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The high head Pelton turbines operate with extreme conditions. In case to need a sudden stop of operation, one of the important parts is jet deflector, which can be in push-out, or cut-of options. The paper presents the optimisation procedure of Pelton Turbine push-out jet deflector shape using numerical simulation of three-dimensional turbulent fl...
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... runner buckets, flow visualization and efficiency measurements. Perrig [7] did the most complete analysis of flow in Pelton turbines. Flow in buckets was investigated through unsteady onboard wall pressure measurements, high-speed onboard 29th IAHR Symposium on Hydraulic Machinery and Systems IOP Conf. Series: Earth and Environmental Science 240 (2019) 022031 IOP Publishing doi:10.1088/1755-1315/240/2/022031 2 and external flow visualizations, water film thickness measurements and CFD simulations. Recent experimental and numerical investigations put full attention on the influence of nozzle geometry and secondary flow on the jet quality [8], [9].Based on numerical and experimental results mentioned above, a mass of new knowledge about ...
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Vortex generating devices are used for vibration reduction in aeronautical applications [1]-[3], many of these are used to improve stability in the rotation of wind rotors allowing better energy efficiency in generators, CFD simulations can reduce the design costs of these devices because their development demands fewer resources compared to the co...
Citations
... For more than 30 years, the computational fluid dynamics has played an important role in the improvement of the hydraulic turbines characteristics (Keck and Sick 2008). Different modifications of the turbine parameters will lead to changes in the characteristic curves, where relative results of these modifications can be accurately predicted (Popovski et al. 2019). Due to the complexity of the transient multiphase flow characteristics and of the geometry of the buckets, the Eulerian method used for the Pelton turbine design developed slowly in the beginning, considering also the limited computation resources available. ...
This paper presents several multiphase and free-surface flow simulations for a Pelton wheel-scaled model. The main result of the numerical simulations was the shaft torque produced. An experimental investigation for four different rotational speeds at design-point condition of the turbine was performed in order to validate the measurements calculated by the computational fluid dynamics model. To reduce computational costs, only half water jet, half nozzle and half buckets were built, due to the axial symmetry of the turbine. The shaft torque from CFD simulations was used to obtain the turbine power output and the runner efficiency. This research provides the methodology and the physical settings for multiphase flow modeling in a Pelton turbine. Firstly, to certify reliability for the simulations, a mesh dependency test was drafted. Thereafter, geometric modifications of the bucket exit angle were carried out. Originally at 15°, the exit angle has been changed to 10° and 20°. The computational model was validated with experimental results and outcomes discrepancies in the range 3.9-8.8%. Higher torque instabilities were found for lower runner speeds. The characteristic power curve for the bucket exit angle at 10° presented the best performance over the entire turbine operating range. The efficiency improvement in relation to the simulations at the design-point condition was up to 1.07%. Flow visualizations are also presented and described in this research.
... The kinematic and dynamic flow parameters are calculated based on CFD simulations. The results of the calculations represent a reliable tool in the procedure of development and construction of Pelton turbines parts [13]. In the last fifteen years, many papers about numerical and experimental analysis of flow in Pelton turbines have been published. ...
... (12) and co-efficient of the Eq. (13) and at lost the force acted on the plate is given by the Eq. (14) all the parameters are observed in the simulation. ...
The design of the spear plays a key role in the Pelton wheel. In general, the spear is useful for increasing the velocity outlet of the nozzle. The maximum amount of the output velocity of the nozzle is mainly controlled by the spear. In this paper, the flow analysis in the Pelton wheel nozzle has been performed by varying the surface design of the spear with different dumps in different shapes and placed at different distances and with different sizes. The simulation in the paper is performed to obtain the optimal shaper and the optimal position for the complexity of the problem. We used the Taguchi design optimization method to obtain the optimal shaper to create the nozzle's higher velocity output. The flow simulation is performed in the ANSYS fluent software and the simulation is performed in fluent with the k-ε; the flow simulation is performed in the two-dimensional analysis. Taguchi optimization is performed in the Minitab software. The most optimal condition for the spear to obtain the maximum velocity is at the following aspect the model is inside a triangle and the overall length of the bump is 1mm and the number of bumps is 4 and the distance between the bumps is 1.75 mm from each other.
