Exhaust Driven Alternator

[cRiPpLe_rOoStEr]

Originally Posted by Air-Hybrid

Unless there are practically no COs or HCs present in the exhaust I believe the cat' temperature is self-sustaining; plus if adding an exhaust turbine presents problems in holding the heat up enough, can't exhaust wrap be fitted?

Exhaust-wrap has many advantages, since it even optimizes the exhaust flow. It's also favorable to aeromods, since it requires a smaller clearance between the body panels and the exhaust pipes when some compound materials are used

[Air-Hybrid]

Just to be clear, I don't think there's any mileage whatsoever in Rankine cycle heat recovery; it's just possible something the size of an artic' lorry could make a go of it, I suppose.

Originally Posted by oil pan 4

Just adding a turbo charger will add 30 to over 80 pounds depending on the application. ... My turbocharger and added piping weighs about 60 pounds and generates about 40 horsepower worth of compressed air the way I use it, but I only use about 1/3 its max rated output.
The turbocharged diesel has no problem producing 2 to 3 times the horsepower and 10%-20% better fuel economy over an N/A diesel.

Right, so assuming these figures are a good guideline, then no diesel lighter than large truck is going to see improvements using a turbo-generator [except in odd cases where a smaller vehicle was almost only used for motorways, and then only in a parallel-hybrid configuration].
There may be better arguments for fitting one to hybrids where a petrol (or other spark ignition) engines are preferred - The Hybrid Miller-cycle, for example, would seem a good fit.

These devices could be of real practical use for more conventional lorries and coaches, where a fairly constant stream of hot gas is produced at highway speeds; it could mean a downsizing of the diesel motor, then running the thing hotter and harder for more of its cycle.

[oil pan 4]

After the turbocharger on a diesel there is not a lot of heat left over.
When driving at 60 mph under light load there is maybe 500'F EGT before the turbine and only about 400'F after.
On hills and during passing EGTs may climb to 600'F.
After that last turbocharger (if using more than one) you will want the exhaust be as free flowing as possible.

[Xist]

Originally Posted by Air-Hybrid

Several hundred degrees Celsius, I imagine.
But (and I assume this is where the question is leading), the ability once hot of the Cat' to remain in the "light-off" temperature zone is dependant on how the levels of incompletely burnt HCs in the exhaust gas as well as it's overall temperature.
With a correctly designed system that includes a bypass valve, a turbo-generator should be perfectly capable of operating effectively without overly cooling the cat' downstream.

No, that is not at all where the question was leading, at least I do not think so, because I do not have any idea what all of that means!

Big words make me sleepy...

"Light-off" is the operating temperature?

What is the relationship between levels of incompletely-burnt hydrocarbons and overall temperature, regarding catalytic converter functionability?

[Air-Hybrid]

Originally Posted by Xist

What is the relationship between levels of incompletely-burnt hydrocarbons and overall temperature, regarding catalytic converter functionability?

Talking of big words! ^^

Nothing happens chemically in a Cat' until it passes a certain temperature, aka the 'light off' temp.
Once hot enough, the relationship is, the more 'incompletely-burnt hydrocarbons' that are present in the exhaust gas, the more reactions will occur between NOx, HC and CO; reactions that all give off more heat.

.... at least, that's what the bloke down the pub told me!

[Air-Hybrid]

Originally Posted by oil pan 4

After the turbocharger on a diesel there is not a lot of heat left over.
When driving at 60 mph under light load there is maybe 500'F EGT before the turbine and only about 400'F after.
On hills and during passing EGTs may climb to 600'F.
After that last turbocharger (if using more than one) you will want the exhaust be as free flowing as possible.

Okay. No diesels large or small then.

Originally Posted by Air-Hybrid

The Hybrid Miller-cycle, for example, would seem a good fit.

I suppose here the problem is that any vehicle big enough not to loose out by adding a TurboGen that weighs 30kg or more is probably only sold as a diesel option anyway. I suppose something of the size of a Lexus RX450h could make use of one.

[cRiPpLe_rOoStEr]

Originally Posted by Air-Hybrid

I suppose here the problem is that any vehicle big enough not to loose out by adding a TurboGen that weighs 30kg or more is probably only sold as a diesel option anyway.

I believe anything available either with a V6 or a V8 following the Miller cycle, eventually with both options across the range, would be a good option to be fitted with a turbocharger/generator combo. The immediate air flow from the supercharger required by the Miller cycle would help to overcome the turbo-lag...

[oil pan 4]

Use a VGT to over come turbo lag.
With VGT you can have a properly over sized turbo on your diesel with no to low lag responce times typical of undersized or compound turbos.

[Air-Hybrid]

Originally Posted by cRiPpLe_rOoStEr

I believe anything available either with a V6 or a V8 following the Miller cycle, eventually with both options across the range, would be a good option to be fitted with a turbocharger/generator combo. The immediate air flow from the supercharger required by the Miller cycle would help to overcome the turbo-lag...

Yes.

Originally Posted by Air-Hybrid

Air-Hybrid:"The Hybrid Miller-cycle, for example, would seem a good fit."
Something of the size of a Lexus RX450h could make use of one.

I thought this seemed an obvious vehicle that was large enough and already use hybrid operation.
Yeah, a V6 Miller-cycle hybrid of ~3 litres could probably support the turbogen and out-perform a 'standard' V8 in the same vehicle, but that's not going to do a lot for the 'Prius buyer' etc.
Maybe packaged with a Volt-style drivetrain it could work better...

[cRiPpLe_rOoStEr]

Originally Posted by Air-Hybrid

Yeah, a V6 Miller-cycle hybrid of ~3 litres could probably support the turbogen and out-perform a 'standard' V8 in the same vehicle, but that's not going to do a lot for the 'Prius buyer' etc.
Maybe packaged with a Volt-style drivetrain it could work better...

Nissan already has a 3-cyl 1.2L Miller-cycle engine available for the Micra (known in certain markets such as Mexico and Brazil as March). If they would ever try a hybrid version of the Versa, for example, that engine might suffice. With a Volt-style drivetrain and a turbo-generator, I believe it could even worth the risk to slap it into some larger vehicle, such as the Altima.