Development of an Electromechanical Model for Piezo Actuated Common Rail Injectors

The challenge for the high speed direct injection (HSDI) diesel engines today is to reduce harmful emissions of diesel engines, such as particulate matter (PM) and Nitrogen oxides (NOx), and enhance the fuel efficiency and power. To meet this challenge, more accurate control of injection parameters such as the injection timing, injection rate, and injection quantity is required. Compared with solenoid actuated injectors, the piezo actuated injectors can reduce the transition time for the start and end of the fuel injection event, resulting in more accurate and faster injections, and are gradually replacing the solenoid injectors. In this study, an electromechanical model of a piezo injector is developed with MATLAB/Simulink. The piezo injector model consists of three subsystems: the piezoelectric stack actuator subsystem, the mechanical subsystem and the hydraulic subsystem. A lumped parameter electromechanical model is used for describing the nonlinear behavior of the piezoelectric stack actuator. Different operating conditions of the injection system are modeled and tested. The model has been used to provide insight into the operating conditions of the piezo injector and highlight the application to injection system design.