Turbine Erosion Research Articles

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

AbstractDeveloping highly accurate sediment erosion testing methods for Pelton turbine overflow components is challenging due to their irregularly curved surfaces. In this study, we designed a method to evaluate the sediment erosion of the Pelton turbine bucket using test blocks with an accuracy of 0.0001 g. In addition, we conducted sediment erosion tests on a model Pelton turbine and conducted an in‐depth study on the installation design of the turbine runner and bucket, the design of the erosion test blocks, and the arrangement; we analyzed sediment abrasion distribution on the bucket's working surface. Our test results show that the bucket splitter edge, as well as the root of the working surface, are heavily worn. The maximum erosion rate of the working face is 0.7669 μm/h, and the maximum erosion rate of the splitter edge is close to 5 μm/h, which is highly consistent with the distribution of sediment erosion observed in Pelton turbines operating under sandy river conditions. This test method is essential for examining sediment erosion in Pelton turbines.

Experimental and computational analysis of air injection as a mitigation technique for silt erosion in hydro turbines

Experimental and computational analysis of air injection as a mitigation technique for silt erosion in hydro turbines

Influence of guide vane skirt structure on sediment erosion of high-head turbine in high hardness and sandy river

Influence of guide vane skirt structure on sediment erosion of high-head turbine in high hardness and sandy river

Investigation of operational settings, environmental conditions, and faults on the gas turbine performance

Abstract Gas turbine engines are complex mechanical marvels widely employed in diverse applications such as marine vessels, aircraft, power generation, and pumping facilities. However, their intricate nature renders them susceptible to numerous operational faults, significantly compromising their performance and leading to excessive emissions, consequently incurring stringent penalties from environmental regulatory bodies. Moreover, the deterioration of gas turbine performance is exacerbated by variations in working conditions based on operational settings and environmental conditions. Past studies have focused on certain working conditions that limit effectiveness in real-world applications where operational settings and environmental conditions vary during operations. The influence of these working conditions on the performance of gas turbines also needs to be assessed, as they can lead to different fault patterns resulting in unplanned maintenance, unnecessary maintenance costs, unsafe conditions and stringent penalties. This study uses the gas turbine simulation program to simulate a high-bypass turbofan engine inspired by Pratt & Whitney PW-4056, analysing the combined effects of operational settings and environmental conditions on engine performance while also incorporating simulations of common gas turbine faults like fouling and erosion in various locations and severities along the gas path. The model’s accuracy is confirmed by low mean absolute percentage errors of 0.004% of thrust at the cycle reference point and 0.15% and 0.28% at 2 km and 7 km altitudes, respectively, demonstrating the model’s robustness across varying operational scenarios. In conclusion, this research highlights the significant effects of operational settings and environmental factors on gas turbine performance, particularly impacting specific fuel consumption and thrust. The study reveals that operational settings and environmental factors significantly impact fuel consumption and thrust. Specifically, compressor fouling and low-pressure turbine erosion increase nitrogen oxide (NOx) emissions by 4.5% and 11.1%, while fouling of nozzle guide vanes and high-pressure turbine erosion raise unburned hydrocarbon by 10.0% and 20.2%, and carbon monoxide (CO) by 3.2% and 5.2%, respectively, compared to a healthy engine. These insights highlight the importance of component-specific degradation in influencing gas turbine performance and emissions.

Evaluation of the jet distortion by sediment erosion in the needle in the Pelton turbines

Abstract In order to succeed in the transition to a more renewable energy sector, the hydropower industry must overcome multiple challenges in the coming decades, including the need for faster and reversible turbines to support emerging renewable energy sources. In addition, the location of new projects in tropical and semi-tropical areas poses unique considerations, as does the increase in sediment. Evaluating sediment erosion in turbines is a critical challenge, which may partly be addressed by analyzing the behavior of water jets from eroded nozzles in Pelton turbines. This paper presents an evaluation of the quality of the jet under various hydraulic conditions, focusing on needle erosion. The study is part of a research project conducted in the Waterpower Laboratory at NTNU, focusing on Pelton turbines. Furthermore, this paper investigates erosion patterns caused by sediments on the needle and explores the impact on jet performance. Through high-speed visualization and image processing, the behavior of a jet from the needle tip to a representative distance downstream has been investigated. The investigation revealed discernible differences between jets with eroded and uneroded needles in size and edge variation.

