Experimental investigation and hydraulic simulation of dynamic effects on diesel injection characteristics in indirect acting piezo-driven injector with bypass-circuit system

Abstract

In recent years, the performance and emissions of HSDI diesel engines have been improved significantly by big progresses in the development of fuel injection equipment. This development is ongoing to fulfill stricter regulations by reducing emissions to near zero-impact levels while minimizing CO2. In most electro-hydraulic injectors for the common rail diesel fuel injection system the injection nozzle is opened and closed by the movement of an injector's needle which is balanced by pressure at the nozzle seat and at the needle control chamber at the opposite end of the needle. In this study, spray experiment and hydraulic simulation of piezo-driven diesel injector with bypass-circuit indirectly acting as a needle's driver have been investigated to evaluate the effect of injection control capability on spray formation processes and to predict the dynamic characteristics of the hydraulic component inside the injector by using AMESim numerical code. Results were compared with a conventional solenoid-driven injector equipped with the same micro-sac multi-hole injection nozzle. Further, a hydraulic model has been verified by comparison with the experimental results. It was found that a bypass-circuit type piezo-driven injector causes a short injection closing delay with where a rapid rate of falling slope of injection and a fast injection response and it had better injection control flexibility due to the hydraulic bypass system. Of course, the predicted simulation results in AMESim environment showed favorable agreement with experimental results.