GB2295587A

GB2295587A - Aerodynamic addenda for road vehicles

Info

Publication number: GB2295587A
Application number: GB9424202A
Authority: GB
Inventors: John Patrick Peter Flynn
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-11-30
Filing date: 1994-11-30
Publication date: 1996-06-05
Anticipated expiration: 2014-11-30
Also published as: GB2295587B; GB9424202D0

Abstract

Aerofoil 4 is attached to the front of a land vehicle 1. Forward movement of the vehicle in the direction of arrow "A" causes areas of uplifting air to be formed around the vehicle. By placing the aerofoil in such an area of uplifting air, lift may be generated by the aerofoil which has both a resultant vertical component and a horizontal component acting in the direction of arrow "A". The result of this is to both reduce effective vehicle weight and to assist vehicle movement through the air. This is intended to reduce vehicle fuel consumption. The aerofoil may be located behind the vehicle, and its angle of attach may be variable. Such variation may be automatic, depending on vehicle payload or speed. <IMAGE>

Description

VEHICLE APPARATUS The invention relates to vehicle apparatus and particularly, although not exclusively, to apparatus for improving the fuel economy of a road vehicle.

There are many devices on the market which have as their main objective, improving the fuel economy of road vehicles. Fuel for road vehicles is a relatively expensive commodity and any saving which could be made is welcome.

According to a first aspect of the invention, vehicle apparatus is provided comprising at least one deflector for fitment to a land vehicle so as to generate lift when the vehicle is in forward motion.

The deflector preferably comprises an aerofoil section.

The generation of lift preferably has the effect of reducing vehicle weight and thereby makes the vehicle more fuel efficient. Preferably, the generation of lift is also arranged to aid forward passage of the vehicle.

Preferably, the aerofoil is provided in a position on the vehicle such that as the vehicle moves forwardly air pushed upwardly by vehicle movement flows over a top surface of the aerofoil faster than air passing under a bottom surface of the aerofoil to thereby generate the lift.

Preferably, the angle of attack of the aerofoil section is arranged such that movement of the vehicle generates lift which has a component acting in the direction of movement so as to assist said movement.

The aerofoil may be positioned attached to any suitable point of the vehicle in which during forward movement, the aerofoil will be in an area of uplifting air. For instance, an aerofoil may be positioned ahead of a main part of the vehicle or in an area behind a main part of the vehicle.

Preferably, the angle of attack of the aerofoil is variable.

Preferably, control means are provided for automatically varying the angle of attack. The angle of attack may be varied according to vehicle payload.

The angle of attack may be varied in accordance with vehicle speed.

In a preferred embodiment, the design of the aerofoil is optimised so as to provide maximum lift at a given angle of attack and at a given cruising speed. The given cruising speed may be between 30 and 70 mph and, in a preferred embodiment, is 60 mph.

At the given cruising speed the angle of attack may be chosen such that the effective weight of the vehicle including payload is approximately equal to the unladen static weight of the vehicle.

A plurality of aerofoils may be provided attached to suitable positions mounting on the vehicle.

The invention includes land vehicles having the vehicle apparatus fitted thereto.

A specific embodiment of the present invention will now be described, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic side view showing typical air flow patterns around a vehicle caused by vehicle movement relative to the air; Figure 2 shows an aerofoil section positioned to the front of the vehicle of Figure 1, placed within an area of rising air; Figure 3 shows a typical aerofoil section; and Figures 4A and 4B are diagrams showing lift calculations.

Referring initially to Figure 1 a vehicle 1, which may for instance be a coach, is shown. As the vehicle moves forwardly in the direction of travel shown by the arrow A, forward motion of the vehicle 1 causes the air around the vehicle to be disturbed so that areas of rising air 2, 3 are formed.

Referring now to Figure 2, an aerofoil section 4 is shown placed within the area of rising air 2 at the front of the vehicle 1. The aerofoil section 4 is attached to the vehicle 1 by connection structure 5. Arrows L, D and R represent the forces Lift, Drag and their Resultant. C represents the chord line. The angle of attack of the aerofoil section 4 is shown as a.

An example of typical settings of angle of attack and values for Lift, Drag etc. will now be given.

In the following discussion, the following assumptions are made: (i) the aerofoil is set at an angle of attack of 120; (ii) the aerofoil is set in air swept up at an angle of 45 ; (iii) the aerofoil is in clean air; (iv) there is no side slip and there are no tip losses.

It is also assumed that the aerofoil is of a type as shown in Figure 3 and that the air density q = 0.0024 Slugs, the forward velocity of the vehicle 1 is 100 feet per second (60mph), the coefficient of Lift CL = 1.06, the coefficient of Drag CD = 0.028 and the surface area, S, of the aerofoil section is 16 square feet.

