Development Work on the Synthesis of a Variable Stroke Slider-Crank Mechanism for a Variable Compression Ratio Combustion Engine

The subject of control of compression and stroke in engines is still a very contemporary research topic, and there is room for research in this matter, as can be asserted from the literature reviewed. In this paper, we report on the systematic methodology followed to perform the synthesis of a variable displacement slider-crank mechanism, needed to convert a non-road small commercial reciprocating single cylinder diesel engine to a variable compression ratio (VCR) engine for academic research purposes. Preliminary dimensions and space trajectories of the projected variable stroke multilink mechanism, constrained by the design of the base engine, were obtained using the coupler curves of Hrones and Nelson’s atlas. A genetic algorithm methodology was implemented to optimize the mechanism performance, as well as to give advantageous compression ratio and displacement behavior, according to both dimensional and kinematic fitness-criteria. A six links Stephenson structure was argued, as the base for a multilink variable stroke slider-crank mechanism, to alter the piston position and stroke variation ranges. With the obtained synthesized mechanism installed in the structure of the base engine, the compression ratio would be varied between 10 and 17.5, at the time that the actual range of piston displacement would be extended in a range between 23 and 38 %. The work conducted is part of a research under work, which pursues to construct the VCR multilink mechanism to install in the available engine.