GB2389826A - Craft propulsion - Google Patents

Craft propulsion Download PDF

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Publication number
GB2389826A
GB2389826A GB0214514A GB0214514A GB2389826A GB 2389826 A GB2389826 A GB 2389826A GB 0214514 A GB0214514 A GB 0214514A GB 0214514 A GB0214514 A GB 0214514A GB 2389826 A GB2389826 A GB 2389826A
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United Kingdom
Prior art keywords
propulsion
propulsion arrangement
mouthpiece
arrangements
arrangement according
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Granted
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GB0214514A
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GB2389826B (en
GB0214514D0 (en
Inventor
John Edward Randell
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Individual
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Priority to GB0214514A priority Critical patent/GB2389826B/en
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Publication of GB2389826A publication Critical patent/GB2389826A/en
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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B63SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63HMARINE PROPULSION OR STEERING
    • B63H5/00Arrangements on vessels of propulsion elements directly acting on water
    • B63H5/07Arrangements on vessels of propulsion elements directly acting on water of propellers
    • B63H5/14Arrangements on vessels of propulsion elements directly acting on water of propellers characterised by being mounted in non-rotating ducts or rings, e.g. adjustable for steering purpose
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B63SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63HMARINE PROPULSION OR STEERING
    • B63H5/00Arrangements on vessels of propulsion elements directly acting on water
    • B63H5/07Arrangements on vessels of propulsion elements directly acting on water of propellers
    • B63H5/16Arrangements on vessels of propulsion elements directly acting on water of propellers characterised by being mounted in recesses; with stationary water-guiding elements; Means to prevent fouling of the propeller, e.g. guards, cages or screens
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C11/00Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft
    • B64C11/001Shrouded propellers
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C27/00Rotorcraft; Rotors peculiar thereto
    • B64C27/20Rotorcraft characterised by having shrouded rotors, e.g. flying platforms
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C29/00Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft
    • B64C29/0008Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded
    • B64C29/0016Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded the lift during taking-off being created by free or ducted propellers or by blowers
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C29/00Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft
    • B64C29/0008Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded
    • B64C29/0016Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded the lift during taking-off being created by free or ducted propellers or by blowers
    • B64C29/0025Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded the lift during taking-off being created by free or ducted propellers or by blowers the propellers being fixed relative to the fuselage
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02KJET-PROPULSION PLANTS
    • F02K3/00Plants including a gas turbine driving a compressor or a ducted fan
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02KJET-PROPULSION PLANTS
    • F02K3/00Plants including a gas turbine driving a compressor or a ducted fan
    • F02K3/02Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber
    • F02K3/04Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber the plant including ducted fans, i.e. fans with high volume, low pressure outputs, for augmenting the jet thrust, e.g. of double-flow type
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02KJET-PROPULSION PLANTS
    • F02K3/00Plants including a gas turbine driving a compressor or a ducted fan
    • F02K3/02Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber
    • F02K3/04Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber the plant including ducted fans, i.e. fans with high volume, low pressure outputs, for augmenting the jet thrust, e.g. of double-flow type
    • F02K3/068Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber the plant including ducted fans, i.e. fans with high volume, low pressure outputs, for augmenting the jet thrust, e.g. of double-flow type being characterised by a short axial length relative to the diameter
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02KJET-PROPULSION PLANTS
    • F02K5/00Plants including an engine, other than a gas turbine, driving a compressor or a ducted fan

Abstract

A propulsion arrangement e.g for an aircraft, comprises a rotor 16 arranged to drive a fluid though a mouthpiece 15 and flow straightening means 11, 15. The fluid exiting the propulsion arrangement is substantially straightened. The mouthpiece 15 may have a polygonal cross section.

