Ground effect coupled with suction fan

[Greg Locock]

The big issue with the fans is that they draw a lot of power. And for that they need to be big. For a given pressure, the power they need is going to be pressure change*volumetric flow rate/efficiency. So given that you know what presssure drop you need (about 3 psi or so from the other thread), then the only ways you can reduce the power requirement are by reducing the leakage rate, or by increasing the efficiency which generally means bigger fans. In a car you rapidly run out of room for fans, so the next thing is to reduce the leakage rate, hence skirts all round the floor. Blasting oodles of air in at the nose is not going to help that.

[wrcsti]

olefud-

The principle of ground effects is different when considering an aircraft or a race car. Anyone that has ever experienced landing on a commercial jet flight has felt the ground effect between an aircraft wing and runway surface. Then there is the additional lift effect produced by helicopter rotors operating in ground effect. The ground effect experienced by an aircraft during landing or a rotorcraft HIGE is momentarily increased lift. The ground effect sought by race cars is continuously greater levels of downforce.

A better comparison to a racecar with a suction fan would be a STOL fixed wing aircraft that uses exhaust-blown wings for additional lift during take-off.

I was going to bring this point. Anyone that has done a high performance takeoff knows what ground effect in airplanes is like. For those who dont know you accelerate while pulling up and hold the airplane pitch up until there is enough lift to take you off the ground. At that speed though youre not going fast enough to fly over ground effect, if you maintain your current speed and climb you will drop out of GE and stall, resulting in a bad crash since you dont have the space to recover. So what you do is take the airplane a few feet off the ground and pitch down. the reduced drag and increased lift will keep you in the air and accelerate much faster, at Vx speed you then return to climb and clear the obstacle. It sounds confusing so heres a video.

http://www.youtube.com/watch?v=OrfH5VD7JVg


And on fan power draw, \the 2j already solved that by having a snowmobile engine to run the fan on. With todays 4 stroke bike engines it can be mounted and chain/belt driven to mount the engine as low as possible. I did describe a possible hydraulic system running off oil pressure in the "road car faster than f1" thread. Even described how to keep it from being too dependant on pressure and how to control fan speed from onboard using the same device.

[adriannewey9864]

the thing is, i dont know how there is enough room on the underside of the car to have a fan and GE sidepods as the fan underside takes up a lot of space as seen on the red bull x1 underside pictures

[millar]

I don't know if this would work, but I've been thinking about the idea of having "sucked" sidepods with a ground-effect floor in between.

You would start with skirting running in a straight line front to back just inboard of the wheels. The area inside that is your GE floor. Outside of that, you make skirted sidepods filling the volume between the wheels on each side. Each of these has a large horizontal-axis fan sucking the "intake" and blowing the rads. The exit air could be directed to whatever low-pressure area at the rear could benefit from the infill.

[turbof1]

the thing is, i dont know how there is enough room on the underside of the car to have a fan and GE sidepods as the fan underside takes up a lot of space as seen on the red bull x1 underside pictures

From what I have readed from the wikipedia page, the mclaren f1 actually did use both ground effect and fans. I am not sure if the f1 uses venturi tunnels though.

[adriannewey9864]

what if the whole underbody(from axle to axle) was sucked by a fan and the surface on top of that was completely flat and on top of that flat surface was the conventional venturi tunnel with skirt on. would the bottom of the ground effect curved plane be equally sucked to the flat top of fan underbody thus negating any venturi downforce, just having the fan suction downforce left

e.g.
\_________/ - underbody
__________ - low pressure venturi tunnel
|__________| - low pressure vacuum skirt
_______________ - ground

[elclingo]

The Brabham-Alfa Romeo BT46B.
This car was very fast but after one race the system was banned.

[flyboy2160]

...
Or of course we could waffle on and on and on and on and on without any numbers. But lots of hand waving. Because they could rename this board F1handwaving for all the technical discussions that take place.

+1 Did you get banned for life for this crack?

[adriannewey9864]

hopefully, people will still be posting on this as it is a very important aspect of creating the dream racing car.

