| Continuously tightening emission standards for heavy-duty diesel engines worldwide have led to a tremendous increase in the required capabilities of the diesel fuel injection systems in the last ten-twenty years, and this trend is expected to continue.;One of the significant enabling technologies available to the fuel injection system developer is the application of a piezoelectric actuation, in lieu of a conventional electromagnetic actuator. When properly designed, piezoelectric actuator is capable of delivering injection events with higher accuracy, precision and repeatability (both shot to shot and injector to injector). Additionally, the piezoelectric actuator can create more injection events consistently compared to a solenoid due to its speed of actuation.;One of the important tools in the development of effective piezoelectric actuators is the finite element analysis (FEA). Multilayer piezoelectric stacks have been successfully analyzed by FEA methods under steady state and harmonic (sinusoidal) excitation. However, published data on transient behavior of the multilayer stack under square pulse voltage is scarce. Meanwhile, the piezoelectric actuator in the diesel fuel injection application will be subjected exactly to such excitation. This dissertation provides a treatment of this modeling problem and provides insight into a stress field inside the stack, highlighting possibility of tensile stresses developing immediately after application and removal of voltage. Modeling offers an opportunity for optimization of the stack geometry for the best performance and response under the constraints of available space envelope, peak electric current and compressive prestress. |