Experimental study of sediment erosion in Francis runner using a non-recirculating test rig

Abstract The problem of sediment erosion in hydraulic turbines has posed challenges in design, operation and maintenance of hydraulic machinery. A study was conducted with a 2 kW model Francis runner for investigating the erosion prone locations. The runner and guide vanes were coated with four different coats of colour (red, yellow, green, and blue). The system was then operated in sediment-laden condition with an average concentration of sediment particles of about 24000 ppm. The runner was operated in sediment-laden conditions for 36 hours and the observations were made after each 4 hours of operation. With increasing hours of operation, the colour coating of the runner was eroded at specific locations and a pattern was revealed showing the areas affected by erosion. The erosion was mostly observed at the trailing edge of the pressure side and the junction of the suction side of the blade and hub. Erosion on the hub was observed towards the leading edge of the runner in the area close to the suction side and the region near the trailing edge of blade. Similarly, the guide vanes were eroded at the pressure side of the leading edge and the trailing edge of the suction side. The causes of erosion were identified as high velocity and acceleration of sediment particles, inter-blade vortex, and vortex due to leakage flow.

Modeling of particle erosion of high-pressure turbine based on dynamic mesh method

In this work, we investigate erosion characteristics of a high-pressure turbine by using Oka erosion model coupled with the dynamic mesh method, which allows for the dynamic change of blade profile. The variation of blade profile, material removal and performance degradation during erosion are quantified for the original blade, and the results are compared with those of an optimized blade previously obtained through multi-objective optimization of aerodynamic and erosion resistance performances. It is found that compared with the original blade, the optimized blade is of higher efficiency and lower erosion, suggesting that the previous multi-objective optimization, albeit ignoring the dynamic change of blade profile, still works for the dynamic erosion process. For either blade, the efficiency decreases slowly at first and drops sharply after a period of erosion, because as the erosion proceeds, the regions occupied by the vortex rapidly expand, leading to the blockage of blade passage. The transient erosion characteristics and particle trajectories indicate that the erosion is initially located near the middle and rear of blade on pressure side and the leading edge on suction side; as the erosion progresses, the erosion mainly occurs near the leading edge on pressure side but almost disappears on suction side.

HVOF-sprayed surface coating with various compositions of Co-NiCrAlY-Al2O3 to minimize sediment erosion in hydraulic turbines

The components of hydropower plants are susceptible to sediment erosion caused by hard particles in the water. These hard particles cause substantial material loss and a reduction in the performance of the hydraulic turbines. The present study deals with the mitigation of sediment erosion in hydraulic turbines by developing a protective coating (CoNiCrAlY-Al2O3 metal-ceramic composite) using a high-velocity oxygen-fuel (HVOF) coating technique. Hardness measurement, surface wettability analysis, and surface roughness measurement were conducted to characterize the coatings, whereas scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS) were performed for metallurgical characterization. The slurry/sediment erosion behavior of bare and coated substrate was investigated using a slurry erosion tester. Experiments were performed for five coating compositions at different impact angles (30° ≤ ϴ ≤ 90°) and velocities (6 ≤ v ≤ 12 m/s). The maximum improvement in erosion performance (reduction in erosion rate compared to bare substrate ≈ 28.12 % at 30°, 9.29 % at 45°, and 11.69 % at 90° impact angle) was obtained for the coating having 12 wt% alumina doped into Co-NiCrAlY. The coating's performance was improved due to increased hardness, high shielding effect, and reduction in impact energy on Al2O3 by using CoNiCrAlY-Al2O3 deposition. The empirical correlation between erosion rate and velocity for both bare and coated substrates has also been proposed.

Effects of sediment characteristics on the erosion of Pelton turbine

As Pelton turbines are increasingly used in high mountain regions because of their unique advantage of high-water head adaptability, the hydraulic characteristics and multi-phase flow behaviour in Pelton turbines have attracted the attention of many scholars. Most notably, the presence of solid particles such as sand exists in natural river systems, which end up in the turbines, causing erosion. This has become an international academic issue which has not been fully developed yet. In this study, three-phase simulations based on Eulerian–Lagrangian methodology are conducted to investigate the erosion phenomenon, especially in the bucket region. Sediment particle characteristics such as size and concentration in both the distribution system and buckets region are analysed. The innovation of this study is that, unlike other erosion investigations, it focuses on the impact angle of the jet flow as this is a unique characteristic of Pelton turbines. Furthermore, the sediment particle's flow characteristics at different bucket rotating angles and how they influence the erosion mechanism are also investigated. Results reveal that larger particles cause greater erosion on the bucket. In small particle and standard diameter conditions, the impact angle is mostly below 5 ∘ . Finally, this study presents the first successful attempt in using rotating angle to describe the erosion in a Pelton turbine. A corrected erosion model adapted to the Pelton turbine is given through regression and proves effective in predicting erosion.

