US1773349A - Fan - Google Patents

Description

g- 19, G. DE BOTHEZAT 1,773,349

FAN

Filed Aug. 7. 1926 2 Shuts-Sheet 1 avwwntoz 500290 67230530502 g 1930. 6. DE BOTHEZAT' 1,773,349

Filed Aug. 7. 1926 2 Sheets-Sheet 2 avwentoz Patented Aug. 19, 193% Trice GEQE DE BOTHEZAT, E NEW YORK}, N. Y.

.FAN

Application filed August 7, 192a. Serial No. 12mm;

My invention relates to rotary fans and more particularly to fans of the disk type.

The object of my invention is to provide an eflicient fan of the disk type for forcing the air in a generally axial direction and capable of developing high static pressures. In disk fans of the prior'art'it has been usual to design and mount each fan blade individually with little or'no regard to the actual behavior of the air currents and without reference to any conjoint action between the blades, and these prior fans are therefore not adapted to produce efi'ective pressure against resistance. An object of my invention is to avoid objectionable waste of energy and to attain a maximum edectiveness in the application of the rotary energy of the fan to the movement of the air and the development of pressure overcoming resistance to the air flow.

In the fan of my invention, the blades are formed and arranged to cooperate together to move the air along smooth lines of flow and to receive the air between opposite sur- 35 faces of the blades so shaped and spaced as to give a maximum effectiveness in developing pressure against resistance, that is to develop a relatively high static pressure between the opposite sides of the fan.

Further objects and advantages of my invention will be apparent byreference to the j following specification and drawings, in

which v Fig. 1 is a plan view of a fan constructed in accordance with my invention.

Fig. 2 is a perspective view of the means for assembling the individual blades with the disk portion of the fan.

, Fig. 3 is a development of the blades of the fan.

s a plan view of a modification embodying the invention,

Fig. 5 is a section al-view of the fan shown in-Fig. 4 and illustrating the mounting of the fan in a casing or channel.

Fig. 6 is a. development of the blades shown in Fig. 4. r

Figs. 7 and 8 are sections on lines 7---7 and C;) 8-8 of Fig. 4, and

Fig. 9 is a detailed elevation of a blade.

in the embodiment of my invention shown in Figs. 1, 2 and 3, a. flat disk or boss 10 is provided with a central hub 11 attached thereto by means of rivets or bolts 12. Parallel sided blades 13 are provided with extensions 14 welded at 15 to a ring-16 having the same outer diameter as the disk 10 and extending at right angles thereto. The blades 13 are unshrouded, being attached to the ringand spaced to provide open spaces at their tips when viewed in a plane perpendicular to the axis of the fan as shown iri Fig. 1. Extensions 14 are provided with sections 17 bent over the edge of the ring 16 and welded'or otherwise attachedto the disk 10 at 18. The attaching of the section 17 to the disk 10 provides a securing means for attaching the ring 16 to the disk 10. The blades are diagonal to the plane of the disk 10 and are curved as shown in Fig. 3. V

- In the embodiment of my invention illustrated in Figs. 4 to 9.inclusive, the fan F is provided with a disk 20, from which extends inaradial direction blades 21. The blades 21 7 are corrugated at 22 where they merge into the disk 20 so as to provide a rigid connection to overcome any strain on the blades, which is greatest at this section of the fan The fan is stamped and die-pressed out of a single piece of sheet metal and can be mounted'on a fan hub 23 by means of screws or rivets 24. A rotating shaft 25 provides a rotating means for the fan. In Fig. -5 the fan is shown in a casing or channel where in practice it is usually confined so as to develop a difference in pressure on its opposite sides, as distin guished from free, delivery. While the volume delivered by the fan will tend ,to increase under free delivery, and as conditions of free delivery are approached, myfan is particularly adapted to maintain efliciency-with in- "crease in static pressure. As a consequence,

the power absorbed at constant speed is substantially the same throughout the entire range from free delivery when there is a minimum resistance to no delivery when the flow is blocked off and there is a maximum resistance.

I have discovered that the efiicienc of the disk fan depends primarily on five eatures, which are:

A. Width ratio;-

B. Blade spacing;

C. Blade angle;

D. Aspect ratio, and,

E. The size of the boss or disk from the center to the inner portions of the blades,

' measured, and n is the number of blades, and

the

Width rat1o or to the extreme tip of the blade.

B. If all the blades of the fan are cut by a cylinder of radius r having for its axis the axis of the fan, a development of the blades will be as shown in Fig. 6, and we have Blade spacing 3 in which it the perpendicular distance between the chords of two consecutive blade sections. w=' the width of the blade.

