Electric Turbocharger
 

Purely hypothetical discussion ahead. Turn back all ye who may say "this is stupid!"

If an exhaust turbine and wastegate are installed on our engine, what is an example of turbine shaft torque and speed? How much energy (temperature and pressure above atmospheric) can be used for regeneration?

Two options for generating power:
- gear down heavily and employ a high-output alternator
- run a DC electric motor in reverse

Similarly, can an intake compressor be run from a DC motor? Not talking the tiny electric superchargers on eBay... I'm talking voltage step-up + 1/2 hp dc motor + centrifugal/twin screw compressor (a la Vortech).

The idea has been tossed around by Subaru: HERE for the next WRX.

I'm just trying to wrap my head around how challenging this would be.

Potential issues:
- Sizing a battery/capacitor bank
- Management of alternator clutching
- Management of battery/capacitor bank discharge rate
- Integrated BOV with instant pressure relief (compressor motor braking)
- Cost and hardware weight would be high.

Potential awesome:
- No lag, as long as you've got battery power.
- Boost pressure can be closely controlled via dedicated feedback controller.
- The system can be switched to "ECO" mode for regenerating energy to supplement the alternator (would require an isolator for starting battery).
- The system can be switched off completely.
- Combination of the above. ECO mode during low load, low rpm driving. Instantly switch on above X% load.

Comments? Discussion?

too many fancy words for me.

I am definitely interested in seeing the results of this.

There's been a lot talk about this from BMW aswell, though I haven't seen anything in a while. One of the biggest problems was moving the electrical power around at the current 12 volt automotive standard. A few OEM's were lobbying to move to 48 volt systems, or even 48 volt partial systems. It seemed from what I read that the infrastructure became a lot more manageable at the voltage.

to keep power up couldn't you essentially make an alternator that is dedicated to power the electric super/turbo charger?

At that point it just becomes a supercharger with a remote pulley.....

Not to mention the losses in creating the electricity and then converting it back into mechanical energy. Supercharger is going to be much more efficient in terms of process than what you are describing @frostbitten.

Yes in theory it can work. Most often it's proposed as a dual stage setup by manufacturers where the electric blower would kick in first, then the actual turbo. It's probably pretty tricky to implement since as far as I know it hasn't made an appearance on any production car even though its been talked about forever.

An arc generator should work as a viable power source right?

On a serious note, how about instead of an alternator dedicated to power the electric supercharger, an alternate battery instead charged by solar cells or "ram air miniature windmills"

though I still think an arc generator would be better...

Actually, BMW is set to release the next gen M3's with a Tri-Turbo system with one of the turbo's being electric supercharger, most likely to spool one of the other two turbos.

What's the big deal designing a controlled electric compressor? Just need a circuit with power sufficient to drive said compressor. Let the engineers figure out the controller. Keep a separate higher voltage circuit, possibly with separate power storage. Regeneration could be the icing on the cake if there are significant gains.

I am a geek.

Call me ginea pig..

Anyone can add one to their cars http://www.turbomagazine.com/tech/04...r/viewall.html

It's brilliant. It's kind of like a supercharger/turbocharger hybrid but with incredible tuning capabilities.

No SC-ish engine drag, uses exhaust to capture energy to spin generator and uses electricity from said generator to spin turbine.

No Turbo lag because the electric motor won't have lag

No need for BoV because the turbine speed can be computer controlled.

Dear Subaru/BMW or whomever... please make this work.

This is something many oems are working on. Everyone wants turbos as they allow you to capture waste heat from the exhaust. However lag has always been the problem here.
IIRC BMW's system uses an electric motor to spool the turbo until there is enough exhaust gas flow to power the turbine. This is going to be a good stopgap measure until thermo-electric generators become cheaper and more efficient. If we could capture even half of the heat which is current wasted out the exhaust and radiator we could double fuel economy.
Lots of people want to think the ICE is dead but the truth is we have a long way to go before that happens.

Need MOAR POWER!!!!

Im going to go out on a limb and say a full reconstruction of OEM voltage (a la 24-48 volts) is a little ways off in the future. Think of the poor aftermarket parts suppliers lol and theres just sooo many places to lose energy in a system like this its crazy!

I suppose they could make it like an aircraft (which btw have 28 volt electrical systems) and have the starter also be be a generator when required to run the turbo at high throttle settings... :iono: I'm more than willing to see it in action

KERS and "mild hybrids" are the key to making electronic turbochargers happen. Alot of racing teams already employ regenerative braking. Some are developing regenerative dampers (using voice coil and piezo tricks). Seebeck generators are only ~5% efficient at converting thermal energy to electricity, so it will be a while for that tech.

If KERS systems become faster and larger capacity, it will be simple enough to integrate an exhaust turbine generator and electric supercharger.

