CA1057720A - Propulsion apparatus - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A propulsion apparatus for use, for example, in aircraft, model aircraft, hovercraft, railway trains, hydrofoils or boats comprising a propellor mounted within a duct. The arrangement of the propellor, various guide vanes, the shaping of the duct, and other parameters providing an unusually efficient propulsion apparatus in which, according to tests carried out by the inventor, provides a partial vacuum relative to ambient in the duct behind the rotor. An important feature is that the blades have a non-arcuate airfoil section.

Description

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l~S7720 The present invention relates to propulsion apparatus for, for example, aircraft propulsion althoua,h other uses will be apparent.
Present propulsion apparatus including propellers have severe limitations.
S As presently employed, propellers comprise large diameter devices external to the structure to which they are affixed. Being relatively unprotected they are, therefore , vulnerable to damage and breakage from objects, such as birds, nearby service vehicles and the like, which their blades may strike while in operation.
Also,due to the fact that propellers are generally exposed to the a~bient allowing the air flow therefrom to spread aftward in a rather uncontrolled manner, the efliciency per horsepower of propeller-driven craft is rather low.
Propellers, unless used in counter-rotating pairs, are torque-producing. The resultant torque is imposed on the aircraft structure and must be compensated for b~

modification of the airflow pattern over the wings and tail section, involving costly peripheral structures and attendant control means.

- 2 -l~S77'~0 Similarly, exposed propellers tend to produce a helical, rather turbulent air flow, which is not only pro-pulsively, inefficient, but also rather noise-producing and, in extreme cases, damaging to the aircraft structure which is, in effect continuously drawn through the turbulent flow.
The present invention provides propulsion apparatus for use with a means for providing motive power comprising a duct having an inlet and an outlet, means disposed within said duct for generating a partial vacuum therein, said means com-prising a rotor rotatably supported in said duct comprising a hub and a plurality of blades equiangularly radiating there-from, flow adjuster means fixialy disposed behind said rotor for receiving air from said rotor blades during use and changing the direction of flow of at least a portion thereof to substantially axial flow along said duct, the leading portion of said flow adjuster means being situated adjacent the rotor blades for receiving air flow directly from the rotor blades, the leading portion of the flow adjuster means conforming substantially to the direction of air flow from said rotor blades, and elongate means for reducing the axial air flow turbulence in said duct disposed axially thereof and extending from said rotor to said exit and having a diameter at its leading end substantially equal to the diameter of said hub, whereby, in use, as the rotor is drivably rotated, a partial vacuum relative to ambient is formed in the duct behind the rotor.

r~/J_ 1~57720 _ The rotor includes a hub and a plurality of equally angularly spaced blades which may have a hub-to-blade diameter ratio between 20-80 and 60-40. Each of .he blades may have a non-arcuate air foil section and a pitch of between 5 and 8~ degrees. Aftward of the rotor are flow adjusters whose function is to reduce the tangential force componant of the air passing through the duct.
In certain embodiments, an air-flow-directing means such as an entry cone is provided forward of the rotor to direct the movemcnt of the input air toward the rotor blades.

The elongate means is incorporated to reduce axial vorticity of ~he aftward flow. In particular, the flow adjusters may be guide vanes radially attached to the elongate means. There IS may be also provided entry guide vanes to optimize air flow.
Preferred embodiments of the invention will now be described by way of ex~mple only, and with reference to the accompanying drawings in whic~:-FIGURE 1 is a schematic plan view partly in cross-section of a model airplane incorporating one embodiment of tne present invention;

FIGURE 2 is an exploded perspective view of one ~5 e~bodiment of the present invention;

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1`~357720 _ FIGURE 3 is a detail view of the interaction between the rotor blades and the ~low adjusters of one embodiment of the present invention;

~IGURE 4 is a perspective, partially cutaway view S of a bladed rotor in conjunction with an a`lternative motive means according to another embodiment of the present invention;

FIGURE 5 is a cutaway view of a portion o~ th~

propulsive apparatus of one embodiment of the present invention showing details of the mounting of the hub to the exit cone;

FIG~RE 6 is a detail cutaway view similar to FIGURE 5, but illustrating an alternative embodiment o~
the invention; and FIGURE 7 is a schematic representation of a further embodi~ent of a propuIsion apparatus in accordance with the present invention.