C. The blade angle is the angle of the blade to the plane of rotation, for example, the angle b, Fig. 6, in which the arrow 0 indicates the direction of movement and the plane of rotation.

D. The .aspect ratio is the ratio of the length of the blade (from the tip to the boss) to its greatest width. v

R Aspect rat1o in which R =total length of blade, and W =maximum width of blade."

E. The size of the boss or disk isto be considered as a certain proportion of the'total fan diameter.

In the course of extended investigation,

theoretically and practically, it has been.

found that to obtain high efliciency the width ratio should be not less than 0.8 or more than 1.2 approximately, the blade angle 12 should i be not less than 15 nor more than 45, the

The quantities r and w are not measured at aspect ratio should be not less than 2.5 and may be much higher, and the blade spacing not less than with vanes as shown in Fig. 6. The blade angle ma be constant or vanable from one end of t e blade to the other. When the blade angle varies its minimum and maximum value should be within the limits mentioned. With the stated limits of width ratio'and aspect ratio the blades turn out to be so spaced as to be not less than fifteen in number.

To'illustrate the motion of the air through the fan, we will take, for example, stream line ,S, S, which crosses the disk area at a distance 1' from its axis. The fan by its rotation produces a suction which creates the motion of the air from S to S (Fig. 5). From the oint S on the stream line remote from the rout of the fan to a point P just in front of the fan thevelocity of the air increases and the pressure decreases. For any stream line we can wr1te, assuming the air does not encounter any resistance pressure) at S.

If on its path from S to P the air encounters resistance then the air pressure at P will be decreased.

The air passin from P to P on the same stream line and ehind the disk area of the fan, the actual component of the air velocity (that is, the component of the air velocity taken along the fan axis) can only vary slightl because the area available for the flow 0 air just in front of the fan and just behind is practically identical. The air, however, passing from P to P acquires a rotational motion behind the fan which rotational motion constitutes a loss for the ventilation phenomena. At point P therefore,

\ the air velocityhas practically the sameactual component 0 as at point P and as a direct consequence of the momentum theorem for the passage of the air from P to P; the

air pressure will take a larger value at P than at P because the fan impels a motion to the air in a direction from S to S. We

can then write in' which I p =air pressure at P Ap=increase in'air pressure due to the passage of the air through the disk area of the fan. i

Substituting for 1 its value found above the air pressure at P3- isequal to p The pressure beyond thefan'will, there- Assuming p, to be the diiference in pressure, we can then write p =the pressure step furnished by a fan. at

the distance r from its axis.

\ For finding the pressure step p, we can write Sz=the angular veolcity of fan rotation rn=the linear velocity lc=the coeflicient depending upon the sha e, dimensions and settings of the an blades.

By carefulinvesti ation it has been found that there is a limite maximum value of the coefiicient k which for convenience will be designated k which can not be exceeded. The greatest pressure step that can be furnished by a disk fan at a distance r from its axis is equal to Therefore, as a direct consequence from the above formula, it is shown that for a disk fan having blades of such shape and setting that the pressure coeflicient would have a constant value along the blades, the pressure step will increase from the fan axis to the blade tips as the square of the distance from the axis. The smallest pressure step furnished by the blades of the fan will determine the pressure differences that a fan can maintain. Thus disk fans with almost constant pressure step along the blades will actually constitute the rational type of disk pressure fan. Gonsidering a fan with blades of such shape and setting that the pressure step coeflicient 70 has its greatest possible value k then a fan rotating with a given angular velocity 0, and which must furnish a given pressure step 39,, the fan disk or boss must necessarily have its radius equal br greater than the value fur-- a nished by the relation P,=Icmr i2 or T=QJ- I km The investigation conducted along the can only furnish a static pressure'of some value with efliciency when the diameter of its disk or boss is made at least equal or greater than approximately 0.4 of, thefan lines here discussed has shown that a disk fan diameter. With such proportioning of the disk or boss the pressure obtainable at the disk or boss is already only about 15% of which can be obtainable at the blade tips. Therefore, the greater static pressure to be obtained with a given angular velocity the greater must be the fan disk or boss. A fan with a disk or boss less than approximately 0.4 of the fan diameter cannot furnish at the disk or boss a pressure step of the same order of magnitude as at its tips and the air delivered by the outer portions of-the blades at higher pressure circulates backwards at the disk or boss of the fan. In a fan furnishing the same pressure step from boss to tips, the coefficient k must have its maximum value at the boss and is progressively decreasing towards the tips, so that in passing from tips toward the boss the shape of the blade should be changed in such a wa to have k increase from tip to boss in or er to have pressure.

constant.

