Waste Heat from Exhaust

[some_other_dave]

Originally Posted by TES111

Also today I was thinking about the drive shaft. Magnets and copper on something that already spins. Another generator of electricity for HHO production.

That energy isn't waste energy, it is used to move the car. Running that sort of setup would put an extra load on the engine; it would take more torque to turn the drive shaft in that case. You'd use more fuel to produce that torque, therefore cutting down on your MPG. This would be like adding an extra alternator onto the engine, though it would be turning the whole time the car is moving.

I don't really understand the water/metal thing, but I don't really have to. It sounds intriguing, even if you're "just" using it to keep your battery topped up. Or perhaps a number of batteries.

-soD

[mopo3]

Why not cover the exhaust pipe(s) with peltier heat pumps to generate electricity.

[cfg83]

jamesqf -

Originally Posted by jamesqf

The turbo in the exhaust thing is being researched, for instance here: Put A Tiger In Your Exhaust

As for the turbo-compounding of aircraft engines, the amusing part is that the engineers eventually figured out that the turbine was more efficient if they removed the piston engine altogether - and so the turboprop was born :-)

I kept following the URLS and found out that the project is closed :

Foresight Vehicle*TIGERS*Project

The Foresight Vehicle funded phase of the TIGERS project was completed in Q2 2007 with successful demonstration of the proof of concept hardware. The technology developed during the TIGERS project was purchased by UK based Controlled Power Technologies Ltd in December 2007 (see press release below).

Controlled Power Technologies Ltd will continue to develop the technology with further engine testing of the latest build level planned for Q2 2008. For further information on TIGERS please visit Controlled Power Technologies

The Controlled Power Technologies is just a banner page, but here is some info from other websites :

Controlled Power Technologies says electric supercharger is ready - AutoblogGreen - Apr 3rd 2008

Controlled Power Technology's Variable Torque Enhancement System (VTES) is currently being shown off in Stuttgart, Germany. According to Guy Morris, engineering director and chief technical officer, "From an idea first conceived in the year 2000, this technology has been progressively developed to the point where it is now a mature well-proven second-generation design, ready to be adopted by carmakers."

VTES can be useful for diesel engines as a near instant air supply to deliver a quick blast of torque with minimal particulate emissions, which could allow for more specific power and the downsizing of the diesel particulate filter (DPF). Additionally, for both gasoline and diesel applications, VTES would allow a smaller engine to behave like a much larger one for quick acceleration when necessary, while still allowing low fuel-consumption the rest of the time.

Green Car Congress: Controlled Power Technologies Acquires Micro-Hybrid Technology from Visteon - 12 February 2008

Controlled Power Technologies Limited, a UK startup formed by automotive executives to focus on carbon-reduction solutions for vehicles, has acquired from Visteon Corporation a portfolio of production-ready, near-term solutions focused on providing micro-hybrid functionality.

A key part of the acquisition arrangement is the transfer of licensing and technical development agreements with Switched Reluctance Drives Limited (SRDL)—a wholly-owned subsidiary of Emerson Electric Company that is based in Harrogate (UK). The new business will continue and extend the technical relationship previously established between Visteon and SRDL.

CarloSW2

[chuckm]

A possible expander (rather than a standard turbo)... Expander

Their engine is pretty cool too, IF it ever becomes a reality.

[elhigh]

Originally Posted by aerohead

,since for every gallon of fuel turned into work,two gallons are lost to heat..

You're driving something that's 33% efficient? I'm not willing to believe that.

Last I heard, the best gasoline engine out there was only 20, maybe 25% efficient at its very very best. Diesels, by nature of their combustion cycle, are a little better.

I could be wrong - I'm remembering from ten years ago and I haven't heard anybody give an efficiency rating since then. Then again, my ride is older than that and so are a lot of other folks' cars.

I'd give body parts to hit 33% efficiency.

[elhigh]

Originally Posted by mopo3

Why not cover the exhaust pipe(s) with peltier heat pumps to generate electricity.