There are various types of structures, vehicular or otherwise, which could be satisfaciorily propelled with the ducted bladed rotor propulsion apparatus of this irlve~tion.
As examples only we list aircraft, model aircraft, hovercraft, r~ilway or monorail trains, hydrofoils and other boats.
_5 ~ 1~57~:0 The propulsion apparatus may be supported on or within the structure by a variety force-transmissive means, usually rigid, such as support by structural members extending above or below the device being propelled, S support above or below aircraft wings and in-board supp~rt (i.e. incorporation of the propulsion apparatus within the structu~e itself).
In the subsequent description, all referen~e will be made to the use of a propulsion apparatus axially incorporated with~n the fuselage of a model airplane, it being understood that this embodiment is merely exemplary and not limiting.
Referring now to the drawing, and particularly to ~IGURE 1 thereof, model airplane lO contains, mounted axially within its fuselage , the propulsion apparatus 30 in accordance with the present invention including a duct 15 having an entrance 20 and exit 25.
Mounted within the duct 15 is a rotor 35 operated by a motor 50, and flow adjusters 65. Also disposed within the duct 15 is an entry cone 60 and an elongate member in the form of an exit cone 70. The exit cone 70 is supported within the duct 15 by the f l ow adjusters 65 and exit guide vanes 85.

~S)S7720 _ Referring now more p~rticularly to FIGURE 2, the rotor 35 comprises a hub 40 and a plurality of blades 45,' in this embodiment the hub 40 and blades 45 bein5 integrally moulded of, for example, a plastics'material. The blade~ 45 S are rigidly attached to the hub and radiate equiangularly from the hub periphery. The blades 45 may be of any convenient'pitch from S to 85 and may be of either constant pitch throughout their length or of variable pitch. The decision as to the angle of the pitch and the variation in pitch throughout the length of the individual blades can be readily made by those skilled in the aerodynamic art ana depen~ on the nature of the particular type of aftward flow desired. If the'pitch'of i -the blades is to be constant along their length~ then the chord of the blades should become narrower at the tip to achieve maximum utilization of the power generated by the motor 50. Alternatively, by varying the pitch of the blades along their lengths one may utiliæe blades of constant chord to retain maximum power utilization efficiency. We prefer to provide blades, as illustrated in FIGURE 2, in which the pitch angle decreases from the blade root to the blade tip wi~h a constant chord. The blades, in section, ~5 p esent ~ non-arcuate, air fo~l ~urface.

.: ' 1 ~S7720 - It has been found that the hub-to-blade diameter ratio should be within 20-80 to 60-40. The optimum hub-to ~~
blade diametex ratio when the propulsion system i5 mounted on the outside of the structure has been found to be about 20 to 80 and when incorporated internally of the structure as in FIGURE 1 to be 2bout S0 to 50.
The flow adjusters or aft stator guide vanes 65 are fixed supported within the duct 15 behind the rotor 35.

These guide vanes 65 receive the air from the rotor blades 45 and direct it axially along the duct 15. ~s is well known,the air flow from the rotor blades 45 contains both axial and non-axial components of motion. Through utilization of the aft guide vanes 65, the non-axial components of air flow are directed axially thus providing addi.ional thrust.
Furthermore, by properly forming the angle and shape of the leading end of the aft guide vanes, the efficiency of this conversion is improved. Thus the leading end of the aft guide vanes 65 is shaped to be at the same angle as the air flow leaving the blades 45. As shown in FIG~RE 3,the aft guide vanes 65 are curved vanes which are supported and oriented, relative to the bladed rotor 35 in such manner as to direct the air flow from the rotox blades along 2 curved path. This path tends to smootnly convert the non-axial l~S77ZO

