US2004571A - Fan - Google Patents

Description

June 11, 1935- G. DE BOTHEZAT 2,004,571

FAN

Filed Sept. 8, 1931 3 Sheets-Sheet l AITTORNEYS June 11, 1935. r 6. DE BOTHEZAT FAN Filed Sept. 8, 1931 3 Sheets-Sheet 3 v INVENITOR 62 01" vP630 Iii/{gal BY.

ATT'ORNEY Patented June 11, 1935 FAN Application September 8,1931, Serial No. 561,524 12 Claims. (Cl. 230-123) This invention relates to rotary fans and par- The air is drawn inward ticularly to fans for delivering a 'gas such as air compressed somewhat and delivered by the 1min'large quantities and against considerable repeller F into the space between sistance.

The object of the invention is to provide such a ther compressed and delivered in a c fa of simple compact structure and high efiistream from the right or outlet end of.

Fig.1 is'an end view of a. fan unit, portional generally to the angl Fig. 2 is a vertical sectional view of the same id under hi h th stream meets t aero. with parts broken away, foil and the square of the velocity W 1 Figs. 3, 4 and 5 are diagrammaticviews illllS- ever there are a number of aerofoils trating the blade action of the impellers, i r w on whi h a, tream of velocit Fig. 6 is a sectional view of an impeller showing directed, t th i resistance R, of ach aer the hub and blade structure,

Figs. 7 and 8 are views similar to Fig. 2 but illustrating modifications,

9 is amend View of a modified form of the aerofoils; this is half the geometric sum of paratus, and

I e only s l eroforl s Fig. 10 1s a corresponding side view of the same and W h n mg 8 a 1 .with parts broken away,

Fig. 11 is an end view of a further modification,

and aerofoil, the so-called down wash in this case being only a local phenomenon afiecting part Fig. 12 1s a side view of the same with parts broken away of the stream only. But in the case of a row of foils (Fig. 4) spreading across the stream, In the embodiment of the invention shown in aero Figs. 1 and 2 a cylindrical housing i0 is provided the whole of the stlieam 1s deflected and the spindles i2 upon which are rotatably mounted the mg 9 the aerofofls' The more, aerofqils there 40 tudinal bolts l5 passing through the bushing the greater W111 be Y streamflefiecfilon P170" Spacers is, giving a very light sturdy Structure to duced by theaerofofls. The air resistance R t housing as a whole A driving Humorv n is of each aerofoil W111 be related to the amount of mounted on top of the housing, carrying th pu1.. deflection the stream undergoes so that the releys l8 and ill at the opposite ends of the shaft, 81815811166 R depends not Only p h entering the pulley g driving the pulley 2g of rotor F and velocity W, but also upon the discharge velocity the pulley l9 driving the pulley 2| of the rotor F As above pointed out, this reslstance by means ofareverse idler combination, described Will be proportional to the Squa of the 5 and claimed in my copending application Serial metric mean W of W and W". If the blades of No. 514,505. A separate housing 22 may be prothe disk fan are cut by a coaxial cylinder. and

together at the top ridge member 25. foilsso that the law of air resistance for the fan stream behind the second fan F no rotation of the final air blaldes will correspond to that of a row of aerofoi S.

If there are two disk fans coaxial and rotating in opposite directions so that both are operating in the same slip stream (the stream created by a rotating blade screw being usually called slipstream), and if as shown in Fig. 5 the aerofoil cross sections represent one blade of each of the disk fans taken at a distance r from the fan axis and if 9 is the angular velocity of rotation, assumed equal but of opposite sense, for both fans, then the air stream in passing the fan F will acquire an angular velocity w, and after passing fan F the air may still have an angular velocity (0" (all these assumptions being referred to a distance r from the fan axis).

The impellers F, F may be so formed. and related that the first impeller F will impart to the stream a rotational component which will be reduced to zero by the action of the second impeller F so that w" equals zero, then there is stream, and there will be no rotational losses in the discharge. The losses are thus confined to the blade losses, impact, friction and the like, and high efficiency will be attained. According to the theorem of moments of momentum, the rotating effect of fan F will be counteracted by fan F when the torques applied to each of the fans are equal in magnitude but opposite in direction. slip-stream leaving fan F will have no rotation because each fan communicates to the air stream equal opposite rotation momentum, and thus the resulting rotation behind the second fan F will be zero.

The conditions under which impellers F, F operate are not identical, and there is, therefore, required a complementary change in the characteristics of these impellers in order that they shall have equal torques under these different conditions. The relative velocity W1-to be used to estimate the air resistance on each blade of fan F-is the resultant of the axial stream velocity 'v and the velocity 1' nrw=r (SB-w) where (0 equals one half (0'. But the relative velocity W2 for the second fan F is the resultant of 12 It thus follows that the magnignitude of W1 or We W1 but the angle of W2 with the plane of rotation of fan F is smaller W1 with the plane of rotation of fan F. Now if the angle of attack of the blades of each fan in relation to W1 and W2 respectively is substantially the same, in order to have the torques equal, fan F must have a smaller total blade area than fan F or a smaller number of blades if both fans have blades of equal size. In addition, since it is desirable to have the angles of attack substantially the same, the blade angles 1 of the blades of fan F must be larger than angles z of the blades of fan F. Only under these conditions can the resultant pressure on the blades be equal, the torques being proportional to these resultant pressures.

