Numerical Analysis of Cavitation-Induced Erosion in High-Pressure Fuel Injectors: under static and dynamic lift conditions

Licentiate thesis, 2024

Fuel injection systems are crucial for all modern combustion engines. These systems often operate under very high pressures to ensure fast spray breakup for optimal fuel air mixing leading to efficient combustion in order to meet strict emission standards. However, this high-pressure environment, combined with complicated geometries, can lead to sudden velocity and pressure changes within the fuel injector, making it susceptible to cavitation – a phenomenon where local pressure drops below the vapor pressure and the liquid fuel suddenly evaporates. Cavitation-induced erosion in fuel injectors affects combustion efficiency and system durability, presenting a challenge for analysis.

This study explores the numerical assessment of cavitation-induced erosion in high-pressure fuel injectors using computational fluid dynamics (CFD). Reynolds-averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) are employed with specific sub-models. Cavitation is modeled using the mixture transport of modified Zwart-Gerber-Belamri approach. The investigation starts with low and high lift static needle positions, comparing the results with experimental data to gain insight into erosion behaviour in an industrial heavy duty injector. To examine the effect of the surface deviations to erosion patterns, static high lift condition is modeled with CAD and Tomography Scan separately. Finally, the effect of the needle motion is carried out by implementing “wobbling” and “lift only” motion profiles using RANS.