Turbine Buckets Research Articles

Advanced high‐precision methodology for assessing sediment erosion in Pelton turbine buckets

Advanced high‐precision methodology for assessing sediment erosion in Pelton turbine buckets

Numerical analysis of cavitation characteristics on front surfaces of different Pelton turbine buckets

Abstract Cavitation may occur in the runner bucket of the Pelton turbine, which could lead to cavitation erosion on the bucket surface. In this paper, three types of bucket were selected to carry out transient multiphase flow simulation at the same operating point of a model Pelton turbine. The hydraulic performance and cavitation characteristics of different buckets were analysed. The 3 bucket models were developed for Pelton turbines operating under the middle-high and the high-water head range, respectively. Results showed that the participation of cavitation model in simulation would slightly affect the working process of the bucket. The cavitation on the front surface of three buckets all happened at the beginning stage of jet inflowing the bucket, among which bucket C had the most serious cavitation on the front surface. This work showed different cavitation characteristics among various types of bucket, and the relevant result suggested comprehensive design considering cavitation characteristics should be done on the front surface of the bucket for a specific range of water head.

Development of a Novel High Head Impulse Hydro Turbine

The Pelton turbine has been widely regarded as the most efficient hydro turbine for high-head applications. However, the Pelton turbine buckets, especially the area commonly referred to as the ‘splitter’, are highly susceptible to erosion, drastically reducing efficiency over prolonged periods of time. This paper demonstrates a novel turbine idea that has been validated through both computational and experimental methods. This turbine addresses the issues associated with the erosion of the splitter through a redesign of the Pelton turbine to remove the need for a splitter and therefore potentially reducing downtime due to maintenance. The computational fluid dynamics (CFD) simulation results show that the turbine is capable of efficiencies greater than 82% with room for further improvement. The practical experimental results also show efficiencies within 6% of an optimized Pelton turbine. The results from this study indicate that through further optimization this turbine design could provide a means to produce power outputs similar to conventional Pelton turbines, with the added benefit of lower maintenance costs.

Experimental and numerical investigation of hydro-abrasive erosion in the Pelton turbine buckets for multiphase flow

Sediment erosion-corrosion is a critical threat to the safe operation of hydro turbines, which may lead to component damage or even complete failure of the turbine. A lack of understanding of the mechanism of sand erosion is a barrier to developing an erosion model to exactly quantify sand erosion in the Pelton turbine. The preeminent objectives of this research work are to determine parameters that influence sand erosion, identify erosion-prone areas in Pelton turbine buckets, quantify the erosive wear experimentally and numerically, determine the impact of erosive wear, and analyze the microscopic mechanism of erosion. Five Pelton buckets made of aluminum, carbon steel, stainless steel, polylactic acid (PLA), and acrylonitrile butadiene styrene (ABS) were used to perform erosion experiments under two-phase, solid-liquid flow conditions. Multi-layer paint modelling technique was used to identify erosion-prone areas. Optical profilometry was used to perform surface roughness analysis and Scanning Electron Microscopy was used to evaluate the microscopic degree of damage due to erosive wear in the Pelton bucket. Mass loss and thickness reduction analyses were performed to quantify the erosive wear. The erosion rates of aluminum, carbon steel, stainless steel, and ABS were 190 %, 86.73 %, 48.79 %, and 5.61 % higher, respectively, compared to PLA and both PLA and ABS demonstrated exceptional resistance.

Review on erosion phenomenon, maintenance, and financial calculation of lifetime as an asset for Pelton turbines

Prevention of greenhouse emissions is the top priority for all countries, which urges them to switch to renewable energy as much as possible. Hydropower is one of the renewables that have high flexibility and at the same time compatibility to be used with any other renewable sources. Moreover, hydropower plants operating in the Himalayas, Andes, and Alps are facing operational challenges due to the high concentration of sediment loads in rivers. Although the arrangement of traditional sediment control mechanisms like dams and sand traps, the erosion tendency of hydro-turbine components operating in this sediment-laden water increases with the increased concentration of sediments. Much past research has been directed towards understanding sediment behaviors, investigation of flow, and effect of concentration, shape, and size, especially with Francis turbines. However, there are very fewer studies regarding sediment erosion and flow behavior in the case of the Pelton turbine. Hence, delving deeper into the flow characteristics, sediment behavior, and performance of the Pelton turbine is important to better understand the flow and sediment pattern of these types of turbines. The paper consists of the evaluation of studies conducted on the flow pattern in the Pelton turbine buckets and its validation with the numerical analysis models using image processing. It is being used in the Waterpower Laboratory at the Norwegian University of Science and Technology, NTNU. This paper also evaluates the scope of investigations about erosion by sediments in Pelton buckets using image analysis and state-of-the-art technology in the hydropower sector. In addition, a review is done about the predictability of erosion based on the measurements of the quantity of sediments that passes through the turbine. This research paper can build a background for quantifying sediment erosion in Pelton turbines with a certain degree of error, which can be utilized as a reference in future studies. The life cycle estimation of a turbine is also analyzed with the consideration of its location and financial return requirements together with the type of maintenance that it may have and the repair that is foreseen, in the case of a non-coated surface.

