Impact of Extended Expansion Stroke on Spark Ignition Engine Operation Indicators with Multiple Linkage System

Increasing the efficiency of an internal combustion engine is possible thanks to the use of an extended expansion stroke relative to the suction stroke. This solution was first patented by James Atkinson in the construction of an internal combustion engine in the XIX century. The article presents a solution using the principle of extended expansion stroke. In the design of Szymkowiak's proprietary engine, a conceptual crank-piston system was used with additional elements enabling the Atkinson cycle to be obtained. A 3D model was created based on which forces acting in the system were tested. The generated piston path profile allowed to characterize its movement. A mobile mesh of the combustion chamber was created, thanks to this a detailed CFD simulation was performed in the AVL Fire software. An important criterion was the assumption of adiabatic characteristics of processes during the combustion. This made it possible to isolate the system from the ambient and, as a consequence, thermal losses were avoided. The Extended Coherent Flame Model (ECFM) combustion model was used, which is characterized by high flexibility of usage in this type of numerical combustion simulations. The fuel used was gasoline. The equivalence ratio has been set to 1. The obtained thermodynamic indices of the combustion process in the spark ignition engine were analyzed and referred to the indices obtained from the conventional engine.