Design And Performance Study Of Marine Low-speed Electro-mechanical Fuel Injector

With the increasing tightening of emission regulations,the global shipping industry’s performance requirements for marine low-speed diesel engines continue to increase,which poses a challenge to low-speed engine fuel systems,requiring marine low-speed injectors for more flexible injection control and higher injection pressure.However,the heavy moving parts of the traditional low-speed injectors and the poor fuel quality seriously restrict the response speed of the marine low-speed injectors,and the low hydraulic efficiency of the traditional low-speed injectors also limits the injection pressure.Aiming at this situation,this paper designed a three-orifice injector to analyze the influence mechanism of main parameters on fuel injection characteristics,optimized oil quantity characteristics and response characteristics,and studied the stability of injector process.Firstly,the conceptual design of the three-orifice injector was carried out.The numerical simulation model of the injector was built and assigned by the hydraulic simulation software platform.The electromagnetic force finite element simulation software was used to establish and optimize the electromagnetic force calculation model,and the electromagnetic force MAP is obtained.The electromagnetic force MAP was input into the numerical simulation model of the injector as an electromagnetic conversion unit.Secondly,the influence law and mechanism of the three-orifice structure parameters on the response characteristics and oil quantity characteristics of the injector were studied.The single-factor analysis of the parameters of the solenoid valve assembly and the needle valve assembly was carried out.The research showed that the diameter of the ball valve and the diameter of the seat,the preload of the solenoid spring,the diameter of the needle seal and the preload of the needle spring had a significant effect on the fuel injection characteristics.The response characteristics and oil quantity characteristics were optimized by multi-objective optimization method.After optimization,the on-time and closing time of the electronically controlled injector were shortened by 0.39 ms and 1.26 ms,respectively,and the opening response speed and closing response speed were increased by 8.23% and 13.56%.Finally,aiming at the stability of multiple injections of the system,a pressure fluctuation decomposition method was proposed,which reveals the main causes of the injection pressure fluctuation and its influencing factors,and studies the influence of the three-orifice structureon the important characteristics of the injection pressure fluctuation and draw the law of its influence.The fluctuation characteristics of multi-injection oil quantity and its influence law were studied.The influence mechanism of the previous injection on the post-injection in the pre-primary injection and the main post-injection was studied.The research shows that the main injection in the pre-main injection process was opposite to the main injection.The phase of the pre-spray was the main factor affecting the fluctuation of the main spray,and the fluctuation of the oil volume in the main post-injection process was affected by the displacement of the rear needle valve in addition to the main post-injection phase.