**1. Introduction**

Hydroelectric power is a renewable energy source and a significant component of worldwide electricity production. Around 17% of the total consumed electricity is produced through hydraulic energy sources [1,2], and almost 65% of the total electricity produced in Latin America is generated by hydroelectric power plants (around 709 TWh/y) [3,4]. However, most of the total technical hydraulic potential (2859 TWh/y) of the region is not harnessed by its installed hydropower capacity. Several large-scale hydropower projects are being currently studied and developed in the Andean region in the hopes of increasing the installed capacity and harnessing a larger portion of the available hydraulic potential. One of the most crucial factors that needs to be taken into consideration during the development of the aforementioned projects is the fact that hard particles are present in almost all rivers of the Andean and Himalayan region, causing considerable the erosion, mechanical wear, and failure of turbine components [3,5].

Sediments flowing through the river deposit in the dam's reservoir, reduce the reservoir's capacity, and increase the erosion wear of critical turbine components, such as: the spiral casing, guide vanes, runner, and draft tube. This phenomenon reduces the lifespan of the turbine and decreases its efficiency, which increases the cost of maintenance over time, leading to economic losses [6,7]. Erosion wear depends on several factors, including particle concentration, velocity, composition, size, and shape. Other variables, namely turbine materials and operating conditions, also have an effect on the erosion rate. Therefore,

**Citation:** Cruzatty, C.; Jimenez, D.; Valencia, E.; Zambrano, I.; Mora, C.; Luo, X.; Cando, E. A Case Study: Sediment Erosion in Francis turbines Operated at the San Francisco Hydropower Plant in Ecuador. *Energies* **2022**, *15*, 8. https:// doi.org/10.3390/en15010008

Academic Editors: Marcin Kami ´nski and Angel A. Juan

Received: 18 September 2021 Accepted: 17 November 2021 Published: 21 December 2021

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erosion reduction strategies can only work effectively after in-depth analyses making a holistic assessment of all the variables involved [8,9].

Extensive research has been conducted on erosion in Francis turbines. In 2013, Singh and Banerjee performed an analysis on the erosion of the runner blades, guide vanes, and labyrinth seals of the Maneri Bhali Stage-II hydroelectric power plant in India. Data collection of sediments at relevant locations and measurements of turbine efficiency were performed during three years to determine the effect of silt erosion on the efficiency of turbines [10]. In 2016, Koirala used a computational analysis coupled with field observations to determine the erosion patterns on the guide vanes of Kaligandaki hydroelectric power plant in Nepal and proposed erosion protection methods [11]. A year later, Masoodi and Harmain presented a detailed comparison of two sediment-laden rivers and their effect on the runner blades of Himalayan hydroelectric power plants in India. A new erosion model was proposed in this study [12]. Most recently, in 2020, Qian et al. executed a study on the erosion wear of the runner blades of a Francis turbine in Jhimruk Hydroelectric Center in Nepal using numerical simulations and comparing the results with the damage of the runners. He proposed changing the opening of the guide vanes to improve turbine efficiency and reduce the erosion rate [13]. Moreover, Noon and Kim discussed and analyzed the latest experimental and numerical techniques to determine sediment and cavitation erosion on different turbine components using baseline data from the Tarbela Dam hydroelectric project in Pakistan [14]. However, all the aforementioned studies were performed in Asia, and no research on the topic has been performed on South America, where similar erosion issues are found.

This study focuses on the analysis of sediment erosion in the Francis turbines of San Francisco hydroelectric power plant in Ecuador. The turbines of this power station suffer erosion wear damage, and to date, no effective strategies have been proposed to reduce the damage. A sediment characterization of the Pastaza River was conducted for this study in order to perform a numerical analysis of the turbines with sediment properties set as close as possible to the real conditions. Finally, a study on the erosion rate and pattern in different components of the turbine was carried out to better understand this phenomenon.
