Abstract
The combustion and efficiency of an extended expansion general-purpose engine employing a multiple linkage system with that of a conventional engine consisting of the same component parts, with the exception of the linkage system. The results show that this extended expansion increases indicated thermal efficiency from 29.6% to 33.2%. In addition, as the piston speed near the compression top dead center of this engine is slow, mass fraction burned depends upon the change in the cylinder volume, relative to the combustion chamber volume during the combustion period. The change of the minimum spark advance for best torque (MBT) timing relative to load is smaller than that of the conventional engine. In addition, measurements of drive loss during motoring operation show that the friction of this engine is approximately the same as that of a conventional engine. As a result, brake thermal efficiency of the test engine was increased by approximately 13%, from 20.1% of the conventional engine to 22.7%, under the EPA mode with fixed ignition timing operation.
Keywords: Power Unit, Thermal Efficiency, Extended Expansion, Atkinson Cycle