Effect of Fuel Mass Flow at the End of Injection on Cavitation and Gas Ingestion in the Nozzle

Abstract

The fuel flow in the diesel engine nozzle has a vital impact on the fuel atomization and spray, and the fuel mass flux affects the internal flow of the nozzle. The visual experimental platform for a transparent nozzle was built to obtain the image of fuel flow in a nozzle with a small sac combining the back-light imaging technology and a high-speed framing camera. A two-phase three-component numerical model, based on the OpenFOAM solver, was calculated to quantitatively analyze gas ingestion and cavitation in the nozzle. The results indicate that at the end of injection (EOI), fuel cavitation and external air backflow (gas ingestion) occur successively in the nozzle, and both phenomena first appear in the orifice and then transition to the sac. Cavitation collapse is the major factor of gas ingestion, and the total amount of gas ingestion and cavitation mainly depends on the sac. The outflow of fuel largely depends on the total amount of cavitation and the inertial outflow of fuel at the EOI. The type of cavitation in the nozzle mainly presents annular and bulk cavitation, the former primarily exists in the sac, while the latter is established within the orifice. Therefore, larger mass flows will contribute to stronger cavitation and gas ingestion.