Study On Injection Characteristics Of Marine Common-rail Injector Under Thermal Effect

With the exhaustion of fossil energy and serious environmental pollution,achieving high efficiency and ultra-low emissions of diesel engines has become the goal of scientific researchers.Meanwhile,the electronically controlled high-pressure common-rail fuel injection system is one of the core technologies for modern marine diesel engines to achieve energy saving and emission reduction.The common rail injector is the core component of the high-pressure common rail system,and its injection characteristics directly determine the quality of the fuel-gas mixture in the cylinder,thereby affecting the economy and emissions of the diesel engine.In this paper,a three-dimensional simulation study of the fuel flow in the orifice of the common rail injector was carried out for the three states of isothermal incompressibility,isothermal compressibility and non-isothermal compressibility of fuel.The calculation results are compared with the experimental data,including mass flow and temperature,which proved that the non-isothermal compressibility flow of fuel needs to be considered in the flow calculation of common rail injector.For the high-pressure common-rail injectors of marine low-speed engines,three-dimensional software Fluent was used to carry out the flow simulation of the oil inlet and outlet hole of the control room,and nozzle hole.The flow coefficient of the above-mentioned hole was obtained,which provided accurate boundary input for the subsequent one-dimensional simulation of the fuel system.The dynamic response experimental study was carried out for the large section high-speed solenoid valve,and the change of armature lift with time in the actual working process of the high-speed solenoid valve was analyzed.Additionally,the modeling methods of solenoid valve models based on dynamic electromagnetic force and static electromagnetic force MAP diagram were analyzed,respectively.Based on the comparison of the calculation results and the experimental data,a reasonable calculation model for the dynamic response of the large cross-section solenoid valve based on the AMESim software was obtained,which provides a basis for the construction of a mathematical model for the low-speed common rail injector with high prediction accuracy.A dynamic injection mathematical model of the common rail injector for marine low-speed engines was established in the AMESim software.This model takes into account the non-isothermal compressibility during fuel flow.The calculated results are in good agreement with the cycle fuel injection quantity and the steady-state temperature rise data at the nozzle obtained from the experiment.Based on the above-verified model,a simulation study of injection characteristics under different fuel temperature and high temperature in the cylinder was carried out.The key parameters and their influence rules affecting the cycle fuel injection quantity of the common rail injector of low-speed engines were revealed,which provided technical support for the optimization design of the low-speed engine fuel system.