Experimental Study on the Effect of Cavitation on Pressure Fluctuations in Optical Diesel Nozzles and Spray Characteristics

The influence of the cavitation effect on the diesel engine nozzle is based on the following aspects: flow and spray characteristics, cavitation erosion on the nozzle wall, and pressure fluctuations of diesel fuel in the system. The first two have been extensively studied, but the research on the third one is rather limited. In this article, the synchronous acquisition, data processing system of cavitation, pressure fluctuations of diesel fuel, and spray characteristics inside the transparent nozzle were examined, then the direct correspondence among pressure fluctuations and cavitation phenomenon was explored. Experimental studies under steady injection pressure and fixed needle lift show that: during the process of transforming hole-to-hole string cavitation to needle-originated string cavitation, the pressure fluctuation amplitude increases significantly. String cavitation under low pressure is easily converted into geometry-induced cavitation due to morphological instability, which has a large disturbance to the spray cone angle. String cavitation under high pressure is more intense with the pressure fluctuation is relatively large and its intensity is weaker than the geometry-induced cavita-tion intensity under the same pressure; however, both the pressure fluctuation amplitude and spray cone angle are much larger. The peak pressure of string cavitation is higher than that of geometry-induced cavitation. In the process of the disappearance, fracture, and fusion of string cavitation, the pressure fluctuation amplitude increases significantly. The results of this experiment play a crucial role in the effective control of pressure fluctuations in the system.