“…Similar results were observed in the experimental study of Zhang and Casey 39 ; and at the needle tip flow velocity is zero similar to Bajracharya et al 37 Furthermore, to examine the effect of nozzle opening on the flow velocity in the injector, the normalized flow velocity based on the ratio of local velocity to maximum possible velocity is plotted with respect to the ratio of radial distance (y) and nozzle diameter (D 0 ), for a distance of ‘D 0 ’ mm from the nozzle exit (Figure 9(b)). Increasing nozzle opening increased velocity along the needle tip as the boundary layer effect was reduced, similar results were observed in the study of Jeon et al 53 Figure 9.(a) Variation of flow velocity with respect to radial distance, for 0.46 stroke ratio at 150 m of the head, (b) Variation of velocity ratio with respect to the radial position at a distance of ‘1D 0 ’ from the nozzle exit.…”
High-head hydropower plants deploy Pelton turbines to harness energy; however, turbine components face severe abrasive erosion due to suspended sediments. The erosion of the Pelton injector leads to the degradation of the jet quality, reducing the turbine efficiency considerably. Recently, the erosion of an internal servomotor design of the injector has been studied numerically; however, the cavitation-erosion synergy was not explored. This study serves as the extension of the literature with an analysis of the hydro-abrasive erosion and inception of cavitation in an injector with an external servomotor of a high-head hydropower plant (HPP). A Eulerian-Lagrangian approach is used to study the effects of sediment properties and flow parameters on hydro-abrasive erosion; whereas, the Schnerr-Sauer model is used to analyze the inception of cavitation. Interestingly, an increase in particle size from 40 microns to 200 microns resulted in a 95.7% reduction in needle erosion; but, led to a two-fold increase in nozzle erosion. For an increase in the plant head from 200 m to 820 m, the increase in erosion rate of the nozzle and the needle is 4.36 and 1.4 times, respectively. Moreover, the possibility of cavitation in the Pelton injector also increases with an increase in the head of the HPP leading the injector to higher susceptibility to the synergic effect of cavitation and hydro-abrasive erosion. This study attempts to assist the hydropower development in high-head regions with a risk of high sediment flow and manage the existing plants efficiently.
“…Similar results were observed in the experimental study of Zhang and Casey 39 ; and at the needle tip flow velocity is zero similar to Bajracharya et al 37 Furthermore, to examine the effect of nozzle opening on the flow velocity in the injector, the normalized flow velocity based on the ratio of local velocity to maximum possible velocity is plotted with respect to the ratio of radial distance (y) and nozzle diameter (D 0 ), for a distance of ‘D 0 ’ mm from the nozzle exit (Figure 9(b)). Increasing nozzle opening increased velocity along the needle tip as the boundary layer effect was reduced, similar results were observed in the study of Jeon et al 53 Figure 9.(a) Variation of flow velocity with respect to radial distance, for 0.46 stroke ratio at 150 m of the head, (b) Variation of velocity ratio with respect to the radial position at a distance of ‘1D 0 ’ from the nozzle exit.…”
High-head hydropower plants deploy Pelton turbines to harness energy; however, turbine components face severe abrasive erosion due to suspended sediments. The erosion of the Pelton injector leads to the degradation of the jet quality, reducing the turbine efficiency considerably. Recently, the erosion of an internal servomotor design of the injector has been studied numerically; however, the cavitation-erosion synergy was not explored. This study serves as the extension of the literature with an analysis of the hydro-abrasive erosion and inception of cavitation in an injector with an external servomotor of a high-head hydropower plant (HPP). A Eulerian-Lagrangian approach is used to study the effects of sediment properties and flow parameters on hydro-abrasive erosion; whereas, the Schnerr-Sauer model is used to analyze the inception of cavitation. Interestingly, an increase in particle size from 40 microns to 200 microns resulted in a 95.7% reduction in needle erosion; but, led to a two-fold increase in nozzle erosion. For an increase in the plant head from 200 m to 820 m, the increase in erosion rate of the nozzle and the needle is 4.36 and 1.4 times, respectively. Moreover, the possibility of cavitation in the Pelton injector also increases with an increase in the head of the HPP leading the injector to higher susceptibility to the synergic effect of cavitation and hydro-abrasive erosion. This study attempts to assist the hydropower development in high-head regions with a risk of high sediment flow and manage the existing plants efficiently.
“…Installed in the same shaft of the centrifugal pump, Pelton turbine is mainly made up of bucket and injectors where the momentum transfer takes place when the jet from an injector interacts with the buckets. [ 123 ] Due to the lack of understanding in the fundamental flow processes and experimental research about the hydromechanics of Pelton turbine, the advancement of this device is still limited. In their recent study, Sani looked into the design and synchronization of Pelton turbine with high‐pressure centrifugal pump in SWRO operation.…”
Section: Strategies For Energy Reduction In Desalination Processesmentioning
With the change in climate patterns, rapid industrialization, and population growth, the increasing water and energy demand became a major concern in the past decades. Desalination has been touted as the answer to the global water crisis, due to its capability in producing high‐quality fresh water from saline water. The continual research and innovations in the desalination field have resulted in the commercialization of large‐scale desalination in many water scarce regions. In the energetic context, all desalination processes are energy intensive. With the necessity to make desalination a more affordable and sustainable process, the energy efficiency of desalination is becoming an important topic. Herein, it is aimed to provide insights into the recent efforts and strategies established to tackle the energy‐related issues of both, thermal‐based and membrane‐based desalination processes. Depending on the principle of various commercial and emerging desalination processes, the directions of energy efficiency improvements, which include operating condition optimization, high‐performance material development, and renewable energy exploitation are discussed. The ideas and strategies reviewed herein, whether in their implementation or theoretical stage, are expected to provide insights into the possible improvement for application in commercial desalination plants.
“…The authors showed that it is important to include the geometries of the injector nozzle and spear in numerical simulations. The friction loss increases for small injector open and low flow rate [15].…”
The characterization of flow through Pelton hydro turbines allows the optimization of their operation and maximization of energy performance. The flow in the injector of Pelton turbines and in the free jet area (the area from the injector outlet surface to the runner bucket inlet surface) is influenced by several parameters: the geometry of injector components (nozzle and injector spear), the injector opening, and the turbine head. The parameters of the free jet flow (velocity distribution, pressure distribution, and jet spread) are reflected in the turbine efficiency. The research presented in this paper focuses on the numerical characterization of flow in the injector and the free jet of a Pelton microturbine. Three injector geometries were considered, with different nozzle diameters: 13.3 mm, 14.4 mm, and 16.3 mm. For each of these geometries, the flow was analyzed for five values of turbine head (H = 15 m, H = 20 m, H = 25 m, H = 30 m, H = 35 m) and six values of injector opening (S = 3 mm, S = 6 mm, S = 9 mm, S = 12 mm, S = 15 mm, S = 18 mm). The results of numerical simulations were used to plot injector flow-rate characteristics and injector force characteristics (the resultant force on the injector spear and the resultant force on the injector nozzle). The highest influence on the flow rate variation is given by the variation of turbine head, followed by the variation of the injector opening and the variation of the nozzle diameter. Increasing the nozzle diameter accentuates the variation of the flow rate versus the turbine head. The variation of axial velocity and pressure in the free jet is presented for four sections parallel to the outlet section of the injector. The injector openings that generate the highest values of velocity/pressure on the runner inlet surface are highlighted. The results allow optimization of functional parameters for increasing turbine efficiency and optimizing the design process of Pelton microturbines.
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