I have fantasized about this for quite some time. Then I ran the numbers on it: pricey. Still, it'd eliminate a parasitic drag on the engine, and could conceivably generate enough current to run even a hybrid's recharging cycle - hell, stick the Peltiers on the engine block, radiator, everything. Anything that gets warm, make that heat do something useful.

[claytori]

Originally Posted by elhigh

You're driving something that's 33% efficient? I'm not willing to believe that.

Last I heard, the best gasoline engine out there was only 20, maybe 25% efficient at its very very best. Diesels, by nature of their combustion cycle, are a little better.

I could be wrong - I'm remembering from ten years ago and I haven't heard anybody give an efficiency rating since then. Then again, my ride is older than that and so are a lot of other folks' cars.

I'd give body parts to hit 33% efficiency.

Actuqlly, the bare engine has efficiency in the low to mid thirty percents but only in the "sweet spots' on the bsfc chart. After you allow for the mechanical losses and parasitic losses (alternator, ac, ps, etc.) the 25% number is realistic. If you drive off the sweet spots the efficiency is much less than this. Oh, turbocharging improves the efficiency slightly by using waste engine heat to compress the incoming charge air. Experience with turbocharged cars is that as inlet charge boost is increased the efficiency increases.

[Big Dave]

What you describe is called compounding.

Compounding can indeed increase eficiency. The old B-29 engine (R-3360 I think) and the Napier Sabre were some of the most efficient engines ever built.

Compounding works well (with some reliability issues) at high engine load, but has no scope for contribution at the low loads used by us MPG seekers. Consider turbo lag. A tirbocharger is a form of compounding where the waste heat engine (the turbo) drives a centrifugal compressor. At a low gas flow and heat rate, the turbo makes almost no boost. At high gasflow rate(high RPM) and high heat rate, it works well enough to require a wastegate to prevent overboost.

For a car, with its very light duty cycle to be able to use compounding the main engine would have to be so underpowered as to be running at high load a high percentage of the time. It ain't worth the effort on a high-MPG car.

[jamesqf]

Originally Posted by claytori

Actuqlly, the bare engine has efficiency in the low to mid thirty percents but only in the "sweet spots' on the bsfc chart. After you allow for the mechanical losses and parasitic losses (alternator, ac, ps, etc.) the 25% number is realistic.

Yet in the searching I did, I found gas turbine efficiencies quoted in the 60% range. Granted, this is for large power-generation turbines, but they aren't fundamentally different than the turbines used in aircraft.

Haven't found anything that gives real-world numbers for automotive-sized units. I'd always gotten the impression that IC engines (gas & diesel) won out over other types for automotive use was not their efficiency, because they are pretty poor in that respect. Gas was cheap, after all, and the desire for fuel economy seldom showed up in other design decisions.

[ohmycivic]

Funny this thread should come up... I'm actually pursuing a patent for a recent idea, a Stirling Engine based radiator. Information on Stirling Engines can be found here on Wikipedia and here at howstuffworks. In short, a Stirling engine converts a difference in temperature between areas into mechanical work (and vise-versa -- cryogenic applications introduce mechanical work into a Stirling engine to create a "heat pump" and keep things nice and cool).

My idea is to essentially use waste engine heat to raise the temperature of the "heated" part(s) of the Stirling engine and to use air flow/outside temperature to cool the part(s) which need to be, thus putting waste energy to good use. The Stirling engine/radiator could makes tons of parts obsolete (such as radiators and associated fluids, metal exhaust -- if the gasses were cooler, plastics could be used -- and with a bit of clever engineering, even air conditioning) and it'd be an amazing companion to the traditional ICE and probably even wind up as a component in some hybrid systems.

In fact, focusing the beam of a parabolic mirror on the heating element of a Stirling engine is (currently) the most effecient way to use solar power. They really are amazing things, sadly overlooked due to their "heat up" time and the problems they suffer due to thermal expansion. But if you want to see one in action you can search Youtube for Stirling Engine -- some of the best examples of how low-tech these can be are made by high school and tech school students -- or you can make one yourself (I got to make something similar to the Can one back in HS physics III).

Too long; didn't read: I'm gay for Stirling engines.