Water flow simulation in a pelton turbine bucket with variable bucket dimensions using computational fluid dynamic

Today, especially among industrialized and developing nations, the usage of renewable energy sources is growing in popularity as a means of supplying energy needs. One of the renewable energy sources that is now being heavily exploited in Indonesia is the potential of water that may be used as a source of electrical energy by establishing a hydroelectric power plant (PLTA). One of the turbines that is frequently used in hydropower plants as a part that may transform water's kinetic energy into mechanical energy is the Pelton turbine. There is not a lot of literature on the design of Pelton turbine buckets. In order to determine the most ideal bucket dimensions that can be used with Pelton turbines, this study presents the conceptual and experimental components of the design and analysis of Pelton turbines based on bucket variations. AutoCAD was used to model the bucket and Pelton turbine, and ANSYS Fluent was used to perform the simulation so that results could be analyzed later. By comparing the simulated data of the blade variants 1 and 2, the ideal blade dimension variation is identified by the blade simulation of variant 1. The blade variation 2 with average torque of 5.859 Nm, average angular velocity of 40.822 rad/s, and average power of 242,970 watts is the most ideal blade. With an average torque of 4,735 Nm, an average corner speed of 40,404 rad/s, and an average power of 196,794 W, the blade 3 model has lower values

SPH method used for characteristic predictions at Pelton turbine buckets: comparing with the mesh-based method

PurposeThe research in this paper helps to understand the difference between the Eulerian method and the Lagrangian method in describing the performance of Pelton turbine buckets, so as to improve the design level and design efficiency of the runner.Design/methodology/approachThis paper used DualSPHysics to calculate the unsteady flow of the Pelton turbine runner bucket and compared it with the mesh-based method to explore the difference between mesh-based and particle-based methods in torque curves, jet flow patterns and pressure characteristics.FindingsIt is noted that the particle-based method is challenging to compare with the mesh-based method concerning accuracy. In addition to better describing the free water film, the particle method also captures many droplets near the water film, but it cannot well describe the negative pressure region on the bucket back and the resulting jet interference after cutting off the jet. Compared with the mesh-based method, the pressure measurement points obtained by the particle-based method generally have shorter periods and violent fluctuations, and the pressure value of some points is underestimated.Originality/valueThis paper helped to calculate the unsteady characteristics of the Pelton turbine by Fluent, CFX and DualSPHysics; exploration jet flow pattern differences between the mesh and meshfree methods; prediction of the flow interference between the bucket back and the jet and the pressure curve of SPH usually has a shorter period and violent fluctuations.

Geometrical Optimization of Pelton Turbine Buckets for Enhancing Overall Efficiency by Using a Parametric Model—A Case Study: Hydroelectric Power Plant “Illuchi N2” from Ecuador

In Ecuador, the implementation of hydroelectric power plants has had a remarkable growth in the energy sector due to its high efficiency, low environmental impact, and opportunities to generate employment. One of the sectors with the greatest benefits from this type of energy has been the rural sector, where several small-scale hydroelectric plants (0.5 MW–10 MW) have been installed, usually with Pelton turbines. Although these turbines are highly efficient, one of the challenges is to obtain the optimal geometry of the bucket to take advantage of the greatest amount of energy from the water, avoiding the separation of the fluid. In this context, this study focuses on the development of an analytical and iterative methodology that allows for the determining of the appropriate dimensions of the buckets to achieve maximum turbine efficiency. For that, a parametric model has been proposed considering the dimensions and main angles of the bucket, the net hydraulic head and the working flow, as well as the power losses. The results of the model have been validated by means of CFD and by contrasting the experimental data obtained from the “Illuchi N2” Hydroelectric Power Plant in Ecuador, and it is concluded that it is possible to improve the turbine efficiency by up to 4%.

