GB2512889B - Vehicle airflow control apparatus - Google Patents

Description

VEHICLE AIRFLOW CONTROL APPARATUS

The present invention relates to vehicle airflow control apparatus, for example such apparatus for landvehicles such as motor cars. A motor car has to function as a product of good engineering while in most cases also beingaesthetically pleasing. There is often a conflict of interest between designers and aerodynamicistswhen deciding of the form of the vehicle. With high speed motor cars, such as those capable ofexceeding 200 or even 300 kilometres per hour, lift can be generated in the region of the rear “axle”area and such fast motor cars require a low co-efficient of lift to prevent them from losing grip incorners and so as to avoid undesirable driving characteristics.

It is also desirable for a motor car to have relatively low drag so that it is economical and/or can travelfaster with a motor/engine providing a given power to the power train.

One aerodynamic device used is a rear “flip”. Some of the earliest effective motor cars to use thesedevices were the Ferrari 250 GTO, and the Aston Martin DP214 and DP215 racing cars which in theyear 1963 where the first motor cars ever to be officially timed at over 300 kph on the very longMulsanne Straight at Le Mans. More recently, boot lid flips have become relatively common amongproduction cars and are included on, for example, the Aston Martin DBS, BMW Z4 and MercedesBenz SLK55 AMG models.

Another aerodynamic device is a deployable spoiler such as used on the Bugatti Veyron Super Sportat the rear of the vehicle. Another known aerodynamic device is a fixed wing at the rear of the vehiclesuch as used on the Aston Martin V12 Zagato and Mercedes Benz C63 AMG Black Series models.Another aerodynamic device is a Gurney flap which is an element which may be fixed to the toptrailing edge of a wing on a racing car and has been used since the 1970s. FR-A-2885343 discloses the use of blowing slots on an MPV or hatchback with a flat roof. EP-A-1506911 shows air blown out near a rear windscreen of a hatchback. EP-A-1907267 shows a motorcar having a horizontal opening for air which has passed a cooling duct. EP-A-1048556 shows anapparatus for emitting air up next to and behind a substantially vertical drop surface behind asubstantially horizontal boot lid - a rather unsightly arrangement due to the exterior nature of theapparatus. EP-A-0467523 discloses air passageways inclined upwards and with baffles disposes inthe passageways.

While some of these devices can be useful to greater or lesser extents from an aerodynamicperformance perspective, they do not always fit in with the objects which vehicle designers may beattempting to achieve from an aesthetic perspective on some projects. Some vehicle designers maydesire very clean lines for the shape of their vehicles, at least when the vehicles are on display or stationary and without a substantial and/or complex arrangements. It is very challenging to engineer avehicle which is capable of very high speed with good vehicle response and stability across the roadspeed range during straight line and cornering manoeuvres while also meeting vehicle aestheticdesign objectives.

The present invention, which is defined in accordance with appended claim 1, aims to alleviate at leastto a certain extent the problems of the prior art.

The present disclosure provides a vehicle airflow control apparatus comprising an airflow blowingarrangement located at or in a vehicle body upper surface for reducing lift away from the vehicle bodysurface when the vehicle is in forward motion, the air blowing arrangement being behind or within adownwardly sloping area of upper vehicle body work.

The downwardly sloping area of vehicle body work may slope down at a slope angle which is at over 5degrees to the horizontal. The slope angle may be from 5 to approximately 60 degrees, for examplefrom about 10 to 40 degrees, for example within 15 to 30 degrees, one example being substantially 20degrees.

The present disclosure also provides a vehicle airflow control apparatus comprising an airflow blowingarrangement located at or in a vehicle body surface for reducing lift away from the vehicle bodysurface when the vehicle is in forward motion, the blowing arrangement and vehicle body surfacebeing arranged and configured to decrease lift and/or drag when a vehicle to which the apparatus isfitted is travelling forwards at a Reynolds number above 2 x 10s or above 3 x 10s.

The present disclosure also comprises a vehicle airflow control apparatus comprising an airflowblowing arrangement located at or in a vehicle body surface for reducing lift away from the vehiclebody surface when the vehicle is in forward motion, the blowing arrangement including a slotextending across the vehicle body surface, the slot having a length in the intended longitudinaldirection of motion of the apparatus of between 2 and 10mm.

