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Electric turbocharger - Oh BOY!

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by bwilson4web, Oct 8, 2010.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The NHW11 Prius is current limited to ~80 A., not counting battery capacity.

    Now this makes a lot of sense especially if the muffler can be replaced by a turbo-generator to salvage the last ergs from the exhaust stream. But the 12V operation is rough.

    I would probably go with some ultra-capacitors to handle the acceleration and then tap the traction battery for the 12 * 220 ~2.7 kW needed in sustained mode. Hopefully, a turbo generator could provide the additional power, after the lag, to minimize the draw. Hummm, that would just over 12 A. for a 220 V traction battery.

    Actually, I'd been thinking about hacking the electric A/C compressor by using a larger displacement, lower back-pressure scroll compressor. The thought being to use the existing A/C compressor electronic drive switched to the supercharger.

    Now there are other issues to consider such as the power limits through the transaxle. We're not going to be making a dragster. But if someone lived in West Virginia or other mountainous areas, an electric, turbocharger would be a sweet solution. And there are some more radical design ideas this begins to suggest.

    How about a weight reduced, 1.5L, electric supercharged engine in a Yaris sized vehicle with the 1.8L transaxle. Fix the steering problem and use independent rear wheel suspension and make the back a 1/2 seat (one cramped or two intimate adults) . . . that could be a really nice 'pocket rocket.'

    Bob Wilson
     
  2. austingreen

    austingreen Senior Member

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    A twin scroll turbo charger will give close to the same performance, while likely giving better fuel economy and less complexity. The problem with twin scrolls has been cost, but hyundai is putting one in its turbo sonata at a reasonable cost. BMW has switched to one twin scroll on its straight 6 engine instead of twin turbos, it now takes an extra 0.1 seconds to 60 but gets 7% better fe. Save that electric motor to make the car a hybrid, and the electric boost completely gets rid of any turbo lag.

     
  3. donee

    donee New Member

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    Hi Bob,

    Getting more energy out of the exhaust stream is something that needs to be done. I am pleased that the 2010 Prius begins that trend, with the exhaust heat recovery system.

    But is there more that can be done? There is significant horsepower in that exhaust flow.

    At least two ways to go about it - use an air-flow engine to create electicity and bring it back to the battery, and direct thrust generation. Some car makers have already done research into Stirling cycle, and closed loop steam engines to generate auxiliary electricty (BMW ?). But, I think it could be even simpler. Something like an air amplifier. These are very effective with high head of air pressure (see manufactureres like Exair). But I wonder if a low head of hot air could be used for such a device too? The idea being to convert the heat energy into more mass flow of cold air.

    This is not without precedence. The WW II Mustang aircraft radiator (in the duct on the lower belly of the airplane) was an aditional source of cruising thrust, that extended range slightly.
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    1) I am happy the article calls it a supercharger, not a turbocharger.

    2) it should be 'easy' for the vendor to make a 200 v version.

    3) a Toyota version might even scroll up just before the ICE starts at times, the after market would not have that kind of integration.
     
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I agree:
    There was a 'compound' turbo-charger that coupled the turbocharger shaft:
    Turbo-compound engine - Wikipedia, the free encyclopedia

    I have a turbocharger in the box I bought for a topping cycle. But I'm stuck trying to figure out how best to couple the energy back to the car. But you've got me thinking about a solution to the heat problem and Enginer solution, topping charge the traction battery, solves the problem.

    Bob Wilson
     
  6. wwest40

    wwest40 Member

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    No, the real answer, technically speaking, is a positive displacement SuperCharger using a combination of mechanical (belt?) drive from the ICE and electric drive using a small CVT/PSD to "sum" the two inputs.

    Take the electric A/C drive assembly, variable frequency solid state AC inverter and permanent magnet rotor AC multiphase drive motor, and turn one input to a small 10HP PSD. The opposite input (1:4 "gearbox") driven by the ICE and the PSD output to the positive displacement SC.

    No throttle butterfly valve required. The SC assembly simply supplies ONLY enough airflow for normal ICE operation. Except at or near WOT, go WOT and the AC drive input will INSTANTLY, virtually so, spool the SC up to BOOST level with the ICE catching up and picking up the SC drive load with rising RPM.

    Add DFI and Toyota's new e/VVT-i technique into the mix and you get one POWERFUL but highly fuel efficient HSD drive system. 15:1 Base/native compression ratio with light, cruising, ICE loading. 13:1 effective CR with/at moderate ICE loads/loading. And then <10:1 effective CR before BOOST, INTERCOOLED BOOST, at WOT.
     
  7. wwest40

    wwest40 Member

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    Speaking of integration see my post.

    PS: Just lost my "shirt" last week in Tunica.
     
  8. donee

    donee New Member

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    Hi WW...,

    The Prius Gen III engine is like 37% efficient. So, at 37 hp operation, there is like still 63 HP leaking away some place. Yep, some of that is in the heat jacket and radiator. But the rest, probably something like 50 hp is coming out the tailpipe. But, its such low grade difuse power its hard to tap.
     
  9. wwest40

    wwest40 Member

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    Yes, and DFI alone might increase that 37% to.....

    So why the delay...??
     
  10. donee

    donee New Member

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    Hi Bob,

    Rear wheel wheel motors....
     