Analysis of hydro-abrasive erosion in Pelton buckets using a Eulerian-Lagrangian approach

One major concern in developing high-head water resources, which usually uses Pelton turbines, especially in geologically young and fragile mountains, is hydro-abrasive erosion. However, the physical mechanism of hydro-abrasive erosion in Pelton turbine buckets is still not well understood as the cumulative erosion is changing with the transient flow in rotating buckets. In this work, a new approach to predict the cumulative erosion on a rotating surface is proposed and applied to Pelton turbine buckets. This method is based on the Eulerian-Lagaraigian approach previously developed by authors and a novel algorithm introduced to predict the impact behavior of particles hitting rotating surfaces. The numerically obtained erosion is validated with 3D-scanned erosion profiles of buckets measured in a prototype plant. Further, a detailed analysis of the flow and hydro-abrasive erosion characteristics with bucket rotation is conducted. The good agreement with field values demonstrates the promising ability of the proposed method for quantitative erosion prediction. Interestingly, the flow interferences between the jet and the water sheet are found to produce a shield layer to prevent particles from directly impacting surfaces and consequently reduce hydro-abrasive erosion. The current work may provide important engineering insights for geometry optimization to reduce hydro-abrasive erosion.

Analysis on influence of bucket angle of Pelton wheel turbine for its structural integrity using aluminium alloy (A390), austenitic stainless steel (CF20), grey cast iron (325) and martensitic stainless steel (410)

Pelton wheel turbine converts gravitational energy of elevated water into a mechanical work. During the process, the turbine buckets experience equivalent stress and total deformation that lead to material failure due to the impingement of high velocity water jet on it. Bucket angle influences the structural integrity of the turbine bucket. Hence it was intended to simulate and study the effect of bucket angle on the equivalent stress and total deformation using different materials viz. aluminium alloy (A390), austenitic stainless steel (CF20), grey cast iron (325) and martensitic stainless steel (410). In this investigation equivalent stress distribution and total deformation in the bucket have been established at various bucket angles (145°, 150°, 155°, 160° and 165°) for the selected materials. Simulation results revealed that lower values of maximum equivalent stress and total deformation occur at the bucket angle of 155°, for all the materials. And the maximum equivalent stress and total deformation induced in the bucket was inferred to be lower for martensitic stainless steel, at all bucket angles. Based on the simulation results, martensitic stainless steel is proved to be a better material for turbine bucket.

Primena reverznog inženjeringa pri projektovanju radnog kola Peltonove turbine

The paper describes the innovative solution for revitalization of hydro turbines by using the techniques of reverse engineering and virtual production. The application of modern digital tools in developing, designing and producing shows substantial benefits in improving the existing hydro turbine. Model testing in these cases is not necessary to implement because as the basis is used the known geometry of existing hydro turbine runners and buckets. Digital tools allow a relatively easy way to develop new geometry, improve hydraulic performances of turbines and reach a greater level of usefulness with minimal costs. This paper aims to show optimized geometry and improvement of the Pelton turbine performance using the presented approach

Comparison of coated and uncoated HSS drill bit on surface roughness, material removal rate and dimensional accuracy of SS410 stainless steel

Stainless Steel 410 (SS410) is 12% chromium martensitic steel which can be heat treated to obtain wide range of mechanical properties. Due to its high corrosion resistance and excellent combination of toughness and strength, it is used for furnace parts, steam turbine buckets, blades, pump, nozzle, automotive parts, aerospace application etc. Considering the challenges in machining of this material, drilling experiments were conducted on SS410 to analyse the effect of various parameters. Coatings always have a positive influence on the tool. It helps to reduce friction in the cut, reducing heat build-up in the drill bit, as well as improving the flow of material out of the drilling point. It also delivers protection against corrosion, rust and water damage. The AlTiN coating provides exceptional oxidation resistance and extreme hardness. This coating works well in very demanding cutting tool applications, especially when tools are being pushed to the max. This paper reports on the investigation of performance of Al-Ti-N coated and uncoated HSS drill bits when drilling SS410. Machining characteristics studied in this investigation include Material Removal Rate (MRR), Surface Roughness (Ra), Ovality. Drilling tests were carried out as per Taguchi’s L16 array using process parameters such as Speed (30, 40, 50, 60 m/min), Feed (F) (0.05, 0.075, 0.1, 0.125 mm/rev) and point angle (P) (100, 110, 120, 130 degree). Comparison of the performance of coated and uncoated drill bits showed that coated drill bits have higher performance than uncoated. By using coated drills surface Roughness and Ovality values of drilling are reduced to an extend of 48.5% and 2%. Material removal rate value is also improved to an extend of 23%.