Effect and mechanism of erosion in Pelton turbine and case studies—A review

Pelton turbines are widely used in hydropower stations located in mountainous regions, especially with water head drop of more than 2000 m. Due to the complex structure and working principle of the turbine, the flow is more complicated than reaction turbines, making the numerical simulation more difficult. The impulse action causes the occurrence of erosion phenomena in Pelton turbines, which will directly decrease the hydraulic efficiency and reduce the turbine's life. For investigating the erosion characteristics, computational fluid dynamics is widely used on variegated platforms according to their unique advantage. Thus, different platforms are introduced and compared in solving the multi-phase flow using a discrete element method or the other meshless methods. In addition, the erosion mechanism is studied and classified in different aspects such as impact angle and impact velocity. However, unlike the feasibility of numerical simulations, experimental work on the erosion mechanism is still challenging to reproduce. Furthermore, the state of experimental research is discussed by listing the various major facilities in operation and comparing their methods of experimental analysis. Case studies all over the world provide a very rich database of erosion patterns which would be highly useful in validation and verification of simulation and experimental results. Studies have shown that particle parameters, such as size, concentration, shape, velocity, and the interaction between particles and material surfaces, significantly impact the erosion of Pelton turbines. In response to this erosion, upgrading materials and implementing geometric optimization have proven to be effective strategies.

Comparative evaluation of sand erosion in reversible turbine at pump mode and turbine mode

During the operation of reversible pump turbine, the flow passing components are often worn by sediments. In this paper, Euler-Euler computational fluid dynamics (CFD) method is used to simulate the liquid-solid two-phase steady flow in several pump modes and turbine modes. Finnie models are used to predict possible wear conditions and further analyze the causes of component wear. Results show that runner is the most easily worn component, which is related to local high flow velocity. The runner erosion position is mainly concentrated in the middle part of the pressure side. The erosion position of guide vane and stay vane is mainly concentrated in the leading edge and trailing edge, which depends on the change of condition. By daily weighted, the turbine mode is found has higher erosion rate than that of pump mode. This study provides the scientific support of anti-erosion of pumped storage units.

Multiobjective Optimization Study On the Aerodynamic Performance and Anti-Erosion Characteristics of a Single-Stage Dusty Flue Gas Turbine

Abstract Solid particle erosion of dusty energy recovery turbine blades has a great impact on the operating economics and safety of the unit. To mitigate the erosion of blade and improve the aerodynamic performance of the turbine, a multiobjective optimization method for turbine cascade based on the experimental design method, genetic algorithm and CFD multiphase flow simulation was developed. The optimization results show that the number of stator and rotor blades and the trailing edge angle at 50% blade span are the main parameters affecting the efficiency and blade erosion of the dusty turbine. By reducing the number of stator blades and the circumferential bending angle of the stator trailing edge, the impingement velocity and impingement probability of particles impinging on the stator trailing edge decrease by 7.5%~16.8% and 8.9%~46.2%, respectively. Additionally, compared with the original design, the flow separation loss and secondary flow intensity of the rotor cascade are suppressed by adjusting the load distribution and inlet attack angle of the rotor; thus, the turbine efficiency effectively improves by 2.28%. Meanwhile, the optimized blade reduces the particle impingement velocity and probability on the rotor leading edge, and the erosion condition of the rotor leading edge decreases by 70%.