The present disclosure also comprises a vehicle airflow control apparatus comprising an airflowblowing arrangement located at or in a vehicle body surface for reducing lift away from the vehiclebody surface when the vehicle is in forward motion, the air blowing arrangement and vehicle bodysurface being configured such that at least one lateral position and at least one airflow speed for theapparatus the airflow blown out from the blowing arrangement towards free stream airflow is sufficientto move a pressure point at a rear of the vehicle body surface forwards relative to its position with theblowing arrangement blocked or inactive (a) forwards over 10cm, typically over 25cm, in someexamples over 40cms such as 40 to 50cm forwards or (b) forwards over 5% of the wheel base lengthof a vehicle to which the apparatus is to be fitted, typically over 10% or 15%, such as between 15 and 20% forwards. The pressure point may be (although is not necessarily) a point at which pressureequals or is greater than free stream pressure.

The present disclosure also comprises a vehicle airflow control apparatus for a land vehiclecomprising a vehicle body surface and a surface member which is arranged to extend generally awayfrom the vehicle body surface and extend laterally thereacross in relation to intended free stream flow,the surface member be positionable with portions of its surface substantially perpendicular to adjacentportions of the vehicle body surface, the surface member being movable from a first position to asecond position in which the surface member protrudes further from the vehicle body surface than itdoes in the first position. In the first position, the surface member may be flush or sub-flush with thevehicle body surface. The surface member may be arranged to act as a Gurney flap.

The present isclosure also comprises a vehicle airflow control apparatus comprising a vehicle bodysurface and a surface member which is arranged to extend generally away from the vehicle bodysurface and extend laterally thereacross in relation to intended free stream flow, and a blowingarrangement in the vicinity of the surface member for blowing air into passing airflow. The blowingarrangement may be formed with an air exit aperture within the surface member. The exit aperturemay comprise at least one slot. The surface member may be arranged to operate as a Gurney flap.

The features of the above aspects of the present disclosure have been found in testing to provideimproved vehicle response and stability across vehicle road speed range during straight line andcornering manoeuvres. At the same time, the blowing arrangement can be very unobtrusive and cansimply consist of one or more apertures or slots in the vehicle body surface and can therefore enableaerodynamicists to engineer vehicles which may be capable of very high speeds with good vehiclecontrol while still meeting the aesthetic objectives of vehicle designers. A number of features which may be incorporated when carrying out any of the above aspects of thepresent disclosure will now be discussed.

The blowing aperture may adapted to blow flow out into free stream or at least nearby passing flowand to create an obstruction to flow travelling over the vehicle body surface and to create a highpressure region upstream of an exit from the blowing arrangement. The blowing arrangement maycomprise a duct leading to at least one outlet aperture or exit. The blowing arrangement may bearranged to jet flow in a direction substantially perpendicular to flow passing the vehicle body surface.However, the jet flow direction may be in any other direction but especially in the longitudinal andvertical plane of the vehicle to which the apparatus is fitted. The blowing arrangement may bearranged to provide the jet flow such that substantially all of the flow from an exit of the blowingarrangement is ejected from the exit in substantially the same overall direction.

The blowing arrangement may comprise an array of blowing elements extending substantially laterallyacross the vehicle body surface. The array may include at least one elongate slot. The array maycomprise a plurality of said slots such as 2, 3, or 4 said slots, which are substantially aligned and arearranged one next to the other across the vehicle body surface, such as comprising aligned left, centreand right slots. Each slot may have a width laterally which is substantially longer than its lengthlongitudinally in the intended direction of motion of the apparatus. The vehicle body surface may bean A-surface. One or more perforated panels areas with a series of small perforations may be used inaddition to or as an alternative to one or more slots, if desired.

The vehicle body surface may comprise an upper body surface. The vehicle body surface mayinclude a roof portion and/or a rear window portion of an occupant space for a vehicle, the roof portionand/or rear window portion lying in front of the blowing arrangement. The vehicle body surface maycomprise or include a boot lid or deck lid such as a rear boot lid or deck lid. When the vehicle bodysurface includes a boot lid or deck lid portion, the blowing arrangement may be formed at least partlyor fully in the said boot lid or deck lid portion. The boot lid or deck lid portion may be arranged to covera rear enclosure of a vehicle, such as an enclosure for luggage and/or vehicle motor/enginecomponents.

When the blowing arrangement includes at least one blowing slot, each slot may have a length in thelongitudinal direction of flow of between about 2 to 8mm, some examples being about 3 and about5mm.

