Blown Diffuser??

[mike]

it possible that all the time we spend on the mclaren's rear wing
that red bull actually had a blown diffuser that stalls at high speeds?
the difference is that it uses exhaust gas which varies with rpm not air speed
that could explain why red bull didn't have a ride height system and yet it is able to be low enough to scrape the ground at quali and do fine in the race
i mean there must be a point where the air speed at the bottom is so high compared to the air at the back that it essentially starts to stall. and since diffuser has little drag it doesnt really increase top speed that much but increase the L/D ratio and since it only works at higher rpm it basically become like an aero traction control (quote by lewis they have twice as much downforce)

the L/D ratio which i think is boosted....applies to mclaren too. when you introduce high speed air to the bottom of the wing it will increase downforce and when the wing comes to a stage where it creates too much drag it starts to stall.

the ride height issue is what i thought supported this idea. since diffuser has the highest L/D ratio you will reduce more downforce per drag when stalled, so increasing ride height with very little top speed gained.
what are your thoughts??? possible?

[noname]

I am not going into details of the 2010 designs as aero is not my strongest point, but idea of stalling diffuser is not new in F1. I remember few years back gossips Ferrari is working (or even using) on something like this, below discussion I found (thx google!) which supports my memory.

http://www.thescuderia.net/forums/showt ... user-Stall

[wesley123]

i doubt it, and if it is the case then Newey should certainly shut its mouth about the F-Duct safety.
If you stall the rear diffuser the air under the floor will not accelerate anymore, thus heap up under the floor making the car unstable, guess what happens then if you hit someones rear wheel with your front wheel. You will simply take off due to the instability of the whole floor

[mike]

but when stalling it still gives downforce. its a graduate step not a 100 to 0 step and if u can design it correctly, which most like can by newey since he try this idea a few years ago.

[kilcoo316]

RBR might have a blown diffuser, but it won't be designed to stall.

The idea of teams actually trying to stall their diffusers a few years back was bullsh!t, and that hasn't changed.

Why stall the thing that balances the car as it gets closer to the ground? (i.e. your front wing height from ground decreases with speed, increasing efficiency - you need a similar effect at the rear of the car or you are gonna have a big longitudinal move in your centre of pressure on the car)




The ferrari flexi floor was to allow more aggressive rake angles and lower front ride height without unduly wearing the plank.

[pgj]

In the Maurice Hamilton book on Williams, Adrian talks about solving one problem they had encountered by stalling the underside of the car.

It may be that that is happening. It might also go some way towards explaining why the car is so good when it is in front but does not appear to have the same degree of overtaking power as the McLaren when it is in traffic.

[raymondu999]

Interesting concept though, and if it IS true, I think it just further cements Newey's place in history as the most innovative designer in F1

[mike]

Why stall the thing that balances the car as it gets closer to the ground?

ride height control!!!!??
if it stalls at similar speed as the mclaren blown wing, then why wouldnt it work? and if they have trouble turning they can back off the gas and it will work as a normal diffuser..

[wrcsti]

I dont get why you would want to stall a diffuser, probably the cleanest way to get downforce on a car and you want to purposely ruin it? If anything Id say a blown difuser would be to create steeper angles while maintaining flow without separation.

[WhiteBlue]

There is some merit to the idea of a blown diffusor but I would look at it from a different point of view. RBR are taking a long time to come up with an F-duct system. Why is that happening?

One possible answer to this question is a flexible rear wing/floor/diffusor assembly. If the rear wing flexes the floor and parts of the diffusor creating a different AoA for the floor and diffusor this would also result in a different rear ride height between quali and race. It would explain why they are so fast with low fuel.

We also know that the RB6 partially blows the upper diffusor with the exhaust gas. What would happen if the rear mounting points of the floor/diffusor/wing combo have a pull up device which softens with heat? Lets say it takes five laps for the device to become fully softened to let the rear floor assembly sag. It would be enough to generate a different behavior.

If RBR have such a design the AoA on the rear wing changes anyway and they may have no urgent need for another aerodynamic stalling device because the effect would be relatively small.

[xpensive]

Using exhaust gases to affect aerodynamics would be xtremely delicate, when Rpm doesn't xactly follow speed or steering. In the early days of diffuser developments, it was not unusual to have the exhausts in the diffuser itself in order to speed things up, but with a sudden lift-off, you'd be in deep ---.

[BreezyRacer]

The new Red Bull diffuser (new in Barcelona) does indeed "dump" exhaust flow into the diffuser, but not in an effort to reduce drag or downforce .. just the opposite. What they are doing is use the exhaust charge to isolate the diffuser from turbulence in the tire wheel assy.

Sounds like no big deal, but only if you've spent engineering time trying to maximize diffuser performance will you know how important this is.

Note that the exhaust is not directly dumped into the diffuser box. It is arranged to flow thru a VG that is open to outer airflow and then into the outer wall of the diffuser box. This is one of those things that everyone will be doing in their new 2011 cars when DD diffusers are banned.

To see pics of all this go to the RB6 thread around sheet 66.

[JohnsonsEvilTwin]

Personally I dont think an exhaust driven diffuser will be that sensitive to changes in RPM.
The Diffuser is most effective at high speed-high air flow situations. In these situations an F1 engine is almost always either at full chat or nearly at full throttle.
Modern circuits dont have the scenario likely to spoil the balance whereby the engine revs drop, but the car is still at highspeed and requires the drive of the exhaust. Only 2 corners i can think of will create an issue, 130R or Eau rouge.

And that is if the driver goes off the gas totally, somthing that rarely happens in these corners.

All in All I see every team adopting this low exhaust with diffuser exit approach next year, at least until it gets banned.....

[raymondu999]

but say after a shift though. The RPMs would drop to, let's say (arbitrary guess) 16500 from 18000. This would cause less gasses to come out onto the diffuser

[JohnsonsEvilTwin]

but say after a shift though. The RPMs would drop to, let's say (arbitrary guess) 16500 from 18000. This would cause less gasses to come out onto the diffuser

Sure but the force would still be high enough to not make such a difference.
The "problem" only arises when the engine drops it revs to near idle levels.
In addition I think RB designed the blown diffuser to have a wide window of operation.