US2169234A - Blower apparatus - Google Patents

Description

Aug. 15, 1939 A. l. PONOMAREFF BLOWER APPARATUS Filed NOV. 2'7, 193'? INVENTOR HLEXHNDER I. PONOMRREFF.

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4 Sheets-Sheet l mlwm ATTORNEY Aug. 15, 1939 A. 1. PONOMAREFF BLOWER APPARATUS Filed Nov. 27, 1957 4 Sheets-Sheet 4 R E m o R H mm m mow G NI i a E DY MB -kzmummm rzmiilu m H m m w. W m m. M w a m s 2 t ET TU n a sT U ww T W I .7 mmunm uukwk 05 6,: mgwwutm 2.5.5

ATTORNEY CRPHGITY a possible.

Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE BLOWER APPARATUS Pennsylvania Application November 27, 1937, Serial No. 176,899

13 Claims.

My invention relates to propeller blowers and it has for an object to provide apparatus of this character which operates with improved efficiency and with reduction in noise.

The improved blower differs over known apparatus of this type in that it includes features contributing to the attainment of the aforementioned objectives. The propeller has a projected blade area ratio of or over, has not less than six blades, and has a blade length of ap proximately ,4; the propeller diameter; and the guide vanes are of airfoil section having blunt.

inlet edges and are spaced from the leaving edges of the propeller a distance of from 9 to 20% of the propeller diameter and preferably from 10 to 16% thereof. Efficiency is improved, not only from the point of View that the novel features contribute to the avoidance of vibration for various reasons, but the rounded and blunt inlet edges of the guide vanes coupled with the spacing of the latter from the propeller secure more efiicient recovery of rotational energy of the air stream discharged by the propeller. Not only should the blower operate to secure the desired static pressure and capacity ef iciently, but it should do so at a maximum speed safely below the critical to avoid excessive vibration of the structure and noise. Both the features of the propeller and of the guide vanes coact to secure highly efficient operation of the blower at the desired static pressure and capacity with suflicient reduction in speed for this purpose. Where the blower is used for forced draft purposes, it is usually desirable to secure operation with high static pressure at a relatively low capacity, and the relatively short propeller blades as well as the propeller blade projected area ratio contribute to the attainment of this result. As to reduction in noise, this is accomplished by avoiding all vibration conditions and air turbulence so far as Mention has already been made of keeping the maximum operating speed safely below the critical speed, but there are other sources of vibration with which features of the invention are concerned. Shortening of the propeller blades raises their natural frequency, and increase in the number of propeller blades raises the fundamental frequency of the noise produced by the propeller, with the result that the resonant speed may be arranged to occur well above the maximum operating speed. The use of the large projected area ratio reduces the possibility of air vibration or pulsations across the propeller. The airfoil guide vanes contribute to reduction in noise, not only because shock losses are largely avoided and smoother operation is secured on account of capacity of the rounded blunt inlet edges to deal with the air stream efiiciently over a wide attack angle range, but, as such guide vanes operate eificiently over a wide range of spacing from the propeller, they may be spaced from the latter sufiiciently to secure a substantial reduction in noise.

Where the blower is of the marine type, as illustrated, it is necessary to have high air velocities to keep the dimensions and weight at a minimum, and this entails the use of an elbow whose radius of curvature is so small that, unless measures to the contrary are taken, excessive air turbulence and consequent noise would occur. Furthermore, the efficiency would be so impaired as to require blower operation at a. higher speed, thereby further tending to increase noise. Therefore, my improved blower, not only includes the aforementioned features contributing to improved efficiency and reduction in noise, but also an elbow with an arrangement of splitter vanes which are effective to reduce turbulence and to improve the efiiciency in consequence of which noise is reduced.

Accordingly, it is a further object of my invention to provide a propeller blower wherein the propeller has blades whose lengths are of the order of A, or less of the propeller diameter, has a projected blade area ratio of the order of 100% and has not less than six blades together with guide vanes of airfoil section having blunt edges which are spaced from the propeller a substantial distance.

