Monday, July 12, 2010

Yet another pre-stolen idea: the electric supercharger

In my not-too-consistent series of “pre-stolen ideas”, here’s another from the automotive front: the electric supercharger, as part of EcoMotors’ new engine design.

Based on my unused mechanical engineering degree, AFAIK, some of the drawbacks of a supercharger are the additional engine friction it provides, and the fact that the boost provided is directly related to engine speed. Since you only really need the additional boost some of the time, my thought was - why not control boost with a near-zero lag electric motor whose output is completely independent from that of the main engine?  Which is of course what EcoMotors is now doing.

Volkswagen is using a twincharger design in their latest creation – a 1.4 liter engine that produces as much power as V6 engines twice the size did a decade or so ago.  EcoMotors seem to have done VW one better, enough for Bill Gates to invest in the company.

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  • A few people are working on this now on a small scale ...

    Apparently brushless DC motors used in things like RC airplanes have gotten to the point where they can deliver about 8hp from a range of 12 to 60 volt supplies ...

    With a single 8hp motor running on a 48 volt battery bank, it is possible to fully drive a small electric supercharger of the size fit to supercharge a 1000cc to 1600 cc engine ...

    So the first applications you might see here are subcompact cars and motorcycles

    check this out:

    By Anonymous Supercharger Performance, at Tuesday, July 13, 2010 3:05:00 AM  

  • Nehal had some thoughts on this on Google Buzz - I'm copying these here:

    Nehal Rahim - I haven't thought about this idea too long, but at first glance, I'm not sure the electric-supercharger will be inherently more efficient than regular hybridization.

    I'm assuming that the electric motor for the supercharger runs off electricity generated by the vehicle electrical system (indirectly from the gasoline) or from brake regeneration, or both. So it is converting kinetic or chemical energy to electrical energy and back to kinetic power, which makes it a hybrid or an EV depending on the power flow path. The difference here is that the conversion is applied to the combustion process instead of directly to the driveline like in a Prius (where the electrical power goes to the wheels along with the combustion power), or in the Volt (where the electrical power alone goes to the wheels, and combustion just creates electricity).

    The biggest losses in hybridization are the inefficiencies in coverting energy from one form to another. The more conversion you do the lower your total efficiency. Seem to me that in the case of the electric supercharger, you are actually doing more of it.

    In a typical driveline hybrid you capture waste brake heat as electrical energy (with some conversion loss) and then apply that electrical energy as driveline torque (with storage losses and one conversion loss).

    In this case you start with the same regen conversion and storage losses. Then you power a motor to compress air (electrical power to torque to pneumatic energy - conversion loss) which then improves the combustion process (pneumatic to chemical energy - conversion loss), which then moves pistons to turn the crank and create torque (chemical energy to kinetic energy - another conversion loss).

    Doesn't this seem like a more roundabout way to create torque from brake regen? Start with torque and eventually end up with torque, but through 3 conversions. Why not just use the motor torque you created turn wheels instead of a turbo or supercharger? You can also have a turbo to compress the air and capture exhaust heat & kinetic energy and capture that energy independently. The turbo will have lag and will be more effective & efficient at higher speeds, but the motor can compensate for the operating ranges not ideal for the turbo.

    At best you will be as efficient as a hybrid driveline, but I doubt it as you are doing a significant number of extra energy conversions. Did I miss an inherent gain in doing it this way that a typical hybrid does not have?

    By Blogger Oskar Austegard, at Wednesday, July 14, 2010 9:04:00 AM  

  • Jul 13
    Oskar Austegard - So A) I think you're probably right about the overall energy equation - there might not be much (if any) to gain vs a regular hybrid setup. but B) I think you're too hung up on the either/or scenario: I believe what they're after is not hybridization for hybridization's sake, but more a twincharger system, and the optimal way to create that twincharger system. So it's not a matter of is this the best way to hybridize an engine, it's is this the best way to twincharge a system.

    But hey, I (unlike Billy G) don't have any money in this, so I don't really care too much. It's just nice to see yet another idea validated...

    9:35 am
    Nehal Rahim - True, it doesn't have to be either/or, but I think a turbocharger itself has to be either/or (but maybe not). In other words, you can have an electric turbo or a traditional one. In addition to this, you can have a hybrid powertrain.

    I wonder if you could have a twin-turbo setup in which one is electric (good off the line at low speed/high torque state) and another exhaust driven that is better at high speeds. I supposed you could, but that sounds like some complex controls.

    These guys are only doing the electric turbo from what I can see, without an exhaust turbo or a hybrid powertrain. I guess I was saying that if they were going to electrify the turbo to harness waste energy, they are probably better off doing that by hybridizing the powertrain instead, but maybe both is even better.

    9:51 am
    Oskar Austegard - See

    So not really a twincharger per se, but an electrically augmented turbocharger

    By Blogger Oskar Austegard, at Wednesday, July 14, 2010 9:04:00 AM  

  • Nehal Rahim - Yeah that makes sense to cover more speed ranges. To better capture waste energy, they need to pair it with some hybridization too in the Powertrain. 10:05 am

    Nehal Rahim - On a related note, ever see the air-hybrid engine concept? We've been seeing Scuderi at a bunch of SAE, Powertrain and Auto shows over the last 2 or 3 years. Seems like a good idea on paper, and they have aworking prototype now. 10:09 am

    Oskar Austegard - Interesting. I especially like the (expected) improvements in reducing Diesel emissions. Of course I'll also take 145hp/liter as in the gas version (that rivals the VW twin charger - the latest Polo GTI is running at 178 hp (or 127hp/liter) - but that's a production vehicle - I'm pretty certain after market chip tuners will boost that beyond 200hp).

    Also - have a look at the EcoMotors OPOC engine design - it's basically a diesel Boxer engine with a second set of pistons inside the cylinders, opposing the "normal" cylinders. Seems complex, but if they achieve what they claim, I don't care...
    "For a given power level, the opoc™ engine is 30-percent lighter, one-quarter the size, and achieves 50-percent better fuel economy compared with a state-of-the-art, conventional turbo-diesel engine."

    I'd like to see the same level of detail that Scuderi provides, for the OPOC engine design... 10:26 am

    By Blogger Oskar Austegard, at Wednesday, July 14, 2010 9:28:00 AM  

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