Exhaust Driven Alternator

[elhigh]

Originally Posted by Nerys

<snip>
the point of lowering the power is not to increase mpg by reducing alternator drag but to ELIMINATE the alternator and water pump drag all together and make the power consumption low enough that "charging" the battery is convenient and not a hassle.
<snip>
maybe your race car would be a toaster without its pump for a few seconds but I can go several MILES with no damage in a pump failure scenario in a metro. plenty of time to realize something is wrong stop and fix it.

It just crossed my mind that the 113ci engine in my Farmall fares pretty well without a water pump. It's a thermosiphoning engine, have you tried removing the water pump and the thermostat, just to see how it does? You might be able to get along with the thermostat in place, but maybe try it without first.

Granted the power output of the Farmall is pretty modest even compared to the lowly Metro, but still it's worth considering. Gotta be absolutely certain there isn't an air bubble or anything in the waterways, though.

Let me point out too that for best performance in a thermosiphon system, add some alcohol to lower the boiling point. Get some vapor (not air) bubbles to form in the system at less than the usual boiling point to lift liquid through the block. If you really wanted to get fancy with it, you'd install a couple of check valves in the top and bottom hoses to ensure that vapor bubbles would cause the entire engine's coolant system to act as a big bubble pump.

[cRiPpLe_rOoStEr]

Originally Posted by elhigh

It just crossed my mind that the 113ci engine in my Farmall fares pretty well without a water pump.

It was not an unusual arrangement afterall... It was even used in the Model T, DKW 2-stroke engines, among others...

[ElPants21]

I like the idea but you would have to math things out. i don't know how many watts it takes to spin up a turbo to say 10lbs of boost, but it gets negated by the added power generated. with an alternator (assuming max efficeincy of the belt drive and that it's rated at 90amps) 90amps x 12volts = 1080 watts / 745.7 = 1.44hp required to turn it under a 90 amp load.

Can that be squeezed out of an exhaust turbine?

[Xist]

Originally Posted by ElPants21

I like the idea but you would have to math things out. i don't know how many watts it takes to spin up a turbo to say 10lbs of boost, but it gets negated by the added power generated. with an alternator (assuming max efficeincy of the belt drive and that it's rated at 90amps) 90amps x 12volts = 1080 watts / 745.7 = 1.44hp required to turn it under a 90 amp load.

Can that be squeezed out of an exhaust turbine?

Sure! If it is attached to another car!

[P-hack]

I don't know much about turbocharger design, but the main question I have is if it can be designed (basically via PV=NRT) to minimize the pressure drop and maximize the temperature drop, thereby extracting more of the thermal energy and creating less back pressure.

[P-hack]

followup, found a basic diagram of turbine PVT transitions here
http://www.skybrary.aero/bookshelf/books/1621.pdf


This turbine is designed for a fair bit of back pressure however, so it can drive the compressor, though the gasses feed a convergent nozzle downstream. I assume the top line is temp, the middle is pressure and the inverted V is velocity. So while the vane stage doesn't do any compressing (temperature stays the same), the blade stage does some expansion, and hence the temperature drop across the blade?

So, does it stand to reason that if this turbine magically did not need vanes that temperature would drop faster than pressure?

(reading about Rankine and Carnot Cycle now)

[P-hack]

umm, while trying to sort out how semi-trucks do fuel injection, I saw this cummins ISX diagram, electrical power from exhaust is not a unicorn (but it is more complicated than that):
http://www.dieselpowermag.com/tech/g...e/viewall.html

Where Will the Extra Energy Come From?
+6%from EGR energy

+2%from exhaust energy

+2%from the eliminationof parasitic accessories

=10%overall improvementthroughout drive cycle

Read more: http://www.dieselpowermag.com/tech/g...#ixzz2WmpoLkK7

they take heat, add fuel to make it hotter, run a turbine generator, ditch the mechanical accessories/alternator, and put some back with an electric motor.

[Diesel_Dave]

That's some old info. I don't have all the links right now, but I know Cummins is currently running a waste heat recovery system on a prototype truck as part of the DOE-funded "Supertruck" program. I'm sure you'll find some info if you Google Supertruck waste heat recovery.

[GTR]

I wonder if the fact that F1 cars are now using the idea expressed in this thread if it no longer qualifies as a unicorn?

"The second addition for 2014 is the introduction of a thermal capture device. The similarly named Motor Generator Unit - Heat (MGU-H), attached directly to the turbocharger shaft, captures exhaust heat and coverts it, like the kinetic system, into electrical energy. This capturing device has the ability to dump power straight into the system on demand or store it in the Energy Store for later use. When activated, the MGU-H gives drivers another electric power shot to the drive wheels via the dedicated generator unit. And unlike the MGU-K, the thermal recovery unit can provide unlimited supplemental power throughout the race. For 2014, Formula 1 has limited energy recovery from the MGU-K to 2 megajoules (MJ) per lap with the ability to release stored energies to a maximum of 4 MJ per lap.

Another fancy power management trick is the way in which the MGU-H thermal unit manages turbo speed. Contrary to a conventional turbocharger system where a wastegate is used to vent out excess engine pressures derived from the turbocharger, the new unit actually controls the speed of the turbocharger impeller. The ability to speed up or slow down the turbo allows teams to not only better manage wastegate pressures in the engine but to spin up the turbocharger low in the rev cycle. As boost is enabled sooner, power comes on quicker, and that power procrastination thing known as turbo-lag essentially disappears from the equation."

Turbocharging and advanced hybrid tech coming to Formula 1 for 2014

[cRiPpLe_rOoStEr]

Originally Posted by GTR

I wonder if the fact that F1 cars are now using the idea expressed in this thread if it no longer qualifies as a unicorn?

Probably... Well, anyway, I'd like to find it in a street-legal car.