Research On The Scavenging Process Of The Opposed Piston Opposed Cylinder Two-stroke Diesel Engine

Energy issues and the environment pollution has been more and more critical with the quickly development of ICE(Internal Combustion Engine)as well as being widely used.Exploring new structure,energy-saving,and environment-friendly ICE has a great significance.OPOC(Opposed Piston Opposed Cylinder)two-stroke diesel engine with high power dendity,low NVH(Noise Vibration and Harshness)and modular design can serve as the power source of UAV(Unmanned Aerial Vehicle)and business and military applications which has good prospects.There is not that much research on OPOC diesel engine which distributed on combustion process,valve timing,scavenging performance,etc.So far ther is short of the comprehensive study on scavenging process.The quality of scavenging process plays a big role on power,fuel economy performance and emission performance.So,studying on scavenging process is necessary.Allowing for the port-to-port uniflow scavenging of OPOC diesel engine,this paper built a 3D simulation model of a typical OPOC diesel engine with the software of ANSYS Fluent including test of mesh independence and turbulent model applicability.Some of the boundary condition was calculated by GT-Power 1D simulation model.The deviation of maximum explosion pressure and power of the engine between 1D simulation result and experiment data is smaller than 15%.The air input deviation between 3D simulation result and experiment data is less than 10% in 1500r/min,2200r/min and 2800r/min conditions.The 1D and 3D simulation models will work in the following study.Studying factors influence on scavenging performance based on the 3D simulation model of scavenging process.Results showed that with the increase of port height-ratio of swirl row,actual air input and scavenging efficiency reduced.But the swirl ratio of cylinder enhanced leading to nearly linearity increased capturing rate.When the port height-ratio of swirl row is 0.5,swirl ratio and actual air input increases with the port tangential angle of swirl row raising maximizing at 34o tangential angle.Also,scavenging efficiency and capturing rate increased at same time,achieving a big boost in scavenging performance.Comparing to original double intake double exhaust airway,scavenging efficiency of the single intake double exhaust distribution is higher with thesame port structure.But actual air input and capturing rate is lower.Besides,four-factors-three-levels orthogonal test of port height-ratio of swirl row,port tangential angle,engine speed and inlet-pressure indicated that the largest impact factor to scavenging performance is engine speed.The second one is inlet pressure,port height-ratio and port tangential angle of swirl row affect a little.Comparing the two port structure factors,port tangential angle has a bigger influence on scavenging efficiency,while capturing rate impacted more by port height-ratio.If inlet pressure is greater more0.97 bar than outlet-pressure,scavenging efficiency could be more than 90%.Actual air input impacted much more by inlet pressure than outlet pressure which is nearly linear correlation.Therefore,raising inlet pressure is the most effective method to improve OPOC diesel engine power.The result of this paper can be used optimizing and exploring prototype of OPOC diesel engine.Numerical calculating through simulation model could guide the structure desin of the engine.