Study of the influence of the needle eccentricity on the internal flow in diesel injector nozzles by computational fluid dynamics calculations

Abstract

(October 2012) In the present paper, a computational study has been performed in order to clarify the effects of the needle eccentricity in a real multihole microsac nozzle. This nozzle has been simulated at typical operating conditions of a diesel engine, paying special attention to the internal flow development and cavitation appearance within the discharge orifices. For that purpose, a multiphase flow solver based on a homogeneous equilibrium model with a barotropic equation of state has been used, introducing the turbulence effects by RANS methods with a RNG k-ε model. The results obtained from this investigation have demonstrated the huge influence of the needle position on the flow characteristics, showing important hole to hole differences.

Analysis of diesel spray dynamics using a compressible Eulerian/VOF/LES model and microscopic shadowgraphy

“…A uniform pressure boundary with a turbulent intensity of 4.4% is applied over the sac entry plane. Thus, any effects due to turbulence or flow asymmetry generated in the passage between the needle and seat [60][61][62][63][64] air. This initial stage is somewhat arbitrary and the rationale is described in Ghiji et al [65].…”

Comparative study of the internal flow in diesel injection nozzles at cavitating conditions at different needle lifts with steady and transient simulations approaches

“…This phenomenon was also detected computationally by means of a simulation of the flow with a Volume Of Fluid (VOF) model implemented in STAR-CD. The effects of needle eccentricity were also studied computationally with OpenFOAM by Salvador et al, 29 who observed important hole-to-hole differences in the internal flow and strong variations in the cavitation generated among the orifices. Salvador et al showed that an eccentric position of the needle produces lower values for mass flow, momentum flux and effective velocity at the nozzle exit.…”

Comparison of Different Techniques for Characterizing the Diesel Injector Internal Dimensions

“…Many of these studies focus on the effects of the injector geometry on the injection system performance [15]- [17]. On the one hand, the dimensions of the injector internal passages, including the control volume orifices, are critical for the injector needle dynamics and consequently the opening and closing slopes of the injection rate profile [18]- [20]. These effects are particularly important when using multiple injection strategies, since the injector acoustics also affect the needle motion [21], [22].…”