WO1995013472A1

WO1995013472A1 - Air moving system with optimized air foil fan blades

Info

Publication number: WO1995013472A1
Application number: PCT/US1994/013074
Authority: WO
Inventors: Joseph Guida; Hani M. Odeh; George J. Carlin
Original assignee: Penn Ventilator Co. Inc.
Priority date: 1993-11-12
Filing date: 1994-11-10
Publication date: 1995-05-18
Also published as: AU1177495A

Abstract

An air moving system for moving air in ducts (35), including a motor (17), having a shaft (19) for rotation about an axis (23) with the shaft extending axially from the motor in the opposite direction from the desired air flow (33). An inner hub (25) is mounted on the shaft, the hub having an elliptical face for directing air around said hub. A plurality of rotor blades (27) are mounted on the hub for pulling air from the face to discharge the desired airflow into the air ducts. A housing (13) surrounds the motor and blades providing a cylindrical clearance (31) between the housing and the outward tip of the blades as they rotate. The blades having a mean camber line producing maximum lift and minimum drag, and the blades having a twist by providing uniform flow over the blade length from hub to tip.

Description

AIR MOVING SYSTEM WITH OPTIMIZED AIR FOIL FAN BLADES

TECHNICAL FIELD

This invention relates to axial fan and centrifugal blower systems. More particularly, the present invention relates to an air moving system for moving air in ducts using axial fans or centrifugal blowers which include blades having a maximum lift and minimum drag to provide superior efficiency of operation.

BACKGROUND ART

Considerable effort has been expending in designing air moving systems for moving air in air ducts. These systems employ fans intending to operate at low pressure ratio and low tip speed. These fans function similarly to aircraft propellers, but have certain significant differences. Typically, since air is intended to be moved into or through air ducts, the fan itself is shrouded or enclosed. The efficiency of the fan is determined by the pressure rise, which is a function of lift.

Of course, the intended purpose of ventilating fans is to operate at below the point where the fans tend to stall and yet produce a maximum pressure rise. The stall point, where the fan starts to break down, causes a large reduction of lift and a corresponding large power increase.

One factor which must be addressed in the design of fans is the Reynolds number. For example, in wind tunnels, the Reynolds number will be in excess of a million, as it is on airplanes and other devices operating in severe turbulence. Air moving systems for moving air ducts, however, operates at a much lower Reynolds number, such as in the order of 60,000 to about 300,000. Propellers of commercial aircraft operate Reynolds numbers between 3,000,000 and 15,000,000. By contrast, sail planes, ultrali te aircraft and gliders will have wing Reynolds numbers below about 350,000.

In a typical room air fan, the Reynolds number is about 60,000 and there is a very low pressure rise. Very little air is actually moved. In air moving systems using fans "to move air in air ducts, it is desirable to move more air than with typical room air fans. These fans, used in air ducts, are driven by standard motors which typically operate at 1700 rpm or in the range of below 1500 rpm to above about 2000 rpm. These fans have a Reynolds number at the root of the blades in the order of 60,000 at the tip of the blades in the order of about 300,000.

To date, efforts have been unsuccessful in borrowing technology from airplane and helicopter blades, primarily due to the significantly different Reynolds number of operation and due to the relatively low rotating speeds and power demands. Nishikawa et al. U.S. Patent Number 4,358,244 discloses a blade for a diagonal flow fan in which

an attempt is made to improve efficiency using difficult to achieve wing profiles or air foil profiles. Noonan U.S. Patent Number 4,412,664 describes and air foil which is useful for rotor aircrafts such as helicopters. An attempt is made to provide a family of air foil shapes to accommodate the life coefficient for these rotor air foils as air flow reaches mach number of near 0.80. This is, of course, way beyond the range of air speed for fan systems.

Wainauski et al. U.S. Patent Number 4,941,803 discloses a family of air foils for use in high solidity factor blades in which the air foil family is characterized by various sections having specific camber. In a similar manner, Kimball U.S. Patent Number 5,064,345 describes a multiple blade fan operating near a heat exchanger such as an automobile radiator. The blades have a high forward sweep of the leading edge angle near the tip of the blade and a high rearward sweep near the blade root. A band is attached to the tips of the blades to reduce recirculation and to improve strength. One other example of blade design is Shenoy U.S. Patent Number 5, 137,427 which describes a quiet tail rotor designed for maximum thrust or lift efficiency. A major portion of the air foil has a predetermined constant air foil cross section with a thickness greater than 12% of the chord length.