A further object of my invention is to provide a propeller blower wherein the propeller has six or more blades, has a projected blade area ratio of the order of 100% and has a blade length which is approximately or less of the propeller diameter.

A further object of my invention is to provide a propeller blower having guide vanes of airfoil section and having rounded or blunt inlet edges.

A further object of my invention to to provide a propeller blower having guide vanes of airfoil section having rounded or blunt inlet edges which are spaced from the propeller a distance of the order of 10 to 16% of the propeller diameter.

A further object of my invention is to provide a propeller blower having guide vanes of airfoil section whose length is of the order of 40% of the propeller diameter.

A further object of my invention is to provide a propeller blower having a diffuser elbow provided with splitter vanes for minimizing turbulence and improving the efiiciency so as to further reduce the production of noise.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in accordance with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a longitudinal sectional view of my improved blower;

Fig. 2 is a sectional view taken along the line II--II of Fig. 1;

Fig. 3 is an enlarged sectional view taken along the line III-J11 of Fig. 1;

Figs. 4 and 5 are diagrams showing variation in the discharge angle of air leaving propellers at different capacities;

Fig. 6 is a development diagram of the propeller;

Fig. '7 is a diagram showing a comparison of efficiency characteristics of thin section and thick section guide vanes;

Fig. 8 is a diagram showing reduction in noise effected by increased spacing of the guide vanes from the propeller;

Fig. 9 is a curved section taken along the line IX--IX of Fig. 1; a

Fig. 10 is a curved sectional view taken along the line X-X of Fig. 1; and

Fig. 11 is a diagram showing improved eiiiciency and static pressures secured by the elbow splitter vane construction.

Referring now to the drawings more in detail, I show a stator structure, at I 0, and a rotor structure at H. The rotor structure embodies a propeller l2 connected to the upper end of a spindle l3 whose lower end is connected to the rotor ll of a prime mover, for example, a steam turbine, at l5, and the stator casing structure has 7 upper and lower bearings l6 and I! for the spindie.

The propeller l2 includes a plurality of blades I! connected at their inner ends to the hub IS.

The casing or stator structure, at It, includes straight and elbow portions 20 and 2|, the straight portion 2! including a converging part 22, a throat part 22 within which the propeller I2 is arranged, and a diverging part 24.

Guide vanes 25 are arranged at the discharge side of the propeller, the outer ends of the guide vanes being joined to the interior of the diffuser part 24 and the inner ends thereof being joined to the central or core sleeve 26 whose upper end is arranged adjacent to and is of substantially the same diameter as the hub l9, which preferably converges in the direction of flow as determined by the desired divergence of the diffuser, and which carries the upper bearing Ii.

Referring now to the improved features of the propeller l2 and of the guide vanes 25 contributing to improved efiiciency and reduction in noise, the propeller has a projected area ratio of 100% or over, has not less than six blades, for example, seven, as shown on Figs. 1 and 2, and has a blade length approximately $4 or less of the propeller diameter; and the guide vanes are of airfoil section having blunt inlet edges and spaced a substantial distance from the propeller. These features also make possible eflicient operation at a relatively high static pressure and low capacity such as usually required for forced draft applications.

Efliciency is improved by the features contributing to reduction or avoidance of vibratory conditions as well as by improved performance of the guide vanes in recovering rotational energy of air discharged by the propeller.

The improved propeller and guide vane features modify conditions of vibration so as to reduce noise substantially and secure eflicient performance under the required conditions of static pressure and capacity at a speed safely below the critical speed with the result that vibration of the structure and consequent resonant noise at the critical speed is avoided. Also such features m0dify other vibratory conditions, or sources of noise generation, as will be immediately pointed out.

In a propeller blower, motion of the propeller blade through the air produces pressure on one side and suction on the other. In the air passage bounded by two adjacent blades, there is the possibility, because of said variation in pressure, of the existence of periodic oscillations of the air leading to the generation of noise. To improve the air passages through the propeller and to avoid the aforesaid oscillations of air, I provide a propeller wherein the air passages are well bounded by the blade surfaces, this result being secured by having a blade projected area ratio of approximately 100 to 120% as shown in Fig. 6..

