Optimal operating conditions for wet ethanol in a HCCI engine using exhaust gas heat recovery

The results suggest that the best operating conditions for the HCCI engine and heat exchanger system in terms of high power output, low ringing, and low nitrogen oxide emissions occur with high intake pressures, high equivalence ratios and highly delayed combustion timing. With a 2 bar absolute intake pressure, an equivalence ratio of 0.55, and a combustion timing near 8 CAD ATDC, 70% ethanol produced a power output of nearly 7.25 bar gross IMEP with low ringing and low nitrogen oxide emissions. This operating point was sustained by using heat transfer from hot exhaust gases into the intake charge, and thus no external heat addition was required - a substantial improvement over prior studies.