The vehicle body surface may be connected to a rear drop down surface located below a rear edge ofthe vehicle body surface. The drop down surface may be overhung, thereby extending downwardlyand forwardly from the rear edge of the vehicle body surface. The blowing arrangement may have arear most portion which is located about 0.5 to 100mm from the rear edge of the vehicle body surface,more typically within about 3 to 50mm some examples being about 35mm and about 10mm, such asabout 7mm or 5mm from the rear edge.

The drop down surface and vehicle body surface may be oriented (in at least one vertical section in alongitudinal plane) substantially perpendicular to one another, the rear edge of the vehicle bodysurface (which is the edge between them) having a radius which is less than 10cm, for example lessthan 5cm, about 1, about 2 or about 3cm being some examples.

The blowing arrangement may include a duct leading to an exit aperture thereof, the duct may becurving gradually towards the aperture. The duct may have a duct supply portion running directlytowards or within about 20 degrees of directly towards the exit aperture, the duct supply portion havinga flow length which is over 5 times the length (in the flow direction inside the duct) of the exitaperture/slot length (in the free stream flow direction) of the blowing apparatus, the flow length of the duct portion for example being 5 to 10 times or about 10 to 15 times this length. This has been foundto increase the performance of the blowing arrangement.

The blowing arrangement and/or vehicle body surface and a vehicle structure in front of the blowingarrangement may be configured such that with at least one speed flow near the vehicle body surfaceis substantially attached and/or lacking in substantial vortices or turbulence. The blowingarrangements thus blow out into such flow.

The blowing arrangement may include a Gurney or surface member arranged to extend generallyaway from the vehicle body surface and extending laterally across the vehicle body surface, thesurface member potentially having a front part positioned upstream of a flow exit aperture or exit slotof the blowing arrangement.

The said aperture or slot of the blowing arrangement may be positioned within the surface member.

The surface member may be positionable with portions of its surface substantially perpendicular toadjacent portions of the vehicle body surface. The surface member may be retractable within and/orbelow the vehicle body surface. A control may be provided for retracting the surface member. Thesurface member may be retractable in response to a signal indicative of stationary vehicle, engine offor travelling at low speed. The surface member may be extendable out from the vehicle body surfacein response to a signal indicative of vehicle motion or travelling at high speed or in response to a driverinput such as a push button. A cover member may be provided for moving over and covering thesurface member and/or the blowing arrangement when the surface member is retracted. The covermember may be arranged to move to a position in which it is substantially aligned with the vehiclebody surface such that with a vehicle to which the apparatus is fitted stationary there is no or issubstantially no prominence within the region of the airflow control apparatus and a high level ofdesign aesthetics or a design objective for little or no prominence may be achieved. A heating arrangement may be provided for the blowing arrangement. Thus, ice, snow or otherprecipitation may be prevented from blocking the blowing arrangement and adversely affectingperformance.

The blowing arrangement may include an air inlet for supplying the airflow to an exit portion of the flowcontrol apparatus at the vehicle body surface. The air inlet may comprise at least one aperturelocated in the region of a rear quarter light window of a vehicle. The air inlet may otherwise compriseanother type of simple A-surface intake, such as a side pod, scoop or discontinuous shut linearrangement. Alternatively, the air inlet may comprise an under floor scoop underneath a vehicle suchas a car to which the air flow control apparatus is to be fitted, or a powered air feed inlet such asinvolving a compressor, turbine or another form of electromechanical or mechanical system.

The blowing arrangement may be configured to decrease lift and/or drag when a vehicle to which it isfitted is operating at a Reynolds number above 2 x 10s or above 3 x 10s for example, above 10 x 10s,12 x 10s or 15 x 10s being other examples, between 2 x 10s and 35 x 10s being consideredachievable, between 3 x 10s and 30 x 10s being quite typical and some examples of successfulapplication being operation at 3.39 x 10s, 16.9x10s and 25.44 x 10s.

The present disclosure also comprises a vehicle including a vehicle airflow control apparatus as setout in any one of the preceding aspects of the disclosure. The vehicle may comprise a land vehicle.The land vehicle may comprise a motor car. The motor car may be capable of operation in excess of200 kph or even in excess of 250 or 300 kph, operation at up to or over about 450 to 500 kph beingenvisaged in some motor car arrangements. The vehicle may, for example, comprise a fastback, GT,saloon, estate, hatchback, SUV or convertible.

The present invention has been found through testing to enable the provision of a motor car capableof operating at high speeds and at relatively high Reynolds numbers with good vehicle response andstability across the full speed range during straight line and cornering manoeuvres. Measurementshave showed an increase in surface pressure on the vehicle body surface (when it is deck lid) upstream of the blowing arrangement of approximately 900Pa. This translates into a very significantreduction in aerodynamic lift at the rear of the vehicle and can also be associated with a reduction ofdrag, thus improving efficiency while providing good high speed handling.

