Analysis of inner flow in low specific speed centrifugal pump based on LES

To investigate unsteady flow in the low specific speed centrifugal pump, a three-dimensional model of a pump that ns is equal to 50 is modeled with the software Pro/E. With standard k-ɛ, SST k-ω and RNG k-ɛ turbulence model, the testing performance of pump is compared with the simulated results. Based on the result of steady flow, the unsteady flow of RNG k-ɛ turbulence model and large eddy simulation (LES) are calculated at both design and off-design conditions. The time domain of pressure fluctuation value of indicator points, which are located interfaces between volute and impeller, has been investigated numerically. The unsteady flow characteristic of pump with RNG k-ɛ turbulence model is compared with LES. The distribution of vortex in the volute is discovered. The results show that in steady flow, an error of 2.6% of RNG k-ɛ is the lowest, SST k-ω of 3.65% is second and the worst is standard k-ɛ of 4.78% at design condition. The calculated precision using RNG k-ɛ model is highest in steady condition. Because of the interaction of relative movement between volute and impeller, the pressure fluctuation can clearly be observed. The flow separation of the blade pressure surface and the stall channels in off-designed condition is the reason that the efficiency of pump operating under off-design condition is low. The vortex intensity is obviously different in the eight sections of the volute and is gradually increasing from first section to eighth section. Large eddy simulation can discover the unsteady flow of the centrifugal pump effectively.