Description

1 2389826
CRAFT PROPULSION
The present invention relates to craft propulsion.
5 In normal aircraft flight, a wing displaces a large volume of air downwards simply and efficiently to lift the aircraft at an acute angle to the horizontal.
In a vertical take-oúf and landing (VTOL) aircraft and in hover aircraft the downward discharge of a large volume of air should be efficiently executed. Known methods often 10 involve the use of a large horizontallylying rotor or propeller. There is known merit in mounting a horizontallylying propeller over an aperture defined in wings of a VTOL aircraft and a hover aircraft. With fixed wing VTOL flight, a propeller does not have to sustain the weight of the aircraft but only overcome the drag on it, so less power is required, fuel consumption is less and the range of the aircraft can be extended.
A fundamental difficulty in the practical realization of such a desirable arrangement is the effect of the vortex(es) generated by the propeller(s) about its vertical axis. A single passenger aircraft configured for vertical take off and landing (VTOL) is described in International Patent Application Number PCT/US99/30271 of Millenium Jet 20 Incorporated. A pair of horizontal fans are arranged in a corresponding pair of vertically oriented fan ducts. Air is forced by the fans through the ducts to lift the aircraft.
However, as the air leaves the ducts vortexes about the shaft axis of each duct are created. The vortexes formed beneath the wings as the swirling air discharged by the propeller entrains the air around it producing a suction region on the underside of the 25 wings because of the negative radial pressure field that exists in such vortexes and this
reduces the lift produced. Generally, assuming similar geometry for each fan and duct pair, these vortex circles balance each other. However, through one being slightly larger than the other or through an external (say, meteorological) force, an imbalancing reaction force can be created. If this occurs the two vortexes can intertwine, the 5 interaction of the vortexes causing instability of the aircraft.
An aim of the invention is to increase the thrust obtained from a rotor accelerating fluid through an aperture in a member of a craft by reducing or substantially eliminating swirl from the discharge stream.
According to a first aspect of the invention there is provided a propulsion arrangement for moving a craft, the propulsion arrangement comprising a rotor arranged to drive fluid through a mouthpiece and flow straightening means so that fluid exiting the propulsion arrangement is substantially straightened.
The propulsion arrangement of the first aspect of invention is designed to straighten exhaust gases eminating therefrom. By contrast, the known jet turbine engine ("turbojet") has a turbine after the combustion chamber. The turbine is driven by the exhaust gases of the combustion chamber. This has the effect of gases flowing from the 20 turbine in a non straight manner. The propulsion arrangement may be applied to turbojets and the like. In a preferred embodiment of the invention, the rotor is designed to provide the thrust or driving force for the aircraft.
The flow straightening means preferably comprises a mouthpiece of noncircular, such as triangular or hexagonal or octagonal, cross section. The flow straightening means may be arranged before the point of the mouthpiece of narrowest cross section, which can save space, and is preferably mounted flow wise behind the rotor. In this way, a 5 vortex, generated initially above the plane of the rotor as air is drawn in, is nullified as the air passes through the depth of the wing, the suction on the underside of the wing is minimised and the lift increased. Also, in this way, fluid forced through the mouthpiece is straightened.
10 In one preferred embodiment of the invention, the rotor is a propeller.
It has been found beneficial in reducing the strength of the vortex for the mouthpiece is of triangular cross-section. If the mouthpiece through which fluid is discharged by the propeller is of hexagonal crosssectional area further improvement is achieved and the 15 flow at the outlet of the mouthpiece has been found to be both substantially free of swirl and also relatively uniform.
Such a mouthpiece may be constructed as a Pairing, shroud, surround or housing on which or in which the propeller can be mounted and such a Pairing can be mounted in a 20 wing. Such a propulsion arrangement, comprising a propeller and hexagonal Pairing, can also be utilised in another plane, such as a sailplane, or in an appropriately shaped fuselage, to provide either lift and/or balance to an aircraft. Such a propulsion arrangement may also be used in a fin, such as a tail fin, where similar considerations apply and elimination of swirl from a rotor or propeller is desirable for efficiency.
( 4 The propulsion arrangement may be used in sea craft and in aircraft, ie. in displacing water or air. an embodiment shown, the Pairing (shroud, surround or housing) is formed in a plane of an aircraft.
s In another preferred embodiment, two propulsion arrangements, each comprising a propeller and a hexagonal Pairing defining a fluid inlet, are mounted in the same plane with a vertex of each lying on the straight line that connects the centres of the arrangements. In yet another preferred embodiment, propulsion arrangements are arranged in a hexagonal pattern in a plane so that any two adjacent propulsion arrangements have respective vertices on the straight line that connects the centres of the two propulsion arrangements. Alternatively, any two adjacent propulsion arrangements may have a 15 common vertex on the straight line that connects the centres of the two propulsion arrangements. In yet another preferred embodiment, six propulsion arrangements are linked so that the vertex of any propulsion arrangement that lies on the straight line that connects two 20 adjacent propulsion arrangements is common to both.
