US2169232A - Blower apparatus - Google Patents

Description

Aug. 15, 1939. w F N RQ 2,169,232

BLOWER APPARATUS Original Filed Sept. 14, 1937 I5 Sheets-Sheet 1 I :IIIIIIIIIIIIII WRRREN 5,5-HNDERS,

Mot/mu 1939- w. B. FLANDERS 2,169,232

BLOWER APPARATUS Original Filed Sept. 14, 1937 3 Sheets-Sheet 3 FIG.&

Q v t a a2 a9 Wnnnsn B. Fmuuma wrimw Patented Aug. 15, 1939 BLOWER. APPARATUS Warren 13. Flanders, Philadelphia, Pa.', assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Continuation of application Serial No. 163,727 September 14, 1937. This application April 8, 1939, Serial No. 266,775

11 Claims. (Cl. 230-120) This application is a continuation of my application, Serial No. 163,727, filed September 14, 1937 and allowed March 29, 1939.

My invention relates to pumps or blowers.

ing my improvement applied thereto;

Fig. 4 is a diagram applicable to Fig. 2;

Fig. 5 is a diagram applicable .to Figs. 1 and 3; and,

Figs. 6, 7 and 8 show further embodiments In a pump or blower having a runner rotating wherein obstruction of recirculation is secured 5 in a casing and whose structure is such that both by wall means carried by the propeller. centrifugal and propeller effects may occur, such Fig. 2 shows a type of pump or blower subject as is the case with a propeller, wherein the flow to the instability referred to. The fluid flow is generally axial, or with runners wherein the through the propeller is generally in an axial fluid initially flows generally in an axial direcdirection and the flow conditions indicated by 10 tion, it has been found that, as the discharge the curve of Fig. 4 to the right of point a apply opening is decreased at constant speed, the preswhen the blower is operated with a volume sure will rise to a certain point, will then fall greater than that of point a and to the left of from 3 to 30 per cent depending upon the depoint I) when the volume is less than that of sign, and then will rise until the discharge openpoint 1). Between the points a and b, pulsations ing is closed. During the range of falling presoccur as the flow condition changes from that in sure, or dip, the flow of fluid, for example, air a general axial direction to that indicated in becomes somewhat erratic and a tendency to Fig. 2. The portion of the curve to the right of centrifugal action becomes apparent. When a covers stable operation, where the axial comthe centrifugal action overcomes the propelling ponent preponderates over the radial component, action at the tips of the vanes or blades, back the latter component being due to centrifugal flow starts; however, until back flow becomes force, and the portion of the curve to the left definitely established, an unstable condition of of 1) corresponds to stable operation where the operation will be encountered, the fluid pressure radial component preponderates; however, in the fluctuating to an undesired extent in many cases. transition range between these points, the un- Accordingly, it is the object of my present instable or pulsating condition arises. vention to provide, in connection with a blower The unstable condition arising because of the or pump having an impeller or rotor equipped centrifugal action at the blade or vane tips apwith vanes or blades whose inlet edges are applies not only to a propeller pump or blower, such proximately radial and wherein the flow at the as shown in Figs. 1 and 2, but also to pumps or entrance is generally in an axial direction, a blowers having combined propeller and centrifuwall or vane means which is effective to obstruct gal characteristics, such as shown in Fig. 3. back flow or recirculation of fluid, and, there- Referring now to Fig. 1, there is shown a confore, to reduce pressure fluctuations. ventional propeller pump or blower including a A further object of my invention is to provide, propeller I0 arranged in the throat portion l I of in connection with propeller blowers designed the converging-diverging housing l2. The profor static pressures of air in excess of 15 inches peller l0 includes a hub I 3 attached to the drive of Water at the maximum operating speed, a shaft l4 and has blades l5 provided with radial vane or wall means closely spaced with respect leading and trailing edges l6 and I1 and with to radial blade edges at one side of the propeller tip edges [8 extending axially and conforming in order to obstruct recirculation of air to refor at least the major portion of the length thereduce pressure pulsations thereof. of to the interior wall of the throat portion II. These and other objects are eliected by my The hub l3 extends forwardly of the leading invention as will be apparent from the followedges l6 and is faired toward the drive shaft, ing description and claims taken in connection thereby providing a converging annulus for supwith the accompanying drawings, forming a part plying fluid to the inlet edges. As just pointed of this application, in which: out, unless the measures to be described are used,