With a projected area ratio of the order of 100%, the propeller develops from 20 to 30% higher static pressure. Accordingly, on account of the use of a projected area ratio of this order, the blower may be operated at a lower speed with consequent reduction in noise.

A propeller blower produces noise of certain defined frequencies. The fundamental frequency corresponds to the numberv of propeller blades times the number of revolutions per minute of time. For example, a three-blade propeller operating at 3600 R. P. M. produces noise of fundamental frequency of 3 60=180 cycles per second. This low fundamental frequency is difficult to absorb by the use of known sound-absorbent material. Accordingly, the number of propeller blades is increased so as to raise the fundamental frequency. With the specific type of apparatus illustrated, I find it advisable to use not less than six blades; however, the number of blades may be as large as practicable from manufacturing and blower efliciency standpoints.

Where the blower is of the high speed type and where a relatively high pressure at low capacity is required, as may be the case with marine forceddraft blowers for combustion purposes, the propeller blades are made shorter than heretofore, for example, not longer than /4, of the propeller diameter. A propeller having blades of this length produces the pressure corresponding to the tip speed at approximately percent smaller air capacity than a propeller having its hub diameter equal, for instance, to A; of the propeller diameter. Furthermore, shortening of the propeller blade results in one which is mechanically stronger, is less susceptible to flutter during operation of the blower, and one having a higher natural frequency of vibration.

Having enumerated the improved features of construction, the improved guide vanes will now be considered. In a propeller blower, air leaves the propeller at an angle to the axis of rotation of the latter; and, to effect eiiicient operation, it is necessary to recover the energy in this rotational component of air velocity by properly designed guide vanes. Experiments conducted with propellers indicates that the direction of air leaving the propeller varies over a wide range along the radial length of the blades and changes with variation of blower capacity relative to the eter.

capacity at the maximum efliciency. Accordingly, as may be seen from Figs. 4 and 5, it would be impossible to design stationary guide vanes with the entrance angle suitable for such a wide variation in direction of the air leaving the propeller. For this reason, I employ thick section guide vanes having blunt or rounded inlet edges, the latter being more suitable for wide variation of the angle of attack as compared with plate vanes having sharp inlet edges and commonly used heretofore.

As shown in Fig. 7, the use of thick section or air foil guide vanes results in obtaining an efficiency curve, curve A, which is much flatter than the curve, curve B, for plate guide vanes and which is desirable for a blower operating over a wide range of pressures and air capacities. While the degree of bluntness of radius of curvature of the rounded inlet edges of the blades is susceptible to a range of variation with provision for a wide variation of angle of attack, as shown, the guide vanes 25 have blunt or rounded inlet edges whose radius of curvature is greater than A; of the maximum guide vane thickness. In other words, I prefer to use guide vanes having rounded inlet edges whose radii of curvature are of the order of from A to the maximum guide vane thickness. A

The improved guide vanes remove the rotational component of the air velocity more efficiently than the guide vanes heretofore used; and, as a consequence, the axial length of the guide vanes may be reduced approximately 35 percent, that is, from 75 percent of the propeller diameter to about 40 percent thereof, without detrimental effect on the blower efficiency. This reduction of axial length of the guide vane results in reduction of the overall length of the propeller blower, this being important especially indicate that the blower efficiency is influenced by the clearance between the discharge side of the propeller and the inlet edges of the guide vanes, Fig. 7 showing a comparison in this respect of an ordinary plate guide vane with the improved blunt edge guide vane. With guide vanes of thin section, the maximum blower efiiciency is secured when the above clearance is equal approximately to 5 percent of the propeller diam- Also, it was found that noise produced by the blower increases rapidly with the decrease of clearance between the guide vanes and the propeller blades, the relationship of noise to clearance being shown by the curve of Fig. 8. The

use of guide vanes with rounded or blunt leading edges makes it possible to move the guide vanes further away from the propeller to a ,distance, preferably 9 to 20 percent of the propeller diameter and preferably from 12 to 16 percent, without any detrimental efiect to the blower efficiency, this being shown by the thick blade section curve, curve A, of Fig. 7, and wherein it will be noted that the efficiency is at a maximum at 12 percent and is rather fiat from 9 to 20 percent.

