Study on Characteristics Optimization of Combustion and Fuel Injection of Marine Diesel Engine

Abstract

Compared with discharge valve chamber volume, high-pressure tubing diameter shows more influence on injection mass and SMD. The opening pressure of needle valve is more sensitive to SMD. An overall simultaneous reduction of pollutant emissions was obtained, alleviating the trade-off relations between NO and soot emissions. Reasonable optimization of spray angle can improve power, economy and emission performance simultaneously. Highlights: The emission requirements of diesel engines are becoming increasingly strict and reducing emissions has become the key technology. In view of this development trend, the influence law of fuel injection on emission is studied in this paper. Numerical studies were performed to analyze the structural parameters of fuel injection system on combustion and emission characteristics of marine diesel engines. The numerical modelling was validated based on single-cylinder diesel engine tests and fuel injection tests. After investigating the single structural parameters on the fuel injection characteristics, the orthogonal method was used to design the double-parameter structural optimization scheme of the fuel injection system. There are 22 optimized cases selected to further investigate using the CFD method by visualizing scalar distributions in cylinder, which was helpful to explain the reason of pollutant formation. Comprehensively comparing the performance of each fuel injection system’s structural optimization scheme, moderate reduction of the discharge valve chamber volume and high-pressure tubing diameter would increase injection mass, along with faster injection rate and boosted injection pressure, leading to reduced Sauter mean diameter (SMD). Considering pollutant emission characteristics as well as economic and power concerns, case D6 with spray angle enlarging 5° showed best performance. Compared with the original condition, there was no NO deterioration and large reduction of soot emission by 65.4%, along with fuel consumption being lowered by 2.18% and more indicated power, by 2.21%. Therefore, reasonable optimization of spray angle can improve power, economy and emission performance simultaneously.