henry wrote:There are two ways of deploying the ES.
It can be used to drive the MGU-K to supplement energy from the MGU-H in self sustain mode. The power out is ICE power plus 120 kW. The ES drain power is 120 minus whatever the MGU-H is generating. It is this drain power that is limited to 4 mJ per lap.
So for the 42 kW MGU-H this can be sustained for 51 seconds.
The other way is when the wastegate is open and the ES drives both the MGUs. The power out is EnhancedICE plus the 120 kW the ES drain power is 120 plus whatever is needed to drive the compressor.
If the compressor power is 80 kW that makes 200 kW drain. The length of time this can be sustained is down to the overall charge level up to the maximum of 33 seconds for the flow to the MGU-K. So if you can find 3 mJ you can run this mode for 33 seconds. This would allow a full laps worth of WOT at Monaco but would leave you over 40 seconds of WOT short at Spa. In fact at Spa with MGU-H at 42 kW you'd still be 20 seconds short of running the MGU-K at 120 kW in Self sustain mode. About 67 kW is needed for that.
At other tracks there is a trickier balancing act, running early parts of WOT with the wastegate open and later in SS mode with ES assist.
For a qualifying lap (no fuel saving required) it would be very easy to reach the 2 MJ limit of harvesting from the MGUK. Even if regen' braking only generates a total of 1 MJ, the ICE can be run in "genset" mode any time the rear wheels need less than the full output of the crankshaft.
With "balls-out mode" requiring 200+ kW of electrical power from the ES, 66 seconds of WOT would require 13.2 MJ from the ES. It is advantageous to run the highest boost possible (within the limits of efficient combustion) since increasing the pressure differential across the ICE increases the "negative pumping work" ie using the ICE as an "air-motor".
The other limit is - the 4 MJ ES can only run "balls-out mode" for 20 seconds before needing a recharge. (That should be sufficient for the longest straight at most circuits?)
Back to the 13.2 MJ target. 2 MJ can come from the K during the lap. A pre-charged ES gives you another 4 MJ leaving 7.2 to be harvested from the H - and not at WOT. I don't think this target is achievable but it does point to the need to have a part load mode which charges the ES primarily from the H. A few techniques that could be used to increase power to the H (all at part load):
- retard ign timing. Reduces work done on the pistons and increases pressure and temperature at EO (exh valve opening)
- cylinder skipping. Increases intensity of pulsation in the exhaust. (bigger "bangs" and longer pauses between bangs)
- exhaust manifold combustion. (Skip ignition only - allowing raw mixture into the exhaust)
- upstream throttling. (unloads compressor, freeing-up turbine power to be accessed by the H)