Improvement of Working Parameters in an Opposed Piston CI Two-Stroke Engine by Modelling Research

Two-stroke opposed piston engines (2sOPEs) have great potential for industrial applications due to their simple design, technology and high efficiency, particularly with a turbocharging system. The paper presents possibilities for altering 2sOPE working parameters by changing geometrical parameters and boosting parameters. Obtaining higher engine efficiency is realised by altering the crank phase shift of the exhaust piston in relation to the transfer piston. It has been assumed that only the piston of the exhaust cylinder changes its position relative to the piston in the cylinder with transfer ports. Modifying the scavenging process by changing pistons’ position through connecting with two crankshafts enables asymmetrical scavenging timing. Closing the exhaust ports before the compression process and extending the time allotted to empty exhaust gases from the cylinder provides greater engine work, and a high boost ratio increases engine power. This type of engine was recently recommended for power plant stations. The paper includes mathematical modelling of thermodynamic parameters of 2sOPE and full analysis of engine work with scavenging and combustion processes for different timing phases. This endeavour is based on the geometry of the compression ignition Leyland L60 engine and uses the author’s own 0-1-D computer program and considering unsteady gas flow and computational fluid dynamics (CFD) modelling. Simulation tests indicate a high scavenging efficiency, good penetration of injected fuel and fast combustion process. The work contains figures of pressure, temperature traces and emissions of the main chemical species in exhaust gases, with comparisons of engine works for different timing phases. Applying a non-symmetrical scavenging process in a 2sOPE by closing exhaust ports earlier increases working parameters. Despite a shorter expansion time, the expansion work of this engine is larger when the exhaust port is opened earlier rather than later. A 2sOPE with earlier opening of exhaust ports decreases nitric oxide emission due to a lower combustion temperature. This study is a contribution for the future realisation of such processes in power plant engines with different fuelling systems