Hydro Turbine Blade Research Articles

DEPOSITION BEHAVIOR OF WC-17Co COLD-SPRAYED COMPOSITE COATING ON HYDRO TURBINE STEELS

Cold spraying is a promising technique for depositing wear-resistant coatings on components like hydroturbine steels. This paper highlights the feasibility of hard WC-17Co coating on 13Cr4Ni hydroturbine steel. The coating was deposited at 25, 30, and 40 bar at 800∘C and 50 bar at 900∘C. Further, different characterization techniques (SEM, XRD) were used to analyze the developed coatings. The Vicker hardness testing was employed to determine the hardness of the coated sample. It was observed that WC-17Co coatings deposited at 40 bar and 800∘C offered a maximum hardness of up to 275 Hv, which is an excellent quality for anti-wear applications in hydro turbine blades.

Development of high pressure cold spray coatings of tungsten carbide composites

The current study used a cold spray technique to create WC-Co cermet coatings. In hydroturbine blade applications, deposition of WC-Co cermets using the cold spray technique is difficult. However, the Cold spray method may totally eliminate WC segment degradation as associated to other conservative techniques like laser cladding, plasma spraying and high velocity oxygen fuel (HVOF). In the present work, nitrogen gas was used to spray WC-12Co powder with a cold spray solution. SEM, EDS, and XRD were used to demonstrate microstructure and do phase analysis. The results suggest that applying cold spray has no effect on the WC phase. By applying cold spray to pre-heated WC-12Co powder with low-density particles, it was effectively applied to a solid substrate with higher hardness and lower porosity.

Mechanisms of slurry erosion in coatings of hydro-turbines

In power generation sector, efficiency of power plant is an important parameter. In hydrodynamic power plants, the prominent reason for efficiency degradation is slurry erosion (SE), which usually results in the form of damage turbine blades and other components costing to the time and money expenses owing to repair and replacement of parts. Over the passage of years, SE has been noticed as the major fallback of hydro-power industries. The prime operating parameters SE are impact velocity, impact angle, slurry concentration, hardness ratio (hardness of erodent particles to that of target material) as well as size and shape; morphology of slurry particles. Researchers have come up with some solutions to deal with the SE issue such as coatings on turbine blades. Coating are considered as suitable and effective remedies for retention of power plant efficiency. The exhaustive available information about SE phenomenon and associated failure mechanisms of concerned materials, either in coated or uncoated conditions is an indicative of its complex and unpredictable nature. This article is written to discuss the prospects of numerous coatings of hydro-turbine blades, their SE and associated failure mechanisms. Especially where hardness of deposited coating layers plays a prominent role in enhancing the SE resistance.

Microstructural and Mechanical Characterization of a Cold-Sprayed WC-12Co Composite Coating on Stainless Steel Hydroturbine Blades

Microstructural and Mechanical Characterization of a Cold-Sprayed WC-12Co Composite Coating on Stainless Steel Hydroturbine Blades

The effects of geometric shapes at different assembly gaps to achieve the optimal hydrodynamic conditions

In turbines, kinetic energy is transferred to the shaft then converted into a rotational motion to move a generator, so having a good design in the efficiency of turbines is important. Studies show that the efficiency of turbines in the presence of shafts has not been investigated so far. Therefore, our main goal in this study is to investigate the effect of shaft presence on the final efficiency of the hydro turbine. In this paper, the flow of fluid passing through the channels around the sharp leading edge cylinders in a tunnel is simulated using Lattice Boltzmann Method (LBM). Fluid streamlines stability, flow velocity rate, and pressure coefficient in channels with different shapes at assembly gaps of 2, 1.75, and 1.5 m have been investigated. The studied channels are considered in seven Airfoil-like shapes, Reverse Airfoil-like, hyperbola, Triangle, Triple triangle, Hexa triangle, and trapezoidal. The results show that the pressure coefficient in all channels decreases by increasing assembles gaps. On the other hand, reducing the pressure coefficient in the channel leads to cavitation. Cavitation causes erosion at the tip of the hydro turbine blades and reduces the life of the turbine. Therefore, the pressure coefficient is one of the most important parameters that depend on the assembly gap. Finally, the result shows that installing Hyperbola channels with an assembly gap of 1.75 m has the best performance in simulated hydro turbines.