A blower constructed as shown in Figs. 1 and 2 so as to take advantage of the foregoing principles has a propeller l2 provided with seven blades 18, having 100 percent projected blade area ratio, and a propeller blade length equal to or less than A; of the propeller diameter. Thick section guide vanes 25 having blunt leading edges are used, these guide vanes being located at a distance of 14.3 percent of the propeller diameter away from the propeller blades and the length of these guide vanes is 39.2 percent of the propeller diameter. It will be obvious, however, that these particular numerical values merely concretely illustrate one example of apparatus having the advantages aforesaid.

In a blower for marine application, for example, for forced draft service, limitations are imposed with respect to overall dimensions and the weight of the unit. Therefore, it is necessary to employ high air velocities to keep the overall dimensions and weight at a minimum. Accordingly, the elbow part 2| of the casing of Fig. 1 is relatively sharp or of relatively small radius. The sharpness of the radius of the elbow portion makes it impossible to realize any conversion of velocity head into static pressure. Furthermore, the air turbulence causes noise. In order to avoid the objections of poor efficiency in converting velocity into static pressure and of turbulence, the elbow portion 2! is divided, by the splitter vanes 30, 3! and 32 into passages 33, 34, 35 and 36 of increasing radii of curvature from the concave to the convex side of the elbow portion. 7

To produce efiicient conversion of air velocity into static pressure in the elbow in Fig. 1, three splitter vanes 30, 3| and 32 are employed, and these splitter vanes are so located in the elbow portion that the ratio of the width or thickness of each passage in a radial direction to the radius of the curvature of the outer bounding surface is approximately the same, that is, if T1. T2, T3, and T4 represent the widths or thicknesses of the passages and R1, R2, R3, and R4 represent the radii thereof, as indicated in Fig. 1, then disclosed and claimed in the patent to Schmidt 1,762,358, June 10, 1930. I have found, as may be seen from Fig. 12, that an elbow portion having splitter vanes, curved generally in the same direction as the elbow portion to provide curved passages of approximately constant ratio of thickness to radius of curvature in the axial plane of symmetry of the elbow portion, as compared to an elbow portion without such splitter vanes, has the effect of substantially improving the maximum efficiency and quietness of operation as well as also making it possible to increase the static pressure. In Fig, 11, the efficiency curve for the elbow portion with splitter vanes incorporated is shown by the full-line curve, which is substantially better than for the elbow casing without splitter vanes and indicated by the dash-line curve. Likewise, the static pressure for the elbow casing with the splitter vane construction and shown by the full-line curve is substantially better than for the elbow casing without the splitter vane structure and indicated by the dash line curve. The improvement in efficiency and pressure developed by the blower, makes it possible, for the same duty, to reduce the blower speed; and, as already indicated, reduction in speed brings about reduction in noise. Furthermore, the splitter vane construction secures more uniform distribution over the air passages in the elbow and reduces turbulence and noise.

Besides the splitter vanes 30, 3| and 32, the elbow casing is provided with the airfoil vanes 31 and 38 arranged at right angles with respect to the splitters 3| and 32, the airfoil vane 31 being arranged in the passage 35 and cooperating with the fairing member or tube 26 to prevent the development of turbulence. Preferably, as shown in the drawings, the tube 26 serves as a shaft tube. In like manner, the vane construction 38 for the passage 36 provides stream-lining about the tube and prevents the development of turbulence and the impairment of efficiency on that account. Thus, by streamlining the tube, where the latter intersects the passages 35 and 36, turbulence that would otherwise be introduced is avoided. Therefore, the tube streamlining reduces turbulence and improves the efiiciency with the result that noise is reduced. With this arrangement of diffuser, the tube 26 avoids a precipitous change in area at the discharge side of the guide vanes 25 and it cooperates with the splitter vanes 3i and 32 and with the vanes 31 and 38 to provide passages with preservation of streamline flow and efficient diffusion or conversion of velocity into static head. Thus, the tube 26 serves in several capacities: it functions structurally as a central member for stiffening and strengthening the casing and guide vane arrangement; it serves as a fairing member to avoid precipitous flow area change; it acts as a shaft tube; and it conducts air to the sealed chamber.