Fig. 1 is a vertical sectional view of a propelan erratic or unstable condition as indicated beler blower incorporating my improvement; tween the points a and b of Fig. 4, will arise Fig. 2 is a fragmentary view of apparatus during t range of fa n p ur s- TO overshown in Fig. 1 without the intercepting wall or come the unstable or pulsating condition, vane or Vane u e; wall means comprising an annular wall or vane Fig. 3 is a longitudinal sectional view of a structure 20 is arranged at the inlet of the blower pump or blower of the centrifugal type and havand belled or curved transversely so as to extend generally in the direction of flow of fluid to 56 the inlet, the discharge edge 2| of the wall or vane structure 20 extending transversely of the radial inlet edges [G of the propeller blades as well as transversely of the spaces between the latter and being arranged relatively close to such propeller blade inlet edges and intermediately of the height of the latter as to positively interfere with the recirculation, indicated diagrammatically by arrows in Fig. 2. Not only does the circumferentially-extending wall means or vane structure 20 serve to obstruct recirculation, but it also serves to promote smooth, streamlined flow of fluid entering the propeller, the circumferentially-extending wall means or vane structure dividing the approaching fluid into converging annuli flowing thereabout and therein and delivered to the propeller blades for translation thereby.

In Fig. 3, there is shown a pump or blower having an impeller or runner 23 with blades or vanes 24, which operate both by propelling and by centrifugal actions. As the inlet edges 25 of the blades or vanes 24 are substantially radial and as flow is generally in an axial direction in the inlet portion of the runner, the arrangement would be subject to the unstable or erratic con-, dition indicated in connection with Fig. 2, that is, when the propelling and centrifugal effects at the tips of the blades or vanes 24 adjacent to the inlet edges come into substantial balance, the pulsating condition will exist until the centrifugal tendency definitely preponderates, whereupon a steady flow condition will ensue. Accordingly, as in Fig. 1, a circumferentially-extending wall or vane structure 26 is arranged at the inlet of the blower or pump and in the general direction of flow of fluid thereto, the discharge edge 21 being closely spaced with respect to the inlet edges 25 and extending transversely of the latter and the spaces therebetween, the vane or wall structure 26 serving to interfere with the back flow condition.

The vane or wall means comprised by the wall structures 20 and 26 of Figs. 1 and 3, respectively, operate to prevent recirculation, indicated by the arrows in Fig. 2, and thus raises the relative position of point b with respect to point a, Fig. 4, and thus reducing or eliminating the dip" and resultant instability. With the guide vane or wall structure installed at the inlet, the characteristic curve of Fig. 4 is changed from that shown in Fig. 4 to that shown in Fig. 5, the latter having no dip and little or no pulsation.

Recirculation is combatted effectively if the vane means is so situated that approximately onethird or less of the total flow passes through the annulus between such vane or wall means and the blade tips.

In Figs. 6, 7 and 8, I show further embodiments of the invention wherein the vane or wall means for obstructing recirculation, instead of being carried by the housing at the inlet of the propeller, is incorporated in and carried'by the propeller.