Numerical Analysis of Francis Turbine being operated in variable speed from sediment erosion perspective

Sediment erosion in hydro turbines is one of the most daunting reasons incurring huge losses to power plant owners located in the Hindu Kush Himalayan region. Repetitive repair and maintenance of runners of Francis turbines installed in such power plants have been one of the major contributor to these losses. There is no measure of how much these power plant owners have lost due to reduction in efficiency brought about by the eroded surfaces of runners. Amidst several optimizations performed in changing the runner design, this study has been conducted to study the applicability of the pre-existing designs being operated in variable speed conditions, irrespective of its practical difficulties. Numerical simulations have been performed to determine the sediment erosion of the runners at different operating conditions. In addition to the guide vane angles, and the amount of sediment injected into the system; which is parametrized as a function of the guide vane angles; rotational speed of the runner has also been varied. Complete efficiency hill diagram and sediment erosion hill diagram have been developed to analyse the efficiency and sediment erosion at several operating conditions. Finally a comparison of the variations in efficiency and sediment erosion upon operating the turbine in synchronous speed and variable speed modes have been shown. Basically, the efficiency of the turbine and sediment erosion on blade surface can be increased and decreased respectively, at off design conditions by operating the turbine in variable speed.

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.

Thermoeconomic Analysis of Subcritical and Supercritical Isobutane Cycles for Geothermal Power Generation

This article presents a novel and comprehensive approach for the thermoeconomic evaluation of subcritical and supercritical isobutane cycles for geothermal temperatures of Tgeo = 100–200 °C. The isobutane cycles are optimized with respect to the maximum net power or minimum levelized cost of electricity (LCOE). Cycle optimization is also included, using a minimum superheat temperature to avoid turbine erosion, which is usually neglected in the literature. The results show that economic optimums are found in the far superheated region, while thermal optimums are obtained with dry saturated or with slightly superheated vapor at the turbine inlet (ΔTsup < 5 °C). Supercritical cycles achieve better thermal performance than subcritical cycles for Tgeo = 179–200 °C. Internal heat recuperation improves the cycle performance: the net power output increases and the LCOE decreases, but specific installation costs (SICs) increase due to the additional heat exchanger. For geothermal temperatures of Tgeo = 120 → 150 °C, the costs are LCOE = 100 → 80 USD2022/MWh and SIC = 7000 → 5250 USD2022/kW, while for geothermal temperatures of Tgeo = 150 → 200 °C, the estimated costs are LCOE = 80 → 70 USD2022/MWh and SIC = 5250 → 4600 USD2022/kW.

Data-driven internet of things and cloud computing enabled hydropower plant monitoring system

Hydropower is one of the renewable energy sources that can play a crucial role to fulfil the global energy demand. However, the performance of the hydro turbine is severely affected by silt erosion and cavitation problems which causes a reduction in the overall efficiency of the plant. Various studies have been carried out and are available in the literature to investigate silt erosion and cavitation issues in hydro turbines. It has been reported that cavitation and silt erosion varies with the variation in discharge under part load and overload operating conditions of the machine. However, very few studies are available to predict the performance of the machine under variable operating conditions. Hence, there is a scope of study for monitoring the performance under these conditions in real-time, as it is difficult to predict the behavior of the machine using the existing models. In view of the above, an architecture of a data-driven IoT-based cloud computing-enabled hydropower plant monitoring system has been proposed under the present study. In order to develop this system, historical plant data has been collected and correlations are developed, which are validated with real-time data on the ThingSpeak cloud. It has been found that the developed model can accurately predict the condition of the hydro turbine with an R2-value of 0.9693 having a mean absolute percentage error (MAPE) of 0.67% at 0.89% of root mean square percentage error (RMSPE), and the power factor with an R2-value of 0.9503, having a MAPE of 0.798% at 0.91% of RMSPE.

A Comprehensive Review on Investigation of Sediment Erosion of Pelton Wheel Turbine

Hydro turbines installed at different hydropower plants face the issue of sediment erosion. Sediment erosion is an ambiguous phenomenon influenced by several parameters, including silt concentration, size, jet velocity, diameter, and fluid viscosity. Silt erosion imposes severe issues for hydropower plants, like shutdown and maintenance costs. The hydro turbine efficiency decreases with the increase in sediment erosion and eventually the breakdown of turbine components. Various researchers conducted small-scale experimental bench studies and numerical simulations to analyze the influence of the above-mentioned parameters on silt erosion, but the actual flow conditions are too complex to simulate. Therefore, no such erosion model has been developed to predict exact erosive wear. This paper presents an extensive review of the literature survey on sediment erosive wear of hydro turbines, both the adopted methodology by previous studies and parameters affecting sediment erosion in Pelton turbine are summarized. Based on literature studies, various aspects of erosive wear, parameters influencing it, and its severe effects on efficiency are thoroughly discussed. Appropriate remedial measurements for erosive wear made by multiple researchers, erosion models developed so far, and their measuring accuracy and the future scope of this research study are articulated in detail.