As shown, the blower casing has an upper straight portion joined to the lower elbow portion, the straight portion having a diverging part at the discharge side of the propeller within which are arranged the guide vanes 25 whose outer ends are attached to the casing and whose inner ends are attached to the fairing or shaft tube. Therefore, the upper end of the tube is supported from the casing by the guide vanes and the lower end is supported by the elbow portion wall, the latter having an opening 39 through which the tube extends.

The upper end of the vertical drive shaft I3 is supported by the bearing l5 carried interlorly by the shaft tube at the upper end portion thereof. The drive shaft extends through the elbow wall, is connected to the rotor ll of the motor device l5 and has its lower end carried by the hearing I! supported from the lower side of the motor device IS, the latter being attached by suspension means 40, for example, a wedge pipe section, to the elbow casing. Thus it will be seen that the two bearings l6 and I! are rigidly supported from the casing and serve the double purpose of blower and turbine bearings.

As the upper end of the tube 26, preferably a shaft tube, is disposed adjacent to the propeller hub l9 and as the bearing I6 is located near thereto, the centrifugal pumping effect of the moving hub would tend to draw lubricant from the bearing and discharge it into the air stream unless counteracted. Accordingly, the principle indicated in the patent to Schmidt 1,407,889, February 28, 1922, is used in a specific way, the upper end of the tube 26 being closed by plate structure including the sealing ring 42 having an annular channel 43 encompassing the shaft and supplied with air from the interior of the tube, the latter having its lower end just below the elbow wall opening 39 so that the upper and lower ends of the bearing are subject to the same air pressure and any entraining or suction effect exerted on the upper side of the channel 43 is satisfied by air.

From the foregoing, it will be apparent that I have provided a blower having features and a relative arrangement thereof which contribute to reduction in noise and improved efllclency while preserving a construction, which is capable of delivering air in quantity and at a pressure suitable for marine forced draft purposes and which is relatively light, strong and of small dimensions particularly in an axial direction with the result that, the space required for installation is minimized. Noise is reduced by avoiding all vibration conditions and air turbulence as far as possible: the features cooperate to produce a blower whose maximum speed is well below the critical, whereby an important source of vibration is avoided; shortening of the blades, not only raises their fundamental frequency but makes possible the attainment of a static pressure at a lessened speed, the static pressure corresponding to the tip speed being attained at smaller air capacity; by the use of six or more propeller blades the fundamental frequency is raised and low frequency vibrations, which are difllcult to absorb, are thereby avoided; a projected area ratio of the order of 100%, for example, from 100% to 120%, in connection with which the number of blades is a contributing factor, assures of blade-bound air passages in the propeller wherein air pulsations or oscillations and consequent noises are avoided, and this area ratio also assures of a high static pressure making possible a lower speed and consequent reduction in noise; and, by the use of guide vanes having blunt inlet edges, shock losses as well as noises incidental thereto are reduced and such guide vanes may be spaced an increased distance from the propeller with consequent reduction. in noise. Eificiency is, of course, improved by the features and arrangements contributing to reduction in noise; and, in this connection, efllciency is aided by the use of the improved guide vanes, as the latter recover rotational energy of air leaving the propeller more efficiently, the rounded blunt inlet edges being more suitable for a wide range of angle of attack of air leaving the propeller, the direction of discharge from the latter varying over a wide range along the radial length of the blades and changing with variation of blower capacity relative to capacity at the maximum efficiency, the more ellicient action of the guide vanes also making it possible to reduce the axial length thereof to such an extent that the overall length of the blower may be reduced even though the guide vanes are spaced a greater distance from the propeller. The spacial requirements of the blower, particularly in an axial direction, are further reduced by having the casing thereof provided with an elbow portion of relatively sharp radius, the elbow portion having splitter vanes curved generally in the direction of the latter and dividing the interior thereof into a plurality of passages whose radii of curvature progressively increase from the concave to the convex side of the elbow portion, the arrangement of splitter vanes minimizing turbulence in the elbow portion, reducing noise, and securing operation at higher efllciency and static pressure.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire,

