Effects of the geometrical features of flow paths on the flow behaviour of a multi-stage labyrinth pressure reducing valve throttling components

It is important to note that an inappropriate design of the valve can generate noise and vibration, causing harmful effects on both personnel and equipment.However, the impact of geometric parameters of throttling elements on the internal flow mechanism of pressure reducing valves and their effect on pressure drop and Mach number is not yet clear. To address this gap, we employ both experimental and numerical methods to investigate the flow mechanism and its impact on pressure drop and Mach number for various geometrical parameters. With these insights, we conduct a sensitivity analysis and adopt the L₉ (3⁴) orthogonal design method to optimize the design of the throttling components. The results demonstrate that steam flow within the MSLPRV operates in a supersonic regime. However, excessively high expansion coefficients (γ) can lead to structural changes that are too drastic, posing challenges for achieving stable pressure reduction and controlling the outlet Mach number within the flow channel. Moreover, we observe that the channel shape and outer wall radius (R/D_H) exhibit a weak functional relationship with the pressure drop and Mach number. To ensure a reasonable pressure distribution within the labyrinth flow channels, it is crucial to adopt a smaller internal wall radius (r/D_H) and appropriate channel depth(λ/D_H). Furthermore, under the same boundary conditions, increasing the number of stages (N) in the throttling components proves advantageous for achieving staged pressure reduction, thereby resulting in lower outlet Mach numbers and reduced kinetic energy within the flow channel. Finally, optimized design of labyrinth flow channels is achieved with expansion coefficients γ = 1.05, stage numbers N = 10, channel depths λ/D_H=1.2, and internal wall radius r/D_H=0.