_ flow components to an axial component which, as well as tend~ng to increase the thrust imparted by the air flow also tends to counter-balance the torque produced by the revolving rotor. Note that the direction of the vertical arrow in FIGURE 3 indicates the direction ~f relative movement of the blades 45.
~ he sectional shape of the aft guide vanes 65 is not particularly critical. As illustrated in FIGURE 3 they may be merely thin sheets of metal extending radially from ~he axis of the rotor apart, of course, from their front end portions which are curved appropriately with respect tot~e pitch of the rotor ~lades 45 and the direction of rotation of the rotor.
Each of the uanes 65 may be;curved at its leading end across its entire width (i.e. exter,ding radially) or only in selected portions. It will be noted that the aft portion of the vanes extend axially of duct 15 to thus direct the air flow in the desired axial direction.
As in the case of the rotor blades 45, the aft guide 2C vanes 65 may each present an air foil section which would a~ain tend to give an increased forward thrust ,o the propulsion apparatus. The aft vane guides will, for ~alanced operation, radiate e~uiangu]arly from the axis, their ~umber may be selected as desired, 'he cri';eria being the ~577~0 amount of flow stabilization desired versus the posible loss of thrust due to friction. As is illustrated, the vanes 65 are supported between the inner surface of the duct 15 and the exit cone 70.
The exit cone 70 in the preferred embodiment has an outer surface which is substantially a sur~ace of revolution which in FIGURE 2 is general,ly conical shape with the ra~ius of the exit cone 70 decreasing in an aftward direction.
Ths radius of the exit cone 70 adjacent the hub 40 is approximately equal to the radius of the hub 40, thereby assisting in a smooth air flow from hub 40 to cone 70. The exit cone 70 functions to eliminate axial turbulence creating currents (the Von Karman effect) normally present in the air flow aft of a rotor blade structure. The exit cone 70 thus smooths out the air ~low and thus enhances the efficiency thereof.
m e method of mounting the bladed rotor 35 and the exit cone 70 may vary, depending on the particular application to which this invention is put. For example, the bladed rotor 35 may be rotatably mounted on the exit cone 70, possibl~ in the manner shown in FIGURE 6, wherein a circular projection 77 ~rom the exit cone 30' is positioned within z circular axial bore 42 within the hub 40' CO that the . .-10-1~3577?.0 bladed rotor 35' may rotate about it. A~ernatively, as shown in FIGURES 2 and 5, the rotor 35 may be supp~rted _-by the exit cone 30 by means of a projection 75 inserted within an axial bore 80 in the exit cone 30 or it may be rotatably supported entirely independently of the exit cone 30, having its own means of support within the duct 15. In the preferred embodiment of FIGURE 2, however, the rotor 35 is attached to the entry cone 60, the entry cone 60 being rigidly attached to or integral with the hub 40, and the -hub 40 is rotatably supported by means of the arrangement of FIGURE 5.
Through appropriate selection of~the pitch and chordof the rotor blades 45, the angle of the leading end of the aft guide vanes and the radius of the exit cone 70, it has been found that a partial vacuum (i.e. pressure below ambient) is created in the duct 15 aft of the rotor 35. It is believed that through substantial elimination or the various flow disturbances and by selecting air foil sections as a~ove described the flow velocity has been substantially increased beyond that expected. Thus, the partial vacuum has been created providing a negative pressure in the duct wlth respect to ambient and the leading edge of the rotor 35. The partial vacuum is greatest immediately aft the rotor means and in , ` lIIS77'~0 the aft guide vanes 65 and gradually decreases toward the exit 25 of the duct 15. As a result, a substantial additional mass of air flow throush the duct is generated protJiding greater thrust than heretofore expected.
To further stabilize and laminarize the aftward air flow as it approaches the exit 25 of the duct 15, exit guide vanes 85 may be emplo~ed. In the preferred embodiment, these are simply a multiplicity of thin metallic sheets aligned parallel the axis of the exit cone 70 and oriented radially from the aft portion thereof in mutually equiangular disposition thereabout.
Other sets of similar guide vanes may be incorpora~ed at - various points along the exit cone. These will further IS stabilize the flow, although there will be some loss of net thrust due to friction. In any event, the guide vanes tend to prevent flow turbulence, which both increases the thxust of the propulsive apparatus and also, by discouraging the formation of flow eddies, contributes to the remarkable ~0 quietness of the apparatus described.
~ he motor 50 ma~ comprise an internal combustion engine, electric motor or any other suitable driving means. It may be supported by the structure external to the duct or, as sno~ in FIGU~E 1, within .he du~t ( by means of motor - 12 _ 1~577z _ supports 52) to provide cooling. The motor is operably connected to the rotor means 35 by means of an axial rotatin~ member 55 which i5 rigidly or othe~wise f rce- _ transmissively connected to the hub 40 of the bladed rotor.

