On the formation of string cavitation inside fuel injectors

• Published in: Experiments in fluids 2014, Vol.55 (1), Article 1662
• Main Authors: Reid, B. A., Gavaises, M., Mitroglou, N., Hargrave, G. K., Garner, C. P., Long, E. J., McDavid, R. M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Computational methods in fluid dynamics; Energy; Energy. Thermal use of fuels; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fluid dynamics; Fluid- and Aerodynamics; Fundamental areas of phenomenology (including applications); Heat and Mass Transfer; Instrumentation for fluid dynamics; Physics; Research Article
• ISSN: 0723-4864; 1432-1114
• DOI: 10.1007/s00348-013-1662-8

The formation of vortex or ‘string’ cavitation has been visualised in the flow upstream of the injection hole inlet of an automotive-sized optical diesel fuel injector nozzle operating at pressures up to 2,000 bar. Three different nozzle geometries and three-dimensional flow simulations have been employed to describe how, for two adjacent nozzle holes, their relative positions influenced the formation and hole-to-hole interaction of the observed string cavitation vortices. Each hole was shown to contain two counter-rotating vortices: the first extending upstream on axis with the nozzle hole into the nozzle sac volume and the second forming a single ‘bridging’ string linked to the adjacent hole. Steady-state and transient fuel injection conditions were shown to produce significantly different nozzle-flow characteristics with regard to the formation and interaction of these vortices in the geometries tested, with good agreement between the experimental and simulation results being achieved. The study further confirms that the visualised vortices do not cavitate themselves but act as carriers of gas-phase components within the injector flow.