Slurry Erosion Behaviour of Low-Temperature Liquid Nitrided 16Cr5Ni Martensitic Stainless Steel

Hydroturbine blades experience erosive wear during operations due to the presence of silt particles. The hydroturbine blades are fabricated from 16Cr5Ni martensitic stainless steels (16/5MSS). In order to mitigate the erosive wear of blades, heat-treated 16/5MSS (16/5HTT) were liquid nitrided at low temperature of 450 °C (16/5M450) and 500 °C (16/5M500) for 10 h in separate batch process. The cumulative weight loss after slurry erosion test of 16/5M450 is found to be 73% less than that of 16/5HTT, whereas the cumulative weight loss of 16/5M500 is found to be 6.7% more than that of 16/5HTT. The enhanced resistance to slurry erosion of 16/5M450 is attributed to high hardness of expanded martensite (αN-Fe) in the nitrided layer. αN-Fe is formed by diffusion of N in the nitrided 16/5HTT. When nitriding is done at 500 °C, then there is a reduction in resistance to the slurry erosion resistance which is caused by the CrN phase.

Tribo-behaviour of nano-structured coatings deposited by various techniques: A review

Tribo-mechanical degradation caused by erosive wear is a very severe problem in hydro power stations, turbine blades, marine environments, aircraft, piston-cylinder mechanisms, and various other industrial components which results in surface damage and hence alters the functionality performance of part components that brings huge economic losses. Higher erosion rates bring pre-mature part failure and hence shorten the service life. In this current investigation, analysis of previous literature and comparative study of different nanostructure, as well as conventional coatings are made in the erosive environment. Parameters affecting the erosion rate like size, type, and shape of erodent particles, impact angle, material property and composition etc. are also discussed. To overcome such instances wear resistant coatings are applied to the component surface to increase the functional service life. The chromium carbide (Cr 3 C 2 NiCr) and tungsten carbide (WC) based nanostructured as well as conventional coatings are commonly used to minimize the erosive wear of part components which are also summarized in this present work.

Erosion-Corrosion Protection Due to Cr3C2-NiCr Cermet Coating on Stainless Steel

Cr3C2–NiCr coatings have been used extensively to combat the erosion corrosion of hydro power turbine blades made of stainless steel. Cr3C2–NiCr coatings are also used in aqueous corrosive environments due to the high corrosion resistance rendered by the NiCr binder. In this investigation, both erosion and corrosion environments are introduced to cermet coating to study corrosion behavior using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The cermet coatings are useful for reducing the risk of deterioration of mechanical properties of hydro power turbines due to the continuous exposure to the erosive and corrosive action of the corrosive environment containing silt. It was observed that Cr3C2–NiCr coating offered a reasonable improvement in corrosion resistance when compared to bare substrate. The corrosion behavior of the coating was studied in a 150 mL solution of 0.1 M NaCl with 2 gms of quartz particles (0.2–0.8 mm) at various rotation speeds (3000, 4500, 6000 rpm) of the solution over a 1 h immersion using potentiodynamic polarization and EIS studies in a specifically designed experimental set-up for erosion corrosion. When compared to the bare stainless steel samples at 3000 rpm and 6000 rpm, the coating showed the highest improvement at 6.57 times and the least improvement at 3.79 times, respectively.

Microstructure and cavitation erosion behavior of HVOF sprayed ceramic-metal composite coatings for application in hydro-turbines

Cavitation erosion commonly occurs in hydro-turbine blades and has been a crucial issue for operation of hydro-turbines. In this paper, high-velocity oxygen-fuel (HVOF) spraying was applied to produce Cr3C2–NiCr and WC-CoCr ceramic-metal coatings. The microstructure and the relationship between the flow velocity and cavitation erosion behavior of the coatings were evaluated, and their cavitation erosion mechanisms at different flow velocities were discussed. Experimental results showed that the WC-CoCr coating exhibited slightly lower porosity and significantly higher microhardness as compared to the Cr3C2–NiCr coating. Both ceramic-metal coatings were combined well with the steel substrate and showed an increase in the volume loss rates with increasing flow velocity. The volume loss rates for the WC-CoCr coatings were lower than that of the Cr3C2–NiCr coatings at each flow velocity. The critical flow velocity of the Cr3C2–NiCr coating was in the region of 33.5–41.9 m s−1. The cavitation erosion process of the Cr3C2–NiCr coatings mainly included removal of chromium carbide particles, coalescence of the craters and brittle detachment of the coating, while the failure mechanism of the WC-CoCr coatings was erosion of the binder phase at 23.4 m s−1, cavitation pits interlinking at 33.5 m s−1, and detachment of the WC particles at 41.9 m s−1.

