US2418012A - Impeller for centrifugal apparatus - Google Patents

Description

March 25, 1947. 'r. CHESTER IMPELLER FOR CENTRIFUGAL APPARATUS 2 Sheets-Sheet 1 Filed Sept. 20, 1945 T. CHESTER IMPELLER FOR QENTRIFUGAL APPARATUS Match 25, 1947.

Filed Sept. 20, 1943 2 Sheets-Sheet 2 Patented Mar. 25, 1947 UNITED STATES PATENT OFFICE 2,418,012 IMPELLER FOR CENTRIFUGAL APPARATUS ThomasChester, Detroit, Mich. Application September 20, 1943, Serial No. 503,134

11 Claims.

impeller, the fluid being discharged from a plurality of tangential ports at the periphery of the impeller into the volute of the casing and thence through an outlet opening from the casing.

Anobject of the present invention is to provide an improved impeller blade which accelerates the fluid entering the ports between the blades with a minimum of turbulence and loss of power.

Another object of the invention is to provide an improved impeller for centrifugal apparatus in which the impeller is provided with a plurality of hollow blades with concave frontal surfaces facing in the direction of impeller rotation and convex back surfaces having ports therebetween which enable acceleration of the fluid from sub stantial rest with reference to arcuate motion around the axis of the impeller to high velocity without substantial turbulence.

Another object of the invention is to provide an improved impeller for centrifugal apparatus in which the forward surfaces of hollow blades are concave and in which the rear surfaces of the blades adjacent the radially inner tips thereof make a relatively low angle with a line joining the radially inner tips of adjacent blades.

A further object of the invention is to provide an improved impeller for fluid pumps or fans in which a plurality of axially-extending blades in the form of portional crescents have concave forward surfaces facing in the direction of impeller rotation and rear surfaces backwardly inclined at an angle in consonance with theneutral path of the fluid which enters the ports of a rotating impeller to provide acceleration of the fluid through the ports between said blades with minimum turbulence.

Other objects and advantages of the invention will appear in the following description of preferred embodiments thereof made in connection with the attached drawing in which Fig. 1 is a vertical section through an impeller in accordance with the present invention taken on the line l-i of Fig. 2;

Fig. 2 is a side elevation of the device of Fig. 1

with parts broken away to show the shape and arrangement of the impeller blades; 7

Fig. 3 is a fragmentary detail view on an enlarged scale showing one type of blade;

Fig. 4 is a view similar to Fig. 3 showing a modified type of blade; and

Fig. 5 is another view similar to Fig. 3 showing a still further modified type of blade.

Referring particularly to the drawings, the

impeller of the present invention may comprise.

any suitable type of supporting structure such as a backing ring secured to a hub ll rigidly mounted upon a shaft l2, which in turn is supported in suitable bearings (not shown) and rotated from a source of power (also not shown). The impeller may also include a plurality of axially extending blades l4 secured to the backing plate I0 in any suitable manner,. such as by welding, and the extending ends of the blades may be similarly secured to a shroud ring I5. The

.impeller is also preferably provided with an rearward face adjacent the radially meta internal deflector It for directing the fluid radially outward into the ports I! between the blades l4 to secure uniform non-turbulent flow through the interior of the impeller. The deflector I6 is preferably a parabola or approximate parabola in axial section. While such deflector measurably increases the emciency of the device, improved results over prior impellers may be obtained .even if the deflector It be omitted.

A suitable blade in accordance with the present invention is shown by way of example in Fig. 3. The blades I4 of this figure are shown as being substantially crescent shaped with the points of the crescent forming the radially inner and outer tips l8 and I9, respectively, of the blades. In general, the forward face of the blades will be concave although the radially inner portion 'of the forward face may, in some instances be substantially straight. It will be further observed that the portion 20 of the rearward face of the blades adjacent the radially inner tip makes a rather small angle with a line joining the radially lnner tip of such blade and the corresponding tip of the next succeeding blade. In general, it has been found that this angle should not be greater than approximately 40 and that it may be as small as 10 or even smaller depending upon the speed at which the impeller is rotated and upon the required relationship between static pressure and velocity pressure, the smaller angles. .f being employed with higher speed impellers and when the static pressure has a high ratio to; velocity pressure. As shown, the portlonno ,the

preferably substantially straight although it may be slightly curved and in general the rearward surface of any one blade is'preferably approximately parallel to the forward face of the next succeeding blade. However, with full crescent shaped blades a port which first con verges and thendiverges with respect to the direction of fluid'flow, as shown in Fig. 3, may be advantageously employed. With the structure shown, fluid entering the ports between the blades is uniform- 1y accelerated without turbulence and delivered at high velocity from the periphery of the impeller.

