Analysis of the Guide Vane Jet-Vortex Flow and the Induced Noise in a Prototype Pump-Turbine

Abstract

The start-up process of a pump-turbine in pump mode is found with obvious noise, especially at the small guide vane opening angle. The turbulent-flow-induced noise is an important part and must be reduced by flow control. Therefore, the computational fluid dynamics (CFD) method is used in this study to predict the internal flow in a high head prototype pump-turbine (the specific speed nq is 31.5) under an extremely off-design condition (Cφ = 0.015 and Cα = 0.096). The acoustic analogy method is also used to predict the near-field noise based on the turbulence field. Special undesirable flow structures including the flow ring between the runner trailing-edge and the guide vane, guide vane jet, twin-vortexes adjacent to guide vane jet, inter stay vane vortex, stay vane jet, and volute vortex-ring are found in a pump-turbine. These complex jet-vortex flow structures induce local high turbulence kinetic energy and an eddy dissipation rate, which is the reason why noise is generated at small guide vane opening angle. Three dominating frequencies are found on the turbulence kinetic energy pulsation. They are the runner blade frequency fb = 64.5 Hz, the dominate frequency in the guide vane and the stay vane fgsv = 9.6 Hz, and the dominate frequency in volute fvl = 3.2 Hz. The flow pulsation tracing topology gives a good visualization of frequency propagation. The dominating regions of the three specific frequencies are clearly visualized. Results show that different flow structures may induce different frequencies, and the induced specific frequencies will propagate to adjacent sites. This study helps us to understand the off-design flow regime in this prototype pump-turbine and provides guidance when encountering the noise and stability problems during pump mode’s start-up.

Experimental and numerical simulation study on the flow characteristics and optimization of structural parameters of displacement agent in partial pressure tools

“…This is because of the influence of the shape of the flow channel, which produces jet flow at the minimum flow channel. When the fluid enters the expanded area of the flow channel, the flow channel loses its function of restricting flow due to the inertia of the fluid, and a certain degree of free flow develops, resulting in the change of flow direction . As the polymer solution flows in a variable cross section, it is a process of contraction before expansion and changes periodically, so the velocity and streamline of the polymer solution in the partial pressure tool change periodically.…”

“…When the fluid enters the expanded area of the flow channel, the flow channel loses its function of restricting flow due to the inertia of the fluid, and a certain degree of free flow develops, resulting in the change of flow direction. 38,[55][56][57] As the polymer solution flows in a variable cross section, it is a process of contraction before expansion and changes periodically, so the velocity and streamline of the polymer solution in the partial pressure tool change periodically. Figures 11 and 12 show the pressure nephogram and pressure change curve of the polymer solution in the partial pressure tool when the flow rate is 10 m 3 /d.…”

Analyses of the spatial and temporal features of the blade pressure‐side cavitation in a pump‐turbine runner in the pump mode

“…To track the transient cavitating flow and understand how cavitation develops, the PTN is applied 33 . It consists of a large amount of well‐distributed monitoring points and can be treated as a mesh over the CFD mesh.…”

“…In this CFD‐based case, the pulsation tracking network (PTN) method is applied to the wall boundaries of a pump‐turbine runner blade passage 33 . The novelty of PTN is that it can study the propagation and attenuation of pulsation in detail.…”

Reduction of flow-induce noise of a high-speed centrifugal pump by applying blade leaning on guide vane

“…Liu et al simulated the flow-induced noise in a centrifugal pump by using a large eddy simulation [11]. Tao et al applied CFD simulation based on Lighthill's analogy method to evaluate the flow-induced noise in a pump and a reversible pump-turbine [12,13]. The above approaches show that CFD simulation is effective in predicting flow noise in bladed turbomachinery and can be used in this case.…”