The blowing arrangement may emit air into passing air flow with a speed higher than free stream airspeed.

The present invention may be carried out in various ways and vehicle airflow control apparatus willnow be described with reference to the accompanying drawings in which:

Figure 1 is a view of pressure distribution on a vehicle body without a blowing arrangement active;Figure 2 is a similar pressure distribution example but with a blowing arrangement active;

Figure 3 shows a CFD depiction of the flow caused by the blowing arrangement of Figure 2, with airjetted out from the A-surface to create an obstacle for the passing air over the boot/deck lid surface;Figure 4 shows a vehicle as in Figures 2 and 3 and including a blowing arrangement;

Figure 5 is a view showing part of a blowing slot of the blowing apparatus;

Figure 6 schematically shows a blowing duct as it approaches the airflow exit at a slot from the flowblowing arrangement;

Figure 7 shows a modified airflow control apparatus having a surface extending generally away from avehicle body surface, the surface member being in an extended position thereof;

Figure 8 shows the apparatus of Figure 7 with the surface member retracted and covered by a cover;Figures 9A and 9B show an A-surface air inlet for use with the devices of Figures 1 to 8; and

Figure 10 shows an arrangement similar to that shown in Figure 4 for air blowing slot of the airflowblowing arrangement and including three separate but aligned slots in a boot or deck lid instead of onelong one.

Figure 1 shows a 44.44 m/s CFD simulation taken along a central vertical plane of a motor car havinga front wind screen 12, roof 14 and boot or deck lid 16 and a rear drop down surface 18. The figurealso shows a powertrain component 20, torque tube 22, transaxle/differential 24 with rear wheel axisgenerally at point 26, as well as fuel tank 28.

Figure 1 shows that there is a positive downward pressure compared to free stream of about 400 Paat a lower part 30 of the front windscreen 12, a negative (lift) pressure of about 400 to 600 Pa at upperpoint 32 of the roof 14 and lift pressure all of the way along from the upper point 32 to rear edge 35which is between the boot lid 16 and rear drop down surface 18, the pressure at the edge 35 being anegative (lift) pressure of about 300 to 400 Pa.

Figure 2 is a similar view in which the motor car 10 has been modified to include a blowing slot 34 asshown in Figures 2 to 16.

The blowing slot 34 is fed from an inlet 36 which in this example is an A-surface inlet 34 located at arear corner 38 of rear quarter light area 40 of the car 10. The inlet 36 is connected to the blowing slot34 by a duct 42 part of which is shown in Figure 6. When the vehicle is in forward motion, as shown inFigure 4, a stream 44 of air passively (i.e. without the use of compressor etc.,) enters into the inlet 38and is fed by the duct 42 to the slot 34 where the stream 44 emerges as a jet 46 which as shown inFigures 3 and 4 extends across the full width of the blowing slot 34 and is directed substantiallyvertically into the passing airflow 48, although the angle of the jet 46 may be varied, for example so asto be perpendicular to the adjacent body surface 16/boot lid surface 16.

As shown in Figure 2, which shows flow at the same speed (44.44 m/s) and Reynolds number (about8.5 x 10s) as that in Figure 1, the blowing slot 34 results in a high pressure area 50 in front of theblowing slot 34 where the pressure is up to about 500 or 600 Pa above free stream air pressure andthe pressure in this area is therefore up to about 900 Pa higher than the same place in Figure 1. Theplace 62 at which the pressure returns to positive or at least zero (gauge pressure compared to freestream) on the boot lid 16 is approximately 40 to 50cm in front of rear edge 34 - and this is with amotor car having a wheelbase of about 2.8 metres. Therefore, negative lifting pressure is no longerpresent for this relatively long distance at the rear of the motor car 10.

Accordingly even with the large back light angle (alpha) between the horizontal/free stream airflowdirection and the adjacent angle of the boot lid 16 (which is marked 65 in Figure 1 as well as “alpha”and is substantially 20 degrees), and despite the curved roof profile at the point 32, the blowing slot 34enables the motor car 10 to be engineered which does not involve significant lift near the rear of the vehicle which will be taken up mainly by the rear wheels on the axis 26. The blowing slot 34 thus hasreduced the negative pressure on the upper surface of the motor car 10 and therefore lift. In place ofthe negative pressure on the boot 16, there is now a high pressure region (at about 400 to 500 Pa orso above free stream) for at least approximately 10cm or more in front of the blowing slot 34 whichcreates down force. The blowing slot 34 creates an obstruction for the flow travelling over the surfaceof the boot 16 creating a high pressure region up stream of the exit 34 from the duct 42. The blowingslot therefore jets fast moving air into the flow vertically and/or substantially perpendicular to theadjacent A-surface, creating the aerodynamic effect of a flip, but without changing the back light angleand without having to have a flip or spoiler.

