F1technical.net

Tommy Cookers wrote:most ? seem to believe that the braking-phase recovered power is limited to 120 kW

The energy flow diagram in the technical regulations clearly show that the MGUK can only give or take 120kW from the ICE.

ringo wrote:Yes it is 120kW max. So the rest will be heat energy off the brakes.

Unless...
if the excess braking energy goes through the crank as engine braking and the MGUH is set to max load.
you can recover a bit there i guess. haven't looked at the details concerning that.

There seems to be some thought that the MGUH can be made to assist with engine braking.

wuzak wrote:

ringo wrote:Yes it is 120kW max. So the rest will be heat energy off the brakes.

Unless...
if the excess braking energy goes through the crank as engine braking and the MGUH is set to max load.
you can recover a bit there i guess. haven't looked at the details concerning that.

There seems to be some thought that the MGUH can be made to assist with engine braking.

Would the rules allow rpm higher than 15,000 during engine braking? Just preventing ignition or fuel injection when 15,000 is exceeded would not stop using high revs to help spin the MGUH. Designing the engine to handle being just an air pump up to 18,000 or more might not be too hard.

chip engineer wrote:

wuzak wrote:

ringo wrote:Yes it is 120kW max. So the rest will be heat energy off the brakes.

Unless...
if the excess braking energy goes through the crank as engine braking and the MGUH is set to max load.
you can recover a bit there i guess. haven't looked at the details concerning that.

There seems to be some thought that the MGUH can be made to assist with engine braking.

Would the rules allow rpm higher than 15,000 during engine braking? Just preventing ignition or fuel injection when 15,000 is exceeded would not stop using high revs to help spin the MGUH. Designing the engine to handle being just an air pump up to 18,000 or more might not be too hard.

No, rev limit is strictly 15,000rpm.

wuzak wrote:

chip engineer wrote: Would the rules allow rpm higher than 15,000 during engine braking? Just preventing ignition or fuel injection when 15,000 is exceeded would not stop using high revs to help spin the MGUH. Designing the engine to handle being just an air pump up to 18,000 or more might not be too hard.

No, rev limit is strictly 15,000rpm.

Ah, so there's some sense in having a top-end rev limit.
Without it we would probably see drivers jump the gears to get ridiculously high revs at braking.

timbo wrote:

wuzak wrote:

chip engineer wrote: Would the rules allow rpm higher than 15,000 during engine braking? Just preventing ignition or fuel injection when 15,000 is exceeded would not stop using high revs to help spin the MGUH. Designing the engine to handle being just an air pump up to 18,000 or more might not be too hard.

No, rev limit is strictly 15,000rpm.

Ah, so there's some sense in having a top-end rev limit.
Without it we would probably see drivers jump the gears to get ridiculously high revs at braking.

Im with you on this one. A few pages back i predicted that drivers would rev the engines close to the 15.000 RPM's during downshifts. Even though upshifts would happen at around 12.000 RPM's. Lets see what happens.

Volume flow rate is 0.2 m^3/s at 15000rpm and 100% VE.
It's hard to know what VE this engine will opperate at. Anyone have an idea? 150%?
Air density will be a wild guess since I have no idea what boost pressure will be along with intercooling. I used 1.18 kg/m^3, but this seems low.
I guessed no heat added to the pumped air even though some will be absorbed, probably too little to account for?
Then you need the exhaust diameter for velocity, 3" ?
I had a bunch of wild guesses and was getting 140+ J/s.
Throw in turbine efficiency and you have some sort of guess. Did I miss anything there?

Playing with the VE and density can make the J/s number jump quite a bit. So maybe there is some energy to be had here?

I bet it is negligible compared with 2-3 MW friction brake power. This is millions of Watt not thousands of Watt. The thermal power of the fuel at full flow is 1.3 MW. Of that you get 3.5 % or 45 kW to the MGU-H when the engine is at full power. Imagine what happens when you just compress the air without fuel. The air will never absorb any thing near the thermal power of the fuel. So perhaps you get 10% of the temperature. If the temp at the exhaust valves is 1100 C°and you generate 110°C by air braking you will get only 4.5 kW or 0.0045 MW brake power. That is 0.18% of the friction brake power.