As is easily discerned, none of these patents describe a system for moving air in air ducts. As noted above, these fans are driven at constant rotation speeds such as, for example, 1700 rpm. Prior art fans have been designed to produce a constant pressure riser and have been figured in various way to accomplish that goal. Typically, the pressure rise is constant only under one set of conditions, and variations in velocity and resistance under operating conditions tend to reduce the efficiency of the device substantially. Fan blade configurations and air foil cross-section design of the prior art have not provided an efficient and effective air moving system for moving air in air ducts.

Accordingly, it is an object of the present invention to provide an air moving system which employs a plurality of axially rotating rotor blades which operate at increased efficiency.

Another object is provide an air moving system which operates efficiently to move air at Reynolds numbers ranging from below about 60,000 to above about 300,000 at motor rotational speeds of about 1500 to 2000 rpm.

Other objects will appear hereinafter. DISCLOSURE OF THE INVENTION

It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, an air moving system has been discovered for moving air in air ducts.

The system of this invention includes a motor having a shaft for rotation about an axis.

The shaft extends axially from the motor in a direction opposite to the direction of the

desired air flow. At the inlet side of the system, the shaft has an inner hub mounted

thereon. The hub has an elliptical face for directing air around the hub and into the blades which are mounted on the hub.

A plurality of rotor blades, preferably three, are mounted on the hub for pulling air from the face of the hub through the blades to discharge air into the air ducts at a desired air flow rate. A housing is included, surrounding the motor and the blades such that the housing is configured to provide a cylindrical clearance between the housing and the outward tip of the blades as they rotate. This clearance is normally small, preferably in the range of about 1/8 inch. The purpose of the housing, in addition to protecting the fan and enclosing the air flow in the desired direction, increases the efficiency by preventing loss of air and eliminating or substantially reducing vibration. In these air moving systems, turbulence is generated at the tip of the blade, particularly at the trailing edge. The close gap of, say for example, 1/8 inch, breaks up this turbulence and substantially improves efficiency. The principal advantages of the present invention are achieved to a great extent due to the improved design of the rotor blades. These blades are formed to have a mean camber line producing maximum lift and minimum drag. Blades have a twist to provide uniform flow over the blade length from hub to tip. Thus, air is moved at the same velocity throughout the blade length, from hub to tip and the lift is therefore constant.

Contrary to most if not all prior art fan systems, the motor which drives the shaft which in turn mounts the hub and blades is located down stream. This location is contrary to prior teaching because it places the motor in the path of the air flow which has been generated by the fans, causing turbulence after the fan. It has been discovered, however, that efficiencies are far greater if there is an unobstructed laminar flow of air into the fan. Loss of efficiency is much less with this configuration. Stated another way, the fan system is more efficient if laminar flow introduced into the blades and turbulence is only generated after air has left the fan blades and is entering the air ducts.

The air system of this invention is designed to produce an air flow with a relatively specific range of Reynolds numbers. Reynolds number of the air being transferred to the air ducts will range from about less then 60,000 at the hub of the fan blades to above about 300,000 at the tip of the blades, and generally will be in a narrower range defined by these lower and upper limits. Motor speed is typically determined by existing fans, and will range from about below 1500 rpm to about above 2000 rpm. The present invention contemplates air foil fan blades having specific as will be described hereinafter. It has been found with the present invention, that proper selection of the blade configuration for a given system will produce efficiencies which have been heretofore impossible to be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects of the present invention and the various features and details of the operation and construction thereof are hereinafter more fully set forth with reference to the accompanying drawings, where:

Fig. 1 is a semi-schematic side elevational view of a tube axial duct fan, with a portion cut away and in section showing details of the fan and motor, an arrow indicates the direction of induced air flow.

Fig. 2 is a right hand end elevational view of Fig. 1 illustrating additional details of construction.

Fig. 3 is an enlarged front elevational view of the 3 blade fan shown in Fig. 1 having blades with an optimized dual surface air foil and of a non-linear twist.

