Abstract
A 5-stroke engine was analyzed using an improved 2-zone combustion model utilizing an equilibrium combustion model to calculate the gas properties in each zone. The flows of inlet, exhaust, and transfer port are handled using quasi-steady 1-D flow models. Heat transfer in the transfer port is also considered. The results are reported as indicated thermal efficiency and power output over a range of operating points and design characteristics, including engine RPM, compression ratio, overall expansion ratio, expansion cylinder clearance volume, and transfer port volume. It was found that the transfer port volume had a significant effect on the overall indicated thermal efficiency. The results were compared with those of a baseline 4-stroke engine. The 5-stroke engine with a compression ratio of 9:1, and an overall expansion ratio of 27:1 achieves a peak indicated thermal efficiency of 47%, representing a 6% increase over the baseline 4-stroke engine with the same compression ratio.
