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Technology / Does hydrogen and oxygen fed to a petrol engine improve performance?

« on: 07/10/2013 04:12:15 »

Some people claim they can get increased gas mileage on their cars by employing an electrolyzer to generate hydrogen and oxygen gas (HHO) which is fed into the combustion engine. Since the energy used for the electrolysis comes from said combustion engine, I don't see how there can be any real increase in efficiency unless this energy would otherwise be wasted (or if the energy comes from application of the breaks, as in a hybrid vehicle). Even with optimal conditions, the electrolyzer will probably waste about 20% of the energy (output = 80% of input).

Is there something I'm missing here? Is there substantial improvement of combustion having some H2 and a little extra O2 in the mix?

102

Physics, Astronomy & Cosmology / Would a blow torch work on Titan?

« on: 22/09/2013 15:20:03 »

Titan's atmosphere is mostly nitrogen, but almost 2% is composed of organic compounds (mostly methane, with some ethane, acetylene and traces of heavier compounds like benzene). Could oxygen by itself be used to fuel a blow-torch in such an atmosphere? How about a combustion engine? Fuel cell?

103

Physics, Astronomy & Cosmology / Hijack a comet?

« on: 11/08/2013 03:20:13 »

Imagine we could cover the surface of a comet with photovoltaics, use sunlight to electrolyze the water in the comet, and store the resulting hydrogen and oxygen. I know insolation at perihelion would have pretty high flux, but I don't know the right constants and equations to use to calculate how much energy it would actually be (even assuming only 10% efficiency in energy storage). I don't know how many orbits it would take to store enough energy.

If we had an unlimited amount of time for electrolysis, and could split all the water in the comet, we could store enormous amounts of energy (up to 15 megajoules per kilogram of fuel).

Combining the kinetic energy of the comet, which is already enough to get it pretty far out from the sun (if the orbit has high eccentricity), and the energy released from the chemical fuel, could the entire comet escape from the solar system? Could it escape with a lot of kinetic energy left over?

104

Physics, Astronomy & Cosmology / Refraction

« on: 11/08/2013 00:32:59 »

Is it impossible for a material (or metamaterial) to have different indecies of refraction along the same axis, but depending on the direction of travel? (ie. light propogates faster in the x direction than it does in -x direction)
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