Analysis And Optimization On The Uniflow Scavenging Process For The Opposed Piston Two-stroke Diesel Engine

Different from the traditional engine reciprocating internal combustion engine, opposedpiston opposed cylinder (OPOC) two-stroke diesel engine has simplified structure, lighterweight, high power density, uniflow scavenging, self-balancing and modular power unit andother advantages. Its performance depends largely on the process of scavenging. The poweroutput of an engine is directly proportional to how much air could be delivered and trapped inthe cylinder and how efficiently the trapped air is utilized. This article takes the method ofone-dimensional and three-dimensional numerical simulation to study the scavenging processof the OPOC engine scavenging process. Analysis the influence of the different structuralparameters of the exhaust port on Coefficient of charge, scavenging efficiency and airdelivery ratio of the intake and exhaust systems, reveal the airflow field of the scavengingprocess, optimize the valve timing and scavenging port structure, for achieve the object ofhigh scavenging efficiency and good scavenging quality. The mainly working content of thepaper is as follows:1. According to the work principle of the OPOC engine and the theory of the dieselengine work process computation foundation, a one-dimensional simulation model of theOPOC engine was established by using AVL BOOST software. Compare with the simulationresult and experimental data which confirmed the model is correct. On this basis, with theusing of the established model, the influences of the height of the exhaust port and the intakeport, the position of the exhaust port and the intake port on the OPOC engine scavengingprocess are researched. And each parameter is optimized; the optimal parameter values werefinal determined. Improve the structural parameters of the diesel engine in accordance withthe calculation results, and improved diesel engine and the original machine numerical simulation. The results show that the power was improved, and the economy has beenimproved in different degrees.2This paper uses AVL FIRE software to conduct three-dimensional simulationcalculation of scavenging process of OPOC engine based on the characteristics of scavengingprocess. And then, analysis the scavenging efficiency of the engine, the air flow and transientflow field in cylinder and validate the model. Change the structure of eddy intake port andsimulate these three schemes respectively, obtain the following conclusions from the results ofthe simulation: the program1is best scheme for clear the exhaust gas. Original angle ofelevation of the eddy scavenging port is too small, so that the airstreams from the annularscavenging port collision in the cylinder, forming a short-circuit gas flow near the centerlineof the cylinder, and the exhaust gas near the cylinder wall is hard to sweep. The angle ofelevation of the eddy scavenging port of the scheme2engine is too big, and then a lot ofpressurized fresh air directly collision on the cylinder wall, the exhaust gas in the vicinity ofthe cylinder wall is not likely to be swept away, so that the scavenging reduce the efficiencyof old and new gas mixing more serious.