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Capturing Waste Heat with Quantum Mechanics
TheMatt writes: "There is a summary of a Phys.Rev.Lett. article up at Nature Science Update that describes a design for a 'quantum afterburner' that would improve the efficiency of an Otto engine. It improves the efficiency by using a laser and maser to extract energy from the hot exhaust of the engine. In fact, the process could enhance performance beyond that of the "ideal" Otto engine."
Can be found here (in PDF form), for all those who like reading physicists physics.
There's no reason for a sig here.
It actually has a big point.
:).
Although what you say may be correct, you have to remember that either using this to cool the intake or even better using it as a below-ambient intercooler on turbos increases the power-to-weight ratio of the engine because you can obviosly get more charge in a cylinder.
Thus you can create a lighter car with the same power and overall the efficiency increases because you have that much less mass to accelerate and that much less rolling resistance on the tires. Granted the efficiciency of the *engine* does not increase, but the efficiency of the entire system [car] does -- and that's the thing in the end that truly matters.
What I'm waiting for is efficient low-temperature thermo-couples to become cheap. That way electricity can be generated from the wasted exhaust heat getting rid of the need for an alternator.
Combine that with regenerative breaking and a few bucks on gas can definately be saved
What you are refering to is VE(Volumetric Efficiency). VE is a major factor in the specific output(PS/Liter or HP/Cubic Inch). Regardless of VE, what we really are looking at is raising BSFC. That is Brake Specific Fuel Consumption. This number shows how much gasoline is required to produce horsepower. New electronically-actuated valves will do much to raise this. On a 4-valve cylinder, over 20% of the engine output is used soley to spin the camshafts and plunge the valves up and down quickly.
Turbocharged engines help by absorbing some of this engine's exhaust and 'reinvest' this kinetic and thermal engergy in the intake. However, it is a losing proposition; even with an intercooler, the more boost you pump, the hotter the intake charge gets. You quickly develop a cycle where you must retard timing to reduce preignition and detonation thus raising exhaust temp's even more. The retardation of the ignition severely reduces power output thus nullifying any boost pressure you are running anyways.
No, turbochargers are good for increasing VE , but do little to alter the fundamental(thermal) efficiency of an engine.
We need a revolution.
You can't legislate goodness. Let each to his own destiny, by will of his freely made choices.
(And many thanks to all the scientists who publish on arXiv).
Doesn't anybody else find it at least slightly funny that someone is proposing putting a Quantum Afterburner (TM) on a piston engine, the essential design of which is 125 years old? After all, there are other ways to recover waste heat in the exhaust that we could be using now, but aren't. Peltier junctions could be used to generate electricity to supplement or replace the function of the alternator once the engine was hot. Someone else here mentioned stirling engines. Maybe that'd be another way to increase the efficiency. Again, maybe you could drive the alternator with it. Of course, the alternator only uses maybe 1 or 2 horsepower anyway, so even eliminating that drag on the engine is only going to be a small improvement.
Than again... how many horsepower does a car use when cruising? Maybe eliminating 1 or 2 horsepower would make a difference. I would assume that this Quantum Afterburner (TM) would be able to recover a much greater amount of the waste heat, too, so maybe it would make quite a difference.
P.S. -- before anybody starts to rant on me for using horsepower, remember, there are metric horsepower too! According to my unit converter, one horsepower equals 1.01387 metric horsepower. Guess the French have different sized horses than the English! Cheers!