GB2332891A

GB2332891A - Aerodynamic lift producing apparatus

Info

Publication number: GB2332891A
Application number: GB9724827A
Authority: GB
Inventors: Kenneth Arthur Austin
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-11-21
Filing date: 1997-11-21
Publication date: 1999-07-07
Anticipated expiration: 2017-11-21
Also published as: GB2332891B; GB9724827D0

Abstract

An aerodynamic lift producing apparatus comprises a collapsable, elongate, tubular envelope 2 of impervious flexible material adapted to be inflated to form a self-supporting tubular rotor 1, means 23 for inflating said envelope and drive means 18,19,20 for rotating the rotor 1 about its longitudinal axis and including a dynamic stabiliser means 30 which produces a dynamic base at an intermediate position in the height of the envelope to stiffen the upper part thereof when it is rotated. The apparatus which uses the Magnus effect can be applied to marine propulsion.

Description

AERODYNAMIC LIFT PRODUCING APPARATUS This invention relates to aerodynamic lift producing apparatus of the kind set forth in UK Patent GB 2 072 112.

In the Patent referred to above an aerodynamic lift producing arrangement is described which comprises a collapsable, elongate, tubular envelope of impervious flexible material adapted to be inflated to form a selfsupporting tubular rotor, means for inflating the envelope and drive means for rotating the envelope about its longitudinal axis.

In apparatus of this kind it is known that when the circular flexible tubular envelope is rotated about its central axis it produces a lift force when place in an air stream flowing normal to the axis. This lift force has a direction normal to the axis and to the free stream flow direction. The lifting effect thus produced is known as Magnus Effect after the person who first investigated the phenomenon in 1853.

The apparatus can be applied to marine propulsion or to any other moving vehicle.

The application is particularly although not exclusively applicable to marine vessels used in fishing and in the construction described in UK Patent GB 2 072 112 the flexible envelope material can be collapsed easily for shore storage, repair or transport.

The present invention is intended to provide an improved construction of the type of device referred to above.

A circular cylinder rotating in fluid flow generates a transverse thrust, the Magnus Effect, which increases as coefficient of lift, C, with increasing aspect ratio, the ratio of cylinder height to mean diameter. Constructing the cylinder as a hollow envelope inflated with low pressure air allows wind assisted propulsion to be applied to a boat or other moving vehicle in a form that is light and strong in use yet easily collapsible for storage or shipment.

From theory, very slim cylinders, hollow or solid, will, when rotated vertically in cantilever from a driven base, develop at some speed a divergent whirl at their tip. It is possible in some cases by quickly increasing power to pass through this first critical speed but the manoeuvre is generally avoided and the cylinder design limited in aspect ratio to operate safely over the whole expected range of operation.

Considering the hollow, inflated construction mentioned above, the proposed invention introduces a "dynamic stabilizer" at an intermediate desired Rotor height to essentially create, while operating, a new dynamic base effectively stiffening the upper part of the rotor and hence increasing the overall safe aspect ratio and realising a higher CL and improved thrust for a given input power and wind speed. Though other construction could be used the proposed flexible "stabilizer" allows the whole Rotor to enjoy the benefits of full deflation and compact stowage at minimum air height for a central drive tube and axle base.

According to the present invention an aerodynamic lift producing apparatus comprises a collapsable, elongate, tubular envelope of impervious flexible material adapted to be inflated to form a self-supporting tubular rotor, means for inflating said envelope and drive means for rotating the rotor about its longitudinal axis and including a dynamic stabiliser means which produces a dynamic base at an intermediate position in the height of the envelope to stiffen the upper part thereof when it is rotated.

Preferably the dynamic stabilizer means comprise a plurality of weights evenly spaced around an intermediate circumference in the height of the flexible envelope and means for securing the weights to support means co-axial with the longitudinal axis about which the envelope rotates.

With the arrangement set forth above the means for securing the weight to the support means can be in the form of a spider having a centre portion for attachment to said support means and a plurality of arms, the outer ends of which are secured to said weights.

The spider preferably has three or more arms.

The support means can also act to locate a shaft on which the envelope is located and this shaft can be in the form of a hollow torque tube co-axially mounted on an axle member.

The spider can be made from a flexible fabric.

The invention can be performed in various ways but one embodiment will now be described by way of example and with reference to the accompanying drawings in which Figure 1 is a cross-sectional side elevation through apparatus according to the invention; Figure 2 is an enlarged cross-sectional side elevation of part of the construction shown in Figure 1; and, Figure 3 is a plan view on the line III-III of Figure 1.

As shown in the drawings the apparatus comprises a rotor 1 in the form of an inflated outer envelope 2 which is made from an impervious flexible material. The envelope 2 tapers from its lower end 3 to its upper end 4 and is closed by an upper cone 5 beneath which is a projecting semi-conical end plate 6. The lower end 3 of the envelope 1 is held between an outer retaining flange 7 and an inner retaining ring 8. The flange 7 and the ring 8 are securely mounted on a base disc 9 on which is also provided a hollow torque tube 10, torque tube extension 11 and a drive pulley 12.

