Exhaust Driven Alternator

[Air-Hybrid]

Whether a manufacturer decides to install Seebeck devices, a 'turbosteamer' setup or a turbo-generator, there will be some increase in back-pressure as heat is turned into work during the exhaust gases' journey to the tailpipe.
The TIGERS system utilises a bypass valve for when the motor is at part-load operation, so the back-pressure is not strangling the engine.

I think any vehicle design would need to be at least a 'mild hybrid' for a turbo-gen to make sense, but it would have to be seen how much additional cost it would be incurred relative to the lifetimes fuel savings. ... it seems to me that it could somewhat improve a hybrid's highway economy; and the same may be true for large trucks (without being hybrid, even) as they are pulling under load for much of their operation.

[Xist]

At what temperature is a catalytic converter designed to work?

[some_other_dave]

Originally Posted by Nerys

electric motors DESIGNED right are extremely reliable.

True, but electrical connections and components multiply the number of failure points, and anything that moves or vibrates is liable to problems from that (e.g., fatigue). There is pretty much just one failure point for the drive on a conventional water pump--the belt. There can be quite a few for an electrical pump; every connection, the relays, the switches (if any), whatever controls you have on the system, etc.

You won't damage the engine if you notice that the pump is no longer working. Most people (including me!) are going to miss that for a while at least. So you need to rig up some sort of very unambiguous signal, like a loud chime or a big light, when the temp gets to a certain point. If you rely on a gauge, the one time you will need to pay attention to it you will miss it. (Murphy's law.)

An electric pump could be a win, but you would need to make the system at least somewhat fail-safe. And you'd need to pay close attention to the design and fabrication of the electrics.

IMHO.

-soD

[Air-Hybrid]

Originally Posted by Xist

At what temperature is a catalytic converter designed to work?

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.

[oil pan 4]

Originally Posted by some_other_dave

True, but electrical connections and components multiply the number of failure points, and anything that moves or vibrates is liable to problems from that (e.g., fatigue). There is pretty much just one failure point for the drive on a conventional water pump--the belt. There can be quite a few for an electrical pump; every connection, the relays, the switches (if any), whatever controls you have on the system, etc.

You won't damage the engine if you notice that the pump is no longer working. Most people (including me!) are going to miss that for a while at least. So you need to rig up some sort of very unambiguous signal, like a loud chime or a big light, when the temp gets to a certain point. If you rely on a gauge, the one time you will need to pay attention to it you will miss it. (Murphy's law.)

An electric pump could be a win, but you would need to make the system at least somewhat fail-safe. And you'd need to pay close attention to the design and fabrication of the electrics.

IMHO.

-soD

I run electric pumps and don't see much benifet over belt driven ones.
The only time the electric pump would shine is if you had an alternatorless power system that provided all the free electrical power you needed.

So unless you have a really good alt delete setup already well tested, up and running don't bother with an electric pump.

[cRiPpLe_rOoStEr]

Originally Posted by Air-Hybrid

Several hundred degrees Celsius, I imagine.

It's usually quoted to be from 500 to 650.

[maxc]

Honda's New Steam-Powered Hybrid Engine

[Air-Hybrid]

Originally Posted by cRiPpLe_rOoStEr

It's usually quoted to be from 500 to 650.

I'm not totally certain on whether a cat' is cable of being able to work to the best of its ability once it passes the 'light-off' temperature, but 'several hundred degrees Celsius' is not a bad fit for most vehicles' light-off point.
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?

[Air-Hybrid]

Originally Posted by maxc

"Honda's New Steam-Powered Hybrid Engine"

...er, new 5 years ago based on the article date.
BMW did a similar experiment, but neither system is very near being fitted to production vehicles so far as I know. ~ Steam system are heavier and more complex than a turbo-generator; nothing that I've seen seems to point to them being of any greater efficiency either... ??

[oil pan 4]

Just adding a turbo charger will add 30 to over 80 pounds depending on the application.
Adding a Rankine cycle would add much more weight for small gains.

For example classical boiler design calls for 10 to 12 square feet surface for each horsepower you hope to generate with a Rankine engine.
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.