Effects of the inlet duct length on the flow field and performance of a cyclone separator with a contracted inlet duct

The inlet duct length may affect the gas flow field and performance of a cyclone separator with a contracted inlet duct. In this study, a numerical simulation using the Eulerian-Lagrangian approach with a one-way coupling method was conducted to evaluate the gas flow field and separation efficiency of the cyclone separators with contracted inlet ducts of different lengths. The simulation results indicated that increasing the inlet duct length led to higher gas tangential velocity in the cyclone body. The effect of the inlet duct length on gas axial velocity was inferior to that on gas tangential velocity. A longer inlet duct reduced both the pressure drop and the separation efficiency. The reductions of the expansion loss at the inlet of the cylinder and friction loss inside the cyclone body contributed the most reduction of the pressure drop as the inlet duct length increased. Generally, when the inlet duct was 1.5 times longer than the cylinder diameter, the effect of inlet duct length on the gas flow field and performance of a cyclone separator became slight. [Display omitted] •Flows in cyclones with contracted inlet ducts of different lengths were simulated.•The effect of inlet duct length on the flow field in the cyclone was evaluated.•The effect of inlet duct length on the performance of the cyclone was evaluated.•Two main factors causing the variation of performance were found and discussed.