Sensitivity analysis of nuclear main pump annular casing tongue blend

Abstract

Based on the Reynolds-averaged Navier–Stokes equations of relative coordinates and the RNG k-ε turbulence model, using our SIMPLE algorithm, we performed numerical simulations for an AP1000 nuclear main pump model with water as the medium. By changing the size of the tongue blend in the annular casing, seven different schemes were designed. Three-dimensional numerical simulations were conducted for the flow within the pump under various settings, and the flow characteristics of the annular casing using different tongue blends were obtained. The results show that for different operating conditions, there is a specific tongue blend that optimizes pump performance. Based on the calculation results, a larger tongue blend leads to a larger flow rate. Off-design conditions caused flow instability, which in turn caused the tongue blend to have a certain impact on the performance of the impeller. However, the performance of the pump was not primarily affected by changes in the impeller performance, but was instead affected by the performance of the annular casing, which was itself affected by tongue blend. When changing the tongue blend, the change in static pressure and total pressure of the annular casing was larger under the condition of 0.6 Qd and was smaller under the conditions of 1.0 Qd and 1.4 Qd. The turbulent kinetic energy in the annular casing changed mainly in the tongue impact zone and outlet diffuser under the condition of 1.0 Qd; furthermore, the turbulent kinetic energy in the whole of the annular casing demonstrated significant changes under the conditions of 0.6 Qd and 1.4 Qd.