Vortex Cascade Features of Turbulent Flow in Hydro-Turbine Blade Passage with Complex Geometry

A large-eddy simulation of three-dimensional turbulent flow for a hydro-turbine in the transitional process of decreasing load from rated power to no-load has been implemented by using ANSYS-Fluent in this paper. The survival space occupied by different scale flow structures for the different guide vane opening degrees was well captured. The flow characteristics in the transitional process were obtained. Different forms of the channel vortex were studied. The features of the vortex cascade and dissipation of the turbulent energy in blade passage were analyzed. The results show that the scales of the vortex structures have a large change in the transitional process of rejecting load, and the vortex distributions in the blade passage are significantly distinguished. The survival space of the different scale eddies in the blade passage is closely related to the scales of the vortex. The survival volume ratio of the adjacent scale vortex in the runner is about 1.2–1.6. The turbulent kinetic energy and eddy viscosity increase rapidly along the blade passage with the small-scale eddies going up, which implies that a dissipating path for the energy in the blade passage is formed.

Improved Resistance of Nanoparticle-Laden Polymer Coatings Subjected to Combined Silt and Cavitation

Abstract Hydropower generation, particularly in the Himalayan region during monsoons, suffers because of the erosion of turbine components, which is due to the high concentration of silt present in water. These high-power machines also suffer from cavitation, especially at off-design conditions. However, erosion caused by the synergistic effects of silt and cavitation can cause more serious degradation, is more complex, and remains an unsolved problem in hydraulic machines. The present work addresses this concern through the systematic study of different polymeric coatings under a controlled silt and cavitation environment. This article discusses the design and development of an experimental facility, where a specimen can be subjected to combined submerged slurry jet along with acoustic cavitation produced by a focused ultrasonic transducer. Novel polymeric coatings made of polyurethane (PU) reinforced with hard nanoparticles (B4C and SiC) of varying concentrations (from 1 to 75 weight percentage [wt. %] being defined with respect to polymer weight) are used in this work. These coatings show erosion resistance superior to the base material (16Cr-5Ni martensitic stainless steel) commonly used to make hydroturbine blades. Results are divided into three divisions. At first, we present erosion kinetics and discuss possible erosion wear mechanisms based on pure silt erosion experiments. Afterwards, pure cavitation erosion and synergistic studies of silt and cavitation studies under different experimental conditions are presented. Base material showed the maximum mass loss rate of ∼22 mg/h, pure PU suffered ∼9 mg/h, while nanoparticle-reinforced PU (10 wt. % B4C or 2 wt. % SiC) has a loss of ∼1.5 mg/h. This shows the tremendous potential that this approach of using polymer laden with hard nanoparticles has in combating the synergetic effects of silt and erosion. The results are well-supported by detailed scanning electron microscope images and analyses to explain the reason behind the successful performance of the coatings.

Dynamic Analyses of the Hydro-Turbine Generator Shafting System Considering the Hydraulic Instability

Hydraulic instability is a complex factor causing the vibration of hydro-turbine generator shafting system (HGSS), and the mechanism is the uneven distribution of flow along the circumference. The common reasons for this phenomenon include the inconsistency of the blade exit flow angle, the relay stroke and the guide vane opening. This paper mainly focuses on the research of the hydraulic instability caused by the inconsistency of the blade exit flow angle. Firstly, based on the Kutta-Joukowski theorem, the hydraulic unbalance force model is firstly presented. Then, considering the chain reaction among the hydraulic, mechanical and electrical instability, a combined nonlinear mathematical model of the HGSS is established. Finally, by using numerical simulation, the dynamic characteristics of the HGSS with the changing of the deviation of the blade exit flow angle, the blade exit diameter and the guide vane opening angle are analyzed. Moreover, it is found that the hydraulic instability determines the overall changing trend of the shafting dynamic behaviors. In addition, some stable ranges of the HGSS are distinguished. But above all, these results can efficiently provide a reference for the design and manufacture of hydro-turbine blades and the operation of hydropower stations.

