US2219499A - Propeller type fan construction - Google Patents

Description

Oct. 29, 1940. T. H. TROLLER v PROPELLVERQ TYPE FAN'CONSTRUCTI ON Fil ed June 15,1938 2 Sheets-Shef 1 Patented Oct. 29, 1940 PROPELLER TYPE FAN CONSTRUCTION Theodor H. Troller, Akron, Ohio, assignor to La-Del Conveyor & Manufacturing 00., New Philadelphia, Ohio, a corporation of Ohio Application June 15, 1938, Serial No. 213,775

1 Claim.

The invention relates generally to apparatus 1 for moving fluids, and more particularly to retary fan construction adapted to produce exceptionally high efiiciencies.

' In my prior Patent No. 2,040,452, issued May 12, 1936, and entitled Fan construction, the reduction in efficiency of rotary fans due to the component of movement of the fluid transverse of its delivery direction is fully discussed, and the patent teaches how to counteract said com.- ponent by the use of straightener vanes and thereby increase efiiciency of the fan.

Said patent also mentions the tendency of a propeller fan to produce a condition at the center of the air stream behind the propeller, where the air is substantially stationary'and substantially no pressure is being built up. It is well known that this condition can be largely overcome by providing a cylindrical inner casing-or fairing coaxial with the outer fairing or delivery duct, which inner casing occupies the space behind the propeller where pressure would not be properly built up by the propeller. V

The present invention provides for utilizing straightener vanes of novel construction and arrangement for attaining higher efficiencies, which vanes are adapted to be combined with certain improved conduit constructions to produce novel anduseful results.

Straightener vanes should eliminate as far' as possible the tangential component of fluid flow transverse to the delivery direction, and in eliminating this component static pressure should be built up in the air, stream equal to th energy of the tangential component of the velocity. In

such conversions of velocity into static pressure, there is a tendency toward building up layers of fluid with slowed down velocity near the walls or all surfaces past which the fluid flows, and this condition may cause losses in energy to the extent of completely breaking down the flow pattern. Such losses may be particularly pronounced in fans of relatively small diameter because the smaller the diameter the greater is the amount of surface past which the fluid flows, in proportion to the volume of the air stream.

It is therefore an important object of the present invention to provide a propeller type fan construction which substantially avoids losses in energy of the air stream connected with its reduction in velocity while passing through straightenervanes.

A further object is to avoid such losses by correlating the design of the straightener vanes and their action on the air stream so as to propcrly regulate the slowing down of the fluid in passing through the-vanes.

Another object is to provide a propeller type fan construction having an outer conduit which varies in cross-sectional area according to the 6 divergence of the straightener vanes surrounded by said outer conduit.

These and other objects are accomplished by the combinations, arrangements, constructions, and relationships of the parts, elements and improvements comprising the present invention, which is disclosed and described herein, and defined in the, appended claim.

In general terms the invention consists in constructing a propeller type fan having straightener vanes so constructed as to properly straighten the flow of fluid and at the same time di-. verging gradually-and uniformly from each other. such vanes being-adapted to be used with an outer duct converging in area over the straightener vanes.

In the drawings forming part hereof, I have shown a relatively small portable propeller type fan embodying the invention, but .it will be understood-that the invention may be applied to various sizes of fans, as well as to stationary propeller type fans.

Figure 1 is a longitudinal view of the improved fan showing the outer fairing in cross section, the rotating propeller and inner fairing in elevation, and the straightener vanes being shown in cross section at their respective junc tions with the outer fairing;

Fig. 2 is an end view looking toward the entrance end of the fan;'

Fig. 3 is a similar end view with the propeller blades being broken away to show the straightener vanes; v

Fig. 4 is an enlarged diagrammatic developed view of two of the straightenervanes, the cross sectional shapes thereof at the inner fairing being represented in a single plane; and

Fig. 5 is a diagrammatic view showing the rate of divergence between opposing surfaces of adjacent blades.

Similar numerals refer to similar parts throughout the several views of the drawings.

The portable propeller type fan which is shown in the drawings is adapted to various uses, and' is particularly suitable for use in a mine where it is desired to convey air from a main ventilated tunnel a considerable distance through a laterally extending entry leading from the tunnel to a room at the working face. In using the fan for this purpose it may be positioned in the 5 the runners I nrepmeferahly with the longitudinal axis or-urerm.