İ have had a couple of intresting developments from inside my own mind.
as you know we do not live in the stone ages of motorsport anymore, thus instead of doing what our predecessors did and try to stop the flow of any air at all, we must live in the present and accept that air will always be flowing in and around the car



look at the picture of a sucked chapparal 2j, look at the rear, extremely unaerodynamic, literally like a brick

so, unless you have an unnecessarily huge fan like on the brabham (which still has a crap ton of drag at the back), to get optimum drag efficiency you should "cut out" the big wall at the back leaving out only the fan turbine, the rest of the space as it is not being used and due to the fact ground effect has incredibly low drag you may as well do something with the air that goes in those "cut out" areas, thus stick a coupl a venturis n skirts on and eureka your actually doing something with the space !

i forgot the second thing sorz !, as soon as i remember i defo will post

btw i know i didnt post in years but i jus forgot man

[xpensive]

...
So given that you know what presssure drop you need (about 3 psi or so from the other thread), ...

3 psi, or 0.2 bar, is actually a lot, over 2 square meters you would get a downforce of some 40 kN or more than 4 tons.

Almost decimal-error for the need, moreover, it would be next to impossible for an axial fan to produce that underpressure.

[andylaurence]

http://static.rcgroups.net/forums/attac ... 1252130849

look at the picture of a sucked chapparal 2j, look at the rear, extremely unaerodynamic, literally like a brick

so, unless you have an unnecessarily huge fan like on the brabham (which still has a crap ton of drag at the back), to get optimum drag efficiency you should "cut out" the big wall at the back leaving out only the fan turbine, the rest of the space as it is not being used and due to the fact ground effect has incredibly low drag you may as well do something with the air that goes in those "cut out" areas, thus stick a coupl a venturis n skirts on and eureka your actually doing something with the space !

The problem is that if you cut a hole in the back and put in a couple of venturis, you'll break the seal on the suction that the fan's trying to do. That big flat surface does create drag, but it does so by creating a low pressure zone, into which the fan pumps air from underneath the car, improving the performance of the fan and therefore assisting downforce. The outer areas can't just be cut out, because they contain wheels. The inner area contains the fan.

[krisfx]

The Brabham-Alfa Romeo BT46B.
This car was very fast but after one race the system was banned.
http://formula1.escharlamotor.org/artic ... age015.jpg

Afaik it was withdrawn, not banned. But the outcome was the same.

[adriannewey9864]

http://static.rcgroups.net/forums/attac ... 1252130849

look at the picture of a sucked chapparal 2j, look at the rear, extremely unaerodynamic, literally like a brick

so, unless you have an unnecessarily huge fan like on the brabham (which still has a crap ton of drag at the back), to get optimum drag efficiency you should "cut out" the big wall at the back leaving out only the fan turbine, the rest of the space as it is not being used and due to the fact ground effect has incredibly low drag you may as well do something with the air that goes in those "cut out" areas, thus stick a coupl a venturis n skirts on and eureka your actually doing something with the space !

The problem is that if you cut a hole in the back and put in a couple of venturis, you'll break the seal on the suction that the fan's trying to do. That big flat surface does create drag, but it does so by creating a low pressure zone, into which the fan pumps air from underneath the car, improving the performance of the fan and therefore assisting downforce. The outer areas can't just be cut out, because they contain wheels. The inner area contains the fan.

surely if you had allocated suction fan skirt area shaped like an airfoil on its side, you could put venturis on either side going UP TO the wheels, not over them =D>

[langwadt]

The Brabham-Alfa Romeo BT46B.
This car was very fast but after one race the system was banned.
http://formula1.escharlamotor.org/artic ... age015.jpg

Afaik it was withdrawn, not banned. But the outcome was the same.

afaik Bernie agreed that he would withdraw it after a few races if the other would keep supporting his position in FOCA
it was then banned by some one else FISA?

[andylaurence]

surely if you had allocated suction fan skirt area shaped like an airfoil on its side, you could put venturis on either side going UP TO the wheels, not over them =D>

I don't know what you mean by that.