Quote:
Originally Posted by IamIan
It works in a steam engine because there is more energy available from the cylinder walls due to the heat of what ever is being burned ... than the energy just from the hot air.
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Well, a piston steam engine is a different animal. Steam is not created in the cylinder, it is let into the cylinder. Water is heated in a pressurized vessel to well above 100C. When a valve is opened to release/inject/whatever the water it instantly converts to steam and will drive the piston down.
Quote:
Originally Posted by IamIan
#1> In a different engine designed to take advantage of it ... the timing of the piston being exhausted could be set equal to the power stroke of an opposed piston ... lower pressure on the second part from cooler temperature exhaust gasses creates a larger pressure difference to move the power stroke piston with.
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On any inline 4, the power stroke of 1 cylinder will always be opposite the exhaust of another. The effect you are describing is similar to what a tuned header does... only without the need for any complex water injection system.
Quote:
Originally Posted by IamIan
#2> If the water is inside a confined heat exchanger pipe ... the water will expand in the pipe which could drive a turbine or other piston... thus extracting some useful energy / work from the otherwise exhaust gas.
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And this is what BMW's gas turbine concept is.