The modified blades 22 shown in Fig. 4 are illustratively substantially similar to the radially inner halves of the blades of Fig. 3 and, to illus-- trate this, the remaining halves of certain of the crescents are dotted at 23 in Fig. 4. The blade form shown in Fig. 4 may be considered to be a portional crescent without limitation to half a crescent illustratively shown thereby and the angle which the portion 24 of the rear surface of the blade adjacent the radially inner tip makes with a line joining the said radially inner tip with the corresponding tip of the next succeedin blade may be substantially that described with reference to Fig. 3. It will be noted that the forward face of the blades of Fig. 4 are rearwardly inclined and in general such rearward inclination is desirable, although the forward faces may have other inclinations as is .old in the art. Again, the forward faces are preferably concave as shown in Fig. 4 but may be substantially straight. In the impeller of Fig. 4 fluid entering the ports between the blades is also uniformly accelerated and discharged outwardly from the ports ofthe impeller with relatively high velocity and with minimum turbulence in the impeller.

The blades of Fig. 5 are a still further modification of the blades of Figs. 3 and 4 in that a portion of a crescent elongated in the circumferential direction of the impeller periphery is employed. Substantially the same considerations as to the inclination of the forward faces of the blades and also rearward faces of the blades as discussed with reference=to Fig. 4 are also contemplated for the blades of Fig: 5. Thus, the

portions 21 of the rear surfaces of each of the blades adjacent the radially inner tip thereof make a relatively small angle with a line joining the radially inner tip of the blade and that of the next succeeding blade. It will be noted that the hollow blades have increased arcuate width in relationltoradial depth as compared with the precedinggflgures, although the arrangement shown is illustrative and the circumferential spacing or pitcli'land also the radial depth can be different fro accelerated in its flow through the ports between the blades and dischargedv from the impeller with minimum turbulence inthe impeller.

From the above description it will be apparent thatlthe blades of Figs. 4 and 5 may be termed portionalijcre'scents derived from the full crescent blades crrig. 3 and that in all of the blade constructions. described, the radially inner portion of e s the .bladelmay be considered to be a portional crescent. While all of the blades illustrated are" shown as having a hollow structure, it is apparent that solid blades may be employed, particularly for impellers having blades of small size. From Figs. 4 and 5 it will also be apparent that the blades are substantially portional crescents injcross section, formed by the truncation or omission of the radially outer portion of the ,lthat shown. Again the fluid is uniformly 4 blades shown by Fig. 3. This truncation is important because it eliminates the necessity of the fluid moving forward along the removed blade portion, with an angular or rotational velocity in excess of the impeller peripheral speed and thereby prevents instability of performance.

One of the important factors providing the increased eflieiency of the present invention is the the spacing can be greater than that shown.

However, the port width measured at approximately half the radial depth of the full crescent, thatis, at the radially outer portion of the substantially triangular blades of Figures 4 and 5, is preferably not greater than approximately half of the arcuate pitch or spacing of the blades, and this port width should not be less than approximately 35% or greater than approximately 65% 'of the distance between corresponding points on adjacent blades measured on they circle at half the radial depth of the full crescents. The ratio of blade radial depth to impeller diameter shown as indicated in Fig. l is merely by way of example and this ratio can be varied within wide limits. Also, the impeller can have a greater or lesser axial length than that shown in Fig. 1 for the same diameter. Preferably all of the corners or tips of the blades shown in Figs. 3,4 and 5 are somewhat rounded although these corners may be relatively sharp without material decrease in efliciency of the device. In Figs. 4 and 5 the portional crescent shaped blades'are approximately triangular in outline, the radially inner tip of each blade constituting the apex and the radially outer side constituting the base. i When considered desirable these outer sides can be omitted or eliminated, in order to reduce centrifugal stresses or for other reasons.

While I have disclosed the preferred embodiments of my invention it is understood that the details thereof may be varied with considerable amplitude without departing from the spirit, and essence of the invention.

I claim:

1. In a rotary impeller for imparting motion to a fluid, a plurality of axially extending blades circumferentially spaced adjacent the, periphery of said impeller; each of said blades being approximately in the form of a portional crescent and positioned to have the point of said portional crescent form the radially inner tip of said blade and to provide a convex rearward surface with respect to the direction of rotation of said impeller, the portion of said rearward surface adjacent said radially inner tip forming an angle with a line joining said radially inner tip with the corresponding tip of the next succeeding blade which is between approximately 10 and 40.

2. In a rotary impeller for imparting motion to a fluid, a plurality of axially extending blades circumferentially spaced adjacent the periphery of said impeller, each of said blades being substantially in the form of approximately a half crescent positioned to have the point of said half and to provide a convex rearward surface with respect to the direction of rotation of said impeller, the portion of said rearward surface adjacent said radially inner tip forming an angle with a line joining said radially inner tip with the corresponding tip of the next succeeding blade which is between approximately and 40.

3. In a rotary impeller for imparting motion to a fluid, a pluralityof axially extending blades circumferentially spaced adjacent the periphery of said impeller, each of said blades havingsubstantially the form of a portional crescent positioned to have the point of said portional crescent form the to provide a convex rearward surface with respect to the direction of rotation of said impeller, said rearward surface being rearwardly inclined, the forward surface of said blades being so positioned that a line joining said radially inner tip and the radially outer extremity of said forward surface is rearwardly inclined and the rearward surface of said blades being positioned with respect to said forward surface to provide ,ports between said blades which have substantially uniform width throughout each port when measured normally of said rearward surface.

