Study on Dynamic Characteristics of High-Speed Solenoid Injectors by Means of Contactless Measurement 2017-01-2313

In-cylinder direct-injected technology provides a flexible and accurate optimization for internal combustion engines to reduce emission and improve fuel efficiency. With increasingly stringent requirements for the emissions of nitrogen oxides (NO_x) and CO₂, the content of injections in an engine combustion cycle has reached 7 to 9 times in gasoline direct injection (GDI) and the diesel engine with high-pressure common rail (HPCR). Accurate control of both time and quantity of injection is critical for engine performance and emissions, while the dynamic response of injector spray characteristics is a key factor.

In this paper, a test bench was built for monitoring the dynamic response of solenoid injectors with high-speed micro-photography and synchronous current collection system. Experimental studies on the dynamic response of GDI and HPCR solenoid injectors were carried out. Comparative study showed that there was a high correlation of the delay time of opening and closing of solenoid valves with solenoid current. The solenoid valves would not open until current rate reached to a threshold value. When they closed, there was a bump in current curve. Based on the above, the dynamic characteristics of solenoid valves such as opening delay and closing delay could be obtained. As for HPCR injectors, by monitoring and analyzing the pressure of injector inlets, injection duration could be further decomposed into opening process, full-open process and closing process. Compared with GDI injectors, the change of injection pressure had a great influence on the opening delay and the closing delay of HPCR injectors, but actual fuel injection duration was different.