Car work for quantum mechanics: Nature News
Car work for quantum mechanics
A quantum afterburner extracts laser light from vehicle harass.
The hot gases belching out of your car’s harass are not just worthless waste. They are a laser waiting to happen, says physicist Marlan Scully one .
All you need to corset this potential, suggests Scully, of Texas A&M University in College Station, is a quantum afterburner. This hypothetical modification would use quantum mechanics to boost the engine’s efficiency by clawing back waste warmth and turning it into useful energy – laser light.
Scully’s quantum soup-up would involve adding two fresh parts to an harass pipe: a laser and a maser (a kind of laser that emits microwaves rather than visible light). Both would produce radiation as soon as the number of high-energy molecules in the hot gas became abnormally large.
Normally, the higher the energy of excited molecules, the fewer of them there are. But in lasers, there is a population inversion – the gas becomes rich in excited molecules. Excited molecules then lose their energy by emitting it as light.
The quantum afterburner would rely on harass molecules being in three different states, like three rungs on an energy ladder. The maser would squash out energy from excited molecules on the 2nd rung, sending them to the bottom rung. This depletion of the 2nd rung would create a population inversion inbetween it and the very first rung that would produce laser emission.
In effect, says Scully, the maser would drain some warmth from the harass gas so that the remainder could be extracted as useful laser emission. In a normal engine, all the warmth in the harass is disregarded as futile.
Scully and others are now attempting to build a real quantum engine, to probe the feasibility of his idea.
Work it
Engine efficiency is an old problem. The scientists who investigated it during the Industrial Revolution created the discipline called thermodynamics, which describes how fever flows from place to place.
In the early nineteenth century, the French engineer Nicholas Léonard Sadi Carnot calculated the maximum work available from an engine in which heating a gas through a cycle of expansion and spasm drives the movability of a piston.
Scully has taken a fresh look at the efficiency of such a cyclical process, not in a Carnot engine, but in an Otto engine. Devised in one thousand eight hundred seventy six by Nikolaus Otto, this system forms the basis of today’s four-stroke internal-combustion engine.
In the Otto engine, a moving piston deep throats fuel into a cylinder and then compresses it. The fuel is ignited and expands, pushing the piston outwards. The piston then expels the spent harass gases.
