Abstract
Based on the introduction of opposed-piston two-stroke (OP2S) gasoline direct injection (GDI) engines, the OP2S-GDI engine working principle and scavenging process were analyzed. GT-Power software was employed to model the working process based on the structural style and principle of OP2S-GDI engine. The tracer gas method and OP2S-GDI engine experiment were employed for model validation at full load of 6000 rpm. The OP2S-GDI engine scavenging system parameters were optimized, including intake port height stroke ratio, intake port circumference ratio, exhaust port height stroke ratio, exhaust port circumference ratio, and opposed-piston motion phase difference. At the same time, the effect of the port height stroke ratio and opposed-piston motion phase difference on effective compression ratio and expansion ratio were considered, and the indicated work was employed as the optimization objective. A three-level orthogonal experiment was applied in the calculation process to reduce the calculation work. The influence and correlation coefficient on the scavenging efficiency and delivery ratio were investigated by the orthogonal experiment analysis of intake and exhaust port height stroke ratio and circular utilization. The effect of the scavenging system parameters on delivery ratio, scavenging efficiency and indicated work were calculated to obtain the best parameters. The results show that intake port height stroke ratio is the main factor for the delivery ratio, while exhaust port height stroke ratio is the main factor to engine delivery ratio and scavenging efficiency.
Highlights
The opposed-piston two-stroke engine (OP2S) concept can be traced to the late 19th century in Europe, and subsequently developed in multiple countries for a wide variety of applications including aircraft, marine vehicles, and land vehicles [1,2,3]
Redon et al [8] conducted an experiment researching an opposed-piston two-stroke engine; the results revealed that opposed-piston engine benefits high efficiency and low emissions
The OP2S-gasoline direct injection (GDI) engine working process simulation model was established based on GT-Power software
Summary
The opposed-piston two-stroke engine (OP2S) concept can be traced to the late 19th century in Europe, and subsequently developed in multiple countries for a wide variety of applications including aircraft, marine vehicles, and land vehicles [1,2,3]. 645.5 Nm at 1400 rpm, because of its potential for high power density and low fuel consumption, and is a viable advanced engine alternative. In the OP2S, two pistons moving in one cylinder make in-cylinder gas motion quite different from the conventional two-stroke diesel engine. Combustion chamber structure is different, resulting in the squish effects near minimum volume center in the OP2S being different from the conventional two-stroke diesel engines. The OP (Opposed-Piston) arrangement has no cylinder head, and the fuel injectors must be installed in the cylinder liner, which may result in a different combustion compared to conventional two-stroke diesel engines. The OP2S-GDI engine has some advantages in being a pure electric vehicle extender, since it is simple and compact, and has high power density and good balance [20].
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