In yet another preferred embodiment, two propulsion arrangements are adjoined in the same plane with an edge of one hexagonal propulsion arrangement parallel to that of another propulsion arrangement but with the parallel edges spaced apart.
According to a second aspect of the invention there is provided a crap comprising a propulsion arrangement in accordance with the first aspect of the invention.
5 A propulsion arrangement in accordance with the invention will now be described by example and with reference to the accompanying drawings, in which Figure I is an isometric view showing a two propeller arrangement and air discharged therefrom, Figures 2a, 2b and 2c are, respectively, an isometric view and two plan views showing another two propeller arrangement and air discharged therefrom, Figure 3 is an exploded isometric view of a propulsion arrangement in accordance with 15 a first embodiment of the invention, Figure 4 is an isometric view of a propulsion arrangement in accordance with a second embodiment of the invention, 20 Figure 5 is an isometric view showing air flow discharged from a propeller of the propulsion arrangement of Figure 4, Figure 6 is another isometric view showing air flow through a mouthpiece of the propulsion arrangement of Figure 4,
Figure 7 is a plan view of a mouthpiece (in broken line) of the propulsion arrangement of Figure 4, showing air flow therethrough, 5 Figure 8 is a plan view of another mouthpiece (again, in broken line), showing air flow therethrough, Figures 9a, 9b and 9c are, respectively, a vertical section through the mouthpiece, a plan view of the mouthpiece, and a further vertical section through the mouthpiece, Figures 1 Oa, 1 Ob, and 1 Oc are vertical section views showing different modifications to the propeller and mouthpiece arrangements, Figures 11 a and 1 lb are, respectively, a front view in section and a side view in section 15 of a propeller and mouthpiece arrangement, Figure 12 is a schematic plan view showing mouthpieces of two side by side propulsion arrangements, 20 Figure 13a shows, in front to back section, a propulsion arrangement set in an aerofoil wmg, Figure 13b shows a section along the wing of the arrangement of Figure 13a,
Figure 13c is a plan view of the arrangement of Figure lab, Figure 14a is a plan view of another propulsion arrangement in accordance with the invention, Figure 14b is a vertical section through the propulsion arrangement of Figure 14a, Figure 15 is a plan view of an aircraft having a propulsion arrangement in each of a pair of wings and also a propulsion arrangement in a rear portion of the fuselage, towards 10 the tail, Figure 16a isanisometric view ofthe aircraft ofFigure 15, Figure 16b is a vertical section through the wing of the aircraft of Figure 15 on the 15 centre-lines of the propellers, Figure 16c is a front view ofthe aircraft of Figure 15, Figure 1 7a is a side view of an aircraft, showing a vertical section through the wing on a 20 line through the centre of the propeller, Figure 1 7b is a vertical section through the centre-line of the aircraft, Figure 1 8a is an isometric view of the aircraft,
Figure 18b shows a vertical section through a wing on the centre-line of a propeller, Figure 1 8c is a side view on a section through the wing, again through the centre-line of 5 the propeller, Figure 19 is a view of a propulsion arrangement incorporated in a vertical fin, Figure 20a shows a view of the propulsion arrangement in Figure 19 from the side, Figure 20b is a section through the tail fin in the horizontal plane through the cenke of the propulsion arrangement, and Figure 21 is a schematic view of a structure comprising six propulsion arrangements.
Two substantially identical propellers 1a, lb are shown isometrically in Figure 1, the propellers being spaced apart by a distance equal to the propeller diameter. The propeller discharges form two vortex cores 3a, 3b and these will circulate air within a vertical cylinder 5. The cylindrical envelope constitutes a potential all-polar vortex 7 20 since the whole envelope is capable of rotation about either of the vortex core axes. The envelope can also rotate about its vertical axis Z-Z, in the direction of either of the vortex cores. Such a rotation is shown in Figure 1, by arrows, 9 in a horizontal plane below that of the propellers la, lb. Such rotation will produce a complex swirling motion beneath the wing and therefore instability of the aircraft. Larger propellers may
( 9 be used, with smaller spacing. This will produce more complex flow patterns but instability will still arise in like manner because of the interaction of the vortex cores.
Thus, in the limit, two propellers may be used where the propeller arcs abut, as shown in Figure 2(a). Two vortex cores 3a, 3b are formed beneath the propellers and these are 5 shown in Figure 2(b). These cores can behave in similar manner to that described with reference to Figure 1, with the same consequences. If a through flow is developed between the vortex cores, due to forward movement of the aircraft, the cores are likely to become staggered, as shown in Figure 2(c), with a resultant tendency for the aircraft to yaw on forward movement.
Figure 3 shows the basic parts of a propulsion arrangement in accordance with one embodiment of the invention. The propulsion arrangement generally comprises a flow straightener 11, a non circular mouthpiece 15 and a propeller 16. A pair of such propulsion arrangements can be accommodated, for example, in wings of an aircraft.
