CFD Simulation And Analysis Of Scavenging Process For Two-stroke Marine Diesel Engine

Scavenging process of two-stroke marine diesel engines largely determines the formation quality of fuel mixture, and then determines the performance of combustion etc. As an important part of the two-stroke uniflow scavenging diesel, the scavenging port's structure directly affects the intake flux of fresh air and the exhaust cleanliness of combustion gas. In addition, the diesel's rotational speed, also affect the process of scavenging.6S50MC-C diesel engine is studied by using the method of CFD (Computational Fluid Dynamic), and CFD software Fluent is applied. First, the number, the elevation/radial angle and the structure of scavenging port are changed, and the scavenging process is simulated. Then the simulation is carried out like above mentioned at different diesel's rotational speed. Some parameters like pressure, temperature, turbulence intensity, mass flow of inlet, velocity etc. and the distribution of these parameters can be obtained. By analyzing its flow status, some reasonable structural and operating parameters can be found.Firstly, the fluid space of port, in-cylinder part, and exhaust passage above the cylinder is modeled. Then, GAMBIT is used to mesh the model, meanwhile, pressure inlet/outlet boundary condition is set. Afterwards, the mesh is imported to Fluent, parameters are set, the dynamic mesh model is enabled, and then calculate begins. Finally, with the help of post-processing procedure, lots of data, contours, vector, path lines etc. can be obtained, so analysis can be done. It can be found with the appropriate range, operating in low rotational speed, increasing the number of scavenging ports, using 0°elevation angle and 20°radial angle may benefit scavenging process and the formation of oil and air. Meanwhile, when operating in lower or higher rotational speed, the influence of elevation angle becomes smaller on the scavenging process. So it can provide theoretical basis for diesel's structural optimization and solving problem of combustion, emission etc., therefore there is a certain practical significance.