Experimental and numerical investigation for the geometrical parameters effect on the labyrinth-seal flow characteristics of fast reactor fuel assembly

Abstract

The labyrinth seal is widely used in the fast reactor fuel assembly to control leakage flow rate, adjust pressure drop and cool assembly outer wall. In the current investigation, a new non-rotating labyrinth seal with right-angle trapezoidal throttle tooth is designed and manufactured, and its flow characteristics are experimentally and numerically investigated. Reynolds number from 61,512 to 81,261 is considered and experiment data were generated from hydraulic experiment conducted at constant water temperature (84 °C) in the labyrinth-seal test section. Numerical results with different turbulence model, wall-normal grid spacing, inlet turbulence intensity and stream-wise grid length are compared with experiment results to demonstrate the effectiveness of numerical simulation. Geometrical parameters have a significant effect on labyrinth-seal flow characteristics. Increasing throttle-tooth number, spacing and throttle-tooth thickness can improve the labyrinth-seal sealing performance, while increasing gap width influences the flow velocity limitation and increases the leakage. Labyrinth-seal resistance coefficient is validated to be independent of Reynolds number (61,512–81,261). It is deduced that the fully rough regime still exists in an annular-tube turbulence flow with high wall roughness. The energy dissipation caused by throttling effect, jet, vortex and secondary transverse turbulence is the main sealing mechanism. Moreover, a leakage-coefficient empirical correlation is obtained by regression analysis of experiment data, which can be used for the structure design of sodium-cooled fast reactor and preliminary estimation of leakage flow rate in similar non-rotating seals.