Direct injection strategies have been successfully used on spark ignited internal combustion engines for improving performance and reducing emissions. Among the different technologies available, outward opening injectors seem to have found their place in renewable applications running on gaseous fuels, including natural gas or hydrogen, as well as in a few specific liquid fuel applications.
In order to understand the key operating principles of these devices, their limitations and the resulting sprays, it is necessary to accurately describe the pintle dynamics. The pintle’s relative position with respect to the injector body defines the internal flow geometry and therefore the injection rates and spray characteristics.
In this paper both numerical and experimental investigations of the dynamics of an outward opening injector pintle have been carried out. The injector average flow rates and instantaneous pintle position have been experimentally measured at a variety of pressures and injection durations using air as the working fluid. In addition to the experimental measurements, the injector internals were thoroughly measured and characterized so that a high-fidelity numerical model could be assembled.
A multi-physics model featuring a simplified electromagnetic representation of the injector solenoid and a spring-mass-damper system for the pintle dynamics integrated with a 1-dimensional computational fluid dynamics description of the internal flow using two-way fluid-structure-interaction coupling was developed in the commercial software GT-Suite. The model is capable of accurately predicting the pintle position and average flow rates, at a variety of conditions, using working fluid pressure and injector current profile as the only inputs.