Tommy Cookers wrote:turbo speed transitions ie 'time constant' can't be better than around 100 millisec ?
there's a lot of inertial load
(I once did this sort of design calculation for a living)
the time constant of the combined ICE and permanently slaved mgu-k will be maybe 25 millisec ?
as with N/A F1 the shifting phases will be managed by modulation of ignition, fuelling, and throttle plates
nominally the complete shift takes less than 50 millisec
so managed turbo throttling etc will be used to help the turbo behaviour in the shifting phases ?
Rotrex provide inertia values for their compressors.
http://www.rotrex.com/Home/Technology/P ... nical_Data
The C38 series seems to have mass flow and pressure ratios in the right ballpark. Inertia is around 9 kg-m2
Max speed is 90000 rpm so they are a little slow for F1 but should be OK given the other assumptions that need to be made.
For MGU-H power we need to guess a power, and hence, torque rating. I will assume 60Kw. Mid way between continuous power generation, 40Kw and continuous supercharger drive, 80Kw.
If the speed is 110,000 rpm we get a torque of 5.2Nm
Assuming the motor is constant torque this gives an acceleration rate of 580 rad/s2. (5500 rpm/s)
This is just the supercharger ( and its drive). The turbine and MGU-H will potentially increase the inertia but this may be compensated by overdriving the MGU-H.
This seems relatively slow to me. The regulations say that the max. delay from torque demand to torque output is 50ms.
If this is the case some control strategies will be needed for drivability.
Keeping the turbo spinning seems good but then what target speed should it spin at?
Alternatively the MGU-K could fill in the delays but if this is open loop how much fill in should be applied?
Or maybe a combination.
Honda seem to have this sorted while Renault seemed to have real problems in Australia, perhaps because of insufficient time to tune whatever strategy they use.
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