portion encompassing the propeller and having a diverging part at the discharge side of the latter joined to the elbow portion; means for driving the propeller including a drive shaft extending through the elbow portion wall, coaxial with said straight portion, and connected to the propeller; splitter vanes in the elbow portion and curved in the same general direction as the latter for dividing the passage thereof into a plurality of curved passages of progressively increasing radii of curvature from the convex to the concave interior sides of the elbow portion; a shaft tube encompassing the shaft, having one end arranged adjacent to the propeller and having its other end opening through the elbow wall; said other end being carried by the elbow wall and terminating adjacent thereto; guide vanes in the diverging part of said straight portion; said guide vanes having their outer ends attached to the casing and their inner ends attached to the shaft tube; a bearing for the shaft carried interiorly by the end of the shaft tube adjacent to the propeller; means for supplying lubricant to the bearing; sealing means between the bearing and the propeller and including an annular chamber encompassing the shaft; and means for supplying air to said chamber from the exterior of the casing and including said shaft tube.

2. In a propeller blower, a propeller having six or more blades and a projected blade area ratio 'of at least 100%; said blades having a height not exceeding one-quarter the propeller diameter; a casing having straight and elbow portions; said straight portion encompassing the propeller and having a divergent part at the discharge side of the latter joined to the elbow portion; means for driving the propeller including a drive shaft extending through the elbow portion wall, coaxial with said straight portion, and connected to the propeller; a shaft tube encompassing the shaft, having one end arranged adjacent to the propeller, and having its other end opening through the elbow wall and carried by the latter; a bearing for the drive shaft and carried interiorly by the shaft tube at the end thereof adjacent to the propeller; guide vanes in the diverging part of said straight portion and having their inner and outer ends attached, respectively, to the shaft tube and to the casing; said guide vanes having rounded inlet edges spaced from 9 to 20% of the propeller diameter from the discharge edges of the propeller blades; splitter vanes in the elbow portion and curved in the same general direction as the latter for dividing the passage thereof into a plurality of curved passages of progressively increasing radii of curvature from the convex to the concave interior sides of the elbow portion; said drive shaft and shaft tube intersecting one or more of said curved passages; and a vane construction for the shaft tube in each intersected passage and streamlined in the direction of flow. I

3. In a propeller blower, a propeller; a casing having upper straight and lower elbow portions; said straight portion encompassing the propeller and having a diverging part at the discharge side of the latter joined to the elbow portion; means for driving the propeller including a motor device and a drive shaft driven thereby; said motor device being arranged below the elbow portion and the drive shaft extending through the elbow portion wall, being coaxial with said straight portion, and connected to the propeller; a shaft tube encompassing the shaft, having one end arranged adjacent to the propeller, and having its other end opening through the elbow wall and carried by the latter; a bearing for the drive shaft carried interiorly by the shaft tube at the end thereof adjacent to the propeller; guide vanes in the diverging part of said straight portion and having their inner and outer ends attached, respectively, to the shaft tube and to the casing; splitter vanes in the elbow portion and curved in the same general direction as the latter for dividing the passage thereof into a plurality of curved passages of progressively increasing radii of curvature from the convex to the concave interior sides of the elbow; said drive shaft and the shaft tube intersecting one or more of said curved passages; a vane construction for the shaft tube in each intersected passage; arranged substantially normally with respect to opposed walls of the passage and joined thereto, and streamlined in the direction of flow; and suspension means for supporting the motor device from the elbow portion.