Figure 3 shows a close up of the effect of the air 46 coming out from the blowing slot 34 into the freestream or adjacent airstream. The fast air coming out from the duct forces air to slow down and travelover the top of the jet 46 of air.

The exit geometry at the blowing slot has a significant effect on efficiency and a blowing slot width inthe direction of flow of both 3mm with a 2mm radius on the edges and larger 5mm slot have beentested, with the 5mm width slot surprisingly performing better than the initially calculated best size of3mm. The larger 5mm slot increases the mass flow of the duct and ultimately the effect that theblowing slot 34 has on lift and drag reduction. Thus, in Figure 5, the distance D, which is thelongitudinal size of the slot along the airflow direction, is substantially 5mm. A slot larger than 5mm could be provided but may not be acceptable from an aesthetic point of view inall cases. As shown in Figure 6, the duct 42 which is a generally hollow element is in the region of theblowing slot 34 angled up towards the blowing slot 34. For a distance E, which is approximately75mm, the direction of flow in the duct 42 is substantially directly towards the slot 34 and is withinabout 10 or 20 degrees or so from being directly towards the slot 34. The inventors have found thatthe sooner the duct 42 curves upwards to face the surface of the boot lid 16 normal from its originalpath, i.e. the path 66 from the inlet 36 which is shown in Figure 6, the more powerful the blowing slot34 is, i.e. the longer the air had pointed up at the underside of the boot or deck lid 16, the better theperformance of the blowing slot 34.

The distance X shown in Figure 6 of the blowing slot 34 to the rear or trailing edge 35 of the deck lidsurface 16 is important and the lesser this distance the more powerful and effective the blowing slot 34is in many arrangements. The distance X is substantially exaggerated in Figure 6 since as can beseen in Figures 3, 4 and 5, the trailing edge of the blowing slot is approximately 5 to 10mm from theedge 34. As shown in Figure 3, the edge 35 between the boot lid surface 16 and the overhung dropdown surface 18 has a relatively small radius which is in some arrangements about or less than20mm. Directly after the blowing slot 34 is a low pressure region of separated flow which cangenerate a concentrated lift force and to minimise this effect, the blowing slot 34 is normally positionedas close to the trailing edge 35 of the deck lid 16 as possible.

It is notable that the entire upper surface of the motor car at the central section of Figure 2 from thewindscreen 12 and over the rooftop 14 and past the deck lid 16 to the rear edge 35 is non-concave -all of the way along, it is convex or substantially flat. For about a first quarter of horizontal distanceback from the leading lower edge of windscreen 12 to rear edge 35, this central section is substantiallyflat or slightly convex, for about a middle two quarters the section is convex and for about a lastquarter the section is slightly concave or substantially flat and sloped down at about 15 to 25 degreesmore specifically at about 20 degrees to horizontal.

The width of the blowing slot 34 across the motor car 10 provides linear performance sensitivity, i.e. asthe slot increases in width (assuming an increasing mass flow to maintain exit velocity), the lift linearlyreduces with the drag. In the real world, where the mass flow stays relatively constant, the lift anddrag continue to decrease with increasing slot width to a point where the exit velocity becomes verylow (approximately equal to or less than 0.2 times the velocity of the free stream flow).

As shown in Figure 7, a surface member 70 or “Gurney” - type member may be positioned upstreamof the blowing slot 34 exit and it has been found that this may cause more flow to be drawn throughthe duct 42. As shown in Figure 8, the blowing slot 34 may be sealed when it is not needed, i.e. whilethe motor car 10 is stationary, has the engine off or is travelling at low speed. Instead of theorientation in Figure 7, in which the surface member 70 is deployed and extends from the A-surface/boot lid 16 of the motor car 10 with the cover panel 72 moved out of the way in the X(longitudinal) and Z(vertical) directions, as shown in Figures 8, the Gurney member or surface member70 is retracted below the height of the boot lid surface 16 and the cover member 72 is slid along andmoved down such that its upper surface is aligned with the upper surface of the boot lid 16 and a rearmost panel element 16A just in front of the edge 35 which leads down to the rear drop surface 18. Ascan be seen in Figure 7, the blowing slot 34 is essentially a gap in the middle of the surface member70 where the blowing slot air is released as the jet 46, part of which is shown in Figure 7. Theconfiguration shown in Figure 8, with the cover panel 72 folded back into A-surface of the motor car10, the Gurney member or surface member 70 is hidden. This allows the arrangement to meet adesign objective for clean lines which may be set in some circumstances yet still provide a goodaerodynamic system. A mechanism or other movement means (not shown) is provided for moving the member 70 and otherarrangements may be used to seal the duct when the vehicle is stationary and/or deployed.

