dren wrote: ↑
Wed Jan 03, 2018 4:46 pm
It's just a way to send to the ES more energy from the K than the direct allowed 2MJ/lap. It's basically electric fuel accumulation as TC stated earlier.
It's a novel idea, but you're forced to carry more fuel in order to accumulate it electrically. I wonder if Mercedes does this since it's fuel load is a bit lower than the rest.
During an F1 weekend, the quali laps, first race lap, and one lap each side of a pitstop are the only ones where you actually need everything
the car has in outright speed, unless you're fighting for track position or overtaking. At all other times, you're managing things like temperatures, tyres and running as energy-efficient a lap as you can to keep the fuel load low.
If you consider the corners on a racetrack as sections where you need to slow enough to make the bend without sliding off the track, you immediately run into a piece of logic that says you should be storing whatever kinetic energy you have on the way into the corner, and deploying it on the way out, in order to *avoid* using fuel to drive the car forwards at the corner exit. This should be obvious.
Obviously, MGU-K will be effective when you need to shed speed anyway, on the brakes, so of course it does this. On most tracks there isn't 2MJ of "on-the-brakes" energy available. You may supplement this with MGU-K charging at other sections of the track than on the brakes, where it hurts you the least in laptime. Perhaps that is where the driver isn't demanding full throttle from the engine, perhaps it's towards the end of a straight, but before you are on the brakes. Depends on how economical you're trying to be with fuel, as you say.
With regard to energy capture versus deployment, a speed difference of minus 1mph when you only have 250m left in a straight and will in any case be braking at 4g in 120m only loses you 1mph for the 120m where you would otherwise have been flat out. If you get to deploy that energy at the start of a subsequent straight, you get +0.9mph for the length of a subsequent straight (which is presumably longer than 120m), or until you choose to fill the ES up again. (assumes 90% roundtrip recovery, fill in with your own value..). That 1mph also might be 5 or 10mph as you need, for your mapping, depending on the rate you want to capture at, and for how long.
Giving up energy the end of a straight in order to deploy it at the start of another, is a sensible strategy.
Limiting yourself to only 2MJ of this by only recovering via the K->ES directly is a poor strategy.
If you can drive the car forwards with 4MJ of recovered energy per lap instead of 2MJ, it'll use less fuel than if that same 2MJ had to be expended by the ICE out of the corner.
Deployment is about area-under-the-graph, and you will compromise end-of-straight in order to reap benefits at the start of subsequent straights.
Put another way: if MGU-K regen was banned while the brakes were in use, do you suppose the teams would stop using it at all?
There are no superspeedway ovals on the F1 calendar, where you run flat out all lap every lap - this is the only type of circuit where self-sustaining turbine-generated MGU-H power straight into the K would be the dominant factor in MGU-H performance, because it's the only one where there's no real acceleration or deceleration. Every track the F1 teams run on has significant speed changes, and where those exist you want to recover and deploy as much as possible.
F1 tracks also have elevation changes. We aren't only recovering from the ICE, we are also potentially recovering potential energy from a vehicle weighing up to 838kg (733kg car + 105kg fuel) rolling down a hill. Obviously the ICE got it up there in the first place.
I think during one of his lectures on optimal control, David Limebeer pointed out that there's about 1MJ available at Spa (extreme example) from elevation change alone. If anyone has thoughts on that I'd like to hear them.