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Old 07-01-2008, 01:11 PM   #31 (permalink)
Andyman
amateur mech. engineer
 
Join Date: May 2008
Location: New York City
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Quote:
Originally Posted by garys_1k View Post
Such would be a perfect application for a Stirling Engine:
Stirling engine - Wikipedia, the free encyclopedia
You may be right. It depends on economics. I don't know where you can buy either a Stirling engine or a steam engine. I've read that Stirling engines don't have a good power to weight ratio. I need to do research to learn more about them. I've read that the ideal Stirling cycle has four steps: 1) compression at a constant low temperature (radiator temperature) 2) heating to the temperature of a heat source 3) expansion at a constant high temperature (the temperature of a heat source) and 4) cooling to the temperature of the radiator. The strange thing about these engines is that they require the cylinder(s) to conduct heat into and out of the the gas during expansion and compression. This has to be done fairly slowly for good efficiency. I suspect that it would be easier to convert a normal gasoline engine to a steam engine than to convert it to a Stirling cycle engine. That would require a different valve system.

According to what I've read about the BMW Turbosteamer, an engine running on waste heat would make about 15% of the main engine power. A car going 60 MPH probably needs about 20 HP on a level road so the waste heat engine should be large enough to produce about 3 HP. If it were more powerful than that, it could produce more power when climbing hills.

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