A Review of Internal Flow Fields in High-Pressure Common Rail Injector Nozzles

High-pressure common rail injector nozzles are key components of the fuel-injection system in modern diesel engines. The internal flow state and nozzle-exit flow characteristics directly affect fuel atomization, fuel–air mixing, and combustion performance. This article adopts a structured qualitative review method to analyze the research progress on the internal flow of high-pressure common rail injector nozzles. The existing research can be summarized into five directions: the influence of nozzle structure and operating parameters, non-circular nozzle structure, visualization experimental research, the influence of fuel properties, and artificial-intelligence-assisted optimization. The results show that nozzle geometry, injection conditions, fuel properties, cavitation evolution, and turbulence characteristics are the key factors affecting the internal flow behavior. However, current research still faces problems such as insufficient multi parameter coupling mechanisms, limited experimental verification under actual working conditions, uncertainty in numerical models, and insufficient generalization ability of artificial intelligence models. Based on the above analysis, future research needs to further develop high-precision multi physics simulation methods, advanced visualization technologies, and multi-objective intelligent optimization strategies to enhance the understanding of the mechanism and optimization design level of high-pressure common rail injectors.