RESEARCH ON PURPOSE OF DETERMINING THE OPTIMAL CONFIGURATION OF BLADES FOR IMPROVING THE ENERGY EFFICIENCY OF DIRECT FLOW HYDRO TURBINE

In this paper we present the results of the research conducted to determine the effective variant of guide vane and hydro wheel blades of direct flow hydro turbine. The aim of the theoretical study is to determine the optimal configuration of hydro turbine blades to improve the energy efficiency of the hydro turbine. As a result of the theoretical study, a mathematical model of a hydro turbine was developed in the interactive COMSOL Multiphysics. With the help of the COMSOL Multiphysics application program, the change in velocity and pressure distribution of water through the guide vanes and hydro turbine blades the optimal shape and angle of the guide device and the hydro wheel blades of the hydro turbine were determined. Based on the results of the research, it was determined the optimal configurations of the hydro wheel blades with high energy efficiency.

Studies on Slurry Erosion Behavior of HVOF Applied Y2O3-Added WC–10Co–4Cr Cermet on 13-4 Martensitic Stainless Steel

Commercially 86WC–10Co–4Cr hard cermet coating is applied via high-velocity oxygen fuel thermal spray process on hydroturbine blade steel, i.e., 13Cr–4Ni martensitic stainless steel to help improve its wear resistance and life against the eroding action of hard silt particles present in the discharge. The erosive wear resistance of 86WC–10Co–4Cr cermet is improved upon by the addition of 2 wt.% of micro-sized yttrium oxide, which serves as a hard phase. These cermet coatings were deposited on 13Cr–4Ni martensitic stainless steel substrates via high-velocity oxygen fuel method to get an average thickness of 350 µm. Slurry pot wear test (duration 40 h) was used to evaluate the erosive wear resistance of the cermet coatings and the bare 13Cr–4Ni martensitic stainless steel substrate. Silica sand (size range 210–297 µm) was mixed with water to make a slurry of 100 kg/m3 concentration. A sliding speed of 4.45 m/s was maintained between the samples and the slurry. The increase in wear resistance of 86WC–10Co–4Cr cermet due to the addition of 2 wt.% yttrium oxide has been explained on the basis of improvement in hardness from 1048 ± 22 to 1154 ± 25 HV and due to densification effect of yttrium oxide.

Research with purpose of defining the lift and drag forces acting on hydro turbine blade with changing attack angle of flow

Abstract. In this paper the results of the research conducted to determine the effective version of hydro wheel blades of direct flow hydro turbine are presented. The aim of the research is to determine the optimal configurations of hydro turbine blades to improve the energy efficiency of the turbine. As a result of the study, a mathematical model of a hydro turbine was developed in the interactive COMSOL Multiphysics. Research was performed in the COMSOL Multiphysics application program with using Reynolds Averaged Navier Stokes method to Navier-Stokes equation for incompressible fluid. Direction of flow to blades with changing attack angle along blades was investigated. The change in velocity and pressure distribution of water through hydro turbine blades was considered. The optimal location of the blades was determined. Defined lift and drag forces acting along the blade. Based on the results of the research, it was determined the optimal configurations of the hydro wheel blades with high energy efficiency. G M T Английский Испанский Итальянский Казахский Китайский Трад Китайский Упр Корейский Русский Турецкий Французский Английский Испанский Итальянский Казахский Китайский Трад Китайский Упр Корейский Русский Турецкий Французский Звуковая функция ограничена 200 символами Настройки : История : Обратная связь : Donate Закрыть

HVOF Sprayed WC Based Cermet Coating for Mitigation of Cavitation, Erosion & Abrasion in Hydro Turbine Blade

