INVESTIGATION OF THE INJECTION RATE CHARACTERISTICS OF DIESEL SOLENOID INJECTORS IN SINGLE AND SPLIT INJECTION STRATEGIES

Understanding injection rate characteristics, particularly dwell-time variations and split injection behavior under high injection pressure, is essential for optimizing diesel combustion processes. This study experimentally investigates these parameters using the high-precision Zeuch method to measure injection rate profiles and fuel quantities for both single and split injection strategies. Experiments were conducted on a six-hole solenoid injector at rail pressures ranging from 800 bar to 1600 bar. A total energizing duration of 1.4 ms was applied either as a single injection or divided into 30%/70%, 50%/50%, and 70%/30% split ratios, with dwell-times varied from 0.2 to 1.8 ms. Results revealed that the first split injection exhibited a rate profile nearly identical to that of the single injection, regardless of dwell-time variation. In contrast, the second split injection was strongly influenced by fuel pressure oscillations within the injector and rail system. Its average quasi-steady state injection rate decreased from 40.1 mg/ms to 38.5 mg/ms as the dwell-time increased from 0.2 ms to 1.0 ms, and then recovered to 40.0 mg/ms when dwell-time further increased from 1.0 ms to 1.8 ms. Short dwell-times (0.2ms) led to merged injection rate profiles, increasing the injected fuel quantity by approximately 21.1% compared to the 0.6 ms dwell-time case, where the two injections were clearly separated. These findings highlight the critical influence of dwell-time on injection rate characteristics and provide valuable insights for optimizing diesel combustion phasing in split injection strategies.