Air can be drawn into the propeller 16 in an orderly and therefore efficient manner through the mouthpiece 15 as shown by the arrows in Figure 3. The air discharged can be passed through the flow straightener 11 as shown by the arrows substantially to eliminate bodily swirl of the air stream to overcome the undesirable effects described 20 with reference to Figures I and 2. Arrangements like that shown in Figure 3 have in the past been used in wind tunnel design but in what is a long history of flight not considered for use in an aircraft itself.
In one embodiment, the mouthpiece 15 has a bell-mouth intake, modified for ease of construction using sheet material. An octagon is formed at the entry section in the mouthpiece 15 shown in Figure 3. A transition is then effected to a circular section at the exit, to match a circular duct 17 for housing the propeller 16.
The circular duct 17 about the propeller 16 inhibits the formation of vortexes about the tips of the propeller.
The flow straightener 11 comprises a tubular housing, which is internally divided by a 10 honeycomb 19 into air passages of triangular crosssection which extend parallel to the longitudinal axis of the tubular housing. Such a flow straightener 11 is lcoown to be effective at straightening the flow of air therethrough. The propeller 16 does have to overcome the flow resistance of the honeycomb 19 however and this increases the power that must be supplied to it. Such a flow straightener 11 also has considerable 15 depth and this is a disadvantage if shallow equipment is required for accommodation in an aircraft wing.
Another propulsion arrangement in accordance with the invention, comprising a propeller 16 and mouthpiece 15 arranged as shown in Figure 4, has been found by 20 experiment to produce efficiently an air stream substantially free from swirl with standard types of aircraft propeller normally used for forward propulsion.
( 11 The efficiency of the propeller 16 with the mouthpiece 15 is explained by the creation of "bicone" vortexes in the flow, which convert swirling motion from the propeller into axial flow.
5 Figure 5 shows isometrically a column 21 of air discharged by a propeller 16 through a circular aperture 23. Because of the swirl imparted by the propeller 16, the rotating column of air acts as a vortex core as previously described when discharged through a wmg. 10 Figure 6 shows the effect of a hexagonal aperture 25 as shown in the mouthpiece 15 of Figure 4. Air from the propeller again flows in a circular path when viewed from above, as shown by a broken line 27 in Figure 6. Because of the tendency of the air to flow along the flat sides 29 of the hexagon perimeter and therefore tangentially away from the circular arc 27, air flows downwards in the vertex regions of the hexagonal aperture 15 25. Since this process is repeated at each vertex, air is caused to flow outwards in six "bicones" 33. Each bicone 33 consists of two cones with a common base and has an included angle at the apex of 60 degrees in the plane of the axis. A bicone 33 is thus the volume of revolution of two equilateral triangles with a common side. Each bicone 33 has an axis which extends between the midpoints of two adjacent sides of the 20 hexagonal aperture 25, forming a group of six bicones 33 as shown in plan view in Figure 7.
The entry plane of the mouthpiece shown in Figure 4 is geometrically similar to the exit plane and a similar pattern of bicones fomls in the entry plane also.
Vorticity arises in the flow because of the action of the propeller, which drives a forced vortex, and vorticity is induced by flow through the angular mouthpiece. Bicones, as defined above, provide a means of analysing flow of the nature described and of 5 designing a mouthpiece accordingly. Thus, a mouthpiece 15 might have an entry cross-section in the form of a dodecagon, so forming twelve bicones 33 around the perimeter as shown in Figure 8.
Bicone vortexes formed in the entry and exit planes of the mouthpiece are 10 complementary. In an efficient arrangement of propeller and mouthpiece, the vortex generated about the tip of the propeller will confonn with the bicone system generated by the mouthpiece. Such a propeller tip vortex 31 is shown in Figure 9(a) in a vertical section through the vertices of a mouthpiece, together with a section of a bicone 33 at the throat (that is, in the exit plane of the mouthpiece) in the region of a vertex, as 15 shown in horizontal section through its axis in Figure 6 and again in Figure 7. Because of the restraint exercised by the mouthpiece, and its shape, the propeller tip vortex 31 expands and contracts to produce a bicone pattern like that shown in plan view in Figure 9(b), in which bicone vortexes 35, 37, 39, 41 are shown on one side of the centre-line which contact the mid-point of a side of the mouthpiece in the entry plane.
20 Smaller bicones 43, 45, 47 are shown adjacent the vertices. Larger bicones also exist.
Thus, a small bicone 45 shown adjacent a vertex 49 exists within a larger bicone 51 that is formed along the same axis, extended to meet the midpoints of the sides of the mouthpiece in the entry plane, so that the sides of the mouthpiece (between the mid-points in the entry plane) form one side of the bicone 51, the other side being
