2. Most p-V diagrams show the power stroke as an “adiabatic process”. Which implies heat loss from the working fluid, the air/fuel charge (A/F). But, that too just ain’t so. If the heat of combustion did not make the engine hot it would collide with the second law of thermodynamics, which in its most understandable wording states “Heat always flows spontaneously from hotter to colder regions of matter.” If none of the heat of combustion went into the engine parts there would be no need for a cooling system and more of the heat’s energy could be converted into work. Professor Oppenheim correctly points out that heat loss to a cooling system could be vastly reduced with more suitable materials than aluminum which needs to be cooled to just over 200 C, or it loses its strength. The combustion chambers of traditional IC engines have to contain a flame front which is over 2.000 C, but aluminum melts at just 660 C, so a massive cooling system is needed so chamber parts aren't damaged.
Thankfully
aluminum is good at moving heat into the cooling medium because it has a thermal conductivity of
237 W/m K. We found a better material,
304 stainless steel, which has a working temperature of over
700 C and a thermal conductivity of just
16.2 W/m-K, which is 15 times more insulative than aluminum. It's like putting on that insulated jacket to slow your heat loss.
Another advantage of 304 SS is its ability to endure temperatures hot enough so that carbon will not condense on it and it is very reflective of radian heat. Another nice advantage of 304 is the combustion temperature if HCCI is used is only about 600 C, not a problem for 304 liners. This lower temperature of combustion also eliminates the danger of igniting the nitrogen into NOx.
Our piston design consists of a frame and top of 304 SS and the skirt is made of graphite which does a good job of conduction cooling of the SS sleeve and has very low friction. Other details are proprietary.