Fig. 4 is a bottom plan view of Fig. 3 clearly illustrating the optimized dual surface air foil having a non-ϋnear twist.

Fig. 5 shows the cross sectional plan of the optimized mean camber air foil obtained by the present invention.

Fig. 6 is a complete set of x/c and y/c coordinates of the optimized air foil shown in Fig. 5. Fig. 7 shows an optimized plate air foil developed by bending flat sheet metal such that its thickness centerline conforms exactly to the mean camber line shown in hig. 5.

Fig. 8 shows an optimized dual surface air foil section, also drawn in accordance with present invention.

Fig. 9 is a complete set of x/c and y/c coordinates for the optimized dual surface airfoil shown in Fig. 8.

Fig. 10A is a graph showing the lift coefficient versus angle of attack for the optimized plate airfoil shown in Fig. 7.

Fig. 10B is a graph showing the drag coefficient versus angle of attack for the optimized plate air foil shown in Fig. 7.

Fig. IOC is a chart showing the max coefficient of lift for Reynolds numbers ranging from 80,000 to 300,000 for the optimized plate air foil shown in Fig. 7.

Fig. 11 A is a graph showing the lift coefficient versus angle of attack for the optimized dual surface air foil shown in Fig. 8.

Fig. 11B is a graph showing the drag coefficient versus lift coefficient for the optimized dual surface air foil shown in Fig. 8. Fig. 11C is a chart showing the max coefficient of lift for Reynolds numbers ranging from 80,000 to 300,000 for the optimized dual surface airfoil shown in Fig. 8.

Fig. 12A is a schematic illustration of a twisted propeller blade having a dual surface air foil cross section of constant blade chord as viewed from the propeller tip to the hub as in side elevation in this illustration the blade has been twisted about the mid point of the chord length and is of a non-linear configuration. Fig. 12B is a schematic illustration of a twisted propeller blade having a dual surface air foil cross section and a constant blade width as viewed from the propeller tip to the hub.

Fig. 12C is a schematic illustration of a dual surface air foil having a constant collective pitch in that from tip to hub the chord of the air foil presents the same angle, there is no twist.

Fig. 13 A is a table showing some of the design parameters and performance data for a typical tube axial fan having 3 blades of a dual surface air foil cross section and a non-linear twist.

Fig. 13B is a table similar to Fig. 13A but for a fan having blades of a linear twist distribution.

Fig. 13C is a table similar to Figs. 13A and 13B but for a fan having blades of a constant collective pitch. BEST MODE FOR CARRYING OUT THE INVENTION

The system of the present invention is shown generally in Figs. 1 and 2 by reference numeral 10. The system includes a base 11 on which is mounted a housing 13. Mounted within the housing 13 is a T-shaped motor mount 15 which supports motor 17. Motor 17 is designed to operate at rotational speeds in the order of 1500 to 2000 rpm. Shaft 19 rotates hub 21 about axis 23. The front portion 25 of hub 21 is elliptical in shape, to assist in the flow of air being drawn in by blades 27.

Each of the blades 27 is considered fr maximize the efficiency of the invention as will be described herein below. Each se,^~ n of each blade functions as an air foil rotating about the axis 23 to produce the - nest rise attainable in the environment of the system. Flow across blade 27 from the blade root 29 to the blade tip 31 is uniform as is the pressure rise over the entire length of the blade. As the fan blades 27 rotate about axis 23, air is pulled into the housing 13 over the elliptical face 25 of hub 21 by blades 27, and is dispersed in the direction of arrow 33 through cylinder 35 and on to other duct sections 39. Air which is drawn in over the ellipse 25 of hub 21 is laminar and generally unobstructed as it is drawn in by the blades 27.

The flow of air through the blades experiences a variation in flow from the root of the blade 29 to the tip 31. Typically, the Reynolds number of air flowing at the hub will be around 60,000, which the Reynolds number of the air flowing at the tip 31 will be in the order of as much as 300,000 or more. Because of the close proximity between the tip 31 of the blade 27 and the cylinder 35, turbulence which is generated at the end of the blade is broken up. As has been mentioned, for a typical fan system of the present invention, a 1/8 inch gap is sufficient to increase efficiency, by avoiding loss of air and reducing or eliminating vibration of the system. The location of the motor 17 on the discharge end of the fan does not offer substantial resistance to flow. This location of the motor is believed to represent an improvement of the prior art.

