Numerical analysis of influence of cavitation characteristics in nozzle holes of curved diesel engines

By targeting at the high-pressure common rail nozzle of diesel engines, we put forward a curved nozzle structure, established six groups of nozzle models with different curvatures. By using the CFD software STAR-CCM+, based on the incompressible fluid volume function (VOF) multiphase flow model, applying the K-Epsilon two-layer turbulence model, combined with the Schnerr-Sauer cavitation model, we investigated the degree of influence of the curved nozzle on the cavitation characteristics in the nozzle hole. Cavitation at the inlet, middle and outlet of nozzles was observed under injection pressure of 50, 100 or 150 MPa. The effects of curvature on cavitation were analyzed in detail according to cavitation volume fraction, cavitation volume content, mass flow, turbulent kinetic energy and velocity coefficient. It was found the curved nozzle can significantly reduce the cavitation degree in the nozzle holes, and the larger nozzle bending led to a smaller cavitation degree in the holes. Meanwhile, the average turbulent kinetic energy increased obviously and the average velocity decreased in both the holes and outlet, but the mass flow did not change much.