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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.

The purpose of this paper is to summarize the progress achieved by the Combustion Engine Laboratory at Technological University of Pereira in the practical implementation of variable compression methods adaptable to small single cylinder industrial engines. Three alternatives to vary the compression ratio have been studied and realized: the first one consists on the modification of the combustion chamber of a commercial diesel engine and its conversion to a dual ignition engine (spark and compression ignition); the second alternative involves the change of the base slider-crank mechanism of a Petter PJ1 engine by a multi-link mechanism controlled to change the piston stroke as well as the compression ratio; and the third alternative consists on the complete design and construction of a novel eccentric cam-based mechanism, developed to vary the TDC piston position, by modifying the distance between the crankshaft and the cylinder head in a custom-built developed engine.

The object of this paper is to present the operability of a variable compression ratio engine developed to study the combustion characteristics of alternative fuels under different speed and load regimes when exploitation parameters are changed. The variable compression ratio engine is a modification of a commercial single-cylinder diesel engine with adjustable combustion chamber volume, fuel, and ignition systems, envisioned to operate in spark ignition or compression ignition mode. After explaining the experimental plan, designed to evaluate the engine performance comprehensively, a sample of the engine performance and thermodynamic results under spark ignition mode for a chosen condition of speed and load operation with three compression ratio values (9, 12, 14) and three gasoline-ethanol blends is detailed. Torque, power, fuel consumption, and in-cylinder-pressure-related indicated parameters for the experimental cases carried out, are compared.