! 13 shown by broken line. The larger of the bicones 35, 37, 39, 41 generated at the tip of the propeller by expansion and contraction of the tip vortex 31 are intercepted in part by the wall of the mouthpiece, because the maximum diameter of the bicone is greater than the minimum distance between the propeller tip and the wall. This produces a suction 5 pressure region on the wall of the mouthpiece and therefore a lift force on the mouthpiece itself. The lift produced by the combination of propeller and mouthpiece is the sum of the thrust due to the propeller and the suction force on the mouthpiece. With arrangements of the kind proposed it has been found experimentally that the total lift is about 15 percent greater than with the propeller alone with aircraft type propellers. The 10 increase in lift achieved by the use of a mouthpiece as described with a propeller depends however upon the pitch and shape of the propeller, since the increase in lift obtained is related to the conversion of swirl into axial flow and therefore to the degree of swirl produced by the propeller in the first place. To the left hand side of the centre-line in Figure 9(b) is shown a plan view of the mouthpiece and also the propeller 15 arc 53. A vertical section is shown in Figure 9(c) on a plane through the mid-points of the sides of the mouthpiece, a section on A-A. With the particular arrangement shown in Figure 9, in which the propeller lies in the entry plane of the mouthpiece, there is a horizontal clearance between the propeller tip and the mid-point of a side of the mouthpiece equal to nearly 12 percent of the radius of the propeller.
Vertical clearance between the propeller tip and the top surface of the mouthpiece may be arranged alternatively or additionally. Figure lO(a) shows a mouthpiece with the propeller mounted above to provide vertical clearance. The sides 55, 57 are shown to be vertical at the throat of the mouthpiece. Alternatively, the sides may be sloped inwards
( 14 considerably, as shown in Figure 10(b). This has been found to have some performance advantage when a propeller with a broad tip is used. It has also been found by experiment that the mouthpiece may be inclined with respect to the plane of the propeller, as shown in Figure 10(c), without greatly affecting the lift produced. With S inclination of the mouthpiece, one side may be brought vertical at the throat and the opposite side sloped (with a mouthpiece having sides symmetrical about the centre-plane). The sides of the mouthpiece do not need to be symmetrical about the centre-plane. Inclination and /or asymmetry of the mouthpiece has practical advantages in enabling a wing dihedral to be accommodated whilst maintaining a propeller axis 10 vertical or the pitch of a wing to be accommodated in design.
A bicone vortex gives rise to pressure variations and therefore the Coronation of series of induced bicones about it. When installed in a wing, a mouthpiece like that shown in Figure 4 may have an exit plane below the bottom surface of the wing, so that a lip is 15 formed (below the wing) at the throat of the mouthpiece. The throat of the mouthpiece may, though, be in the plane formed by the underside of the wing to minimise obstruction to flow in forward flight. When the throat of the mouthpiece lies in the lower surface of the wing, the connation of induced bicones around the throat can have adverse effects by reducing lift and/or stability. Measures can be taken to minimise such 20 adverse effects by controlling induced bicone formation. One method is to extend downwards two sides 59, 61 only of a mouthpiece, as shown in front view in section in Figure Il(a) and from the side in Figure ll(b), the sides extended downwards being those which extend in the direction of forward motion of the aircraft so as to present minimal obstruction to flow past the underside of the wing.
( 15 Another method, illustrated in a plan view in Figure 12 is to locate two mouthpieces side by side with vertices on a line connecting the centres of the mouthpieces. Bicones with axes perpendicular to the line connecting the centres of the mouthpieces (that is, 5 aligned with the direction of forward movement) then become linked, in a larger bicone 63 shown by broken lines in Figure 12. In the illustration in Figure 12, the two mouthpieces 15a, 15b have a common vertex (in the entry plane). Bicones formed by a fuselage between two mouthpieces can be used to link and thereby control the bicones formed at the throat of a mouthpiece. This is because any bicone, such as bicone 63, 10 does not exist in isolation but itself forms part of a larger bicone. Whereas the bicones 33a and 33b represent vortexes, the bicone 63 straddles the centre line of the aircraft and represents a flow structure which is symmetrical about the centre line. Rotation of bicone 63 as a vortex would tend to overturn the aircraft and it is an object of design of the fuselage in particular, and the aircraft in general, to prevent this. Maintaurung a 15 symmetrical array of vortex bicones which have axes aligned in the direction of forward motion of the aircraft is a means of achieving this with efficiency. The outline aircraft designs shown in Figures 15 to 18 have been determined by such consideration.
Wing tip vortexes are of great importance in this respect. The wall of a mouthpiece at the throat may be serrated or indented to locate fixed bicones in the exit plane of the 20 mouthpiece.
In the present invention, energy supplied to the propeller that would normally be absorbed in the production of swirl produces useful thrust by means of the Pairing.
Consequently, a propeller of high blade pitch that produces much swirl can be used
with the hexagonal Pairing and yet be efficient in producing thrust. Furthermore, the torque on the propeller drive that arises in the production of swirl is countered by contrary torque on the fairing as swirl is removed. This latter feature is important in flight because countering propeller drive torque otherwise requires the expenditure of 5 additional power, as with a tail rotor of a helicopter, or the balancing of torque when more than one rotor is employed. The balancing of torque imposes restraints on design and can have undesirable side effects, such as when the combined flow from two counter-rotating rotors is deflected by variation in atmospheric conditions and flow over other aircraft components, such as the fuselage.