Storage is already getting there. Ultracapacitors (like the Maxwell units) are still pretty expensive, but the technology is there. The car audio competitors have developed some amazing systems that maintain voltage at insane current draw:
http://i651.photobucket.com/albums/u...1-32-22_96.jpg

Typically DC motors run at 90 or 180V, but you can get custom windings from most manufacturers. I'd imagine the starting circuit will stay at 12 or 24V, but the KERS systems will be stored at a higher voltage and connect via step-down transformers and a really big diode bridge.


side note: If you think the Toyota/BMW collaboration is just about making a car, you're forgetting just how many patents and R&D hours the Prius has clocked. You're also forgetting all the EfficientDynamics research that has gone into BMW's plug-in hybrid turbodiesel.

@serialk11r

This is your type of discussion, right?

you need a lot higher voltage to put out the crazy power necessary to compress massive amounts of air really quickly. current brushless motors about the size you'd want in a turbo/supercharger/nutty electric hybrid thing (like a 700 size rc heli motor) can make 6-12hp, and they weigh very little. i'd call it an eventuality at this point... just a matter of time before it's possible, then some day practical.

it makes sense that it would be best used to spool a turbo, since keeping up with the airflow demands at high rpm would require a ton of power (and generate a ton of heat).

That's one of those ideas that's so simple and yet so brilliant. I love it. :thumbup:

There's a really cool duality to this if it plays out the way I think it might.

When diesels first came out they needed a supercharger to run. Two stroke diesels with the ports in the sides of the cylinder walls didn't have the ability to create sufficient suction and keep the intake port sealed off during combustion, so they absolutely had to be force fed.

I wonder how long it'll be before they stop designing intake port head flow to ever work in a vacuum/ And I wonder what that'll do the shape of the posts.

This is a much more interesting thread than i expected. You could run an alternator off a turbo exhaust housing also. Not neccesarily as efficient as a normal turbo but would be interesting none the less.

I remember reading about a possible future WRX/STI platform.
Not hard specs, but a supposed theory.

The turbo has an electric motor matted that can engage/disengage.
At low RPM electric motor assist the turbine = reduced/no lag.
Disengages when the engine produces enough exhaust gasses itself to spool.
Thermal energy from exhaust housing is converted to charge the units separate battery.
That battery or cell is also supplied power from vehicles power supply.



Off topic below.

Above speculation plus a new light weight, smaller, AWD chassis has me excited.:happyanim:
As of now, one can only dream.:sigh:

Don't do it. Been tested don't work. There's a clip on YouTube on those electric turbo.

read
the
thread

this is not about the ebay electric turbos for sale

this is about theory and developing a future electrically powered turbo utilizing advanced battery/capacitor tech

From my experience from playing with alternators, generators, and electronics with motors. I can tell you that it is possible to do, but this application eats too much efficiency out of the system to be... efficient.

I can see a three phase AC generator being used to power a three phase electrical motor to power the turbo.

The reason that we use the mechanical TC's and SC's is that they have a high efficiency at the moment. Efficiency as in when we convert energy from one system to another we lose energy.

You know that fan motor that you put in font of your car when you dyno it? That is what I'm talking about, or very close. Yes a 120V AC motor would do the job. Now I just need a 120V alternator.

Hm... brb

Its possible but not worth it, simply due to weight(electric motor+cap/bat+drive) and other way of making more power cheaper/easier.

KERS(at least mecanical one) are use for specific usage in specific race regulation, not as efficient in the real world.

As for voltage or type of voltage, there no really link with the power an electric motor give, its mostly all about want kind of caracteristic you want from motor and how it is built(High amperage generate more heat in component(loss), so best to keep low by having higher voltage).

I think, if I would go for some crazy design(did not say its feasable) for higher power in short burst, I would start by having directly an electric motor that replace the drive shaft(weight would be low as for gravity), possible torque(due to large surface) quite high, could be use as regenerative device, since connect directly with the rear tyre, or with the engine when clutch engage, would not put more stress on the engine. And would not take any efficacy(MPG) out of the current system.

Lot's of talk about "how" it could work, but what about "how long" will it last? There will obviously be a trade off for useful time and battery / capacitor size, but what do you consider "enough" before it putters out? One lap on an auto-X course? Several laps on a big boy track? Are we only looking for a boost at low RPMs or will this also keep the turbo spool'd in between shifts (mitsu did that right?) because that'll play into how long the juice lasts.

How long would to recharge it would you find acceptable? For instance my very mild hybrid CRZ takes quite a bit longer to recharge when you compare it to the useful battery. It's (lol, sadly) a better hybrid if you switch between normal and ECO modes instead of just leaving it in ECO (eats the battery charge quick).

The efficiency could be there in a hybrid where you already have a secondary electrical system in place, and get power from regenerative breaking.

As for KERS its not just for race use anymore, new systems are making it into production cars as we speak. Porsche, and Ferrari already have production models with KERS, and Volvo, BWM, and Toyota have systems in development.

Subaru were talking about using the heat from the exhaust to generate electricity not the pressure and momentum from the exhaust that turbos utilise.
There may well be more energy in the exhaust heat which is currently only a problem not a benefit.
My question is how will they convert heat into electricity and the only solution I can think of is to use the fuel cell principle.
You have to wonder if other waste heat, at much lower temperatures, from the cooling systems could also be used instead of being dumped to atmosphere??

