To reduce the transient pressure oscillations (hunting) in pilot valves used in control systems of nuclear power plants, this study investigates the effect of orifice angle design using computational fluid dynamics (CFD). A conical orifice geometry with a base radius of 1.25 mm and a length of 1 mm was modeled with varying angles (10°, 20°, and 30°). The models were analyzed using transient flow simulation in ANSYS CFX, applying a k-ω turbulence model to accurately capture near-wall flow characteristics. The results showed that larger orifice angles led to reduced pressure hunting, improving system stability. Additionally, velocity and pressure distributions demonstrated smoother flow and smaller fluctuations at higher orifice angles. The findings indicate that optimizing orifice angle is an effective strategy to suppress pressure hunting in pilot valve systems.

Abstract
1. 서 론
2. 유동해석
    2.1 Analysis model
    2.2 Mesh
    2.3 Methodology
    2.4 Results and Discussion
3. 결 론
References

• 곽효서(Assistant professor, Mechanical Engineering Major, Dong-Eui University) | Hyo-seo Kwak Corresponding author