4. In a propeller blower, a casing having straight and elbow portions and the straight portion including converging, throat and diverging parts; a propeller in the throat part of the straight portion; said propeller having six or more blades, a blade height of the order of A; the propeller diameter and a projected area ratio of at least 100%; guide vanes carried interiorly of the diverging part of the straight portion and arranged at the discharge side of the propeller; said guide vanes having rounded blunt inlet edges providing for efficient operation over a wide attack angle range and spaced from 9 to 20% of the propeller diameter away from the discharge side of the propeller; said guide .vanes having an axial length of the order of 40% of the propeller diameter; and splitter vanes in the elbow portion curved generally in the same direction as the elbow portion and dividing the interior of the latter into a plurality of curved passages whose radii of curvature increase from the convex to the concave interior sides of the elbow, said splitter vanes and walls of the elbow portion being so spaced that, in the axial plane of symmetry of the elbow portion, the ratio of passage thickness in the direction of the radius of curvature to the radius of curvature is approximately constant for all of the passages.

5. A propeller blower, a casing construction including throat and diverging portions; a pro peller in the throat portion and having a hubya drive shaft arranged coaxially of said throat and diverging portions and having one end connected to the hub of the propeller for carrying the latter; a. shaft tube encompassing the shaft and having one end arranged adjacent to and aligned with the propeller hub; guide vanes arranged at the discharge side of the propeller and having their inner and outer ends attached respectively to the exterior of the shaft tube and to the interior of the diverging portion of the casing construction for supporting the shaft tube from the latter; said guide vanes being spaced from the discharge side of the propeller a distance of the order of 9 to 20 percent of the propeller diameter and each being of curved airfoil section having a rounded inlet edge; means for driving said shaft; spaced bearings for the shaft and including a bearing arranged adjacent to the propeller; and means for supporting the bearings from the casing construction and including the shaft tube carrying internally the bearing adjacent to the propeller.

6. A propeller blower, a casing including straight and elbow sections; the straight section being vertically disposed and the elbow section being joined to the lower end thereof; said straight section including a throat portion and a diverging portion arranged therebelow; a propeller in the throat portion and having a hub; a drive shaft arranged coaxially of the straight section, having its upper end connected to said hub, and extending through and below the elbow section wall; a shaft tube encompassing the shaft, having its lower end opening through the elbow wall, and having its upper end terminating adjacent to the propeller hub; guide vanes arranged at the discharge side of the propeller, having their outer ends joined to said diverging portion, and having their inner ends joined to the upper portion of said shaft tube; a bearing for the upper end of the shaft and carried interiorly by the upper portion of the shaft tube; a structure depending from and carried by the elbow section and axially aligned with the straight section; a lower bearing for the shaft carried by the depending structure; and a prime mover for driving the shaft; said prime mover being embodied as a part of the depending structure and including a rotor arranged between the lower bearing and the elbow section.

-7. In a; propeller blower, a casing including straight and elbow sections; the straight section being vertically disposed and the elbow section being joined to the lower end thereof; said straight section including a throat portion and a diverging portion arranged therebelow; a propeller in the throat portion and having a hub; a drive shaft arranged coaxially of the straight section, having its upper end connected to said hub for carrying the propeller, and having its lower end extending through and below the elbow section wall; a shaft tube encompassing the shaft, having its upper end aligned with and terminating adjacent to the propeller hub, and having its lower end opening through the elbow wall; said lower end of the shaft tube being carried by the elbow section wall and terminating adjacent to the latter; guide vanes in the diverging portion of said straight section; said guide vanes having their outer ends attached to the inner surface of the diverging portion and having their inner ends attached to the exterior surface of the shaft tube; a bearing for the upper end of the shaft and carried inter-iorly by the upper por-' tion of the shaft tube a structure depending from and carried by the elbow section and axially aligned with the straight section; a lower bearing for the lower end of the shaft and carried by said depending structure; a prime mover for driving the shaft; said prime mover being embodied as a part of said depending structure and including a rotor connected to said shaft; means for lubricating saidv bearings; sealing means between the upper bearing and the propeller and including an annular chamber encompassing the shaft; and means for supplying air to said chamber including the shaft tube and openings formed tending to and carried by the elbow section wall; guide vanes in the diverging portion of said straight section; said guide vanes having their outer ends attached to the inner surface of the diverging portion and having their inner ends attached to the exterior surface of the tube; splitter vanes in the elbow section and curved in the same general direction as the latter for dividing the passage thereof into a plurality of curved passages; said tube intersecting one or more of said curved passages; a vane construction for the tube in each intersected passage, arranged substantially normally with respect to opposed walls of the passage and joined thereto, and streamlined in the direction of flow.