Figure 13a shows in section a unit comprising a propeller 16 and a mouthpiece 15 set in an aerofoil wing section that has a flat underside 65, a rounded leading edge 67 and trailing edge 69. Figure 13c shows in plan two such units, 71 and 73, mounted in the wings, 75, of an aircraft, the wings being of rectangular plan form and of the aerofoil 15 section shown in Figure 13a. Figure 13b shows a vertical section through the common centre-line of the two units.
It is anticipated that in some circumstances it will be advantageous to employ units as illustrated in Figures 14a and 14b. Two units, 77 and 79, are shown mounted astride a 20 fuselage 81 in Figure 14b in a vertical section through the centre-lines. A plan view of the units is shown in Figure 1 4a.
A unit comprising a propeller and mouthpiece of the kind described can also be utilised in another part of an aircraft, such as a tail plane, or in an appropriately shaped fuselage,
( 17 and may be used to provide lift and/or to balance an aircraft, or for propulsion if inclined to the horizontal.
One side of an aircraft having a unit in each of a pair of wings and also a unit located in 5 the rear portion of the fuselage, towards the tail, is shown in plan view in Figure 15.
The unit mounted in the tail section of the fuselage can, by varying its thrust, be used to adjust the pitch of the aircraft for vertical or horizontal flight. The fuselage is of trapezoidal section, brought to a point at the nose and to a horizontal trailing edge at the tail. An isometric view of the aircraft is shown in Figure 1 6(a), a vertical section through the wing on the centre-lines of the propellers in Figure 16(b) and a front view of the aircraft in vertical flight, with the nose pitched upwards, in Figure l6(c). Figure 17(a) shows a side view in a vertical section through the wing on a centre-line through the propeller in 15 vertical flight, with the nose pitched upwards as shown in Figure 16(c). Figure 17(b) shows a vertical section through the centre-line of the aircraft in forward flight. The upwards pitch is reduced in forward flight, compared with that for vertical flight, so that the discharge from the propellers is inclined backwards to provide forward propulsion.
20 Forward propulsion can be achieved by other means. In Figure 18, a tractor propeller is shown mounted at the nose of an aircraft that has a wing similar to that shown in Figures 15 and 16. Figure 18(a) is an isometric view of the aircraft, Figure 18(b) shows a vertical section through a wing on the centre-line of a propeller and Figure 1 8(c) is a side view on a section through the wing, again through the centre-line of the propeller.
The fuselage is of trapezoidal section between the wing and the nose, but the nose is rounded in this case and the upper surface of the fuselage is contiguous with the upper surface of the wing at the rear. Because forward propulsion is by tractor propeller, the discharge from the propellers does not need to be inclined backwards to provide 5 propulsion and the lift propellers in the wing do not need to be powered in horizontal flight. The aircraft can be supported wholly by the wing and lift on the fuselage in horizontal flight. In vertical flight, flow produced by the tractor propeller can be diverted downwards by guide vanes to support the nose of the aircraft and maintain the fuselage horizontal.
In order to provide a thrust perpendicular to the axis of the propeller, the discharge from a unit comprising a propeller and a mouthpiece may be deflected. This is illustrated in Figure 19, in which a unit 85 is incorporated in a vertical fin 87. A deflector 89 of aerodynamic section is mounted in a horizontal plane through the centre-line of the unit 15 with its leading edge 91 in the plane of the discharge opening. By deflecting the discharge stream upwards or downwards as shown by the arrows, 93 and 95, a vertical force is obtained.
A view of the unit in Figure 19 from the side is shown in Figure 20a, which shows 20 schematically the tail fin of an aircraft (such as a helicopter) in which the propeller of the unit functions as a tail rotor. A section through the tail fin in the horizontal pleurae through the centre of the unit 85 is shown in Figure 20b. The limits of the deflector 89 are shown in Figure 20b by broken lines at the edges of the unit discharge opening, but the deflector may extend further forwards and backwards. The rear section of the tail fin
( i9 is shown as a rudder flap 97. Neither the deflector on the discharge side of the opening nor a flap downstream of it affects the operation of the unit since the propeller 16 is free to draw air from all directions on the inlet side of the plane of the propeller and the fairing of the unit acts on the air drawn into the propeller and passed through the fin. Figure 21 shows schematically six units 101, 103, 105, 107, 109 and 111,
all in the same horizontal plane and linked together at vertices. This arrangement can provide a lifting platform supported around the periphery. This provides a clear area in the centre region, free from propeller discharge. A wing can be incorporated in the central region, 10 to reduce fuel consumption in horizontal flight, and/or the space used for other equipment or for load carrying purposes. Units can be linked in other patterns, to meet particular requirements, because of the freedom from swirl of the individual propeller discharge streams. Swirl tends to cause interaction between streams and consequent instability.

