New methodology for the identification of the leakage paths and guidelines for the design of common rail injectors with reduced leakage

The static leakage of a common rail (CR) injector is the flow-rate that is recirculated from the injector when the pilot-stage is not actuated. It is a critical issue in the development of modern CR injectors, because it can limit the maximum rail pressure level. An experimental methodology for splitting the static leakage between the contributions that pertain to the different leakage paths has been developed and applied to an innovative solenoid injector for the Brazilian, Russian, Indian, and Chinese (BRIC) market. The weak point of this injector was the excessively high static leakage compared to solenoid injectors for the European and U.S. markets. The static leakage splitting procedure allowed the sources of this leakage to be determined and a newly designed prototype was manufactured on the basis of the outcomes of this analysis. The new prototype featured a significant reduction (up to 54%) in the static leakage, compared to the original injector, and its leakage performance was almost the same as the typical one of Euro 5 solenoid injectors. Finally, a finite element method (FEM) analysis has been carried out on the improved BRIC injector. Guidelines are provided for a more refined design of some critical pieces of the component internal layout in order to further reduce its static leakage.