So much for that idea. I thought they used heat from the fuel to generate electricity. Should have looked it up instead of relying on assumptions!

Maybe a modern version of the heat pump?

@neutron256

KERS can be the same thing as an hybride cars per definition(Kinetics energy recovery system), my point is mostly in the technology use in actual "KERS" system, mostly use it as short burst of energy(that's the difference with "hybrid" car, as they are design for fuel economy/long term usage of recovered energy).

As you stated, Porsche, Ferrari use it, that prove my point, its for race/high performance application with a specific usage. The fact is that technology have been develop for political reason, gas engine pollute, high performance car had bad reputation with green people, meaning bad image for racecar and the industry=less money.

They could use that kind of semiconductor http://www.pcbfacile.com/media/DT12-8_a.pdf, the cost is high and life short. Again alot of way of doing thing.

Now now, gem, I know I have told you before, it's Guinea. lol

Unfortunately, this concept is currently not be feasible, given the off-the-shelf components that are currently available to us.

We'll assume that a geared SC or TC are one and the same here. A typical supercharger that produces even a few psi of boost will likely consume about 20hp or so to run.

For the power levels that the current SC guys are trying to achieve, you're probably looking at closer to 40-50hp to run the SC.

A typical automotive alternator outputs around 90-120amps or so and a high output (audio guys use) unit may crank out upwards of 200 amps.

One HP equates to 746 watts. In order to achieve 20 hp, you'd need 14,920 watts of power. Given a typical alternator output of 14.4 volts and 200 amps, you'd still only see 2,880 watts of continuous power. You'd need 6-200amps alternators in order to drive the SC constantly under load, with just enough left over to run the car's electrical system.

While it's possible to have the alternator charge a set of say, very expensive lithium ion batteries... the extra weight, expense, and complexity would not make it a very viable option and you'd still not be able to use it at will.

Maybe if the automotive world adapted a 96 or even 120 volt system, this idea would actually be somewhat feasible.

Tuning would be interesting too, unless you had a very expensive motor controller or an elaborate bleed off system, otherwise you'd have a lot of boost down low when the SC switches on and very little boost up top.

This is always an interesting topic of discussion. Feel free to correct the math if it's off. If anyone wanted to try it out, check out this link, but think mini shot of nitrous at a very high price. ;)

http://www.turbomagazine.com/tech/04.../photo_02.html

Porsche and Ferrari use KERS because they have a lot of experience with it from the racing world. There are plenty of non-supercar manufacturers developing it. Yes it is best for a short burst of speed, like getting the car moving again after coming to a stop which is when engine output is at its least efficient. It has a ways to go before its ready for most production cars, but I have little doubt it will become as common as electric hybrids soon.

It's far more practical to use the electric motor to assist the engine at low speeds than it is to have it try and compress the intake charge. Either way you'll need a bunch of lipos and a fancy speed controller, so may as well just make it a hybrid and not worry about packaging constraints and lost energy in the electric 'turbo'.

This is precisely what I was hoping to find out. A light-duty supercharger uses 20 HP to generate 60 hp.

20 hp = 15 kW. At 12V, that's a 1250 A alternator. At 90V (a convenient setup for DC motors), that's a 167 A alternator, which is much more feasible. Lots of windings and more power to dissipate through the rectifiers, but it's possible.

If they used a bank of ultracaps to stabilize the system and store recovered energy... I could see 2 of these installed across the rear axle: Maxwell 75V bank

That's 188F of capacitance at 75V. 1/2 * C * V^2 = 529 kJ. Let's say you're running the 1/4 mi and want free flowing exhaust, so the supercharger is running 100% off KERS. You get 3 full runs. Running with the exhaust turbine on would probably not drain the pack at all, but the back pressure would hurt power levels.

Power to weight ratio. Batteries add 110 lbs. turbine/supercharger/motors/wires, etc. might add 90 lbs. 160 hp / 2600 lbs vs 220 hp / 2800 lbs. That's a 25% increase in power-weight ratio using only wasted energy from the engine.

Just sayin', the technology may not be there yet, but that doesn't make it impossible or even a bad idea.

really? you guys believe this crap works?

I believe that air compresssors compress air.

I believe that generators generate electricity.

I believe that batteries and caps store electricity.

Whether it can be done efficiently or effectively, is what the discussion is about. As an R&D engineer, I see dissenting opinions and welcome the perspective they can provide... but don't be surprised if non-contributing discussion is ignored. Remember the first thing I wrote:
This was actually talking to you.

or you could go with a heavy flywheel, bolt a supercharger to the flywheel just as the starter is, then you dont have to worry about belts!

http://www.tdi-plc.com/catalog/image...BRZ%20GT86.png

or strap an alternator to the flywheel in the same fashion, vary voltage depending on how much power you need to run the electric supercharger. This way you can create instant boost at any rpm. this means you can run any psi at any given rpm

Are we assuming that using the electrical energy stored to produce boost will produce more power than simply using it to drive a brushless electric motor?
I find that very hard to believe.