Abstract
The electromagnetic valve (EMV) is a critical control element in modern diesel fuel injection systems, determining the precision and stability of injection timing. Under high-pressure and high-frequency operating conditions, the interaction between thermal effects and magnetic performance significantly influences valve dynamics and reliability. This study establishes a thermal–magnetic coupled simulation model to investigate the influence of temperature rise on electromagnetic characteristics and dynamic response behavior of diesel injector valves.

Using finite element analysis (FEA) and multi-physics coupling techniques, the transient magnetic field, eddy current distribution, and coil temperature evolution were jointly simulated. The model incorporates nonlinear magnetic material properties and temperature-dependent electrical resistivity to accurately represent real operating conditions. Simulation results show that coil temperature increases lead to a notable decrease in magnetic flux density and attraction force. When the temperature rises from 25°C to 150°C, the magnetic attraction force drops by approximately 14%, and the valve response delay increases by 22%.

To mitigate performance degradation, various thermal management strategies were analyzed, including optimized coil winding density, improved core materials with higher Curie temperature, and the introduction of heat-dissipating channels within the housing. The implementation of a copper–graphite hybrid heat path reduced coil temperature rise by 18%, effectively maintaining stable electromagnetic performance during continuous high-speed operation.

Experimental validation using a high-frequency injector test bench confirmed the simulation accuracy. The measured coil temperature, magnetic flux, and actuation timing correlated closely with simulation results, with deviations within ±5%. The proposed thermal–magnetic coupled model thus provides a reliable prediction tool for performance evaluation and design optimization of injector electromagnetic valves.

Keywords: diesel injector, electromagnetic valve, thermal–magnetic coupling, multi-physics simulation, dynamic response, temperature effect

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1. Introduction

2. Modeling and Governing Equations

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4. Experimental Validation

5. Conclusions

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CFD–DEM Coupled Simulation and Early Warning Model of Spray Hole Clogging Process in Injector Nozzles

Abstract
The clogging of injector nozzle orifices is one of the key factors leading to unstable fuel injection, poor atomization, and increased emissions in diesel engines. This study proposes a computational fluid dynamics–discrete element method (CFD–DEM) coupled approach to investigate the microscale evolution mechanism of the clogging process in injector spray holes and to establish an early warning model based on flow field variation characteristics.

In the simulation, the liquid–solid two-phase flow inside the nozzle was modeled, where soot particles, fuel impurities, and cavitation bubbles were considered as discrete elements. The CFD module solved the transient fuel flow, pressure distribution, and cavitation behavior, while the DEM module tracked the particle motion, collision, and adhesion within the spray hole. A coupled interaction algorithm was implemented to capture the feedback effects between fluid dynamics and particulate accumulation under different injection pressures and temperatures.

Results show that when the particle diameter exceeds 2 μm and the local wall temperature surpasses 120°C, adhesive particle accumulation near the hole entrance significantly accelerates clogging formation. The velocity gradient and wall shear stress were identified as key parameters influencing deposition patterns. Furthermore, the study developed an early warning model using characteristic indicators such as injection flow rate decline, pressure oscillation amplitude, and cavitation frequency shifts. The model successfully predicted the onset of clogging with an accuracy above 92% when validated against experimental injector flow data.

This research provides both theoretical and engineering insights for real-time monitoring and clogging prevention in high-pressure fuel injectors. The established CFD–DEM framework enables multi-physics coupling analysis of complex particulate–fluid interactions and offers a foundation for future optimization of nozzle geometry and fuel filtration design.

Keywords: injector nozzle, clogging process, CFD–DEM coupling, multiphase flow, particle deposition, early warning model