The torque tube 10 is provided with upper bearings 13 and lower bearings 14 which are located on an axle member 15 which is mounted on a base plate 16 provided with resilient mounting means 17 for securing it to a ship or vehicle structure. The base plate 16 also carries an electric motor 18 with a drive pulley 19 which can drive the pulley 12 through a flexible belt 20. Thus, operation of the electric motor 18, driving through the belt 20 onto the pulley 12, causes the disc 9 and the rotor mounted on it to rotate.

The upper end of the torque tube extension 11 is closed by an end member 21 which also acts to secure the upper end of an inner cone 22, the lower end of which is also held in position by the flange 7 and ring 8. This inner cone can also be made from a flexible material similar to that used for the envelope 2.

In the arrangement described above an electric motor is used to drive the rotor but any other suitable power arrangement can be used as the direction of drive of the rotor can be reversible.

Air for inflation/deflation of the rotor passes through a valve 23 and a pressure relief valve 24 is mounted centrally on the top of the member 21.

The dynamic stabiliser means which produces a dynamic base at an intermediate position in the height of the envelope to stiffen the upper part thereof when it is rotated is indicated by reference numeral 30. This device comprises a plurality of weights 31 evenly spaced around an intermediate circumference in the height of the flexible envelope, in this case slightly below half of the vertical height.

As is most clearly shown in Figure 2 each weight 31 is held in position on the envelope 2 by circular flexible material patches 32 which are firmly secured to the envelope material. A weight 31 is in the form of a flat disc with a central opening through which protrudes a D-hoop 33. Beneath the base 34 of the hoop is a further circular patch 35. The whole assembly is secured with adhesive and firmly fastened to the inside surface of the rotor envelope 2. In the construction being described three such weights are provided at an intermediate circumference in the length of the envelope.

The means for securing the weights 31 to a support means provided by the torque tube extension 11 is in the form of a spider 36 made from a flexible fabric similar to that of the rotor envelope 2.

The outer end of each arm 37 of the spider 36 is doubled around the pin 38 of a D-shackle 39 and the loop of the shackle passes through the D-hoop 33, as shown in Figures 2 and 3.

The centre portion 40 of the spider 36 is provided with a circular opening (not shown) which passes over a boss 41 on the upper end of the member 21 and is held in place by a retaining ring 42.

At rest, each stabilizer arm 37 is in slight tension against the inflated diameter of the rotor envelope 2 but when the rotational speed of the rotor is increased the weights 31 respond to their curved path exerting centrifugal force on the rotor envelope 2 and in each stabilizer arm 37 this is proportional to the peripheral speed squared, that is twice the rotor speed, rpm. four times the radial force. The combined effect is to essentially create a new dynamic base for the rotor envelope approximately at the height of the dynamic stabilizer above the true rotor base defined by the flange 7 and ring 8.

As rotor speed or wind speed increases, the transverse thrust or lift of the rotor increases in response to, first, the square of the wind speed (V) and second, substantially directly as the ratio between rotor peripheral speed and wind speed. It will be seen that the weighted "stabilizer" arms directly oppose and counteract internally the imposed side thrust (lift) to maintain rotor stability over the whole range of operating conditions at sea.

The first critical speed of a cantilevered rotor bearing uniform transverse load is essentially a function of the inverse of the height (H) times root total distributed load (W) times height (H). If the height is doubled the first critical speed REDUCES by a factor of four, conversely, if the height is halved, the critical speed INCREASES by a factor of four.

Inclusion of the "dynamic stabilizer" allows a substantial increase in aspect ratio for a desired rotor operating speed and hence improvement in coefficient of lift and thrust for a given input power.

In the construction described above three weights 31 are provided but provided they are evenly distributed any other suitable number could be employed with suitable connecting means to a central support.

The upper part conical end plate 6 prevents air spillage over the top of the rotor thus increasing efficiency.

With the construction described above it will be appreciated that the rotor can be collapsed when the air pressure is released thus allowing the apparatus to be stowed when not required.

Claims

CLAIMS 1. An aerodynamic lift producing apparatus comprises a collapsable, elongate, tubular envelope of impervious flexible material adapted to be inflated to form a self-supporting tubular rotor, means for inflating said envelope and drive means for rotating the rotor about its longitudinal axis and including a dynamic stabiliser means which produces a dynamic base at an intermediate position in the height of the envelope to stiffen the upper part thereof when it is rotated.
2. An aerodynamic lift producing apparatus as claimed in claim 1 in which said dynamic stabilizer means comprise a plurality of weights evenly spaced around an intermediate circumference in the height of the flexible envelope and means for securing said weights to support means co-axial with the longitudinal axis about which the envelope rotates.
3. An aerodynamic lift producing apparatus as claimed in claim 2 in which the means for securing said weights to said support means is in the form of a spider having a centre portion for attachment to said support means and a plurality of arms, the outer ends of which are secured to said weights.
4. An aerodynamic lift producing apparatus as claimed in claim 3 in which said spider has three or more arms.
5. An aerodynamic lift producing apparatus as claimed in claim 2, claim 3 or claim 4 in which said support means also acts to locate a shaft on which said envelope is located.
6. An aerodynamic lift producing apparatus as claimed in claim 5 in which said shaft is a hollow torque tube co-axially mounted on an axle member.
7. An aerodynamic lift producing apparatus as claimed in claims 2 to claim 6 in which said spider is made from a flexible fabric.
8. An aerodynamic lift producing apparatus substantially as described herein with reference to and as shown in the accompanying drawings.