To form the inlet 36, the side glass the rear quarter light 40 has been rolled inboard to reveal anopening comprising the inlet 36.

The inlet 36 may be replaced while still providing the same type or similar blowing slot 34 in which theair is controlled/forced to react with the free stream upon leaving the duct 42. Other possible intake method includes simple A-surface intakes, such as side pod, scoop, discontinuous shut lines etc, andunder floor scoop, similar to that shown in Figure 4 but underneath the motor car end/not on an A-surface, or a powered air feed, such as involving a compressor, turbine or other electro-mechanicalsystem.

The blowing arrangements described herein may have a working range where the effects of the deviceare measurable from 40 to 200 mph, although this range can be extended to well above 200 mphbecause the effects of the blowing slot increase with vehicle speed and this has been shown both withCFD and on test drives. It is considered therefore that the blowing arrangements described in thepresent application can be used on motor cars at the speeds up to equal to or in excess of 260 or 300mph for road vehicle applications. In aerospace applications, higher speeds are envisaged.

With the Reynolds number as calculated by multiplying the wheel base length of the vehicle which is2.803 meters by the density of air at 15°C which is 1.225 kg per cubic meter and multiplying by thevelocity of the free stream air in meters per second, and then dividing by the viscosity of the air at15°C which is 1.81 x 105 kg per meter per second, the arrangements in the present applicationoperate at 40 miles per hour at a Reynolds number of 3.39 x 10s at 200 miles per hour of 16.96 x 10sand at 300 miles per hour of 25.44 x 10s. CFD analysis so far has shown that the blowing arrangement designs in the present application havethe following performance capabilities on a vehicle as shown in Figures 2, 3 and 4, although thevalues will change dependent upon the application of the blowing slot and the specific vehiclegeometry. With an arrangement as shown and described with reference to Figures 2 to 6, the dragreduction as Cd is 10 and rear axle lift reduction is Ci_r is 35. For the arrangement shown in Figures 7and 8 the drag reduction Cd is 4 and rear axle lift reduction Ci_r is 50. These are very useful reductionsin drag and lift suitable for improved economy, stability and road handling.

Physical tests have been performed using first an unmodified vehicle 10 similar to that shown withreference to Figure 1, second with the vehicle 10 modified to have a blowing arrangement asdescribed with reference to Figures 2 to 6 and third with the vehicle 10 modified to have anarrangement similar to that in Figures 7 and 8 with a deployed surface member or Gurney member 70as shown in Figure 7.

The motor vehicle was instrumented to provide data along with drive evaluation and measurementsincluded surface pressures, vehicle ride height, suspension displacement, lateral accelerations andvehicle speed. A series of tests were carried out and the test procedures explored vehicle responseand stability across the full vehicle road speed range during straight line and cornering manoeuvres.The tests also evaluated various failure modes, operation with one or both side windows open, in yawand with one side inlet 36 blocked.

The test measurements showed an increase in surface pressure on the deck lid upstream of theblowing slot 34 of approximately 900 Pa translating to a significant reduction in aerodynamic lift actingat the rear of the vehicle.

The professional test driver noted the following information and it must be noted here that theunmodified vehicle 10 compared to average road vehicles is already exceptionally fast with highlysuperior and safe vehicle handling, so the results are comparative only.

UNMODIFIED MOTOR CAR

Compared to the modified vehicle 10, vehicle stability at 200 kph and 250 kph sine sweep manoeuvrehad a smaller under steer limit. The car 10 slid from the rear. MOTOR CAR MODIFIED AS IN FIGURES 2 TO 6

The vehicle stability was improved during 200 kph and 250 kph sine sweep manoeuvring. There wassome understeer at the limit and the car slid from the rear. The rear lift appeared to be reduced, givingthe rear tyres more capability at the limit. MOTOR CAR MODIFIED WITH BURN SLOT AS SHOWN IN FIGURE 7

Vehicle stability was improved at 200 kph and 250 kph sine sweep. There was understeer at the limit.The car slid from the rear when provoked. The rear lift appeared to be significantly reduced giving therear tyres more capacity and capability at the limit.

