GB2138757A

GB2138757A - Vehicle drag reduction system

Info

Publication number: GB2138757A
Application number: GB08311098A
Authority: GB
Inventors: Edmund John David Nightingale
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-04-23
Filing date: 1983-04-23
Publication date: 1984-10-31
Also published as: GB2138757B; GB8311098D0

Abstract

A drag reduction system for a vehicle, comprises a stabilising plate spaced from a portion of the vehicle, the surface of said portion facing the plate being shaped to define with said plate a venturi duct. The stabilising plate comprises a wing 12 exerting a downthrust on the car when the car is in motion, and the wing 12 defines the venturi in combination with a casing 11 which is supported beneath the wing and which covers parts of the vehicle engine. <IMAGE>

Description

SPECIFICATION Vehicle drag reduction system The present invention relates to a vehicle drag reduction system and more particularly to a drag reduction system which is connected with an aerodynamic stabiliser system at the rear of the vehicle. It is particularly, although not exclusively, directed to a drag reduction system for high performance vehicles such as racing cars.

It is known in the field of motor racing to improve the speed and roadholding properties of cars by providing, at a location above the driving wheels, an aerodynamic wing. The wing is angled so that the air flowing past produces a downward force which is transmitted to the rear driving wheels to improve their contact with the road surface.

It is important that the shape of racing cars is such that they offer the least possible resistance to the air they pass through. However, at the rear of the car a low pressure area or slipstream is generally present and the drag caused by this slipstream increases as the vehicle speed increases.

It is an object of the invention to improve the aerodynamic properties of a vehicle and reduce the drag, and optionally to improve the efficiency of its engine.

According to the present invention there is provided a drag reduction system for a vehicle, the system comprising a stabilising plate spaced from a portion of the vehicle, the surface of said portion facing the plate being shaped to define with said plate a venturi duct.

Preferably the venturi duct is defined at or near the rearmost portion of the vehicle.

Advantageously the vehicle engine exhausts into a low pressure zone of said venturi duct.

By definition, a venturi duct or tube is a convergent divergent or tube which accelerates and streamlines an air flow or flow of other fluid and causes inter alia a suction source as a low pressure zone downstream of the throat.

An embodiment of the invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically a longitudinal section and front elevation of a prior art car; and Figure 2 shows diagrammatically a longitudinal section and front elevation of racing car embodying the present invention.

Referring now to the drawings, a racing car embodying the prior art is shown in Fig. 1.

Besides those parts which are well known and not essential for the understanding of this invention, it comprises an aerodynamically shaped body 1, an engine indicated generally by 2, and an aerodynamic angled stabiliser wing 3 supported above the body. It is commonplace in racing cars that the engine 2 forms the rear part of the car and that it is not totally enclosed in an aerodynamic casing, whereby the flow of air past the car is disturbed and "parasitic" drag results. This is in addition to the inevitable drag caused by the slip-stream.

The stabiliser wing 3 is held on supports clear of the engine and, due to its shape, it exerts a downward force on to the rear driving wheels.

Referring now to Fig. 2, a car embodying the invention has a casing 11 at the upper surface at the rearward end, which casing extends across the width of the car. The stabiliser wing 12 of this car has a lower surface, the contours of which correspond to the contours of the casing 11. The two surfaces form a venturi duct 1 3 which has a throat 14 at the point where the surfaces approach one another most closely. The sides of the duct may be panelled to enclose totally the venturi duct 13, or left open to give a slightly iess efficient venturi duct.

The stabiliser 1 2 is constructed with light ribs which may have lightening holes to reduce the weight or be constructed of lightweight material. In operation the stabiliser still acts as such and produces a downward force on the rear of the car. However, the effect of the venturi duct 1 3 is to accelerate the flow of air in the duct and to create, as a consequence, a zone of low pressure within the duct rearwardly of the throat 14.

The accelerated air flow exits from the rear of the duct as a smooth flow and therefore reduces considerably the drag caused by turbulent air flow at the rear of the vehicle. The casing 11, by covering some protrusions of the engine, may also reduce some of the parasitic drag.

The exhaust outlets 1 6 from the engine of the vehicle are located within the venturi duct downstream of the throat in a low pressure zone. The exhaust gases are therefore withdrawn from the outlets and entrained into the flow. The heat of the exhaust gases, given up to the air flow, causes the rate of flow of the air to increase still further, and thereby the drag experienced by the car is further reduced.

An additional advantage is that exhaust gases are removed from the engine under suction and the engine need perform no work to eject them. Thus the efficiency of the engine may be improved.