Numerical study on effect of operating condition and solid concentration on hydro-abrasive erosion of high head Francis turbine

The powerplants in the Himalayan region are generally subjected to hydro-abrasive erosion. The deterioration of components due to erosion causes reduction in performance, changes the fluid flow pattern and even the breakdown of the turbine. In the present work, the Bhilangana-III powerplant Francis turbine is considered a reference turbine for numerical investigation using the computational fluid dynamics (CFD) tool. The study presented an evaluation of hydro-abrasive erosion of high head Francis turbine for the different operating conditions and sediment concentrations. The modified Grant and Tabakoff erosion model is used for the erosion rate calculation. To investigate the effect of various operating conditions, the study is conducted at part load, best efficiency point (BEP) and high load. Also, to examine the impact of suspended sediment on the erosion of turbine components, the solid concentration varies from 500, 1200, 2000, 3000 and 4000 ppm. The observed erosion pattern is similar at all operating conditions for the stay vane, guide vane and runner, but the density of erosion is different. The observed deterioration density due to erosion is higher for part and full load than in the BEP condition. The guide vanes and runner vanes are highly susceptible to erosion due to higher absolute velocity and relative velocity at guide vane and runner vane, respectively. The observed erosion rate variation is qualitatively in-line with the on-field turbine erosion condition. It is also found that the increase in erosion rate with the sediment concentration is almost linear but more than 90% and 79% higher for the runner than stay vane and guide vane, respectively.

Application of hydro-abrasive erosion model from IEC 62364:2019 standard in Francis turbines

Hydro-abrasive erosion in hydraulic turbines is critical and one of the prominent issue due to its association with maintenance costs and production losses in the hydropower plant. IEC 62364:2019* standard guide focuses mainly on hydroelectric powerplant equipment and provides the standard on particle abrasion rates on several combinations like operating conditions, component materials properties, water quality among many factors. With the consideration of different critical parameters, a theoretical model of abrasion rate on hydraulic turbines is proposed by IEC 62364:2019. Present study is conducted to elucidate the several terms used in the theoretical model of abrasion rate for Francis turbine as per the guidelines. The work has taken account into run-off river (RoR) hydropower plant consisting of Francis runner operating in sediment laden rivers in the Himalayan area. Theoretical expected erosion depth for runner inlet, runner outlet, guide vanes facing plates and labyrinth seals is calculated. Characteristic velocities of runner (Wrun) and guide vanes (Wgv) were estimated to be 32.26 m/s and 35.05 m/s respectively. Particle load was calculated based upon the sampling data available from the site. Measurement data from field observation during overhauling was used for comparison with the data calculated from empirical relation. For 229 hours operation of turbine, observed abrasion depth varies from 8.1 mm in guide vanes to 1.5 mm in labyrinth ring corresponding to calculated values of 7.53 mm and 1.89 mm for same components. Results shows good correlation among calculated values from IEC and measured values from the site. An optimized solution can thus be devised based on the evaluation of hydro-abrasive erosion along with energy production and maintenance expenses.*IEC 62364:2019. Hydraulic machines - Guidelines for dealing with hydro-abrasive erosion in Kaplan, Francis, and Pelton turbines. Edition 2.0 (March 2019) International Electrotechnical Commission, Geneva, Switzerland [1]

Measurement of sediment particle size distribution and shape using dynamic imaging analysis

Hydropower plants operating in fragile mountainous regions face severe sediment erosion of hydraulic turbines, resulting in decreased efficiency, frequent power interruptions, and downtime for maintenance. The sediment size and shape are detrimental to the hydraulic turbines and influence sediment erosion. Sediment management is a crucial aspect of tackling sediment erosion in hydraulic turbines. The traditional method of measuring particle size and shape is time-consuming, labour-intensive, and usually requires statistical analysis. The present study applies the recent technique of dynamic imaging analysis to determine the particle size distribution and shape of sediment. Five different silt-sand mixtures have been used to check the ability of dynamic imaging analysis. Further, the repeatability and reliability of the results were checked by carrying out five repeated measurements of each sample under the same condition in a short period of time. This study will help the researchers and sedimentologists to adopt the dynamic imaging analysis technique for measuring particle size and shape and help the instrument developer in designing a better future version of the instrument.