... Han et al. [7] confirms the secondary flow and Dean vortex structure in the distributor and thus jet deforms outside the distributor. Popovski et al. [8] presents the optimization procedure of Pelton turbine push-out jet deflector shape using numerical simulation of three-dimensional turbulent flow in order to minimize the forces, stresses, deformations and torque of jet deflector servomotor and found that using different shapes of jet deflector can lead to significant reduction of the hydraulic forces and torque and, consequently to reduction of the servo motor torque. [9] simulated a high-speed water jet by five rotating Pelton buckets by the FVPM simulations. ...
As hydraulic resource is widely developed in high mountainous area, design and optimization of Pelton turbine have attracted more and more academic attention especially in ultra-high hydraulic head condition. Computed Fluid Dynamics (CFD), as an effective tool to simulate flow in Pelton turbine has been proved to be practical and used widely. Mechanism of the energy loss produced by erosion is investigated through numerical simulation. Simulation is then confirmed by is then by comparing with the experimental results in clean water flow condition. Through CFD, under Eulerian-Eulerian methodology, three-phase erosion flow is then calculated and complex flow in runner region are analysed. Comparing with clean water condition, the hydraulic efficiency of the turbine decreases in erosion condition, the particle mixed in the flow will disturb the water distribution on the working side of the bucket. Finally, the torque produced by water and particle are then distinguished quantitatively. As the erosion phenomenon exists which confirmed by the experiment in the literature, the particle disturbs the water distribution and then decreases the total torque and definitely decreases the hydraulic efficiency around 9 %. It reveals that the energy loss caused by the erosion phenomenon plays an important role in power plant.
... The history of turbine's development starting from water wheels of early 19 th century was reviewed by 63 Viollet [6], which showed a progressive development in the turbine's unit power, range of operations and 64 efficiency along the years. Although the concept of water-wheel was developed in early 1800's, the concept 65 ...
... considerably affected by the stationary components surrounding the runner. Some numerical studies have 334 tried to capture the flow physics and possible design optimizations for the nozzle [60][61][62], deflector [63] 335 and the casing [64,65]. An elbow pipe present upstream of the nozzle was seen to deflect the water jet to 336 the same direction due to the formation of circulations at the inlet side of the elbow pipe [60]. ...
Impulse turbines are widely used in hydropower plants around the world due to their high efficiency in a larger operating range compared to reaction turbines. State of the art Pelton turbines can give over 90% efficiency at the designed operation load. However, there lies a possibility of improving the efficiency at off design condition for these turbines by optimizing the design of the nozzles, runner and/or housing. Prediction of the performance of the turbines by numerical techniques allows a quicker design optimization and at a much lower cost. In the case of impulse turbines, the use of CFD is limited by the complex nature of the flow, interaction of the jets, water/air mixture and interference of water after the impact on the successive buckets. Unlike reaction turbines, where the performances of the turbines could be studied through time-independent analysis to some extent, transient simulations are inevitable for the impulse turbines. Moreover, need for the multiphase models add to the overall complexities of CFD. Some recent development includes the use of Lagrangian scheme, which has reduced the computational efforts significantly. In the conventional Eulerian schemes, it is found that the numerical domains are usually simplified, either by using symmetry (half bucket) or rotational periodicity options. With the development of the computational capacity, some recent studies have also performed full turbine's simulation, using nearly 50 million mesh elements. The design optimizations are performed on the shapes of the bucket, jet, deflectors as well as the turbine's casings. However, validation of the numerical solutions remains a challenging topic with the quality of the mesh being used currently. Nevertheless, progresses in the numerical techniques and computing power within the last 15 years have strengthened the prospects of utilizing CFD and FEM as primary tools for validating and optimizing the design of the impulse turbines.
