New High Quality Diesel Nozzle DLLA157P855 for Injection Nozzle Diesel Engine Parts

Abstract
Cavitation inside high-pressure fuel injector nozzles is a critical factor influencing spray formation, fuel atomization, and injector durability. Under extreme injection pressures exceeding 200 MPa, local low-pressure zones often cause vapor bubble nucleation and collapse, leading to pressure fluctuation, erosion, and unstable spray behavior. This study establishes a multiphysics coupled model integrating fluid dynamics, cavitation thermodynamics, and structural response to investigate the mechanisms of cavitation generation and its suppression strategies in injector nozzles.

Using Computational Fluid Dynamics (CFD) combined with the Rayleigh–Plesset cavitation model, the internal flow field was simulated under varying needle lift, injection pressure, and temperature conditions. The results revealed that cavitation primarily originates near the orifice inlet corner and expands along the inner wall due to sharp pressure gradients and high shear flow. The collapse of vapor bubbles near the outlet produces strong micro-jets and shock waves, which induce wall erosion and pressure oscillation.

To accurately capture the dynamic interactions, a fluid–structure interaction (FSI) model was developed, coupling the transient wall deformation with the cavitating flow field. The analysis indicated that structural elasticity slightly reduces local pressure peaks but may also amplify secondary cavitation under resonance conditions. Experimental visualization using a transparent acrylic nozzle and high-speed imaging validated the numerical predictions, showing strong agreement in cavitation morphology and oscillation frequency.

Several cavitation suppression strategies were proposed and evaluated, including:

1. Orifice geometry optimization (rounded inlet and convergent-divergent profiles) to mitigate pressure drop;

2. Surface micro-texturing to control boundary layer separation and stabilize flow;

3. Material modification and coating application (e.g., DLC, ceramic-based coatings) to enhance erosion resistance.

Simulation results showed that the optimized design reduced the cavitation volume fraction by 34% and improved outlet flow uniformity by 21% compared with the baseline configuration.

In conclusion, the study demonstrates that a multiphysics coupled simulation framework is essential for accurately predicting cavitation dynamics and guiding structural design improvements. The proposed suppression strategies provide a theoretical and engineering basis for developing next-generation high-pressure injectors with improved durability, reduced flow fluctuation, and enhanced atomization performance.