Developing Small Variable Compression Ratio Engines for Teaching Purposes in an Undergraduate Program

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 main goal of the project was to recognize and assess the possibility and means of modifying, adapting and building low cost variable compression ratio research engine units, for teaching purposes in Mechanical Technology program. To achieve this goal many design, technological, and experimental tasks were accomplished. The paper provides an overview of the VCR mechanisms developed.