' In Figs. 6 and 7, the propeller vanes 29 have one or more circular walls 30 cooperating with the propeller vanes to divide the flow passage into concentric annuli, the circular walls preventing recirculation from one annulus to another. While, in Figs. 6 and '7, each wall structure 30 extends for the full axial length of the propeller, in Fig. 8, the wall structure or structures 30a are shown as extending for a less distance relatively to the propeller. It is, therefore, to be understood that, where the wall structure forms a part of the propeller, it may be arranged in any suitable way so long as it is effective to obstruct recirculation, and where the wall means extends for a distance less than the length of the propeller flow passages, it is preferably arranged so as to be effective at the inlet edges of the propeller.

In the application of propeller blowers for such purposes as forced draft, air pulsations are objectionable both on account of the effect thereof on combustion and of the necessary mechanical strength of the boiler setting to resist such pulsations. As long as static pressures at the maximum operating speeds did not exceed or 12 inches of water, neither difficulties on account of pulsations nor recognition of the latter came to light; however, when it was endeavored to raise the static pressure at the maximum operating speed approximately to inches of water, the pulsation problem manifested itself as an impediment limiting static pressures unless it could be overcome in some way, and it was found that vane means constructed and arranged as hereinbefore described would function to achieve this result. I have found that the vane means makes possible even higher static pressures, for example, of the order of 30 or 40 inches of water at the maximum operating speed. Therefore, the vane means is peculiarly useful with forced draft propeller blowers designed for static pressures of 15 inches or more at the maximum operating speeds. Where the vane means is carried by the housing, the spacing thereof with respect to radial edges of the propeller blades should be kept as small as practicable, for example, for best results, the spacing should not exceed three percent of the propeller diameter. Furthermore, while the vane means may be so situated that the annular area between it and the propeller blade tips relative to the annular area between the hub and the blade tips may vary over a wide range, I prefer to have the vane means so located that the ratio of these areas is about The term vane or wall means, as used herein, is to be understood to mean one or more wall structures associated with the propeller and carried either by the latter or by the housing for interrupting recirculation. It is to be understood that the term "propeller is used herein in the sense of a rotary element having blades or vanes for translating fluid and that the fluid passages between blades or vanes may be covered by a housing or casing structure carried by the blades or vanes or separate therefrom. Furthermore, the propeller maybe of the axial flow type, or predominantly so, or partly axial and partly radial flow. In other words, it may be of any type having an axial flow part and on that account having the capacity of developing recirculation and consequent pressure pulsations. Where the wall means is supported from the easing, it defines a small or running clearance with respect to propeller blade edges, it being understood that, by running clearance", is meant that the spacing is as close as practicable in view of structural considerations such as fabrication of the structure and lack of machining of the adjacent edges.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is: i

1. In fluid translating apparatus, a convergingdiverging casing having a throat portion; a propeller arranged in the throat portion and includmajor portion of the axial length of the latter;

and wall means carried by the casing and extending circumferentially at one side of the propeller to provide for flow of fluid as annuli therein and thereabout; said wall means being arranged in the direction of flow in the portion of the casing within which it is located and having an edge disposed transversely of the length of the adjacent blade edges, intermediately of the length of the latter, and with running clearance spacing with respect thereto to afford such resistance to recirculation of fluid that pressure pulsations thereof are substantially reduced.

2. The combination as claimed in claim 1 wherein the wall means is arranged at the inlet side of the propeller.

3. The combination as claimed in claim 1 wherein the wall means is located. sufficiently 7 near to the blade tips that greater flow area is provided between the hub and the wall means than between the latter and the blade tips.

4. Thecombination with fluid propulsion apparatus including a propeller having a hub and a plurality of blades defining flow passages therebetween, said blades having radially-extending inlet edges and defining axial flow portions of said passages beginning at the inlet edges and extending forsubstantial portions of the length of the hub and of the blade tips, and housing means cooperating with the blade tips to cover the flow passages; said apparatus, due to flow condi tions existing in the axial flow portions of said passages, operating in an unstable and pulsating manner at a critical zone occurring at an intermediate capacity, operating stably with a decided axial-flow propeller characteristic at higher capacity, and operating stably with a decided centrifugal characteristic at lower capacity: of means cooperating with the blades to prevent instability and pressure pulsations at said critical zone; said means comprising a wall extending circumferentially to provide. for flow of fluid as annuli therein and thereabout and having an edge disposed transversely of the radial edges of the blades, intermediately of the length of the latter, and with such degree of closeness thereto that recirculation of fluid is so effectively resisted that pressure pulsations of the fluid are substantially reduced throughout the critical zone.

