Experimental Investigation and Theoretical Modeling of Piezoelectric Actuators Used in Fuel Injectors

Piezoelectric actuators are increasingly used in fuel injectors. Experimental results for soft Lead Zirconate Titanate (PZT) actuators have shown that a significant amount of heat is generated when they are driven under high frequency and/or high electric-field magnitudes, both of which occur in fuel injectors. They also exhibit hysteretic nonlinear behavior when driven under high electric-field magnitudes. A mathematical model for self-heating that accounts for different controlling parameters relevant to fuel injection is developed in this paper, as well as a domain-switching model for PZT materials. The switching model is based on changes in potential energy, and accounts for full thermo-electromechanical coupling and the effect of temperature on domain switching. It is assumed that 180 switching is a two-step process caused by two 90 domain switching occurrences. The model shows good agreement with experimental results at different temperatures.