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Posted by D Sherman [72.47.9.228] on Wednesday, July 06, 2011 at 10:19:23 :
In Reply to: what would be wrong posted by clueless [201.202.29.210] on Wednesday, July 06, 2011 at 09:52:11 :
I thought of adding an electric "booster" pump, but they tell me an electric has to be mounted where the fuel will run down into it by gravity, which means below the bottom of the fuel tank, and if the line loses its prime, it won't pump and could burn out. Plus, if the diaphragm on the mechanical pump cracks, which is usually what happens, the electric one will just push fuel through it and out onto the ground or into the crank case.
As for the water injection, that was tried on aircraft back around WWII. The idea is thermodynamically sound if you can get just the right amount of liquid water into the combustion chamber to have it get turned to steam by the combustion. Theoretically it will extract heat that would have gone out the exhaust and use it to create steam pressure to help push the pistons (or turbine). Cooling the exhaust has other benefits too. Injecting water into the carburetor doesn't help much because it either evaporates before it gets to the cylinders, which displaces oxygen and provides no thermodynamic advantage, or gets sucked in as a film on the walls where it doesn't boil enough to do any good. So, it needs injectors that spray water mist directly into each cylinder. Unless you use distilled water, there are issues with deposits building up, and no matter what water you use, corrosion is a possible problem. From what I've read, a lot of people worked on water injection for a long time, because it sounds so good in theory, but nobody made it work in a practical engine. I have a vague recollection that the main reason for trying it in WWII aircraft was for its anti-knock properties, so that they could use a higher compression ratio, and maybe to cool the exhaust valves, not for fuel economy.
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