Therefore, a set of two coaxial disk fans rotating in opposite directions in their mutual slip stream will have highest efficiency when the slip does not rotate. This condition of no rotation will be realized when the torques applied to the fans F, F are equal in magnitude and opposite in direction, and this equalityof torques can only be realized-for two fans rotating speed-when the first fan has more blades than the second, in case of blades of equal width, and the blade angles of 21 carries the the blades of the first fan F are larger than the blade angles of the blades of the second fan, these blade angles being taken with respect to the plane of rotation.

Since as above explained the rotational energy communicated to the air by the first impeller can be fully recovered by the second impeller, it is advantageous to form the blading of the first impeller to impart a high rotational component to the stream, thus giving the discharge from the first impeller F additional energy. To achieve this, very high blade angles are used in the first impeller F, generally higher than 45, and the second impeller F, as explained above, has a smaller blade angle, as a rule smaller than 45. In this way the air drawn in by the first impeller F of the pair has imparted to itnot only the full axial velocity required for the desired delivery, but also a'very high angular velocity around the axis so that the resultant stream line, particularly in the outer portions of the flow, may be at an angle as high as 45, as shown by a thread line interposed in the stream. This means greatly increased efiiciency for the first impeller calculated on the basis of a total energy delivered to the discharge. Ordinarily, a large proportion of the energy of this whirling discharge would be turbulence due to the whirl. With cooperating second impeller F, however, this whirl is effectively and efficiently recovered so that the final discharge is substantially axial in direction, and the high whirl of the fiow entering the second impeller enables it to also operate very efliciently on the stream as a whole so that the combined effects of the two impellers represent increase in efficiency over that attainable by a single impeller producing the same delivery against the same pressure.

The above conclusions have been'tested and confirmed and high efiiciencies, substantially have been attained, and it is found that the static pressure developed by a properly cooperating pair of disk impellers and the air volume delivered thereby are substantially double the pressure and delivery of a single disk impeller of the same diameter and speed. Both the pressure and the volume are doubled.

Consequently, good air deliveries and high attainable at relatively low speeds, resulting in the very important characteristic of quietness in operation. The cooperating series of impellers-thus build up pressure from stage to stage while efiiciently and silently passing large quantities of air by impeller-blower action.

In Fig. 6 one form of construction of the impeller is shown built up of four parts. The hub blade 28 by means of the connecting disks 29. The blades 28 are bent to form flanges fitting between the disks 29 and riveted thereto as indicated at 3|, while the inner portions of the disks 29 are fastened to the fiange of the hub 21 by the through rivets 30.

In the modification shown in Fig. I there are a series of impellers I, II, III and IV receiving the air flow at the left and discharging it at the right. The impellers I and IV are mounted on one shaft 35 passing through a hollow are mounted the impellers II and III. Bearings 31 and 38 of stays 39 and 40 support'the shaft. The hollow shaft 36 is either mounted on the shaft 35 stays 39 and 40 at each end. are driven by pulley 4| lted to the pulley 42 at the left end. of the motor 43, the pulley 44 at the shaft 36 on which so that pulleys 4| and 45 are driven in opposite ponents. Then the second impeller recovers this 5 directions. For small powers a cross belt could rotational energy and finally delivers the air be used instead of the reversing idlers. This under increased pressure and with the discharge construction provides two pairs of impellers with substantially axial in direction. the members of each pairrotating in opposite I claim:

directions. The impellers II and III have the 1. A fan unit consisting of a housing and a l0 l5 velocity imparted to the flow by the impeller I. charging the gas at the opposite end of the series In Fig. 8 a modification is shown providing for with substantially no rotation of the discharge six or eight impellers in series. Impellers I, IV, around the axis, and means for driving said im- V and VIII are mounted on one shaft 50 passing pellers with relatively opposite rotations at subthrough two hollow shafts 5|, 52 on which are stantially the same speed the impellers rotating mounted respectively the impeller sets II, III, in opposite directions having their respective 20 VI and VII. The impeller set II,-III on hollow blade widths and blade angles and the number shaft 5| is driven by the pulley 53 from the moof blades different as to at least one of these I 25. motor'pulley 55 and the reversing idlers 56. The operating conditions. 5

