Research On Working Cycle Of Doubly Two - Stroke Diesel Engine

Double opposed two stroke diesel engine is opposed piston opposed cylinder engine(OPOC engine). Due to its special structure, it had received extensive attention and research. Compared with the engine had traditional structure, special structure and the different working process of OPOC engine has many advantages, such as compact structure, light weight, small vibration, low noise, low fuel consumption and high power density.Due to the structure characteristics and operation mode of single cylinder double piston of OPOC engine are different from piston movement forms of the traditional internal combustion engine, Firstly, I analyzed the motion laws of internal and external piston of OPOC engine, On this basis, the variation of flow area of the inlet and outlet was obtained, which provided a reference for one dimensional performance simulation of OPOC engine.A one-dimensional simulation model of OPOC engine was established, and the performance of the OPOC engine is analyzed and the correctness of the one-dimensional model is verified. On this basis, taking the left cylinder of OPOC engine as the research object. I built the simulation model of 3D working process. The data of Pressure and temperature of the boundary condition can be obtained by one-dimensional simulation. Further analysed two stroke three-dimensional transient cycle(included free exhaust, scavenging, after inflation, compression, combustion and expansion) of the OPOC engine in different working conditions, investigated the transient changing law of the cycle under different speed, included sweep gas quality, gas flow, mixture formation and combustion and emissions generation.Analysis showed: with the increase of the rotating speed, the scavenging efficiency and the delivery ratio decreased gradually, the capture rate increased, and the maximum cylinder pressure decreased. In the process of sweeping gas and expansion, the average temperature in the cylinder increased with the increase of the rotating speed. In the process of combustion, the average temperature in the cylinder did not varies with the speed. Injector begined to inject the fuel at 345°CA, and ended at 370 degrees CA, the fuel begined to combust at 352°CA and ended 390°CA. The lower the speed, the higher degree of combustion reaction. The formation conditions of NO is high temperature and enriched oxygen, the formation conditions of Soot is high temperature and hypoxia, and the reaction occurred near of the high temperature region formed in the place of fuel oil beam end and the fuel and the wall surface collided each other. The mean NO mass fraction decreased with the increase of rotational speed, the maximum mass fraction of Soot also decreased with the increase of rotational speed. But due to oxidation, the final mean Soot mass fraction increased with the increase of rotational speed.