  11. deltron3030

    deltron3030 New Member

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    is there any inherent danger in recaptuing the "free" hp/energy of tailpipe exhaust? Makes me wonder why such a simple idea hasnt been realized en masse
     
  12. wwest40

    wwest40 Member

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    Most modern day passenger cars do exactly that. They use the HEAT of the exhaust to bring the catalyst up to, and keep it up to, the >800F temperature it requires to be operational.

    But if you do anything, ANYTHING, other than factory equipment, to restrict the free flow of the exhaust gasses you stand a reasonable chance of doing damage to the engine, if not sooner, then later.

    The earlier VW and the Porsche 911 used the exhaust heat to provide cabin heat but that became less viable as the EPA requirement to QUICKLY raise the catalyst temperature to the operational point and keep it heated to within a fair tight temperature range became the norm.

    The Toyota Atkinson cycle implementation, delayed closing of the intake valve, in the HSD system, is the most current attempt to make more use of energy otherwise lost in the exhaust flow. But while that results in a rather substantial FE improvement it also that results in a 2.0L engine having only the effective HP of a ~1.5L engine. Not a big deal if you have a battery and an electric drive motor or two to make up for that loss.
     
  13. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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  14. Rybold

    Rybold globally warmed member

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    Once plug-in hybrids become greater in numbers on the roads, with larger battery packs, I can see the trend of electric turbo chargers becoming a much more viable option. However, why not just use an exhaust-powered turbo charger?

    The GenIII Prius increased highway MPG over the GenII Prius because it increased from a 1.5L to a 1.8L. Why not just use a 1.5L that is turbocharged? Toyota likely did not do that because it would further increase the cost of the vehicle.
    An aftermarket turbo would benefit the Prius as the electric motors are not active beyond X mph. However, as time moves forward, the electric motors are increasing the speeds at which they operate. On the PHV Prius, the electric motor remains active up to 60mph. On the new Hyundai hybrid coming out in January, the electric motor remains active up to 62mph. There is little need for a turbo if the electric motor can provide the additional power needed to accelerate. Five years from now, the electric motors will likely contribute a lot more horsepower and turbochargers may not be needed at all on hybrids. Of course, they will likely remain a fun aftermarket item for at least another decade.

    Here's a hypothetical question: if the electric motor in your plug-in Prius could produce 80 horsepower (in addition to the current 1.8L engine, would you still want a turbocharger?)

    Here's another question (non hypothetical - I want to know the answer, if someone knows it)... If the electric motor could do all of the accelerating and the engine was only needed to maintain constant speed, could a 1.0L engine maintain a Prius at 70mph on the highway?
     
  15. bwilson4web

    bwilson4web BMW i3 and Model 3

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    • turbo-lag - the electric turbo charger is not subject to the exhaust flow, power limits, but responds to the accelerator pedal input as well as ICE rpm in milliseconds.
    • matched boost - it is easy to manage the amount of boost without drawing excessive power. This avoids the variable vane, turbine sections found on some Euro cars.
    • no boost at low power - most of the time the car is in a low-power setting and does not need the boost. This expands the efficient power range.
    • integrated ICE and turbo management - the valve advance, ignition and boost become a software managed, integrated system. This could lead to some new modes that further keep the ICE in peak BSFC regions.
    Bob Wilson
     
  16. Rybold

    Rybold globally warmed member

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    I could see a benefit there.

    Even if the motors and batteries increase in size, and the motors play a much greater role in acceleration, do you still see a turbo as something the ICE would benefit from?
     
  17. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Yes, as part of an integrated system with the engine and transaxle.

    Bob Wilson
     
  18. Flaninacupboard

    Flaninacupboard Senior Member

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    Absolutely!! Prius would need ~20hp to maintain 70mph. The 1.0 engine fitted in the IQ has 67bhp output. Your problem comes when you exhaust the battery pack, so you want something much larger than the prius has (8kwh or so?) but then your control software is pumping 20hp to the wheels and 15kw off to the battery pack until it's back at a happy SOC, not necessarily the most efficient design (USBSeawolf would certainly hate it....)

    A Turbo'd 1.0 would be good, low boost still gives great efficiency, high boost gives you 100bhp reducing the battery requirement.
     
  19. qbee42

    qbee42 My other car is a boat

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    Through history there are many good examples, although most have been used on large or stationary power plants and prime movers. Co-generation is an excellent example, where waste heat from electrical generation is used for domestic heating. Some systems have also used a Sterling Cycle engine to extract useful work from exhaust heat.

    With marine steam engines it was common to use double or triple expansion to extract more work from the same amount of fuel. While this isn't exactly the same as the exhaust from an internal combustion engine, the concept is similar.

    Tom
     
  20. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Sorry I missed this question earlier:
    [​IMG]
    The red line is the amount of power needed to sustain an NHW11 on a level road without a head wind (the scale on the right is for the 1.5L engine.) The problem is any significant grade, a hill, or a head wind, rapidly moves the energy required up:

    • ~65 hp up 8% grade @70 mph - this is 100% of the maximum ICE power for the 1.5L engine
    • ~65 hp into a 30 mph headwind @70 mph - again, 100% of the maximum ICE power for the 1.5L engine
    Usually, a hill has two sides so energy can be gained on the downgrade. But a headwind, you need to find a front or wait a day for the pressure system to move over the route or divert to avoid it. A former, 1.5L, VW-microbus owner and driver, I'm well aware of these limits.

    Bob Wilson