As is clear from Fig. 1, the fan shown is a three blade configuration. These blades have an optimized dual surface air foil having a non-linear twist. Fig. 3 indicated some important radial dimensions for a typical fan which has been built in accordance with the present invention. Specifically, R_d is the radius of the inner diameter of chamber 35 which, in practical embodiments will be about 8J25 inches. R_b is the radius of the three blades, shown here at 8.0 inches. R_h the radius of the hub, shown here at 2.4 inches. The blade chord, which is a constant width, is 5 inches. The gap between the tip 31 of blade 27 and the cylinder 25 is measured by subtract R_b from R_d. In this case, it is 1/8 inch.

Turning now to Fig. 4, the configuration of the blades is illustrated in greater detail. These blades are designed to move air at the same velocity throughout the length of the blade from hub portion 29 to tip portion 31. Lift is constant in this configuration and much greater efficiency is achieved.

In Fig. 4, blades 27A and 27B are slanted back while blade 27C is perpendicular to the plane of the paper. Blade 27C illustrates the twist that is imparted to the blade over its length. 27H illustrates the blade at its intersection with hub 21 and 27T represents the blade at its tip. Views 27H and 27T of the blade 27C illustrate the twist of the blade, but, since it only represents the blade at the hub and at the tip, it is not possible to see from this view that the twist is linear or non-linear.

Fig. 4 also illustrates an enlarged view of hub 25 and its elliptical shape. The ellipse of hub 25 is shown as a 1:3 ellipse in Fig. 4.

The air foil blades of the present invention have been designed to produce optimum lift and drag coefficients and achieve the objects of the present invention in te- .. of efficiency and the like. These blades were developed with an intention that they be

easy to manufacture, have no hysteresis loop in the Reynolds number range from below about 60,000 to above about 300,000, and that they have small or no lift variation over that Reynolds number range. It is desired that the lift coefficient maximum be greater than or equal to 1.2 and that there be a low minimum drag coefficient.

Shown in Fig. 5 is a cross-sectional plan view of the optimized mean camber for a plate air foil obtained in accordance with the present invention. The dimensions are based on a unit chord len C so that when a blade size is selected, all of the dimensions are fractional portions of the chord length. In Fig. 5, the position of the maximum camber is at 0.50C, or at the middle of the chord line. Shown in Fig. 6 are the x/c and y/c layout coordinates for an optimized mean camber for a plate air foil of the present invention, shown in Fig. 5, where the maximum camber is shown as 0.060C, occurring at x/c = .5. It is also noted that the mean camber line is symmetrical from x/c = 0, to x/c = 1, the length of the chord line. The air foil profile shown in Fig. 5 represents the preferred mean camber line of the present invention. X defines a station along chord r with respect to the leading edgt of the ι: air foil. Y defines the vertical distance to the mean camber line with respect to the chord C.

Fig. 7 represents an optimized plate air foil developed according to the principles of this invention by bending a flat sheet of sheet metal to conform exactly to the mean camber line shown in Fig. 5. The plate has a thickness of 0J62C and extends + or -

0.081C on either side of the mean camber line. Again, the maximum camber is at 0.50C and is 0.060C. The entire thickness in the Y direction is OJOC, as illustrated on the left hand side of Fig. 7.

While the air foil shown in Fig. 7 has demonstrated surprising and superior efficiencies, even more effective fan system operation can be achieved using a dual surface air foil such as that shown in Fig. 8. Again, this air foil has a mean camber line but it is slightly different than the camber line shown in Fig. 5, for example. The mean camber line, as is always the case, is defined as the mid distance between and upper surface and a lower surface of an air foil. In Fig. 5, the theoretical optimum for a plate type foil was derived and is shown by its x/c and y/c coordinates in Fig. 6.

For the air foil shown in Fig. 8, which is a dual surface air foil, the mean camber line is still defined as the mid distance between the upper surface and the lower surface. However, since the surfaces are not identical, the location of the mean camber line will be different.