You may want to look on those as 120kW for all corners but put more focus on the energy and what amount of energy you can get from 120kW if the car brakes for x amount of time in corner x.

ringo wrote:http://img716.imageshack.us/img716/1025/hdc.png
You may want to look on those as 120kW for all corners but put more focus on the energy and what amount of energy you can get from 120kW if the car brakes for x amount of time in corner x.

I get about 1MJ.

Where did those figures come from WB?

Time and max power for each corner from the Brembo file. They do this for each race. You can download it in PDF from their site. I simply copied the data to an Excel file. Equally to Canada I made the assumption that average brake power is 50% of max Brembo brake power. The I applied fixed biases to front/rear and electric/ friction. dead easy. I just don't find the time now to re do the sheet for variable electric/friction braking. I also do not know how the downforce distribution to front and rear is and how much dynamic load transfer from rear to front plays a role in F1.

WhiteBlue wrote:I bet it is negligible compared with 2-3 MW friction brake power. This is millions of Watt not thousands of Watt. The thermal power of the fuel at full flow is 1.3 MW. Of that you get 3.5 % or 45 kW to the MGU-H when the engine is at full power. Imagine what happens when you just compress the air without fuel. The air will never absorb any thing near the thermal power of the fuel. So perhaps you get 10% of the temperature. If the temp at the exhaust valves is 1100 C°and you generate 110°C by air braking you will get only 4.5 kW or 0.0045 MW brake power. That is 0.18% of the friction brake power.

I was looking at the KE of the air since the engine is bacially an air pump. I figured the thermal energy would be negligible.
But since I don't know certain numbers, it's hard to say either way. Only a bit of swag.
But, by changing the VE and or the air density, the number jumps substantially.

Here is quite nice piece about new engines. A lot of knowledge gathered in a sinlge article.

Original [Polish] - http://www.f1talks.pl/2013/08/20/co-juz ... napedowych
Google translation [English] - http://bit.ly/19vbbok

WhiteBlue wrote: Equally to Canada I made the assumption that average brake power is 50% of max Brembo brake power.

Thing is, the graph of power vs time during a F1 braking is far from linear, the very high peak lasts very little time because the grip is strongly related to downforce hence speed.
At high speed you have very high grip (and drag contributing to deceleration too) but as speed decreases, and it does it quick... the rate of deceleration decreases quite rapidly too, and with it the power applicable.
This means that in practice the majority of braking time is spent at relatively low speed, and with relatively low power applicable, thus average of power applied in braking is not 50% of max, quite a bit less.

For instance, if we take the velocity profile from Alonso's Monza race lap last year:


Calculate total power as (v*a*mass), remove from it an estimate of the power of aero drag (assuming rho SCd = 1.28 kg/m, which means aero power at peak speed = 475kW), and multiply by 0.45 (rear brake bias), what we get as estimated power applied on rear axle is this:


blue is the total applicable with available grip, green indicates 120kW level and red dotted indicates the max recovery rate usable.

Integral over time of red dotted gives the ideally recoverable energy, 1.45 MJ.

And that is assuming that the electronic bias control allows to completely override the rear hydraulic circuit doing the braking on rear end solely with the MGUK at low speed.
If that is not possible, or not desirable for example for driver's feeling/feedback related reasons, recoverable energy is even less.

Same calculation repeated for Abu Dhabi race lap again from Alonso:


Power removed aero drag power (here assuming rho SCd is 1.56kg/m) and rear axle only:


Integral of red dotted => 2.05MJ.

I picked these two tracks because in my experience from having done similar calculations in the past, Abu Dhabi is one of the best tracks for energy recovery in braking, while Monza is one of worst, so the above can be IMO a good indication of the two extremes.

Which means that in almost all tracks recovery 2MJ from braking, lap after lap, will be quite challenging, in not few just impossible.

f1motta wrote:Here is quite nice piece about new engines. A lot of knowledge gathered in a sinlge article.

Original [Polish] - http://www.f1talks.pl/2013/08/20/co-juz ... napedowych
Google translation [English] - http://bit.ly/19vbbok

Nice find!!!
It looks like a lot of info that we here have been talking about. Knock was the one thing that kinda surprise me though. I really didn't think it would be much of a problem based on the lower power that some of us have calculated. Maybe it will be more then I personally thought.

TC's post about the turbo's way of generating power (when and how much) through out the rpm range is talk about in this article also.

It kinda sounds like the MGUH will be the boost controller in this article?