1. A drag reduction system for a vehicle, the system comprising a stabilising plate spaced from a portion of the vehicle, the surface of said portion facing the plate being shaped to define with said plate a venturi duct.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Vehicle drag reduction system The present invention relates to a vehicle drag reduction system and more particularly to a drag reduction system which is connected with an aerodynamic stabiliser system at the rear of the vehicle. It is particularly, although not exclusively, directed to a drag reduction system for high performance vehicles such as racing cars. It is known in the field of motor racing to improve the speed and roadholding properties of cars by providing, at a location above the driving wheels, an aerodynamic wing. The wing is angled so that the air flowing past produces a downward force which is transmitted to the rear driving wheels to improve their contact with the road surface. It is important that the shape of racing cars is such that they offer the least possible resistance to the air they pass through. However, at the rear of the car a low pressure area or slipstream is generally present and the drag caused by this slipstream increases as the vehicle speed increases. It is an object of the invention to improve the aerodynamic properties of a vehicle and reduce the drag, and optionally to improve the efficiency of its engine. According to the present invention there is provided a drag reduction system for a vehicle, the system comprising a stabilising plate spaced from a portion of the vehicle, the surface of said portion facing the plate being shaped to define with said plate a venturi duct. Preferably the venturi duct is defined at or near the rearmost portion of the vehicle. Advantageously the vehicle engine exhausts into a low pressure zone of said venturi duct. By definition, a venturi duct or tube is a convergent divergent or tube which accelerates and streamlines an air flow or flow of other fluid and causes inter alia a suction source as a low pressure zone downstream of the throat. An embodiment of the invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically a longitudinal section and front elevation of a prior art car; and Figure 2 shows diagrammatically a longitudinal section and front elevation of racing car embodying the present invention. Referring now to the drawings, a racing car embodying the prior art is shown in Fig. 1. Besides those parts which are well known and not essential for the understanding of this invention, it comprises an aerodynamically shaped body 1, an engine indicated generally by 2, and an aerodynamic angled stabiliser wing 3 supported above the body. It is commonplace in racing cars that the engine 2 forms the rear part of the car and that it is not totally enclosed in an aerodynamic casing, whereby the flow of air past the car is disturbed and "parasitic" drag results. This is in addition to the inevitable drag caused by the slip-stream. The stabiliser wing 3 is held on supports clear of the engine and, due to its shape, it exerts a downward force on to the rear driving wheels. Referring now to Fig. 2, a car embodying the invention has a casing 11 at the upper surface at the rearward end, which casing extends across the width of the car. The stabiliser wing 12 of this car has a lower surface, the contours of which correspond to the contours of the casing 11. The two surfaces form a venturi duct 1 3 which has a throat 14 at the point where the surfaces approach one another most closely. The sides of the duct may be panelled to enclose totally the venturi duct 13, or left open to give a slightly iess efficient venturi duct. The stabiliser 1 2 is constructed with light ribs which may have lightening holes to reduce the weight or be constructed of lightweight material. In operation the stabiliser still acts as such and produces a downward force on the rear of the car. However, the effect of the venturi duct 1 3 is to accelerate the flow of air in the duct and to create, as a consequence, a zone of low pressure within the duct rearwardly of the throat 14. The accelerated air flow exits from the rear of the duct as a smooth flow and therefore reduces considerably the drag caused by turbulent air flow at the rear of the vehicle. The casing 11, by covering some protrusions of the engine, may also reduce some of the parasitic drag. The exhaust outlets 1 6 from the engine of the vehicle are located within the venturi duct downstream of the throat in a low pressure zone. The exhaust gases are therefore withdrawn from the outlets and entrained into the flow. The heat of the exhaust gases, given up to the air flow, causes the rate of flow of the air to increase still further, and thereby the drag experienced by the car is further reduced. An additional advantage is that exhaust gases are removed from the engine under suction and the engine need perform no work to eject them. Thus the efficiency of the engine may be improved. CLAIMS

2. The invention of Claim 1 and in which the duct is defined at or near the rearmost portion of the vehicle.

3. The invention of Claim 1 or Claim 2 and in which the vehicle engine exhausts into a low pressure zone of the duct.

4. The invention in accordance with any of the preceding Claims and in which the plate is so shaped as to exert a downthrust on the vehicle when the vehicle is in motion.

5. The invention of Claim 4 and in which the stabilising plate is mounted above the vehicle engine whilst the said portion facing the plate covers parts of the engine.

6. The invention of any of the preceding Claims and in which the venturi duct is opensideed.

7. A drag reduction system substantially as described herein with reference to and as illustrated in the accompanying drawing.

8. A vehicle incorporating a drag reduction system in accordance with any of the preceding Claims.

9. A vehicle according to Claim 8 and comprising a rear-engined racing car.

10. Means, suitable for putting or intended to put into practice the invention defined in any of the preceding Claims.