Abstract

Rotor-stator interaction (RSI) in the centrifugal pump-as-turbine (PAT) is a significant source of high amplitude of the pressure pulsation and the flow-induced vibration, which is detrimental to the stable operation of PAT. It is therefore imperative to analyze the rotor-stator interaction, which can subsequently be used as a guideline for reducing the output of PAT noise, vibration and cavitation. In addition, it is important for a PAT to have a wide operating range preferably at maximum efficiency. In order to broaden the operating range, this work proposes a multi-condition optimization scheme based on numerical simulations to improve the performance of a centrifugal PAT. In this paper, the optimization of PAT impeller design variables (b2, β1, β2 and z) was investigated to shed light upon its influence on the output efficiency and its internal flow characteristics. Thus, the aim of the study is to examine the unsteady pressure pulsation distributions within the PAT flow zones as a result of the impeller geometric optimization. The numerical results of the baseline model are validated by the experimental test for numerical accuracy of the PAT. The optimized efficiencies based on three operating conditions (1.0Qd, 1.2Qd, and 1.4Qd) were maximally increased by 13.1%, 8.67% and 10.62%, respectively. The numerical results show that for the distribution of PAT pressure pulsations, the RSI is the main controlling factor where the dominant frequencies were the blade passing frequency (BPF) and its harmonics. In addition, among the three selected optimum cases, the optimized case C model exhibited the highest level of pressure pulsation amplitudes, while optimized case B reported the lowest level of pressure pulsation.

Highlights

  • The need for electrical power today is on the rise, owing to the population and economic growth.Life without electricity today is practically impossible and unpleasant because it has become a part of our everyday life

  • Is critical to themethod reliability of the optimization optimization a PAT relies on simulation the numerical simulation which starts from the results

  • The selected centrifugal PAT is distinguished by the problem of low operating range and high pressure pulsations

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Summary

Introduction

The need for electrical power today is on the rise, owing to the population and economic growth. Life without electricity today is practically impossible and unpleasant because it has become a part of our everyday life. Getting electricity to remote areas poses a problem due to the topographical nature of these areas. Most remote areas have streams and rivers with high and low head that can be difficult to generate electricity at a cheaper rate. To curb this problem, the ideal method is to apply the pump-as-turbine (PAT) technology which has the tendency to generate electricity at a cheaper rate and be more environmentally friendly. In contrast to other types of small hydraulic devices, PAT has the advantages of being small, relatively cheap and easy to produce and Mathematics 2020, 8, 1714; doi:10.3390/math8101714 www.mdpi.com/journal/mathematics

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