S The motor 50 may be mounted fore or àft of the rotor 35 or even remote therefrom with a drive connection as may be deemed appropriate. Other means of operable coA~nection such as gears, a flexible belt, etc., may also be utilized as desired.
Other forms of motor may also be u~ilized. F~r example, as showrA in A~IGUA~E 4, an annular shroud 46 with projections 47 may be ~orce-transmissively secured to the tips of the blades 45. Ordinarily this will be accomplished by welding lS or brazing the blade tips to the interior surface of the shroud or by moulding in one integral piece. The motive force is provided by a high-velocity stream of fluid, such as air, from a source (not shown), such as a compressed air bottle or an air compressor, directed at the projections in ~G a direction tangential to the shroùd 46. In order to prevent interference between this hish-velocity flow and the p~imary flow through the duct 15, some shiel~ing should be provided.
Typically, as sho~ in FIGUA~E 4, this will consist of placing 5 the shroud a6 into an an~Aular groove 48 cut into the irAterior - ~3 -l~S7720 _ surface 49 of the duct 15.and providing a means for entrance . of the high-velocity ~luid into the channel thus created ; and exit therefrom. Typically, the projections 47 will extend radially from the shroud 46, as shown. However, they may project in a forward or aftward axial direction, tne high-veloclty fluid flow still being projected toward them in a direction tangential to (and, here, slightly forward . . of-or aft of, respectively) the shroud 46. In any event, the projections should be equiangularly spaced about the ro.or axis to provide balanced.operation of the bladed rotor 35.

For further optimization of performance of this .. invention, the entry cone 60 may be provided to smoothly direct the flow of inlet air to the rotor blades 45. Strictly speaking, the entry cone 60 need not be a cone, in the sense of having a ~riangular longitudinal section. Prerer~ly, its outer surface will present an air foil surface of revoluti.on . to provide increased forward thrust, as above explained.
Xowever, it may be of any shape, preferably h2ving its outer surface co,~prise a surface of revolution, wherein the radius increases gene-ally in an aftward direction. Ordinarily, the radius at the point c].osest to the bladed rotor 35 will be approximately.equal to that of the hub 40. While the e~trance cone and the bladed rotor may be separate from one . ..

~53577ZO
_ another and separately mounted. In the typical case they will be rigidly attached. Furthermore, where the motor 50 is contained within the duct 15 ahead of the rotor 35, the entrance cone 60 may function to interconnect the motor 50 S and the rotor 35. In the case where the huh i~ not attached to the entry cone 60, the axial rotating member of the motor may be jo-ned to the hub 40 through an axial bore through the entry ~one 60.
Referring now more particularly to FIGURE 7, there is iliustrated in schematic form further fea~ures of a propulsion apparatus in accordance with the present invention. As is illustrated in F~GURE 7, a duct 102 includes an outwardly flared inlet or mouth 104 adapted to facilitate the entry of air therein. An entry cone 108 is also illustrated, its terminus 110 adjacent a hub 112 of a rotor 114 ~eing substantially the same diameter as the hub 112, thus assisting in a smooth transition of air flow across the hub of the rotor 114. In addition, there is also illustrated entry or forward guide vanes 120 which are disposed immediately forward ihe rotor 114.
Typically, in the absence of guide vanes 120, air flc~7 enters the duct 102 in straight axial flow configuration as shown by the arxows 106. Upon engagement with the rotor blaZes, ~wo of which are sho~m schematically at 116 and 118, l~)S77ZO
_ the air flow would change direction as a result of the non-arcuate air foil section of the rotor blades and the rotation thereof. Such change of direction would occur as a result,of the leading edge of the rotor blades biting S into the air flow as is well known to those skilled in the art. However, it has been determined that by appropriate selection of the entry vanes 120 to change the air flow direction fro~ that illustrated at 106 to that as shcwn by - the arrows 122, the work 102d upon the rotors is somewhat decreased, ther2b~ providing a more efficient utili~ation of the horse power available from drive means 200.
As is the case with the aft guide vanes, it has been determined that the cross-sectional configuration of the forward guide vanes should be that of an air foil surface which again enhances the forward thrust of the propulsion apparatus in the ma~ner and for the reasons as above describea. The direction of the air flow ~riting from the rotor blades 116, 118 has been schematically illustrated in FIGURE 7 b the arrows 124. Again, by selecting the aft guide vanes, illustrated schematically at 126, to have a leading ed~e 12~
which substantially matches the direction of the air flow as indica'ced by the arrows 124, the efficiency of the system and its thrust has been increased~ Again as indicated in ~IGUP~ 7, ~`

1~577'~0 the cross-sectional surface illustrated for the aft guide means 126 is an air foil surface selected for the reasons and with the results as a~ove described. _ _ It will also be noted by reference to F~URE 7 that the forward end 130 of exit cone 132 is increased 'n diameter from the terminus adjacent the hub 112 to provide a configuration which matches the direction of the air flow ~iting from the rotor blades as illustrated by the arrows 124.