9. In fluid translating apparatus, a casing including straight and elbow sections; said straight section including a throat portion and a diverging portion connecting the throat portion to the elbow section; a propeller in the throat portion and having a hub; means for driving the propeller; a tube having one end aligned with and terminating adjacent to the hub of the propeller at the discharge side of the latter and having its other end extending to and carried by the elbow section wall; guide vanes in the diverging portion of said straight section; said guide vanes having blunt inlet edges providing for efficient operation over a wide attack angle range and spaced from 9 to of the propeller diameter away from the discharge side of the propeller; said guide vanes having their outer ends attached to the inner surface of the diverging portion and having their inner ends attached to the exterior surface of the tube; splitter vanes in the elbow section and" curved in the same general direction as the latter for dividing the pas sage thereof into a plurality of said curved passages; a vane construction for the tube in each intersected pa'ssage, arranged substantially normally with respect to opposed walls of the passage and joined thereto, and streamlined in the direction of flow.

10. In fluid translating apparatus, a casing including straight and elbow sections; said straight section including a throat portion and a diverging portion connecting the throat portion to the elbow section; a propeller in the throat portion and having a hub; means for driving the propeller; said propeller having six or more blades, a blade height of the order of A or less of the propeller diameter and a projected area ratio of at least 100%; a tube having one end aligned with and terminating adjacent to the hub of the propeller at the discharge side of the latter and having its other end extending to and carried by the elbow section wall; guide vanes in the diverging portion of said straight section; said guide vanes having blunt inlet edges providing for efficient operation over a wide attack angle range and spaced from 9 to 20% of the propeller diameter away from the discharge side of the propeller; said guide vanes having their outer ends attached to the inner surface of the diverging portion and having their inner ends attached to the exterior surface of the tube; splitter vanes in the elbow section and curved in the same general direction as the latter for dividing the passage thereof into a plurality of said curved passages; a vane construction for the tube in each intersected passage, arranged substantially normally with respect to opposed walls of the passage and joined thereto, and streamlined in the direction of flow.

11. A propeller blower comprising a casing, a

propeller in the casing, and transversely curved guide vanes carried interiorly of the casing at the discharge side of the propeller for converting rotational movement of air discharged from the propeller into axial movement, and whereinto minimize the noise level with maintenance'i-ofhigh efiiciency, the guide vanes are of airfoil section and have rounded blunt inlet edges providing for efficient operation throughout a wide range of angle of attack for air discharged from the propeller and spaced from 9 to 20 per cent of the propeller diameter away from the discharge edges of the propeller blades.

12. The combination as claimed in claim 11 wherein the inlet edge of each guide vane has a radius of curvature of the order of from onequarter to one-half the maximum guide vane thickness.

13. A propeller blower comprising a casing, a.

propeller in the casing, and transversely curved guide vanes carried interiorly of the casing at the discharge side of 'the propeller for converting rotational movement of air discharged from the propeller into axial movement, and wherein, to minimize the noise level with maintenance of high efliciency, the propeller has six or more blades, has a projected blade area ratio of 100 per cent or over, and has a blade length of the order of 25 per cent or less of the propeller diameter and the guide vanes are of airfoil section with rounded blunt inlet edges providing for efiicient operation throughout a wide range ofj angle of attack for air discharged from the pro peller and spaced from 9 to 20 per cent of the propeller diameter away from the discharge edges of the propeller blades.

ALEXANDER I, PONOMAREFF.

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