The hub of the propeller preferably has at its entrance end a suitably rounded nose indicated at II and is preferably secured on a motor shaft. II for being driven by a motor I! which is mounted within the inner fairing ii. A plurality of radially extending propeller blades 14 are secured to or with the hub, four of such blades being shown in the drawings. The blades ll may be-of substantially standard de sign, having a greater pitch at the hub than at their outer ends, and are designed to deliver air in the direction of the arrows in Fig. 1 when rotated counter-clockwise in the direction of the arrow in Fig. .2.

The inner fairing i3 is coaxial with the outer fairing 1 and is supported therein by a series of circumferentially arranged vanes l5 preferably located behind or downstream from the blades ll and secured at their inner ends to the inner fairing 13 and at their outer ends to the outer fairing '1. Electric conductors for supplying current to the motor 12 may be passed through suitable passages in one of the vanes 15, if desired.

The entrance or upstream end of the inner fairing I3 is preferably cylindrical and conforms in diameter to the hub 5, and the delivery end it may be tapered down to a point substantially in accordance with the shape of a conventional airship hull, so as to present a minimum of resistance to the air flow.

The entrance end of the outer fairing is preferably outwardly flanged as shown at 1 8, in .accordance with the usual practice, and that portion of the outer fairing which surrounds the propeller blades II is cylindrical as shown at 19 and of suflicient diameter to provide a. slight clearance between its inner surface and the outer ends of the blades M.

The portion 20 of the outer fairing which surrounds the vanes '15 and to which the outer ends of the vanes are secured, may be and preferably is tapered or converged inwardly from the upstream ends to the downstream ends of the vanes to form a conical section extending throughout the lengths of the "vanes, for a purpose to be described.

the downstream end of portion 2! to the delivery end of the outer fairing, th outer fairing may be and preferably is formed cylindrical as indicated at 2| designing the straightener vanes 15, their general shape :and contour may be calculated ac cor-ding to practice or from the formulae given in my prior Patent No. 2,040,452, but neither of these methods gives any definite data on the amount and rate of divergence between adjacent vanes as measured at intervals throughout lengths of opposing surfaces of the adjacent vanes from their entrance to delivery ends.

I have found that by gradually and substantially uniformly increasing the distance between the surfaces of :adiacent vanes measured perpendicularornormal tothedirection ofthe airflow therebetween, the desired axial movement of the air stream at the delivery ends of the vanes is obtained with a minimum of energy losses connected with the reduction in velocity of the air stream in through the vanes.

Fig. 4 is substantially a development in a single plane of two adjacent vanes I! and I5 taken at their radially inner ends where they connect with the cylindrical outer surface of the inner fairing 13. The corresponding surfaces of the vanes are indicated by the curved lines 23 and 23', and the curved lines 24 and 24, respectively, the opposing surfaces of the adjacent vanes being indicated at 24 and 23 respectively. and forming an air channel therebetween.

The angle of the entrance ends of the vanes with the longitudinal axis of the propeller substanidally coincides with the direction of movement of the air delivered by the propeller through the vanes as indicated by the arrow 25 in Fig. 4, which direction of movement is the resultant of the axial and transverse components of movement produced by the propeller blades.

The cross sectional shape of the vanes at the inner fairing as represented in Fig. 4 is necessarily such that the distance measured circumferentially between corresponding surfaces 23 and 23and between corresponding surfaces 24 and I!" is equal throughout, as represented by the distance 11 measured vertically in diagram matic Fig. 4 between corresponding surfaces at points taken at random. At the same time the design of the vanes is such that the width of the air channel between opposing surfaces 24 and 23' increases gradually and at a substantially uniform rate from the entrance end to the exit end of the channel between the vanes.

By way of example, the rate of divergence be-' tween the opposing surfaces of adjacent vanes may be shown as indicated in Figs. 4 and 5. In Fig. 4 the median line r-:c representing the direction of iluid flow is laid out between surfaces 24 and 23 and a series of points A to I laid out at intervals thereon. At these points the distances a to i to the opposing surfaces 24 and 23' is measured-in directions perpendicular or normal to the tangents to line :r:: at those points.

