Abstract
We summarize the results of a theoretical second law (exergy) analysis of an idealized internal combustion engine operating in flame versus volumetric (e.g., HCCI-like) combustion modes. We also consider the impact of exhaust heat
recovery. Our primary objective is to better understand the fundamental differences (if any) in thermodynamic irreversibility among these different combustion modes and the resulting impact on engine work output. By combustion
irreversibility, we mean that portion of the fuel energy that becomes unavailable for producing useful work due to entropy generation in the combustion process, exclusive of all other heat and friction losses. A key question is whether or not volumetric combustion offers any significant irreversibility advantage over conventional flame combustion. Another key issue is how exhaust heat recovery would be expected to change the net work output of an ideal piston engine. Based on these results, we recommend specific research directions for improving the fuel efficiency of advanced
engines.
