Solid-liquid multiphase flow and erosion in the energy storage pump using modified drag model and erosion model

Abstract

In order to achieve the carbon neutrality, the wind and solar power have greatly developed in recent years, which leads to a challenge of unpredictability and intermittence for the power grid. A new concept of energy storage pump station is proposed, which uses the large pump to store water from the downstream reservoir to the upstream reservoir in cascade hydropower stations, and consumes the electricity from wind and solar power. However, due to the high sediment content of rivers in China, erosion is a critical issue that damages components and shortens the operational life of energy storage pumps. In this work, an improved calculation model based on modified drag model and modified erosion model is established to investigate the solid-liquid two-phase flow and erosion characteristics in an energy storage pump. In the calculation model, a modified drag model by considering the effect of turbulence intensity is proposed, and a modified erosion model by considering the effect of particle Stokes number is proposed. An erosion experiment on a 90° elbow pipe is used to validate the accuracy of the improved calculation model, and the maximum error of erosion rate between experiment and calculation is 1.86 %. Then, solid-liquid flow and erosion in a centrifugal pump with the specific speed of 102 are numerically calculated under particle sizes of 0.01 mm, 0.05 mm, 0.1 mm, 0.25 mm, 0.5 mm, 0.75 mm and 1 mm, respectively. Results show that particles tend to accumulate at the hub and blade pressure side as particle size increases, which results in a rise in non-uniformity of particle distribution in impeller. Meanwhile, the non-uniformity of erosion in impeller strengthens with particle size increase, and erosion in impeller under particle size of 1 mm is 1245 times more than that under particle size of 0.05 mm. A new evaluation method of effect level of parameter on erosion of a centrifugal pump by using Stp = 1 is proposed. When Stp < 1, particle impact velocity is the primary factor on erosion, and the average erosion rate decreases with particle size increase. When Stp > 1, the particle number impacting the wall is the primary factor on erosion, and the average erosion rate increases with particle size increase.