The formulae for the calculation of Lift and Drag are, respectively, 0.5qV'CLS and 0.5qV2CDS respectively.

From the substitution of the abovementioned values into the formulae, Lift = 0.5(0.0024 x 1002 x 1.06 x 16) = 203.52 lbf and Drag = 0.5(0.0024 x 1002 x 0.028 x 16) = 5.376 lbf. Using pythagoras' theorem, the Resultant may be calculated as being 203.59 lbf. This calculation is illustrated diagrammatically in Figure 4B. Because angle o is 1.50 (i.e. tan 6 = 5.376/203.52) it can be seen that the Resultant force of 203.59 lbf may be resolved into vertical and horizontal components as shown in Figure 4A, the Resultant making an angle of 43.5" with the vertical component.From this, it follows that there is an uplifting vertical component generated which has a value of 203.59 cos 43.5 = 147.68 lbf and there is a horizontal component having a value of 203.9 sin 43.5 = 140.14 lbf.

It can therefore be seen that for a vehicle speed of 100 feet per second (60 miles an hour) there is a component generated which aids forward motion of the vehicle and there is also a component generated which tends to reduce effective vehicular weight.

From the above discussion, it can be seen that as the vehicle moves faster (if angle of attack remains the same) both vertical and horizontal lift increase so as to aid movement of the vehicle through the air and to effectively reduce the weight of the vehicle thereby improving fuel consumption.

As an example to illustrate how drag may be reduced for the vehicle as a whole, the normal amount of drag on a coach having a frontal area of eight feet by eight feet can be worked out according to the formula 0.5qV2S and this works out at 768 lbf. The reduction in drag due to the horizontal lift component of 140.14 lbf gives a percentage decrease in drag of (horizontal load/drag) = (140.14/768) = 18.24%.

In a particular preferred embodiment, a control system is linked to the aerofoil so as to control the angle of attack of the aerofoil as a function of vehicle speed and pay load so as to provide consistent handling of the vehicle under all conditions.

Whilst it will be appreciated that the provision of a single aerofoil section mounted to a vehicle 1 has been discussed, more than one aerofoil section could of course be provided and they may be integrated with vehicle design so as to optimise the situation.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. Vehicle apparatus comprising at least one deflector for fitment to a land vehicle so as to generate lift when the vehicle is in forward motion.

2. Apparatus according to claim 1, wherein the deflector comprises an aerofoil.

3. Apparatus according to claim 1 or 2, wherein the generation of lift has the effect of reducing vehicle weight.

4. Apparatus according to any of claims 1 to 3, wherein the generation of lift is arranged to aid forward passage of the vehicle.

5. Apparatus according to any of claims 2 to 4, wherein the aerofoil is provided in a position on the vehicle such that as the vehicle moves forwardly, air pushed upwardly by vehicle movement flows over a top surface of the aerofoil faster than air passing under a bottom surface of the aerofoil to thereby generate the lift.

6. Apparatus according to any of claims 2 to 5, wherein the aerofoil has an angle of attack which is arranged such that movement of the vehicle generates lift which has a component acting in the direction of forward movement so as to assist said movement.

7. Apparatus accordingly to claim 6, wherein the aerofoil is positioned attached to any suitable point of the vehicle in which during forward movement, the aerofoil section is in an area of uplifting air.

8. Apparatus according to claim 7, wherein the aerofoil is positioned ahead of a main part of the vehicle.

9. Apparatus according to claim 7 or 8, wherein the aerofoil is positioned in an area behind a main part of the vehicle.

10. Apparatus according to any of claims 2 to 9, wherein the angle of attack of the aerofoil is variable.

11. Apparatus according to claim 10, wherein control means are provided for automatically varying the angle of attack.

12. Apparatus according to claim 10 or 11, wherein the angle of attack is varied according to vehicle payload.

13. Apparatus according to claim 10, 11 or 12, wherein the angle of attack is varied in accordance with vehicle speed.

14. Apparatus according to any of claims 2 to 13, wherein the design of the aerofoil is optimised so as to provide maximum lift at a give angle of attack and at a given cruising speed.

15. Apparatus according to claim 14, wherein the given cruising speed is within the range of 30 to 70 miles an hour.

16. Apparatus according to claim 15, wherein the given cruising speed is approximately 60 miles an hour.

17. Apparatus according to any of claims 14, 15 or 16, wherein at the given cruising speed the angle of attack is chosen such that the effective weight of the vehicle including pay load is approximately equal to the unladen static weight of the vehicle.

18. Apparatus according to any of claims 2 to 17, wherein a plurality of aerofoils are provided attached to suitable mounting positions on the vehicle.

19. Vehicle apparatus substantially as hereindescribed with reference to the accompanying drawings.

20. A land vehicle having vehicle apparatus in accordance with any of the preceding claims.