Design of a Dynamic Fuel Flow Estimator For a Piezoelectric Fuel Injector

An increasing desire for flexibility in a diesel engine's fuel injection system to help meet emissions, fuel consumption, and noise requirements motivates the use of piezoelectric actuated fuel injectors. Piezoelectric injectors can deliver more pulses per cycle and obtain tighter pulse spacing than solenoid injectors. Obtaining complex profiles is challenging, however, due to highly coupled dynamics inside the injector. Online estimation of injected flow rate shape could allow for closed-loop control of the piezoelectric injector, allowing the injection of sophisticated flow profiles. This paper summarizes the development of a physics-based, closed loop fuel flow estimator. Available measurements of piezo stack voltage and rail-to-injector line pressure are used for dynamic state estimation. Estimator results are compared against both open-loop simulation and experimental data for a complex profile of tightly spaced, varying sized pulses and shows improvement.