Failure modes have been considered and can be dealt with by failure controller outputs as follows.Failure modes of ice packing, detected with pressure measuring equipment, can be handled by afailure controller output consisting of a transmission of a heating signal to a heater means (not shown)for the duct 42, a driver warning signal and/or speed limiter signal. Failure of the Gurney or surfacemember 70 failing to deploy be handled by a failure controller output comprising a driver warningand/or a speed limiter signal. A failure of the Gurney or surface member 70 failing to stow can behandled with a driver warning. A failure mode of one or more windows at the side of the vehicle beinglowered can be handled by no action being necessary. A failure mode of a duct 42 leaking can behandled by a failure controller output consisting of a driver warning.

Figure 10 shows a modification in which the blowing slot 30 of Figure 4 is replaced by three blowingslots 34 which are placed in line across the boot lid 16.

The blowing slot may instead of a length of 5mm in the flow direction of freestream flow have a lengthfrom 2mm to 8mm. The width of the blowing slot across the motor car may be chosen for theapplication and in some arrangements 30cm in length over a rear haunch panel 80 may be used andin others a width of around 1.5 meters across the span of the rear of the motor car can be used. Thesimulations in Figures 1 and 2 are run at 44.4 meters per second. At this speed, the air exiting the duct was 50 meters per second. The exit angle from the duct can also be varied and the range of plusto minus 60° relative to normal to the surface of the boot lid 16 has a desirable effect. The larger thevelocity exit, the steeper the angle that can be used. The main operating window is between 45°aiming upstream from normal to 30° downstream from normal.

Claims (37)

1. A vehicle airflow control apparatus comprising an airflow blowing arrangement located at or ina vehicle body surface near a rear of the vehicle body surface for reducing lift away from the vehiclebody surface when the vehicle is in forward motion, the air blowing arrangement being behind or withina downwardly sloping area of upper vehicle body work, wherein the blowing arrangement is arrangedsuch that, in use, airflow blown by the blowing arrangement is passively supplied to at least one exitaperture of the blowing arrangement through a duct from an A-surface air inlet comprising at least oneopening located at a rear corner of a rear quarter light area of the vehicle.

2. Apparatus as claimed in claim 1 in which the downwardly sloping area of vehicle body workslopes down at a slope angle which is at over 5 degrees to the horizontal.

3. Apparatus as claimed in claim 2 in which the slope angle is (a) from 5 to approximately 60degrees.

4. Apparatus as claimed in claim 1,2 or 3, wherein a side window of the rear quarter light area ofthe vehicle is rolled inboard to reveal said at least one opening.

5. Apparatus as claimed in claim 4, wherein said rear corner is a rearmost corner of the rearquarter light area of the vehicle.

6. Apparatus as claimed in any one pf the preceding claims, wherein the blowing arrangementincludes a slot extending across the vehicle body surface, the slot having a length in the intendedlongitudinal direction of motion of the vehicle of between 2 and 10mm.

7. Apparatus as claimed in claim 6 in which the slot length is substantially 5 mm.

8. Apparatus as claimed in any one of the preceding claims, wherein the air blowingarrangement and vehicle body surface are configured such that at at least one lateral position and atleast one airflow speed for the apparatus the airflow blown out from the blowing arrangement towardsfree stream airflow is sufficient to move a pressure point at the rear of the vehicle body surfaceforwards relative to its position with the blowing arrangement blocked or inactive (a) forwards at least10cm, or (b) forwards at least 5% of a wheel base length of a motor car to which the apparatus is to befitted.

9. Apparatus as claimed in any preceding claim in which the blowing arrangement is adapted toblow flow out into or at least towards free stream flow, so as to create an obstruction to flow travellingover the vehicle body surface and to create a high pressure region upstream of the exit aperture of theblowing arrangement.

10. Apparatus as claimed in any preceding claim in which the blowing arrangement is arranged tojet flow in a direction (a) substantially perpendicular to flow passing the vehicle body surface or (b)substantially vertically.

11. Apparatus as claimed in any preceding claim in which the blowing arrangement is arranged toprovide a jet flow such that substantially all of the flow from the exit aperture of the blowingarrangement is ejected from the exit aperture in substantially the same overall direction.

