Exhaust Driven Alternator

[dmodified1]

actually how about the absence of pressure to spin the alternator, use the vacuum from the intake to spin the generator there would be no lag because there would be no restriction on the exhuast side. once it overcomes the restriction it operates like a normal motor.

[some_other_dave]

That would put some large pumping losses into the intake. I'd say probably not worthwhile.

-soD

[mwebb]

pumping losses or effects on engine operation would not matter
IF the system only functions during decel

max difference in pressure ambient to intake is about 13psi which is about the same as 26" of vacuum , during decel ,

max difference in pressure ambient to exhaust can be much higher and is not limited to the value of barometric pressure which is about
14.7 psi = 30"hg
at sea level
i have measured exhaust back pressure well over 20 psi during WOT snap on engines with restricted cat converters

using the engine as an air pump to pressurize an accumulator to spin up the alternator (or choice c something else )
ONLY during decel
will have little to no effect on the efficiency of the engine when running in a condition other than decel

[markweatherill]

An alternator doesn't produce a constant power. It varies according to demand.
So it would create a varying restriction in the exhaust, which would impact the engine's power.. and probably noise output.

[cRiPpLe_rOoStEr]

A few years ago BMW was developing a steam-driven alternator to be heated by the exhaust as an attempt to recover some energy. That might work in a hybrid...

[Air-Hybrid]

This idea has been discussed, quite rationally on the main boards already...

Originally Posted by Air-Hybrid

"TIGERS (Turbogenerator Integrated Gas Energy Recovery System) is a water cooled switched reluctance generator coupled to an exhaust driven turbine. It is capable of operating in exhaust temperatures > 900ºC, at speeds up to 80,000rpm, delivering a shaft power of 6kW"

Controlled Power Technologies... TIGERS

Does-tigers-turbogenerator Work?

[Diesel_Dave]

The main issue is this:

exhaust turbine=expensive
alternator belt= cheap

[jamesqf]

Originally Posted by Diesel_Dave

The main issue is this:

exhaust turbine=expensive
alternator belt= cheap

Wouldn't even say that's the main issue. The main issue is that for anything other than a hybrid, it's going to generate way more electric power than the car can use. A typical alternator might put out a maximum of around half a kW, but only a small fraction of that most of the time. Even with lights on, a car might only use a couple of hundred watts, if that.

[oil pan 4]

If you really want to do something with all the heat going out the exhaust on a typical vehicle get a diesel and put a turbocharger or 2 on it.
Before I turboed I saw EGTs in the 1000'F to 1100'F all the time, now they rarely go above 800'F and normally stay between 400'F and 600'F.
These are all preturbine temperatures too.

[maxc]

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