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Improvement of Working Parameters in Opposed Piston CI Two-Stroke Engines by Modelling Research
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 15, 2020 by SAE International in United States
The opposed piston two-stroke engines (OPE) have very high potential for industrial applications by simple design, technology and also by high efficiency, particularly with turbocharging system. The paper presents possibilities of change working parameters of two-stroke diesel engine with opposed pistons by changing geometrical parameters and charging parameters. Obtaining of higher engine efficiency is realized by change of crank phase shift both cylinders. It was assumed that only the piston of the exhaust cylinder changes its position relative to the piston in the cylinder with transfer ports. Modification of scavenging process by changing pistons' position connecting with two crankshafts enables asymmetrical scavenge timing. Decreasing of shorter time of closing exhaust ports before compression process and longer expansion process give higher engine work and with high charging ratio increases engine power. This type of engine is recently recommended for power plant stations. The paper includes mathematical model of thermodynamic parameters of opposed CI two-stroke engine and full analysis of engine work with scavenge and combustion processes for different timing phases based on geometry of the CI Leyland L60 engine by using own 0D computer program taking into account unsteady gas flow and also CFD modelling. Simulation tests indicate a high scavenge efficiency, good penetration of injected fuel and fast combustion process. The work contains figures of pressure, temperature traces and emission of main chemical species in exhaust gases with comparison of engine works for different timing phases. Applying of non-symmetrical scavenge process in the two-stroke OPE by earlier closing of the exhaust ports increases working parameters. Despite shorter expansion time the expansion work of this engine is bigger at earlier exhaust port opening than at later opening. Two-stroke OPE with earlier opening of exhaust ports enable decreasing of NOx due to lower combustion temperature. The study is an input for realization of such processes in a future of power plant engines with different fuelling systems.