Resistance characteristics of labyrinth throttle based on central composite design

<bold>Background</bold>Labyrinth throttle can greatly reduce pressure in a short distance and reduce fluid noise and vibration, hence is widely used in engineering fields such as nuclear power to control and adjust the flow, pressure and velocity of coolant fluid, ensuring the safety and stability of nuclear power plant system. Because the thermal hydraulic parameters of the reactor are often adjusted during design and operation, the pressure drop required to be achieved through the labyrinth throttle will also be adjusted. The local resistance coefficient of labyrinth throttle is determined by many factors, including the number of baffles (<italic>n</italic>), the distance between baffles (<italic>d</italic>) and the ratio of baffle height to pipe diameter (<italic>C</italic>). At present, the relationship between the local resistance coefficient of labyrinth throttle and these factors is not clear.<bold>Purpose</bold>This study aims to investigate the specific impact of geometric parameters on the local resistance coefficient, offering insights for the design of labyrinth throttling components.<bold>Methods</bold>Firstly, the labyrinth throttling parts with baffle height of 60 mm, baffle spacing of 15 mm, thickness of 10 mm and number of 20 were taken as the research object for mesh independence analysis. Subsequently, several throttles with different parameters were designed, and the distribution of flow velocity and pressure and the change of pressure drop inside the labyrinth throttle were studied. Then, according to the central composite design, 15 throttles with different parameters were designed and their local resistance coefficients were calculated using computational fluid dynamics software FLUENT. Finally, the independent effect and mutual effect of different parameter changes on the local resistance coefficient were calculated, and the specific influence of geometric parameters on the local resistance coefficient was obtained.<bold>Results</bold>The calculation results show that when the inlet mass flow rate is constant, the local resistance coefficient is mainly related to the ratio of baffle height to pipe diameter and the number of baffles. The ratio of baffle height to pipe diameter plays a major role, and the baffle spacing has little effect on the local resistance coefficient. The independent effect factors of the labyrinth throttle's geometric parameters are <italic>M</italic>(<italic>C</italic>)=67.275 03, <italic>M</italic>(<italic>n</italic>)=17.482 66, and <italic>M</italic>(<italic>d</italic>)=-0.592 72, while the mutual effect factors are <italic>I</italic>(<italic>n</italic>,<italic>C</italic>)=12.617 24, <italic>I</italic>(<italic>d</italic>,<italic>C</italic>)=7.769 52, and <italic>I</italic>(<italic>n</italic>,<italic>d</italic>)=0.102 1.<bold>Conclusions</bold>Simulation results of this study demonstrate that the primary considerations should be the influences of the ratio of baffle height to pipe diameter and the number of baffles when designing a labyrinth throttle for liquid lead-bismuth flow to adjust its local resistance coefficient, providing a certain reference value for the optimization design and engineering application of labyrinth throttling parts in lead bismuth circuit.