5. The combination with fluid propulsion apparatus including a propeller having a hub and a plurality of blades defining flow passages therebetween, said blades having radial y-extending inlet edges and defining axial flow portions of said passages beginning at the inlet edges and extending for substantial portions of the length of the hub and of the blade tips, andhousing means cooperating with the blade tips to cover the flow passages; said apparatus, due to flow conditions existing in the axial-flow portions of said passages, operating in an unstable and pulsating manner at a critical zone occurring at an intermediate capacity, operating stably with a decided axial-flow propeller characteristic at higher capacity, and operating stably with a decided centrifugal characteristic at lower capacity: of means cooperating with the blades to prevent instability and pressure pulsations at said critical zone; said means comprising a wall extending circumferentially to provide for flow of fluid as annuli therein and thereabout, disposed forwardly of the propeller, and having its discharge edge extending transversely of the blade inlet edges, intermediately of the length of the latter, and with running clearance spacing with respect thereto to afford such resistance to recirculation of fluid that pressure pulsations thereof are substantially reduced through the critical zone.

6. The combination with fluid propulsion apparatus including a propeller having a hub and a plurality of blades defining axially-extending flow passages therebetween, said blades having radially-extending inlet and discharge edges and axially-extending tip edges, and a casing cooperating with the tip edges to cover the flow passages; said apparatus, due to flow conditions existing in said flow passages, operating in an unstable and pulsating manner at a critical zone occurring at an intermediate capacity, operating stably with a decided axial-flow propeller characteristic at higher capacity, and operating stablywith a centrifugal characteristic at lower capacity: of means cooperating with the blades to prevent instability and pressure pulsations at said critical zone; said means comprising a wall disposed at one side of the propeller and extending circumferentially to provide for flow of fluid as annuli therein and thereabout and having an edge arranged transversely of the adjacent radially-extending blade edges, intermediately of the length of the latter, and with such degree of closeness thereto that recirculation of fluid is so effectively resisted that pressure pulsations of the fluid are substantially reduced throughout the critical zone.

7. The combination with a propeller blower designed for static pressures of inches and above of water at the maximum operating speed and including a'propeller hub and a plurality of blades defining axially-extending flow passages therebetween, said blades having tip edges and radially-extending inlet and discharge edges, and a casing cooperating with the tip edges to cover the flow passages; said blower, due to flow conditions existing in said flow passages operating in an unstable and pulsating manner at a critical zone occurring at an intermediate capacity, operating stably with a decided axial-flow propeller characteristic at higher capacity, and operating stably with a centrifugal characteristic at lower capacity: of means cooperating with the-blades to prevent instability and pressure pulsations at said critical zone; said means comprising a wall disposed at one side of the propeller and extending circumferentially with respect to the latter to provide an edge arranged transversely of the adjacent radially-extending blade edges, intermediately of the length of the latter, and with such degree of closeness thereto that recirculation is so effectively resisted that pressure pulsations are substantially reduced throughout the critical zone.

8. The combination as claimed in claim '7 wherein the wall is carried by the casing and is spaced from the adjacent propeller radial edges a distance not exceeding-three percent of the propeller diameter.

11. The combination as claimed in claim 7 wherein the wall is carried by the casing and is spaced from the adjacent propeller radial edges a distance not exceeding three percent of the propeller diameter and wherein the annular area between the wall and the blade tips is about 20% of the annular area between the hub and the blade tips.

WARREN B. FLANDERS.

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