Kate invented one day that why the turbo compounding could not be implemented with electric motors, because that way the usually unfeasible gearbox from normal turbo compounding becomes unnecessary and the gearing is instead implemented with the electric motor and the generator where the generator rotates at higher revolutions than the motor that is used to decrease the load the combustion engine sees.
We were in assumption that this was a new invention, but it seems that it has been used in heavy machinery already, e.g. by Catepillar. This in turn also means that it is feasible.
The challenge would be how to place the generator to the shaft of the turbo. Usually turbos do not have a place where to fit the generator but they are closed packages which are not easily modifiable.
The idea would be to increase fuel efficiency with the compounding and increase the shaft horse power without loading the combustion engine anything more. The electric motor could have an additional lithium polymer batter pack which could increase the power even more on takeoff, so the plane would have on critical take off situation somewhat more power than the combustion engine can output, so in other words, for example getting 80 hp out of a 60 hp HKS700E.
This would result that using impossibly small engine power would become a possibility in a wider variety of airframes. On a twin 2 x 80 hp is a lot more than 2 x 60 hp, single engine performance on 60 hp is very poor in any case without any tricks done to increase the power temporarily.
A quite small lithium polymer battery pack would be enough since assuming 300 fpm climb rate on a single engine, this results 3 minutes to 1000 feet AGL where it should be safe to turn back to the runway and perform landing even with a very low power output of a single engine. So it would be well enough for the extra power from the battery pack last only for 3 minutes. This kind of battery pack would not be that heavy, and the brushless DC electric motor is also pretty lightweight.
Any comments on this?
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