Numerical Simulation On Lateral Combined Spray And Combustion Of Dual Opposed Diesel Engine

Dual opposed diesel engine have both the structure advantages of opposed piston engine and opposed cylinder engine. Due to the special opposite intake and outlet piston form which makes traditional engine piston relative velocity is twice faster than dual opposed diesel engine. At the same time, the special arrangement of the inlet and exhaust port determines that the mixture can only rely on weak swirl, which easily lead to non-ideal mixing effect, high soot and NOx emissions during fuel injection and combustion, etc.In order to improve the emission performance, this paper intended to study the fuel injection and combustion process of dual opposed diesel engines by optimizing the key parameters of its spray and combustion. the main research content and results include:(1) According to the motion law of dual opposed diesel engine inlet and exhaust piston and its special structure, the intake and exhaust piston top surface shape and the cylinder sleeve which were extracted by using three-dimensional model software were joint to build combustion chamber physical model, and then lateral combined spray and combustion progress mesh model of dual opposed diesel engine were established.(2)The asymmetric injector volume bomb experiment showed that the injection pressure and combustion chamber pressure is the main factor which affected the shape of spray. Based on the test results, mesh adaptation and model study on the adaptability were carried out to determine the size of the grid and turbulence model for dual opposed diesel engine spray and combustion calculation.(3) Aimed at different injector hole arrangement mode and pre injection scheme of duel opposed diesel engine, the dual opposed diesel fuel spray progress and combustion were simulated. It could be concluded that the uniform distribution of fuel oil in the combustion chamber can be realized by the proper arrangement of injector holes, and the pre injection method can shorten the ignition delay period, which enlarge the distribution range of the combustible mixture in the cylinder. With the increase of pre injection fuel quantity, the production of nitric oxide increased, while the peak of the emission of carbon smoke decreased.(4)Pre injection and post injection scheme has a weak effect on reducing nitricoxide emissions, while post injection scheme has a more significant effect on reducing the soot emissions, and the bigger the interval angle between main-injection and post injection is, the more soot emissions decreased. When the volume of the rear spray amount is 5% of the main injection, the proper large main injection and post injection interval angle will help to reduce the soot emission.(5) Simulated the calculation of dual opposed diesel engine lateral combined spray and combustion, the results show that: under different conditions, through reasonable hole layout and appropriate pre injection and post injection scheme can be a certain way to reduce nitric oxide and carbon smoke emissions.The results of this study have certain guiding significance for low emission combustion of dual opposed diesel engine.