rotating in opposite directions; This combinapair rotating in opposite directions with respect to each othe 5 also by central bearing 60 and end bearings 6| ing their respective blade widths and blad and 62. The hollow shaft Si is journaled in the angles and the number of blades diiTerent as to bearing 63, and' hollow shaft 52 in bearing 64, at least one of these features and so related that from the housing by any desired form of stay cal under normal operating conditions. members, such as those indicated at B5. 3. A fan unit comprising a pair of coaxial disk 40 Instead of reversing by idler pulleys, a reversfan impellers drawing a supply of gas at one ion so as to give drives in opposite directions at proportionately large, and the following impeller the opposite ends of the motor. being adapted to substantially neutralize said In Figs. 9 and 10 a motor 60' is mounted on'a rotation and deliver the stream substantiallybase 6| supporting th f n h ing the axially, the impellers rotating in oppositedirec 50 s provided for by reversing gears contained in blades so related that their torque resistances are the extension housin a he nd f he m substantially identical under normal operating 35 tor 60'. conditions. In Figs. 11 and 12 a further modification is 4. A fan unit comprising apair of coaxial'disk shown in which the motor 65 carries the imfan impellers drawinga supply of gas at one Dellers F, F, the motor being mount d by s ys end, passing it through the space between the 66' in the casing 61' on base 68'. Reducti n impellers, and discharging it at the opposite end, 0 g aring is p ovided between e tor a matu e the first impeller havinglarge angle blades adapt-. and the impell r ha this gearing f he imed to impart a rotation 'of over 25 to its dis-' peller F being enclosed in the ca While charge stream so that the rotational energy in the gearing or the impeller is enclosed n the discharge is proportionately large, and the the casing 70'. The entire motor assembly forms following impeller having relatively fewer blades one unit and the reduct n gearings are e nat angles smallerthan those of the preceding imstructed to drive the impelle in opp direcpeller adapted to substantially neutralize said tions. rotation and deliver the stream substantially axpair imparts a rotation to its discharge so that 5. A fan unit comprising a pair of coaxial disk the stream lines between the impellers of each fan impellers drawing a supply of gas at one pair are generally helical and with a helix angle end, passing it through the space between the widths and impellers, and discharging it at the opposite end, the first impeller having blades at angles over 45", adapted to impart a rotation of over 25 to its discharge stream so that the rotational energy in the discharge is proportionately large, and the following impeller having blades at angles less than 45 adapted to substantially neutralize said rotation and deliver the stream substantially axially, the impellers rotating opposite directions having their respective rotary speeds and blade widths and the number of blades so related that their torque resistances are substantially identical under normal operating conditions.

6. A fan unit consisting of one or more pairs of disk impellers in series, the impellers of each pair rotating in opposite directions with respect to each other, a housing in, which said impellers are mounted and means for driving said impellers, the first impeller of each pair having more blades than the second impeller of the pair,

the impellers rotating in opposite directions having their respective rotary speeds and blade blade angles so related that their torque resistances are substantially identical under normal operating conditions.

'7. A fan unit consisting of one or more pairs of disk impellers in series, the impellers of each pair rotating in opposite directions with respect to each other,'a housing in'which said impellers are mounted and means for driving said impellers, the first impeller of each pair having more blades and larger blade angles than the second impeller of the pair,

speeds and blade widths so related that their torque resistances are substantially identical under normal operating conditions.

8. A fan unit consisting of pairs of disk impellers in series, the impellers of each pair rtating in opposite directions with respect to each other, a housing in which said impellers are mounted and means for driving said impellers, the first impeller of each pair having larger blade angles than the second impeller of the pair, the impellers rotating in opposite directions having their respective rotary speeds and blade widths and the number of blades so related that their torque resistances are substantially identical under normal operating conditions.

9. A four-stage fan unit comprising two pairs of impellers in series, each pair separated by intervening air spaces of greater axial extent than the impeller blades, the impellers of each pair having their individual impellers rotating in the impellers rotating in opposite directions having their rotary rotating each opposite directions and means for driving all of said impellers from a single motor, the impellers rotating in opposite directions having their respective rotary speeds and blade widths and bladeangles and the number of blades so related that their torque resistances are substantially identical undernormal operating conditions.

10. An eight-stage fan unit comprising four pairs of impellers in series with the individual impellers of each pair rotating in opposite directions, and means for driving all of said impellers from a single motor comprising a shaft for the first, fourth, fifth and eighth impellers and separate shafts for the second and third and sixth and seventh impellers, and a single motor means for driving said first mentioned shaft in one direction and the remaining shafts in the opposite direction, the impellers rotating in opposite directions having their respective rotary speeds and blade widths and blade angles and the number of blades so related that their torque resistances are substantially identical under normal operating conditions.

11. A fan unit comprising, housing symmetrical about mounted on said axis, rotating each of the two fans constituting a pair in opposite directions and with speeds having at all times a definitely predetermined ratio, the blading for the first impeller having high blade angles designed to create a pronounced spiral flow, the second impeller having much smaller blade angles, and the blade width and blade area being designed to give the second impeller substantially the same torque in reverse direction as the first impeller and to convert the spiral flow into an axial flow at higher pressure than at entry into the pair.

12. A fan unit comprising, in combination, a housing symmetrical about its axis, disk fans mounted on said axis, driving means suitable for of the two fans constituting a pair in opposite directions and with speeds having at all times a definitely predetermined ratio, the blading for the first impeller having high blade angles designed to create a pronounced spiral flow, the second impeller havingv much smaller blade angles and fewer blades, and the blade in combination, a its axis, disk fans width and blade area being designed to give' the second impeller substantially 'the same torque in reverse direction as the first impeller and to convert the spiral flow into an axial flow at higher pressure than at entry into the pair.

GEORGE or: BOTHEZAT.

driving means suitable for

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