12. Apparatus as claimed in any preceding claim in which the blowing arrangement comprises anarray of at least one or a plurality of blowing elements extending substantially laterally across thevehicle body surface.

13. Apparatus as claimed in claim 12 in which the array includes at least one elongate slot.

14. Apparatus as claimed in claim 13 in which the array includes from two to five said slots whichare substantially aligned and are arranged one next to the other across the vehicle body surface.

15. Apparatus as claimed in claim 13 or claim 14 in which each slot has a width laterally which issubstantially longer than its length longitudinally in the intended direction of motion of the vehicle.

16. Apparatus as claimed in any preceding claim in which the vehicle body surface (a) is an A-surface, (b) is an upper body surface (c), includes a rear window portion of an occupant space for thevehicle, the rear window portion lying in front of the blowing arrangement and (d) includes a rear decklid, in which the blowing arrangement is formed at least partly in said deck lid.

17. Apparatus as claimed in claim 16 in which the deck lid is arranged to cover a rear enclosure ofa vehicle, such as an enclosure for luggage and/or vehicle motor/engine components.

18. Apparatus as claimed in claim 13 or any other preceding claim when dependent upon claim 13in which each slot has a length in the longitudinal direction of flow of between about 2 to 8mm, someexamples being about 3 and about 5mm.

19. Apparatus as claimed in any preceding claim in which the vehicle body surface is connectedto a rear drop down surface located below a rear edge of the vehicle body surface.

20. Apparatus as claimed in claim 19 in which the drop down surface is overhung, therebyextending downwardly and forwardly from the rear edge of the vehicle body surface.

21. Apparatus as claimed in claim 19 or claim 20 in which the blowing arrangement has arearmost portion which is located about 0.5 to 100mm of the rear edge of the vehicle body surface,more typically within about 3 to 50mm, some examples being about 35mmm, about 10mm, about 7mmor about 5mm.

22. Apparatus as claimed in any one of claimed 19 to 21 in which the drop down surface andvehicle body surface are oriented in at least one vertical section in a longitudinal plane substantiallyperpendicular to one another, the rear edge of the vehicle body surface having a radius/curvaturewhich is less than 10cm, preferably less than 5cm, about 1, about 2 or about 3cm being someexamples.

23. Apparatus as claimed in any preceding claim in which the duct has a duct supply portionrunning directly towards or within about 20 degrees of directly towards the exit aperture, the ductportion having a flow length which is over 5 times the length in the longitudinal flow direction of flow inthe duct of the exit aperture/slot of the blowing apparatus in the longitudinal direction of free streamflow.

24. Apparatus as claimed in any preceding claim in which the blowing arrangement includes asurface member arranged to extend generally away from the vehicle body surface and extendinglaterally across the vehicle body surface.

25. Apparatus as claimed in claim 24 in which the surface member has a front part thereofpositioned upstream of the exit aperture or an exit slot of the blowing arrangement.

26. Apparatus as claimed in claim 25 in which said exit aperture or slot of the blowingarrangement is positioned within the surface member.

27. Apparatus as claimed in any one of claimed 24 to 26 in which the surface member ispositionable with portions of its surface substantially perpendicular to adjacent portions of the vehiclebody surface.

28. Apparatus as claimed in claim 27 in which the surface member is retractable within the vehiclebody surface.

29. Apparatus as claimed in claim 28 in which a control is provided such that the surface memberis retractable in response to a signal indicative of stationary vehicle, engine off or travelling at lowspeed.

30. Apparatus as claimed in claim 28 or claim 29 in which the surface member is extendable outfrom the vehicle body surface in response to a signal indicative of vehicle motion or travelling at highspeed.

31. Apparatus as claimed in any one of claimed 28 to 30 in which a cover member is provided formoving over and covering the surface member and/or the blowing arrangement when the surfacemember is retracted.

32. Apparatus as claimed in claim 31 in which the cover member is arranged to move to a positionin which an upper surface thereof is substantially aligned with the vehicle body surface.

33. Apparatus as claimed in any preceding claim which includes a heating arrangement for theblowing arrangement.

34. A vehicle including a vehicle airflow control apparatus as set out in any one of the precedingclaims.

35. A vehicle as claimed in claim 34 which comprises a land vehicle.

36. A vehicle as claimed in claim 35 which comprises a motor car.

37. A vehicle as claimed in claim 36 which comprises a fastback, saloon, estate, hatchback, SUV or convertible motor car.