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Steam Jet Thrust Hybrid
Use engine waste heat for steam jet propulsion
  (+1, -3)
(+1, -3) 		  [vote for,
against]


Start with a hybrid electric car (edit: Diesel non-hybrid would be a better starting point) and direct the exhaust to boil water or heat a metal chamber for a steam jet. When the water is hot enough, speed up with the electric motor (a fixed amount of thrust is worth more power at high speed), fire the steam jet, and then slow down with regenerative braking (edit: just try to use it mostly at high speeds).

A steam jet should be relatively simple for a waste heat recovery device. A low volume water pump and maybe a shut-off valve and no other moving parts.

caspian, Dec 14 2006

Four stroke Atkinson cycle engine. http://en.wikipedia...kinson_cycle_engine
[BJS, Dec 14 2006]


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       My Prius has relatively little waste heat. The engine controller has to run the engine to provide EXTRA heat on startup just to get the catalytic converter to run properly.
Galbinus_Caeli, Dec 14 2006
   

       The Toyota Prius hybrid, Ford Escape hybrid, and Toyota Camry Hybrid all use the Atkinson cycle, which creates less waste heat than conventional Otto cycle engines. And almost all hybrids have relativly small engines anyway so they would't have very much waste heat.   

       So basically this specific idea would be very non-effective.
BJS, Dec 14 2006
   

       So how big would the tank be to carry all that water? I'm guessing that to carry any signifigant amount of water it would have to be at least a few gallons and the last thing cars need is more weight
acurafan07, Dec 14 2006
   

       I was thinking of it using about as much water as fuel, so either an equal sized tank or about a quarter as big. Running out of jet water doesn't prevent the car from working, so it can be a bit smaller. The weight could well be a problem which limits how much water is carried.   

       Amount of waste heat: any heat engine is technically going to have a significant amount of waste heat, proportional to its power output, but maybe the exhaust temperature would be too low if the Atkinson cycle engine is efficient enough.   

       If it is high enough temperature, even if only to make the catalytic converter work, there should be plenty of heat.   

       My device features several hazards to make it more interesting, but unfortunately less practical.   

       1: the speeding up and slowing down could be dangerous driving. 2: getting blasted directly by the steam jet. 3: possible low visibility in clouds from the steam.   

       However, number 3 could be useful in car chases.   

       Also, people could attach food to the front of their cars, and if the driver in front was feeling generous, they could steam another car's food while stopped at traffic lights.
caspian, Dec 16 2006
   

       Well in that case, [+]. If it was mounted either really high up on the car or really low, it probably wouldn't blast steam on anything important. But unless regenerative braking is an important part of the idea, my suggestion would be to lose the electric part of it and go with a turbo diesel engine and steam jet. Diesels are about 15% more efficient than gasoline engines and generally produce more heat, so they would be better suited for a steam jet than either an Atkinson or Otto cycle gasoline engine.
acurafan07, Dec 16 2006
   

       The electric hybrid was so you could go fast while the jet was activated and then slow down before losing much energy to drag. It's probably not worthwhile, motor/generator/battery losses could wipe out any gains. I'll change that.   

       The getting blasted I was thinking of was if someone was standing behind the car. If the jet was too low it might damage road surface too.
caspian, Dec 17 2006
   


 
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