Now if the line .:r-:: is laid out as a straight line as shown in 5 and the points A to I are laid out at the same intervals thereon, the distances a to i measured in opposite directions from line 2-2: and perpendicular thereto will determine points through which inclined straight lines 2! and '23 may be drawn corresponding to the curved lines 24 and 23 in 4. The angles Q which the inclined straight lines 24 and 23" make with the median line :r-r should be approximately 11, and may vary from 11 to say 13, although I do not wish to be limited to these exact figures. divergence is equivalent to an increase in width of approximately one unit in live unitsof length.

Due to the diiliculties in accurately designing the cross shape of the vanes in order to obtain the desired results, it may be that in the intervals from A to B and B substantially to C, the distances from the line :x:-: to the surfaces '7 andj! will be substantially constant,

as represented in Figs. 4 and 5, but this has no appreciable sited; on the obtained at the delivery end of the channel between two adjacent vanes. As shown in Figs. 4 and 5 irom the point C to the point I at the delivery end of the vanes,

the width or the channel measured perpendic hind the propeller into iar or normal to the direction of air flow increases at a uniform rate.

In the example given, if the velocity of the airentering the vanes in the direction ofarrow 25 is approximately feet per second, I have found that the velocity at the delivery end of the vanes in an axial direction will be approximately 12 feet per second, if the portion iii of the outer fairing surrounding the vanes is cylindrical. By

designing the vanes in order to produce the grad- I ual and uniform divergence therebetween, as previously described, this reduction in velocity of the air stream is properly regulated so as to substantiallyavoid losses in energy, with the result that very high efiiciencies are attained.

The efficiency of the straightener vanes in transforming the energy connected with the circumferential component of the air velocity beother useful energy can often be further increased by converging the portion of the outer conduit by an amount up to the amount of divergence between the vanes.

- This converging of the outer conduit 20 is useful not only when the higher energy contained in the higher axial velocity is immediately useful, but I have found that often, even though this axial velocity energy must be transformed by a following diffusor into static energy, the overall efficiency of the total arrangement is better than that of vanes with a cylindrical outer conduit 20.

I have found that in the example given, by varying the cross sectional area of the portion 20 of the outer fairing equivalent to reducing its diameter from the entrance end of the vanes to the delivery end by one unit in a vane length measured axially of fifteen units, the axial velocity of the air' stream at the delivery end of the vanes will be approximately equal to the velocity at the entrance end in the direction of arrow 25, or 15 feet per second.

In other words, the amount of convergence of the portion 20 of the outer fairing is calculated to produce an axial velocity at the delivery end of the vanes substantially equal to the velocity of the air at the entrance end in the direction of its movement at that point. The convergence of rection it enters the vanes the portion 2d should not be too sharp because no .materlal gain in reducing the straightening losses could be expected thereby, whereas the friction on the wall and vane surfaces would be increased due to the resulting high velocity so as to give rise to new sources of losses in energy.

Thus by combining the gradual and uniform divergence of the straightener vanes-with a corresponding convergence of the outer fairing around the vanes, the axial velocity of the air flow after passing through the vanes is substantially equal to its velocity in the direction of flow entering the vanes, and the energy losses in passing through the vanes are substantially avoided by the designated divergence of the vanes, thus providing a propeller type ly high efficiencies.

I claim:

Propeller fan construction includingv a longitudinally extending outer fairing, a streamlined inner fairing coaxial with the outer fairing, a propeller mounted for rotation in said outer fairing axially thereof for delivering fluid through said fairing, ranged straightener vanes secured to said outer and inner fairings axially adjacent to s aid propeller, the entrance ends of said vanes being disposed at an angle substantially equal to the angle of fluid flow delivered by said propeller and said vanes being curved throughout their lengths to fan attaining extremerate from the entrance ends to the delivery ends of said vanes, and the portion "of the outer fairing surrounding the vanes being converged from the entrance ends to the delivery end thereof by an amount so related to the divergence between adjacent vanes as to produce an axial fluid velocity at the delivery ends of the vanes not greater than the total velocity of the fluid in the difrom the propeller.

THEODOR H. 'I'ROLLER.

a series of circumferentially ar-- bring their delivery ends in axial alignment with

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