It follows that beginning from the boss the blades must have the proper shape and settings. I'n fans where the blades are simply secured to a flat boss and then twisted to the proper setting there will always be a section from the boss to the point where the blade has its proper setting where no pressure step will be created and the air will leak backwards during the operation of the fan. When theboss is formed with a diameter approximately 0.4 the fan diameter pressures can be obtained to force the air forward against resistance, the characteristics of the blading being maintained within the limitations above set forth.

For an example of the foregoing principles of my invention it has been found that a fan.

of 18" diameter with a boss or disk of 9 diameter rotated at the relatively low speed of 1150 R. P. M. has developed static pressure when delivering 1500 cubic feet per minute. The power absorbed by the fan is only about H. P., which indicates the high efliciency of fans constructed in accordance with my invention. This is, as far as known to me, the most eflicient fan ever produced.

It is to be noted that fans constructed in accordance with my invention will operate at low speeds as well as high speeds, that is, pressure will be developed. at low or high speeds, the pressure, of course, increasing with increase of speed.

ates a suction and the air is drawn to it in 11,624, filed Feb. 26,1925.

an axial direction. The air upon passing through the fan acquires in addition to its axial motion a rotational motion given to it by the fan. The air forced through the fan is a smooth flow 'in an axial direction with a rotational motion in all parts of the flow and is free from irregular and cross currents.

The flow as it leaves the fan takes the form of a rotating mass with substantially equal axial pressures forcing the flow, and any obstruc tion placed within the flow will not tend to make the flow deflect backwards because any deflection of the flow at an pressure is ofiset by'another section of the ow of equal pressure. a

- This case is a continuation in art of my co-pending prior application gerial No.

I claim:

1. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and to force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having a boss diameter. of substantially 0.4 of the overall fan diameter, a width ratio between 0.8 to 1.2, a blade angle between 15 and 45, and an aspect ratio of 2.5 or over. n

2. A disk -fan adapted for installation in connection with an opening or conduit to receive power from a shaft and to force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having a boss diameter of substantially 0.4 of the overall fan diameter, a. width ratio between 0.8 and 1.2, a blade angle between 15 and 45, and an aspect ratio of 2.5 or over, and a blade spacing of one half or more.

3. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and to force air in a generally axial direction and to produce static pressure between the oppoiste sides of the fan and overcome resistances in the path of the air stream, said fan having a boss diameter approximately 0.4 of the fan diameter such that the pressure obtainable at the boss is at least 15% of the pressure obtain able at the blade tips, a blade angle between 15 and 45, and an aspect ratio such that the length of each blade from hub to tip is substantially greater than the width of each blade from entrance edge to discharge edge,

and a number of blades at least 15.

' 4. A disk -fan adapted for installation in connection with an opening or conduit to receive power from a shaft and to force air in a generally axial direction and to produce static pressure between the opposite sides of .ratio 2.5 and blade spacing one half or more.

5. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and to force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having blades so formed and set with relation to each other that the blade spacing is not less than onehalf and the pressure co-eflicient at the root of the blade is at least equal the pressure coeflicient at the tip of the blade, the diameter of the boss of the fan being such that the pressure obtainable at the boss is at least 15% of the pressure obtainable at the blade tips, said fan having a width ratio from .8 to 1.2 approximately, and a blade angle between 15 and 45 approximately.

6. A disk fanadapted for installation in connection with an opening or conduit to receive power from 'a shaft and to force air in a generally axial direction and to produce static pressure between the opposite sides of that the blade spacing is'not less than one-- eter of the boss of the fan being such that the pressure obtainable at the boss is at least 15% of the pressure obtainable at the blade tips, said fan having a width ratio from .8 to 1.2 approximately, a blade angle between 15 and 45 approximately, and an aspect ratio of approximately 2.5 or more.

7. A disk fan adapted for installation in connection with an opening or conduit to ree ceive power from a shaft and to force air in a generallyaxial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having blades so formed and set with relation to each other that the blade spacing is not less than one-half and the pressure co-eliicient at the root of the blade is at least equal the pressure coeflicient at the tip of the blade, the diameter of the boss of the fan being such that the pressure obtainable at the boss is at least 15% and 45 approximately, said fan having at least 20 blades.

8. A disk fan adapted for installation in connectlon with an opening or conduit to receive power from a shaft and force air in a generally axial direction and to produce static pressure between the opposite sides of the fan an to overcome resistances in the path of the air stream, said fan having a disk diameter of 0.4 of the fan diameter and blade spacing not less than one-half so that the pressure at the hub is a substantialproportion of the pressure at the blade tips, and with the blades formed and spaced to give dynamic impulses to the airsufiiciently frequently to develop and maintain a static pressure of at least one third inch and to deliver air at the rate of more than three thousand cubic feet per minute for each one third horse power received from the shaft.

9. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and to overcome resistances in the path of the air stream, said fan having a disk diameter of 0.4 of the fan diameter and blade spacing not less than one-half so that the pressure at the hub is a substantial proportion of the pressure at the blade tips, and with the blades formed and spaced to give dynamic impulses to the air sufiiciently frequently to develop and maintain a static pressure of at least one-third inch and to deliver air at the rate of more than three thousand cubic feet per minute for each one-third horsepower received from the shaft, so that the efficiency is greater than 50%, the said blades being adapted to impart to said air a velocity of at least one half the, average linear velocity of the blades.

10. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and to overcome resistances in the path of .the air stream, the said fan having a disk diameter of 0.4 of the fan diameter and blade spacing not less than one-half so that the pressure at the hub is a substantial proportion of the pressure at the blade tips, and with at least 15 blades formed and spaced to give dynamic impulses to the air sufliciently frequently to efficiently develop and maintain a static pressure of at least one third inch, said blades being adapted to impart a velocity to the air at least one half the average linear Velocity of the blades so as to deliver air at the rate of more than three thousand cubic feet per minute for each one third horse power received from the shaft so that the efliciency is greater than 50%.

11. In a disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft, the combination with a central hub or disk of substantially .4 the overall diameter, of a series of not less than 15 blades projecting from the periphery of said hub or disk, and formed and spaced to have a width ratio between .8 and 1.2 and a blade angle between 15. and 45 and to deliver air substantially parallel to the axis of the fan, and to force said air against a counter pressure and to give dynamic impulses to the air sufficiently frequently to efliciently develop and maintain a static pressure of at least one third inch, so that the power received from the shaft is converted by the rotation of the fan blades mainly into the energy imparted to the delivered air.

12. A disk fan as set forth in claim 1 in which the blades are of substantially constant width from hub to tip.

13. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having blades of substantially the samewidth from hub to tip and formed and set with relation to each other to have a width ratio between .8 and 1.2 and a blade angle between 15 and 45 and to overlap at'their inner portions near the hub when viewed in a direction along the axis with a gradual decrease in the overlapping from the hub outward so that at their outer ends the blades are non-overlapping, said blades being adapted to develop and maintain a static pressure of at least one third inch, and to deliver air at the rate of more than three thousand cubic feet per minute for each one third horse power received from Ego shaft so that the efficiency is greater than 14. A disk fan ofclaim 13 in which each blade is warped between hub and tip so as to be more nearly normal to the axis at the tip than at the hu 15. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having blades aerofoil shaped so as to reduce the drag of the blades and of substantially greater length than width so as to have an aspect ratio greater than 2.5, the diameter of said hub or disk being 0.4 of the fan diameter such that the pressure obtainable at the boss is a substantial proportion of the pressure obtainable at the blade tips so that the blades are adapted to maintain a static pressure of at least one third inch and to deliver air at the rate of more than three thousand cubic feet per minute for each one third horse power received from the shaft so that the efliciency is greater than 50%.

16. A disk fan adapted for installation in awidth ratio connection with an opening or conduit to receive power from a shaft and force air in .a generally axial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having blades aerofoil shaped so as to reduce the drag of the blades and of. substantially greater length than width so as to have an aspect ratio greater than 2.5, and warped between the hub and tip so as to be more nearly normal to the axis at the tip than at the hub, the diameter of said hub or disk being 0.4 of the fan diameter such that the pressure obtainable at the boss'is a. substantial proportion of the pressure obtainable at the blade tips so that the blades are adapted to maintain a static pressure of at least one third inch and to deliver air at the rate of more than three thousand cubic feet per minute for each one third horse power received from the shaft.

17. A disk fan adapted for installation in connection with an opening or conduit to receive power from a shaft and to force air in a generally axial direction and to produce static pressure between the opposite sides of the fan and overcome resistances in the path of the air stream, said fan having blades of substantially eater length than width and tween 0.8 and 1.2 and a blade width at any point substantially greater than the perpendicular distance between the blades at said point, and a boss diameter substantially 0.4 of the overall'fan diameter, said blades being formed from a single sheet so as to be integrally connected together at their inner ends and bent atan angle to the plane of the boss and tapered inwardly so as to have a greater width toward their outer 40 ends.

GEORGE 1m BOTHEZAT.

Images