Claims (1)

  1. Claims
    1. A propulsion arrangement for moving a craft, wherein the propulsion arrangement comprises a rotor arranged to drive fluid through a mouthpiece and flow 5 straightening means, so that fluid exiting the propulsion arrangement is substantially straightened. 2. A propulsion arrangement according to any preceding claim, wherein the flow straightening means comprises a mouthpiece of non-circular cross section.
    3. A propulsion arrangement according to Claim 2, wherein the mouthpiece is of polygonal cross section.
    4. A propulsion arrangement according to Claim 3, wherein the mouthpiece is of 15 triangular cross section.
    5. A propulsion arrangement according to Claim 3, wherein the mouthpiece is of hexagonal or octagonal cross section.
    20 6. A propulsion arrangement according to any preceding claim, wherein the flow straightening means is arranged before the point of the mouthpiece of narrowest cross section. A propulsion arrangement according to Claim 6, wherein the flow straightening 25 means is mounted flow wise behind the rotor.
    8. A propulsion arrangement according to any preceding claim, wherein the rotor is a propeller.
    9. A propulsion arrangement according to any preceding claim, wherein the 5 mouthpiece is constructed as a fairing, shroud, surround or housing on which or in which the propeller is mounted.
    10. A propulsion arrangement according to any preceding claim, wherein the propulsion arrangement is mounted in a wing.
    11. A propulsion arrangement according to any of Claims 1 to 9, wherein the propulsion arrangement is mounted in another plane, such as a sailplane, to provide either lift and/or balance to an aircraft.
    15 12. A propulsion arrangement according to any of Claims 1 to 9, wherein the propulsion arrangement is mounted in an appropriately shaped Fuselage, to provide either lift and/or balance to an aircraft.
    13. A propulsion arrangement according to any of Claims 1 to 9, wherein the 20 propulsion arrangement is mounted in a fin, such as a tail fin.
    14. A propulsion arrangement according to any preceding claim, wherein the propulsion arrangement is mounted in a sea craft or in an aircraft
    15. A propulsion arrangement according to any preceding claim, and a second propulsion arrangement according to any preceding claim, wherein the two propulsion arrangements, each comprising a propeller and a hexagonal fairing defining a fluid inlet, are mounted in the same plane with a vertex of each lying on the straight line that S connects the centres of the arrangements.
    16. A propulsion arrangement according to any of Claims 1 to 14, and five additional propulsion arrangements according to any of Claims 1 to 14, wherein the six propulsion arrangements are arranged in a hexagonal pattern in a plane so that any two 10 adjacent propulsion arrangements have respective vertices on the straight line that connects the centres of the two propulsion arrangements.
    17. A propulsion arrangement according to any of Claims 1 to 14, and five additional propulsion arrangements according to any of Claims 1 to 14, wherein the six 15 propulsion arrangements are arranged in a hexagonal pattern in a plane, and any two adjacent propulsion arrangements have a common vertex on the straight line that connects the centres of the two propulsion arrangements.
    18. A propulsion arrangement according to any of Claims 1 to 14, and five 20 additional propulsion arrangements according to any of Claims 1 to 14, wherein the six propulsion arrangements are linked so that the vertex of any propulsion arrangement that lies on the straight line that connects two adjacent propulsion arrangements is common to both.
    19. A propulsion arrangement according to any of Claims 1 to 14, and five additional propulsion arrangements according to any of Claims 1 to 14, wherein two propulsion arrangements are adjoined in the same plane with an edge of one hexagonal propulsion arrangement parallel to that of another propulsion arrangement but with the 5 parallel edges spaced apart.
    20. A craft comprising a propulsion arrangement in accordance with any of Claims 1 to 19.
    10 21. A propulsion arrangement substantially as described herein and with reference to any one or more of Figures 3 to 12.
    22. A wing or fin substantially as described herein and with reference to Figure 13.
    15 23. A craft substantially as described herein and with reference to any one or more of Figures 14 to 21.
GB0214514A 2002-06-22 2002-06-22 Craft propulsion Expired - Fee Related GB2389826B (en)