By selecting the forward edge 130 of the exit cone 132 to have such configuration, the amount of turbu-ence which may otherwise be generated is substantially decreased. It will also be noted that immediately adjacent the rotor 114, the exit cone 132 has a diameter which substantially m2tches that of the hub 112. As was previously descri~ed, exit vanes 134 are utilized to further reduce any ~xial vortic;ty and also to support the exit cone 132 within the duct 102.
The exit cone 132 in some applications may be extremely short and unsupported, as is illustrated for the entry cone lQ8, thus eliminating the necessity for the exit vanes 134.
Through the uiilization of a siructure as i;l~ustra~ed in FIGURE 7, measurements taken along the duct 102 commencing immediately aft of the rotor 114 has shown that a pressure exists within the duct 102 which is negative with l~S7720 _ respect to ambient and with respect to the pressures immediately forward of the rotor 114. More specifically, a pressure measured at -8.5 inches o water was found to exist. This pressure gradually decreased aft along the duct 102 until a measurement at the exit thereof, a pr~ssure of -4.2 inches of water was obtained. It is this negative pressure internally of the duct 102 which it is believed causes the high mass flow of air through the propulsion apparatus constructed in accordance with the present invention.

As is iiiustrated in E'IGURE 7, the drive means 200 may be supported internally of the exit cone 132. Alternatively, the drive means 200 may be supported internally of the duct 102 but externally of the cone 132 or partially in both and may be connected by any suitable drive means 202 to the rotor 114.
While in the illustrated preferred embodiments of this the inventio~ apparatus is essentially uniaxial and coaxial with a duct whose internal surface is substantially a surface of revolution, this coaxiality is not necessary . Thus, while the uniaxiality of the propulsive mechanism is -easonably important, the duct 1~ need not even be circular in cross-section, and the mechanism need not be centrally located within 5 it, although if it is not, som~ loss of efficiency ~ill be _ experienced. In particular. it is possible to arrangea number of mechanisms side by side within a large duc' having an oval, rectangular or other convenient cross-section.

S The invention is not restricted to the details of the foregoing examples. For example, the shaft with respect to which the rotor 35 rotates might be a structure other than the exit cone ~O.

20 . .. ...

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Propulsion apparatus for use with a means for providing motive power comprising a duct having an inlet and an outlet, means disposed within said duct for gener-ating a partial vacuum therein, said means comprising a rotor rotatably supported in said duct comprising a hub and a plurality of blades equiangularly radiating therefrom, flow adjuster means fixedly disposed behind said rotor for receiving air from said rotor blades during use and changing the direction of flow of at least a portion thereof to sub-stantially axial flow along said duct, the leading portion of said flow adjuster means being situated adjacent the rotor blades for receiving air flow directly from the rotor blades, said leading portion of said flow adjuster means conforming substantially to the direction of air flow from said rotor blades, and elongate means for reducing the axial air flow turbulence in said duct disposed axially thereof and extending from said rotor to said exit and having a diameter at its leading end substantially equal to the diameter of said hub, whereby, in use, as the rotor is drivably rotated, a partial vacuum relative to ambient is formed in the duct behind the rotor.

2. Apparatus as claimed in claim 1 in which said blades have a non-zero angle of pitch increasing from the blade root to the blade tip.

3. Apparatus as claimed in claim 1 in which the blades have a chord which decreases from blade root to tip.

4. Apparatus as claimed in any of claims 1 to 3 in which the blades have a non-arcuate airfoil section.

5. Apparatus as claimed in any of claims 1 to 3 in which said flow-adjuster means includes a plurality of equi-angularly disposed radially extending guide vanes each of which has an airfoil section.

6. Apparatus as claimed in claim 1 further including entry air flow guide means disposed adjacent and upstream of said rotor to facilitate air flow onto said rotor blades com-prising a plurality of guide vanes each having a trailing edge conforming substantially to the leading edge of said rotor blades.

7. Apparatus as claimed in claim 6 in which each of the guide vanes has an airfoil section.

8. Apparatus as claimed in claim 6 or 7 further including a flared inlet having said guide vanes disposed therein said flared inlet and said plurality of guide vanes being removably attached to said duct means.

9. Apparatus as claimed in claim 1 in which said elongate means includes a surface of revolution at least part which is conical and in which, from the leading end of said elongate means, its diameter increases and then decreases to form said conical part.

10. Apparatus as claimed in claim 9 in which the diameter from said leading end to the largest part is disposed at an angle substantially equal to the angle of air flow leav-ing said rotor blades.