Dissertation help – split electric turbochargers.

[Vonrho]

Hello all.

I’m just posting this in hopes I can get a bit of help with information for my dissertation.
The information in this post probably will not be used in the dissertation, this is more finding contacts/places to start, but if anybody does have any useful information on the system feel free to post it, the more the merrier.
This post will be on a few other forums.

So basically, the dissertation is a feasibility review into the use split electric turbochargers for use in motorsport. I think Ferrari patented this system or similar for their road cars.
In case you aren’t aware split electric turbocharger is just where it is a separate electric “compressor” and exhaust side electric generator.
Its role is similar to the MGU-H however the idea is, since only one side is charging and one side is compressing, they should be under less stress than an MGU-H, so the level of engineering should be lower and then hopefully the price should be lower too.
Also, those are the only major components that need implementing (for the forced induction system, it will probably need a sizeable battery) and you don’t need to effectively mould a turbocharger around the unit, also making it a bit cheaper.
There is other advantages and disadvantages to the system however cost is likely to be the main part as BTCC are moving to hybrid and Formula 2’s series boss stated they aren’t looking at Formula One hybrid systems due to cost grounds. So, this system may be a good alternative for those categories and others.
Anyway, that’s the premise, it’s a feasibility review so I can say its suitable or its not suitable so don't worry about information contrary to mine or someone else's.

So, if anybody has any information, opinions, contacts or anything else regarding this system, or MGU-H for that matter as it will effectively be battling that system, please feel free to post it below or message me.
Thanks for reading, will look forward to your responses.

 

[Richard Dastardly]

So that's an electric supercharger and a turbo-generator? sure the compressor would probably be under less stress, but the turbine for the generator is going to have all the stress of the exhaust side of a turbocharger anyway, surely? the hot exhaust is the same, and the torque load is also the same. The advantage of having a motor-generator there is you can keep it spinning off-load, so at least that's a little less stress perhaps ( although you can do that with a full turbocharger anyway ) - and you don't need a wastegate because you control the link to the compressor.

I'd think this system was concocted to get rid of turbo lag completely rather than any complexity reduction - I mean you've got two turbines, two motors and a battery instead of a turbine and a wastegate. What's the overall efficiency of the system compared to a conventional turbo?

 

[Vonrho]

Hi Richard, effectively yes its and electric supercharger and a turbo-generator.

Sorry if I didn’t make this clear, its main purpose is to effectively be an alternative to MGU-H style systems.

So realistically, if it’s not used in conjunction with a hybrid system the disadvantages will almost certainly outweigh the advantages. So if there’s no hybrid deployment a conventional turbocharger and wastegate will be far more suitable. But my investigation is to try and determine whether it is an improvement or not.

Yes the generator will still be exposed to heat and that’ll be difficult to design around, similar to the MGU-H, there’s little getting around this in regards to exhaust energy recovery systems unfortunately.

Efficiency wise is where it falls down as standard turbochargers (and MGU turbos) have a physical link between the exhaust and the compressor so everything from generation to deployment will lose energy, unfortunately I’m yet to fully research that section.

 

[Richard Dastardly]

What type of motors are being used? industrial motors seem to be up to mid 90s percent efficiency these days, but I'm pretty sure the articles I've read are about constant-speed AC motors. You can build variable speed squirrel cage motors - they use them in trains, for instance - but the control electronics are horrendous as you're controlling speed by varying the frequency of the supply to the motor. Doesn't sound like something you'd use for this! I don't know much about permanent magnet AC motors but I believe the issues are the same anyway. More basic motors were in the 85-91% efficiency area iirc. On top of efficiency losses in the motors, there's the obvious mechanical loss from two installs.

Balanced against that is that you have a pool of energy to use for propulsion as well as the compressor, zero turbo lag, plus not driving the compression turbine will mean much more exhaust harvesting over MGU-H type installs. Good luck working out the relative efficiency of the overall system under driving conditions ( perhaps you can try it over something like a lap of a circuit ) rather than just the turbo replacement part...

From a hybrid point of view at that point you start wondering why the engine is there & you're not just burning fuel in a bigger turbo-generator.

 

[Vonrho]

Well the motors will be based on the research I can find. I was looking at publications from SAE that were using DC motors for electric superchargers, although can't remember right now.
I think f1 MGU-H's are supposed to be around 96% efficient, or something along the lines. But if I'm going from a budgetary standpoint maybe f1 tech isn't the best example.
Yeah there's a lot to work out, very daunting, that's why I'm posting stuff like this seeing if anyone can post up any gems or new avenues to look into to just make my thesis a bit stronger. Thanks for the input so far Richard.

 

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