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GB0214514A GB2389826B (en) 2002-06-22 2002-06-22 Craft propulsion

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Application Number Priority Date Filing Date Title
GB0214514A GB2389826B (en) 2002-06-22 2002-06-22 Craft propulsion

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GB2389826A true GB2389826A (en) 2003-12-24
GB2389826B GB2389826B (en) 2006-08-23

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015001290A1 (en) * 2013-07-05 2015-01-08 Lindsay Gatward Assembly of a duct and a fan for hovercraft or aircraft propulsion
EP3366586A1 (en) * 2017-02-27 2018-08-29 AIRBUS HELICOPTERS DEUTSCHLAND GmbH A thrust producing unit with at least two rotor assemblies and a shrouding
US10737766B2 (en) 2017-01-26 2020-08-11 Airbus Helicopters Deutschland GmbH Thrust producing unit with at least two rotor assemblies and a shrouding

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2556384A1 (en) * 1975-12-15 1977-06-16 Becker Ingbuero W Low noise thruster for ship - with ducted impeller inside larger hexagonal duct to reduce resonant vibrations
GB2209314A (en) * 1987-09-02 1989-05-10 Manuel Munoz Saiz Lifting arrangement by direct thrust of the engine flow to vertical take-off aircraft
JP2000335488A (en) * 1999-05-27 2000-12-05 Kawasaki Heavy Ind Ltd Duct propeller device
US6159062A (en) * 1997-04-24 2000-12-12 Taylor, Jr.; Guy High performance boat prop guard
US20010040062A1 (en) * 1999-05-21 2001-11-15 Lewis Illingworth Lifting platform

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2556384A1 (en) * 1975-12-15 1977-06-16 Becker Ingbuero W Low noise thruster for ship - with ducted impeller inside larger hexagonal duct to reduce resonant vibrations
GB2209314A (en) * 1987-09-02 1989-05-10 Manuel Munoz Saiz Lifting arrangement by direct thrust of the engine flow to vertical take-off aircraft
US6159062A (en) * 1997-04-24 2000-12-12 Taylor, Jr.; Guy High performance boat prop guard
US20010040062A1 (en) * 1999-05-21 2001-11-15 Lewis Illingworth Lifting platform
JP2000335488A (en) * 1999-05-27 2000-12-05 Kawasaki Heavy Ind Ltd Duct propeller device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015001290A1 (en) * 2013-07-05 2015-01-08 Lindsay Gatward Assembly of a duct and a fan for hovercraft or aircraft propulsion
GB2518138A (en) * 2013-07-05 2015-03-18 Lindsay Gatward Ducted fan assembly
GB2518138B (en) * 2013-07-05 2019-08-21 Gatward Lindsay Ducted fan assembly
US10737766B2 (en) 2017-01-26 2020-08-11 Airbus Helicopters Deutschland GmbH Thrust producing unit with at least two rotor assemblies and a shrouding
EP3366586A1 (en) * 2017-02-27 2018-08-29 AIRBUS HELICOPTERS DEUTSCHLAND GmbH A thrust producing unit with at least two rotor assemblies and a shrouding
US11220325B2 (en) 2017-02-27 2022-01-11 Airbus Helicopters Deutschland GmbH Thrust producing unit with at least two rotor assemblies and a shrouding

Also Published As

Publication number Publication date
GB2389826B (en) 2006-08-23
GB0214514D0 (en) 2002-08-07

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Effective date: 20130622