Shown in Fig. 9 are x/c and y/c coordinates for the air foil shown in Fig. 8. In column 1 , x/c is the distance along the chord line from the leading edge to the trailing edge of the air foil. The middle column represents the length along the Y axis for the upper surface and is designated yus/chord length. Similarly, the last column of Fig. 9 r. presents the Y _. . distance .he lower surface of the dual surface air foil a designated YLS/chord from the leading edge at 0 to the trailing edge at 1.0C.

As can be seen from Fig. 8 and as is shown in the coordinates set forth in Fig. 9, neither the upper surface nor the lower surface are symmetrical. The position of maximum camber is at 0.430C, that maximum camber being a distance of 0.0547C. The maximum thickness of the air foil is 0J6493C.

Figs. 10A, 10B and IOC demonstrate the efficiency of the present invention in terms of certain necessary and desirable properties. Data presented in these Figs, is based upon the plate air foil shown in Fig. 7.

In Fig. 10A, the lift coefficient is measured for a variety of angles of attack, , demonstrating that the lift coefficient can exceed 1.2. Similarly, in Fig. 10B, the drag coefficient with respect to that same angle of attack, , is shown is achieve the purposes of the present invention. The relationship of Reynolds number with respect to the maximum lift coefficient, C_{l max}, is shown in Fig. IOC.

In the same manner, Figs. 11 A, 11B and 11C report the same values for the duel surface air foil of Fig. 8, once again demonstrating that superior efficiency has been achieved with the present invention.

Figs. 12A, 12B and 12C represent three variation in the method of twisting the air foil blades. In Fig. 12, the dual surface air foil is shown in cross section, viewed from the tip to the hub in side elevation. Note that the blade has been twisted about the mid point 41 of the chord length and is of a non-linear configuration. That non-linearity is achieved because the changing angle of displacement of the air foil chord line is not constant for each and every equal increment of blade length.

This is contrasted with the twisted dual surface air foil blade shown in Fig. 12B which has what is known as linear twist. In this illustration, the blade has been twisted about the mid point of chord. In this instance, the changing angle of displacement of the air foil chord laying is constant for every equal increment of blade length, thereby presenting a linear configuration. Finally, Fig. 12C illustrates a similar dual surface air foil which has a constant collective pitch such that the air foil presents the same angle of attack from the tip to the hub.

Figs. 13A, 13B and 13C illustrate design parameters and some performance data for a fan system of the present invention using a dual surface air foil cross section and various form of twist distribution. Specifically, Figs. 13A, 13B and 13C represent non-linear, linear, and constant pitch distribution respectively, corresponding to the letters of Figs. 12A, 12B and 12C.

While various embodiments have been shown in the description above, it will become apparent to those skilled in the art that various modification and changes can be made without departing from the spirit of the present invention.

Claims

CLAIMSWhat is claimed is:

1. An air moving system for moving air in ducts, comprising: a motor having a shaft for rotation about an axis, said shaft extending axially from said motor in the opposite direction from said desired air flow; an inner hub mounted on said shaft, said hub having an elliptical face for

directing around said hub;

a plurality of rotor blades mounted on said hub for pulling air from said face to discharge said desired air flow into said air ducts; a housing surrounding said motor and blades, said housing providing a cylindrical clearance between said housing and the outward tip of said blades as they rotate; and said blades having a mean camber line producing maximum lift and minimum drag, and said blades having a twist by providing uniform flow over the blade length from hub to tip.

2. The system of claim 1 wherein said desired air flow has Reynolds number at the hub of about 60,000.

3. The system of claim 1 wherein said desired air v at said tip has a Reynolds number of about 300,000.

4. The system of claim 1 wherein said motor rotates said shaft at a speed ranging from about 1500 to about 2000 rpm.

5. The system of claim 1 wherein said blades have a non-linear twist to impart constant flow across the length of said blades.