The performance of a Pelton wheel is influenced by the jet created by the nozzle. Therefore a Computational Fluid Dynamics (CFD) simulation was proposed in this study to examine the significant output parameters (outlet velocity, outlet pressure, and tangential force component) and input parameters (different pressures and spear locations). In addition, the influencing parameters and their contributing percentages to the performance of the Pelton wheel were calculated using different optimization techniques such as Taguchi Design of Experiments (DoE), Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), Grey Relational Analysis (GRA) and Criteria Importance Through Intercriteria Correlation (CRITIC). The effect of input factors on the output response was examined with DoE, and the results show that the inlet pressure had the most significant impact (97.38%, 99.18%, and 97.38%, respectively, for all different spear sites with 99% confidence level). In terms of preference values, the TOPSIS and GRA results are comparable (best ranks for simulation runs #24 and #25 and least ranks for simulations #2 and #3, respectively). The J o u r n a l P r e-p r o o f CRITIC results for the pressure parameter are in good agreement with the Taguchi ANOVA analysis. The last spear location (5 mm after the nozzle outlet), with an inlet pressure of 413685 Pa generated the best result when employing the TOPSIS and GRA techniques. The outlet pressure of the nozzle was found to have a significant impact on the flow pattern of the Pelton Wheel based on the analysis of the CRITIC, Taguchi, and CFD results.
Pelton turbine can not only utilize the high head hydraulic resources but also recover the flow kinetic energy in the pipeline. It is more and more widely used. Thus, the research on improving the efficiency and performance of Pelton turbine is important. In this paper, Boltzmann method is used to study the influence of different runner widths on the performance of a micro Pelton turbine. And two micro Pelton turbines with runner widths of 25mm and 20mm are taken as the research object. Then turbine efficiency is calculated and the internal flow characteristics of micro Pelton turbine are analyzed. The results show that the runner width has obvious influence on the efficiency. When the runner width decreases from 25mm to 20mm, the turbine efficiency decreases by 1.16%. Besides, the turbulence area in the runner decreases, and the velocity decreases. But the turbulence intensity and vorticity in the runner is enhanced, which causes more serious hydraulic loss.
The difficulty of delivering electrical power to rural areas motivated the researchers to
explore more accessible power sources. Hydropower is considered a desirable option due to its
sustainability and lower costs. Pelton turbines have been widely used in hydropower plants because
of their low installation and maintenance costs. This study provides a computational fluid dynamics
(CFD) model for Pelton turbine performance under various flow conditions. The model is based on
the conservation of mass principle, Newton’s second law, and the first law of thermodynamics. It is
used to predict the torque produced by a turbine at different rotational speeds. Previously published
experimental results for the same turbine geometry and flow parameters were used to validate the
model’s predictions. Validation revealed that the model can reproduce the experimental results. This
provides the required robustness for its use as a tool for turbine design and modification.
The Pelton turbine is the most widespread and efficient impulse hydropower turbine. The Pelton casing is a static, but key component: the internal hydrodynamic phenomena affect the performance of the hydropower plant, the vibration of the equipment and water quality (dissolved oxygen downstream). However, the literature information is very fragmented and not well organized, so that the design is generally based on empirical rules and on proper know-how of hydropower companies. In this paper, the state-of-the-art of the Pelton casing is reviewed and organized under three macro areas: hydraulics, mechanics (vibrations and weight) and aeration. The preliminary design procedure is described and discussed in light of recent scientific results, and the open questions and research challenges are highlighted. Innovative case studies are described (including counterpressure operation) and a dataset of installed casings (not available in literature) is elaborated to derive an empirical equation to estimate the casing weight. The efficiency can be improved by 3% by an optimal fluid dynamic design and a better understanding of the internal hydrodynamics. Proper inserts can improve the hydraulic efficiency by 2%, reduce the weight (by about 12%) and better bear the vibrations. Several scientific questions are still open, and a better understanding of the fluid structure interaction is needed to improve efficiency, operation and water quality.