Experimental and Numerical studies on Opening and Velocity Influence on Sediment Erosion of Pelton Turbine Buckets

Sediment erosion of Pelton turbines seriously damage the economic benefits and safe operation of the power station under the high head. The gas-liquid-solid three-phase unsteady flow calculation was carried out using the Eulerian-Lagrangian method to study the influence of velocity and nozzle opening on buckets torque and erosion. Experimental research were carried out under the condition of clear water and sediment-laden flow, the experimental results are in good agreement with the numerical simulation results, which proves the reliability of the calculation model and calculation method. The conclusions obtained from the numerical simulation are as follows: after adding the sediment particles, there is a slight delay of the bucket torque curve. Compared to clear water, the maximum torque of a single bucket will increase by about 2% in sediment-laden flow under different scenarios (the particle concentration is 1%, the particle size is 0.1 mm, the velocity range is 28–32 m/s, and the nozzle opening range is 50%–100%). For particles with strong flowability, the erosion region is highly consistent with the high-pressure zone. The increase in the velocity will increase the erosion rate on buckets. The nozzle opening change has little effect on the erosion region and maximum erosion rate. Meanwhile, the number of eroded buckets is three at the same moment, which is not affected by the nozzle opening change. This paper could provide some theoretical assistance for runner manufacturing, optimization design, and maintenance.

Feasibility Study of PVC Pipes as Vertical Axis Wind Turbines Type Savonius Bucket for Remote Areas Application

Independent power plant based on renewable energy is a good solution to solve electricity crisis in remote areas. Wind is a source of energy that has every country in the world. A study of the utilization of PVC pipes as a material for Savonius turbine buckets has been carried out in order to reduce the investment costs of wind turbines. The feasibility test has been carried out in four runners: the 2-bucket without and with overlap and the 3-bucket without and with overlap. All the runners are made using PVC pipes. Based on results, the 2-bucket with overlap is the right solution for remote areas because it has a higher coefficient of performance of 8.39%, and the range of tip speed ratio is wider between 0.57-0.65 compared to others. Compared to aluminum bucket material, the PVC pipes are more profitable because they are easy to make, cheap and good performance. Furthermore, the investment cost of a Savonius turbine bucket made from PVC pipe (USD 37.34) is cheaper than the pico hydro type Turgo (USD 48). Thus, the PVC pipes as materials for making Savonius turbine runner are recommended for remote areas application because the materials are cheap and easy to access (widely available in the market).

Defect assessment in gas turbine blade coatings using non-contact thermography

Abstract Thermal Barrier Coatings (TBCs) are inevitably applied on combustion chamber liners, gas turbine buckets, gas turbine vanes, etc. for lowering the metal temperature. They play a major role in enhancing the life of components exposed to higher temperature during operation of gas turbines. Performance of TBCs is dependent on the coating procedure, type of coating material and bond strength between bond coat layer and TBCs. Amongst various techniques which are available for quantitative and quality assessment of the TBCs, non-contact thermography is one of the most promising techniques. The present work deals with simulating thermal cycling on coatings using Finite Element Methods (FEM) for understanding possible locations of residual stress development within the coatings due to thermal cycling. Subsequently, experimental thermal cycling of TBCs and their sequential study of defect formation using non-contact thermography are reported. Comparison of experimental studies and FEM results showed good correlation. Further, microstructural characterization of samples exposed to thermal cycling confirmed that the defects observed during thermography are due to delamination. These studies will be useful to predict defect formation in TBCs during operation of the gas turbine components.

A review on erosion of a Pelton turbine bucket

Hydro-power energy is the most efficient renewable energy sources in the world. India stands in the top ten hydropower generation countries list. Pelton turbine is a well-known hydropower extraction machine. The Pelton turbine buckets play an important role in the efficiency of the hydro turbine which is in continuous interaction with high velocity jet and there are possibilities of damages to the bucket in the form of erosion as water contains small debris as sediments. Eroded buckets greatly reduce the efficiency of the turbine. Attempt is made by researchers to developed co-relations to evaluate wear rate and efficiency reduction based on the practical data. The majority of erosion takes place at splitter areas. An erosion cannot be eliminated, but it can be reduced by some amount. The results of the mathematical model indicate that the effect of silt size to the wear rate is 0.0001 gram per gram of bucket weight for a particular silt concentration and the result of silt concentration to wear rate is 0.0007 gram per gram of bucket weight for a particular silt size. The normalised efficiency loss is increased to 0.13% for a specific silt size with the variation of silt contraction. The average wear rate is nearly 3.1 mm per year for laboratory-scale Pelton turbine bucket; which is manufactured from brass and bronze materials. The coating of various materials over the buckets are used by researchers to reduce erosion. Among all coating materials, WC-Co-Cr gives better results against erosion.