6. The system of claim 1 wherein said twist is linear to provide near constant flow of air from said hub to said tip.

7. The system of claim 1 wherein said twist is at a constant angle.

8. The system of claim 1 which includes three blades, each having an air foil profile with a camber line having x/c and y/c coordinate values, where x is the distance along the chord length and y is the distance perpendicular to the chord length to the surface and c is the chord length, said values being as follows:

x/c y/c

0.0000 0.0000

0.0050 0.0027

0.0075 0.0038

0.0125 0.0058 0.0250 0.0101

0.0500 0.0172

0.0750 0.0231

0J000 0.0281

0J500 0.0366 0.2000 0.0433

0.2500 0.0487

0.3000 0.0529

0.3500 0.0560

0.4000 0.0583 0.4500 0.0596 0.5000 0.0600 0.5500 0.0596 0.6000 0.0583 0.6500 0.0560 0.7000 0.0529 0.7500 0.0487 0.8000 0.0433 0.8500 0.0366 0.9000 0.0281 0.9250 0.0231 0.9500 0.0172 0.9750 0.0101 0.9875 0.0058 0.9925 0.0038 0.9950 0.0027 1.0000 0.0000

9. The system of claim 1 which includes three blades having dual surface air foils having x/c, y/c upper surface and y/c lower surface coordinates as follows, where x is the location along the chord length, c is the chord length, and y is the perpendicular deviation from the chord length to the appropriate surface:

X/CHORD YUS/CHORD YLS/CHORD

0.000000 0.000000 0.000000

0.003544 0.015836 -0.015137

0.014127 0.030677 -0.026518

0.031599 0.045492 -0.031320

0.055715 0.060636 -0.032676

0.086135 0.075641 -0.032857

0.122432 0.089956 -0.032407

0J64095 0J03048 -0.031557

0.210538 0J 14389 -0.030405

0.261106 0J23424 -0.028967

0.315090 0.129435 -0.027184

0.371729 0.132075 -0.024919

0.430226 0J31219 -0.021826

0.489759 0J26743 -0.017533

0.549490 0J . -.770 -0.012099

0.608579 0J07640 -0.005917

0.666193 0.094063 0.000143

0.721524 0.079495 0.005448

0.773791 0.065291 0.009596 0.822261 0.052086 0.012313

0.866250 0.040113 0.013464

0.905141 0.029490 0.013056

0.938385 0.020258 0.011218

0.965516 0.012408 0.008211 0.986151 0.005883 0.004425

1.000000 0.000000 0.000000

10. A fan for moving air in ducts, comprising: an inner hub adapted to be mounted on a shaft, said hub having an elliptical face for directing around said hub; and a plurality of rotor blades mounted on said hub for pulling air from said face to discharge desired air flow into said air ducts, said blades having a mean camber line producing maximum lift and minimum drag, and said blades having a twist by providing uniform flow over the blade length from hub to tip.

11. The fan of claim 10 wherein said desired air flow has Reynolds number at the hub of about 60,000.

12. The fan of claim 10 wherein said desired air flow at said tip has a Reynolds number of about 300,000.

13. The fan of claim 10 wherein said blades have a non-linear twist to impart constant flow across the length of said blades.

14. The fan of claim 10 wherein said twist is linear to provide near constant flow of air from said hub to said tip.

15. The fan of claim 10 wherein said twist is at a constant angle.

16. The fan of claim 10 which includes three blades, each having an air foil profile with a camber line having x/c and y/c coordinate val_.es, where x is the distance along the chord length and y is the distance perpendicular to the chord length to the <" "face and c is the chord length, said values being as follows:

x/c y/c

0.0000 0.0000

0.0050 0.0027

0.0075 0.0038

0.0125 0.0058 0.0250 0.0101

0.0500 0.0172

0.0750 0.0231

0J000 0.0281

0J500 0.0366 0.2000 0.0433

0.2500 0.0487

0.3000 0.0529

0.3500 0.0560

0.4000 0.0583 0.4500 0.0596

0.5000 0.0600

0.5500 0.0596

0.6000 0.0583

0.6500 0.0560 0.7000 0.0529

0.7500 0.0487

0.8000 0.0433

0.8500 0.0366

0.9000 0.0281 0.9250 0.0231

0.9500 0.0172

0.9750 0.0101

0.9875 0.0058

0.9925 0.0038 0.9950 0.0027

1.0000 0.0000

17. The fan of claim 10 which includes three blades having dual surface air foils having x/c, y/c upper surface and y/c lower surface coordinates as follows, where x is the location along the chord length, c is the chord length, and y is the perpendicular deviation from the chord length to the appropriate surface:

X/CHORD YUS/CHORD YLS/CHORD

0.000000 0.000000 0.000000 0.003544 0.015836 -0.015137 0.014127 0.030677 -0.026518 0.031599 0.045492 -0.031320 0.055715 0.060636 -0.032676 0.086135 0.075641 -0.032857 0.122432 0.089956 -0.032407 0J 64095 0J03048 -0.031557 0.210538 0.114389 -0.030405 0.261106 0J23424 -0.028967 0.315090 0.129435 -0.027184 0.371729 0J32075 -0.024919 0.430226 0J31219 -0.021826 0.489759 0.126743 -0.017533 0.549490 0.118770 -0.012099 0.608579 0J07640 -0.005917 0.666193 0.094063 0.000143 0.721524 0.079495 0.005448 0.773791 0.065291 0.009596 0.822261 0.052086 0.012313 0.866250 0.040113 0.013464 0.905141 0.029490 0.013056 0.938385 0.020258 0.011218 0.965516 0.012408 0.008211 0.986151 0.005883 0.004425 1.000000 0.000000 0.000000

18. A method of moving air in ducts, comprising: pulling air into a housing surrounding a motor having rotor blades mounted on a hub, said housing providing a cylindrical clearance between said housing and the outward tip of said blades as they rotate, said blades being mounted on a hub and having a mean camber line producing maximum lift and minimum drag, and said blades having a twist by providing uniform flow over the blade length from hub to tip; and discharging air into said ducts.

19. The method of claim 18 wherein said desired air flow has Reynolds number at the hub of about 60,000.

20. The method of claim 18 wherein said desired air flow at said tip has a Reynolds

number of about 300,000.

21. The method of claim 18 wherein there are three blades, each having an air foil profile with a camber line having x/c and y/c coordinate values, where x is the distance along the chord length and y is the distance perpendicular to the chord length to the surface and c is the chord length, said values being as follows:

x/c y/c

0.0000 0.0000

0.0050 0.0027

0.0075 0.0038

0.0125 0.0058 0.0250 0.0101

0.0500 0.0172

0.0750 0.0231

OJOOO 0.0281

0J500 0.0366 0.2000 0.0433

0.2500 0.0487

0.3000 0.0529

0.3500 0.0560

0.4000 0.0583 0.4500 0.0596

0.5000 0.0600

0.5500 0.0596 0.6000 0.0583 0.6500 0.0560 0.7000 0.0529 0.7500 0.0487 0.8000 0.0433 0.8500 0.0366 0.9000 0.0281 0.9250 0.0231 0.9500 0.0172 0.9750 0.0101 0.9875 0.0058 0.9925 0.0038 0.9950 0.0027 1.0000 0.0000

22. The method of claim 18 wherein there are three blades having dual surface air foils having x/c, y/c upper surface and y/c lower surface coordinates as follows, where x is the location along the chord length, c is the chord length, and y is the perpendicular deviation from the chord length to the appropriate surface: X/CHORD YUS/CHORD YLS/CHORD

0.000000 0.000000 0.000000 0.003544 0.015836 -0.015137 0.014127 0.030677 -0.026518 0.031599 0.045492 -0.031320 0.055715 0.060636 -0.032676 0.086135 0.075641 -0.032857 0.122432 0.089956 -0.032407 0J 64095 0J03048 -0.031557 0.210538 0J 14389 -0.030405 0.261106 0J23424 -0.028967 0.315090 0.129435 -0.027184 0.371729 0J 32075 -0.024919 0.430226 0J31219 -0.021826 0.489759 0J26743 -0.017533 0.549490 0J 18770 -0.012099 0.608579 0J07640 -0.005917 0.666193 0.094063 0.000143 0.721524 0.079495 0.005448 0.773791 0.065291 0.009596 0.822261 0.052086 0.012313 0.866250 0.040113 0.013464 0.905141 0.029490 0.013056 0.938385 0.020258 0.011218 0.965516 0.012408 0.008211 0.986151 0.005883 0.004425

1.000000 0.000000 0.000000