In the second part of his look at technical developments in 2011, John Beamer examines the hot topic of exhaust-blown diffusers.
Also, a look at the ongoing dispute over the new engine rules for 2013.
Exhaust Blown Diffusers
After much commotion at the start of the season with Renault’s sidepod-exiting exhausts and McLaren’s infamous aborted ‘octopus’ the majority of the front-runners have now imitated Red Bull’s design.
The regulations allow slots in the outermost 50mm of the floor. Red Bull tunnel the exhaust under the floor and exits them in this ‘free’ zone, feeding the hot exhaust gasses into the diffuser.
There are two alternative designs. One is to use the starter motor hole for the same effect but the slot is small and the performance gains minimal.
The second is to simply blow the exhaust over the top of the floor, which doesn’t feed the diffuser directly but does create a region of low pressure aft of the diffuser structure reducing the pressure gradient under the floor. Mercedes has stuck with this solution.
This configuration has caused Mercedes much trouble with overheating rear tyres. In Spain the floor of the Mercedes sprouted a turning vane beside the rear tyre to channel air away from the rubber.
One trend to go hand in hand with exhaust blown diffusers has been the application of special engine maps to ensure a consistent flow of exhaust gasses even when the driver is off throttle. This has been dubbed ‘hot-blowing’, but it is set to be heavily restricted after the next race in Valencia.
By retarding the ignition and igniting fuel in the exhaust when the throttle is closed, hot gasses continue to feed the diffuser, generating more downforce.
This technique has a dramatic effect on fuel consumption. Renault estimated that its engines are consuming around 10% more fuel in a race then they were last year because of the retarded ignition approach.
Teams runs two maps: one for qualifying where more fuel is burned to drive faster, more consistent flow; and one for race day which burns less fuel.
A week before the Spanish Grand Prix the FIA made the surprise announcement that off-throttle diffuser feeding was to be restricted.
The precise wording of the revised regulation is still pending but it is likely to mandate engine throttles closing to 10% of their maximum when the driver is off the gas. That is a significant change and will vastly reduce the efficacy of engine mapping.
All the front teams are effected – especially Red Bull and Renault – and a protest delayed the introduction of the ban until Silverstone. Renault in particular could suffer as the front exhaust exists are likely to suffer a larger performance drop-off under the proposed regulation changes.
Another controversy from 2010 that has refused to die down is the application of flexible body work, particularly for the front wing.
Recall that Red Bull’s car seemed to magically lower its nose at high speed creating extra downforce. Despite the FIA’s attempts to tighten the regulations the RB7 sports the same advantages.
After the Malaysian Grand Prix, when it was clear that Red Bull still had an advantage, utterances from Aldo Costa (Ferrari’s technical director at the time) and Ross Brawn suggested that they believed the more stringent regulations would put an end to flexible bodywork.
They didn’t. Rather, it appears that under the static load test the RB7’s front wing flexes less than its rivals.
However the test is still flawed. In full flight the RB7’s wing flexes a little down but also appears to move backwards a little. This degree of fine tuning will take a lot of skill (not to mention expense in terms of computer software and resources).
It’s fairly straightforward to achieve this kind of bending. By altering the composition of the carbon fibre lay-up process the final, cured product will exhibit different tensile characteristics. There are many parameters at play include lay-up orientation, autoclave temperature/curing time, fibre thickness, resin constitution, and so on.
But the difficult part is controlling these variable to make a wing that behaves exactly as desired under load.
This requires deep understanding of structural mechanics as well as flow analysis – a combination of Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) techniques.
Despite the immense computing power F1 teams throw at CFD their simulations can only provide an estimate of actual flow – throw in the need to solve FEA equations and the problem compounds. It is thought that through a venture with MSC Software that Red Bull has managed to get around some of these problems and has a very good read on the FEA-CFD interlinks.
The 2013 regulations, in particular the rules, have received a lot of attention.
At the last World Motor Sport Council meeting the FIA said the controversial new engines rules could be postponed pending a vote to be taken by the end of the month.
The FIA announced in December a switch to 1.6 litre, 4 cylinder engines would take place in 2013. These would include a more powerful Kintic Energy Recovery System and turbo-charging to produce roughly the same power output as the current V8 engines do.
The hopes this might entice more car manufacturers to enter the sport appear to have been in vain so far. Volkswagen, one car manufacturer which was being targeted, instead announced it would compete in the World Rally Championship.
The only engine builder not currently active in F1 to announce plans so far is PURE, a new manufacturer led by former BAR team principal Craig Pollock.
Along with a feeling that the new rules have not had the desired affect of attracting new manufacturers, there are concerns about the cost of building engines for a new formula.
But in seems inevitable the sport will ultimately need to embrace a more modern solution that follows the car industry trend for smaller, less thirsty engines.
There will also be changes to the aerodynamic rules. Initially a proposal was put forward to simplify the front wing and allow more design freedom underneath the car as this was thought likely to improve overtaking.
However, as we’ve seen this year, altering mechanical grip (via the new Pirelli tyres) is a more effective way to encourage overtaking. Some teams were worried that removing the shackles from floor development would just create a new aero arms race just as costly as the current one.
History supports that hypothesis and as a result those plans have been scaled back. The 2013 aero regulations will be based on the 2011 rules but with tweaks to reduce the design intricacy of the front wing and to further restrict bargeboard and sidepod wing development, which the original 2009 rules did not completely eliminate.
This is a guest article by John Beamer. If you want to write a guest article for F1 Fanatic you can find all the information you need here.
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