Selection of Erosive Wear Rate Parameters of Pelton Turbine Buckets using PSI and TOPSIS Techniques

Hydro turbine machineries erosion due to silt is a complex issue for the effective practice of hydropower plants. Erosion caused by silt of the Pelton turbine buckets is a compound phenomenon that depends on size of silt particles , silt particles concentration , velocity of jet , and working time . This paper deals with the influence of silt erosion for various silt loaded factors and effective parameters. The preference selection index (PSI) and technique for order of preference by similarity to ideal solution (TOPSIS) approaches has been adopted to find optimal set of parameters which offers the highest performance for the Pelton turbine. Based up on the results obtained from both PSI and TOPSIS approaches it is found that optimal performance has been provided by A-1 alternate with geometric and flow parameters as , , and respectively.

Effect of Microstructure and Mechanical Properties of Austenitic Stainless Steel 1.6mm Butt Welded by Plasma Arc Welding

Plasma Arc Welding (PAW) is more tolerant to joint misalignment than Laser Beam Welding (LBW) at a lower cost [1]. The present study deals with the assessment of mechanical and metallurgical properties of butt welded 1.6 mm thick austenitic stainless steel similar (SS304 and SS304) by using plasma arc welding technique. Similar butt-Welded joints were analyzed by using mechanical (Bend test, Erichsen cup test, tensile test) and metallurgical (Optical macroscopic and microscopic images) characterization methods. The bead width and depth of the butt welded 1.6mm thick butt joined SS304 was analyzed by macroscopic and microscopic images [2]. The Erichsen cup test was conducted on the weld specimens. The indentation was made on the weld specimens. In the similar metal joint the depth of indentation is high, which shows that the similar metal joint has better formability. This makes them appropriate for practicing in the aircraft industries (engine parts), automotive sector (engine-parts and assemblies) chemical processing, food processing, turbine buckets, pumps and valve parts [3]. Keywords: SS304, PAW, Butt weld, Erichsen Cup Test, Microstructure

Analytical modelling and mechanism of hydro-abrasive erosion in pelton buckets

Hydro-abrasive erosion, a severe issue in hydraulic turbines, is caused by sediment laden flow leading to shutdowns and losses. In this study, a simplified analytical model is developed which describes the relationship of hydro-abrasive erosion in Pelton buckets with sediment properties, erosion velocity, turbine material property and duration of erosion. This model has been validated by comparison with both experimental measurements and literature, and shows strong agreement for most of the parameters. Further, mechanism of erosion in various parts of the buckets made of 6 types of material (3 types of steel, 2 coatings and bronze) were analysed from scanning electron microscope (SEM) images. The mechanism of erosion in different parts of Pelton buckets was found to be strongly related with the flow pattern in that part. The metallic turbine buckets showed plastic deformation whereas coatings showed crack formation initiating material removal. The study shall be useful for design and material experts working in the field of hydraulic machinery.

Novel trends in modelling techniques of Pelton Turbine bucket for increased renewable energy production

Pelton turbines have been used for harvesting clean energy from water jet for over 100 years. The wide range of their applicability and the robustness with minimal onsite monitoring and carbon free energy production makes them one of the most desired hydro turbines for renewable energy production. Pelton turbine buckets are subject to complex turbulent multiphase flows with free surfaces, thus received lot of attention from Computational Fluid Dynamics (CFD) researchers to visualise the flow patterns. In addition, the bucket geometry optimization has been a prevalent research stream using analytical and graphical methods. Both of these investigations fields have resulted in significant improvement in the performance of the Pelton Turbine system. However, the design investigations for each feature are carried out independently due to the complexity in incorporating large number of design parameters. Thus, analysing the complex fluid flow on each pre-optimized design was rather challenging due to expensive computational needs of CFD and limited manufacturing possibilities. Today, development of accurate and inexpensive CFD models and innovative manufacturing technology such as rapid prototyping has made complex freeform shape possible to simulate and manufacture. Hence, any bucket designs disregarded in optimization on the basis of manufacturing feasibility can now be possible to manufacture and is worth investigating. This will require the combination of CFD and design optimization field of investigation with novel analysis approach. This paper examines these fields of studies with the view to establish the background for such novel approach. This approach could be a foundation for design optimization of turbomachinery or any reaction surface leading to increased production of renewable and sustainable energy from existing resources.