4. In a rotary impeller for imparting motion to a fluid, a plurality of axially extending blades circumferentially spaced adjacent the periphery each of said blades being substantially convex with its radially inner portion inclined at an angle not greater than approximately 40 to a line joining the radially inner tip of said blade to the IUD radially inner tip of said blade and of said impeller, each of said blades being substantially in the form of a portional crescent poresponding tip of. the next succeeding blade which is between approximately 10 and the forward surface of said blades being so positioned that a line joining said radially inner tip and the radially outer extremity of said surface is approximately radial.

5. In a rotary impeller for imparting motion to a fluid, a plurality'of hollow blades each having the form of a portional crescent truncated'by the omission of the radially outer tip, said portional crescent being elongated in the circumferential direction of the impeller periphery and disposed about the circumference of, said impeller, the frontal face of each of said blades with reference to the direction of impeller rotation being approximately radial and the back face of each of said blades being substantially convex with its radially inner portion inclined at an angle not greater than approximately 40 to a line joining the radially inner tip of said blade to the radially inner tip of the next following blade, the

' width of the port between successive blades measured at half the radial depth of the full crescent bein not greater than approximately haif of the arcuate pitch of the blades.

6. In a rotary impeller for imparting motion to a fluid, a plurality of hollow blades each having in cross section the shape of a truncated crescent and disposed about the circumference of said impeller, the frontal face of each of said blades being concave and inclined with reference to the direction of impeller rotation in accordance with the required relationship between total pressure and the peripheral velocity and the back face of said radially radially inner tip of the next following blade, the circumferential width of the port between suecessive blades measured at half the radial depth of the full crescent being not greater than approximately half of the arcuate pitch of the lades.

7. In a rotary impeller for imparting motion to a fluid, a plurality of axially extending blades circumferentially spaced adjacent the periphery of said impeller, each of said blades being substantially in the form of a portional crescent positioned to have the point of said portional crescent form the radially inner tip of said blade and to provide a convex rearward surface with respect to the responding tip of the next succeeding blade which is between approximately 1,0" and 40, and

and rear surfaces of said blades being positioned to provide a port therebetween which has substantially uniform width throughout said port when measured normally of the said rearward surface. i

8. In a rotary impeller for imparting motion to a fluid, a plurality of axially extending blades stantially triangular in cross section with one corner directed inwardly to form a radially inner tip of said blade, each of said blades having a concave forward surface and a convex rearward surface with respect to the direction of rotation of said impeller, said forward and rearward surfaces being positioned to provide ports between the blades having substantially uniform width throughout said ports when measured normally of said rearward surface.

9. In a rotary impeller for imparting motion to a fluid, a plurality of axially extending blades circumferentially spaced adjacent the periphery of said impeller, each of said blades having substantially the form of a portional crescent positioned to have the point of said portional crescent form the radially inner tip of said blade and to provide spect to the the portion a convex rearward surface with redirection of rotation of said impeller, of said rearward surface adjacent inner tip forming an angle with a line joining said radially inner tip with the corresponding tip of the next succeeding blade pitch of the blades.

10. In a rotary impeller for imparting motion to a fluid, a plurality of axially extending blades mferentially spaced adjacent the periphery of said impeller, each of said blades having the shape of a fractional crescent and being positioned to have the point of said fractional crescent form the radially inner tip thereof and to provide a convex rearward surface with respect to. the direction of rotation of said impeller, said rearward surface being inclined backwardly and the forward and rearward surface of adjacent blades being positioned to provide a port therebetween which has substantially uniform width throughout'said port when measured normally of said rearward surface, the circumferential width of the port between successive blades measured at half the radial depth of the full crescent being not greater than approximately half of the arcuate pitch of the blades.

11. In a rotary impeller for imparting motion to a fluid. a plurality of axially extending blades circumferentially spaced adjacent the periphery of said impeller, each of said blades being substantially triangular in cross section with one corner directed inwardly to form a radially inner tip of said blade, each of said blades having a concave forward surface and a convex rearward surface with respect to the direction of rotation of said impeller, said forward and rearward surfaces being positioned to provide ports between the blades having substantially uniform width throughout said ports when measured normally of said rearward surface, the portion of said rearward surface adjacent said radially inner tip forming an angle with a line joining said -,radially inner tip withthe corresponding tip of the next succeeding blade which is between approximately 10 and 40 degrees, said ports having a circumferential width measured at the radially outer portion of said blades which is not greater than approximately half of the arouate pitch of the blades.

THOMAS crmsrm.

aaraacncas crrap The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Number French Aug. 12, 1878 Certificate of Correction Patent No. 2,418,012.

LESLIE FRAZER,

Fz'w'st Assistant Commissioner 0 f Patents.

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