaped multi laded It is preferable to curve the casing at g, 5, between the point 1: and the outlet to ease the flow, of the bac current into the ports between the blades.

5 In Figs. 5 and 6 I have shown the blades somewhat deeper in proportion to the diameter of the fan-wheel than in the preceding diagrams, as I find that deepening them to this extent greatly enhances stiffness and rigidity 10 of construction and does not to any very material extent diminish theirefiicienc in operative effect. My invention is not imited to an definite proportion between the depth of the blades and the'diameter of the l 5 drum or betweenitheir depth and length. In the construction of pressure-fans according to In present invention I may advantageou y make the blades shorter and deeper than the proportions stated ascpreferred in my former patent.

e resent invention is not limited to what I fiave herein referred to as the drum form of fan, nor to the general type of fans set forth in my'aforesaid atent. It is als 2 5 applicable, although with ess advantage, to centrifugal fans of the ordinary pressureblower type. As one illustration of such application of my invention I show in Figs. 7 and 8 a fan somewhat resembling the ordinary o ressure-blower, but modified so as to emody in art the principles of m invention. In these ures, A is the fan-whee and B the casin he fan-wheel has curved blades a, usual y mounted between conical or dished 3 5 plates H H, one or each of which has a central inlet-opening forming the eye. Such rotary member may be variously mounted-for example, by means of a central disk I, attached at its outer part to the blades and at 40 its center to a hub on the shaft D. It is common in the hitherto ordinary construction of such fans to provide a series of short blades of approximately the shape of the blades :1 and at intervals to extend these blades inwardly, forming lon blades, as shown in dotted lines at (1. These inward extensions 0 have been thought necessary to impart the requisite pressure the air. They have.been commonly tapered at their o inner edges in the manner shown by dotted lines a in Fig. 8 and projected more or less within the circumference of the eye. In ap-- plying my invention to a fan of this charac ter it is necessary to cut away the portions a (i preferably entirely, so that all the blades Shall be of approximately equal depth radially, as shown by full lines in Fig. 8,

whereby a free and unobstructed space is rovided within the series of blades for the Internal How of the back current through and across the fan-wheel.

Figs. 9 and 10 show the application of my invention to a fan of the ordinary paddlewheel t pe. With this form of fan it is also desirab e that the inner edges of the blades with the construction shown in m' should be'cutaway, so that ame shall not project within the marginal boundary of the eccentrically-located eye at that portion of its circumference where it is in closest prox imity to the path of said inner edges. Thetqo dotted lines a indicate the hitherto ordinary and detrimental inward extension of the blades and the solid lines a the extent to which they should. be cut away to give best results in accordance with my herein-described invention. The outer contour of the inclosing casing of this fan is shown in Fig. 9 in solid lines B B as hitherto ordinarily made, and while my herein described invention is applicable in conjunction with such 86 outer contour of the casing it is referable to have the casing of the form s own by the dotted lines B B, which is in accordance pending application. The same referenceetters are used for the parts of the eccentric eye as in the revious description as the application will e clearly apparent from the drawings.

Although I have described my invention as a fan for acting upon air, yet it s to be un 90.. derstood that it is applicable also wltn other fluids. It is highly advantageous for use as a centrifugal pump for water or other liquids. The operation with a liquid differs from the operation with air only to the extent that the 5 fluid operated upon is of different weight and specific gravity and is-ineompressible.

My invention may be otherwise modified in many respects without departing'from its essential features.

What I claim, and desire to secure by Letters Patent, is

l. A centrifu al fan or pump comprising a snail-casing, and a fan-wheel mounted eccentrically therein, whereby when operating 10' against a pressure of suction, there 1s established a current of fluid rentering said fanwheel and moving across the intake-chamber thereof, that portion of said intakechamber traversed by said current being practi- 11o cally unobstructed, and said fan or pump having its eye disposed with its greatest area of inlet on the side of the intake-chamber which is opposite to that across which said current passes.

2. A centrifugal fan or pump, comprising a snail-casing, and a fan-wheel mounted eccen trically therein adjacent to one side thereof, said fan-wheel havin a practical] unobstructed intake-cham er, and sai casing 120 havin an eye disposed eccentrically to the Y axis 0 rotation of the fan-wheel, and adapted to deliver a larger proportion of fluid to that side of the fan which 18 farthest from the casing.

3. A centrifu al fan or pump comprising a snail-casing, and a fan-wheel mounted eccentricallv therein, adjacent to the dischar e side thereof, said fan-wheel having an unob structed intake-chamber, and said casing hav- 1 3o ICC ing an eye disposed eeeentrieaily to the axis of the fan-wheel, and with its'greatest area. on the side of the casing which is opposite the discharge side thereof. 5 4. A eentrifu el fan or pump comprising a snail-casing, and a fen-wheei mounted eccentrieally therein, adjacent to the dischar e side thereof, said fen-wheel airing on 11110 strueted inteke-ehamber, and e1d easing heringzen eye disposed eceentrioally to the axis of the fan wheel, end with its greatest area on the side of the casing which is opposite the discharge side thereof, and said eye having;

4 eeid an or pump havingite eyedisposed eev substantially straight portion h on sueh r5 eherge side.

on the side of the casing whieh is opposite the discharge side thereof, and said eye having a 2 5' substantially straight portion h h on suehdister Whie 5. A centrifugal fan or pump eomiirisinge. snail-casing, end a. fan-wheel IIIOUIIiEGd'E-EEII etreeted that its blades do not extend within the periihery of thee e on the side of, the 3817-.

is no tt e fen-wheeiexis.

7. A centrifuge fan or porn comprising a and a an-wheei; mounted therem,

eentlieeiii to the aide ofretetiofio the fee wlieei; and said fen-wheei so eeeetruoted that its blades do not extend the periphery ef the eye In witness whereof I haverhereunto siined SAMUEL GLELAND DAVIDSON. Witnesses:

Jon Moon, Teams DIXON.

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