Considerable advancement has been made over the last decades in various thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new troubles and industrial requirements. WC-based hard metals are widely used in industry mainly are being developed for a wide variety of applications to resist wear, erosion and cavitation due to their high hardness and toughness. Slurry erosion, abrasive wear andcavitation erosion problems are found in turbine runners as well as in other parts of the system. Slurry erosion complications are especially important during rainyPeriods in hydroelectric power plants owing the growth in the number of abrasive particles impacting the exteriors, especially in systems where the comprehensive clarification process is not possible. Portions in interaction with fluids usually needdistinctmaintenanceincluding time consuming heat treatments processing, welding, use of super alloy etc. Thermal spray coatings are appears as a practical alternative to the costly and health hazardous hard chrome plating to repair components and prevent excessive wear because during the deposition process no significant changes to the microstructure of substrates. The term thermal spray describes a family of processes that use chemical or electrical energy to melt (or soften) and accelerate particles of a material which is then deposited on a surface. HVOF sprayed cermet coatings have very low porosity, high hardness, high abrasive resistance, good wear resistance. The review presents the concerns related to materials and the fabrication process of protective wear resistant coatings by thermal spraying methods used for the protection of hydro turbine system.

Advance Applications of Nanomaterials: A Review

In this paper, recent applications of nano science and technology are discussed. Nano technology is spreading rapidly across the world as a more powerful technology. Nanotechnology controls the matter at its atomic level, thus the properties like strength, hardness, durability, etc. of matter are considerably affected under the scale of nanometers (10-9m). Its small size and high surface to volume ratio gives very special and unique properties to it, which can be used in our practical problems. The essential needs of today’s industry are to design and develop a higher efficient system with minimum losses. The use of nano science is able to fulfill this current requirement with maintaining high accuracy. Nano technology is broadly used in various fields, mainly in wear and corrosive environments such as nano composite materials, nanostructured coatings (in hydro turbine blades, coal fired boiler etc.), cutting tools, nano fluids (to increase heat transfer rates of fluid), building materials and in automotive industries to enhance the effectiveness of that particular system. In present investigation, the aim is to review the advance applications of the nano materials.

Slurry Erosion Behaviour of Pack Boronized 13-4 Martensitic Stainless Steel for Hydro Turbine Blades

Pack boronizing of hydro turbine blade steel i.e. 13Cr-4Ni martensitic stainless steel (13-4 MSS) has been conducted as a protective coating against silt erosion. A boride coating of approximately 40 µm was deposited on the samples. Slurry pot method was used to evaluate the erosive wear resistance in which samples were rotated in an abrasive slurry of 100 g/litre silica sand (size 210 – 297 µm) in water at a speed of 4.45 m/s for a period of 40 hrs. Higher wear resistance of pack boronized 13-4 MSS has been attributed to the higher hardness of boride coating (2300 VHN) over that of bare 13-4 MSS (345 VHN).

Gas transfer in a bubbly wake flow

The present work reports simultaneous bubble size and gas transfer measurements in a bubbly wake flow of a hydrofoil, designed to be similar to a hydroturbine blade. Bubble size was measured by a shadow imaging technique and found to have a Sauter mean diameter of 0.9 mm for a reference case. A lower gas flow rate, greater liquid velocities, and a larger angle of attack all resulted in an increased number of small size bubbles and a reduced weighted mean bubble size. Bubble-water gas transfer is measured by the disturbed equilibrium technique. The gas transfer model of Azbel (1981) is utilized to characterize the liquid film coefficient for gas transfer, with one scaling coefficient to reflect the fact that characteristic turbulent velocity is replaced by cross-sectional mean velocity. The coefficient was found to stay constant at a particular hydrofoil configuration while it varied within a narrow range of 0.52-0.60 for different gas/water flow conditions.

Microstructure and Wear Behavior of Single layer (CrN) and Multilayered (SiN/CrN) Coatings on Particulate Filled Aluminum Alloy Composites

This article presents the slurry erosive wear behavior of single and multilayer coatings on granite powder reinforced aluminum alloy composites for hydro-turbine blade material. The composites were fabricated by stir casting technique with different weight fraction (0, 2, 4, 6wt.%) of granite powder in 1050 aluminum alloy. In this study, the slurry jet erosive performance of uncoated, single layer and multilayer coating granite powder filled alloy composites in a slurry jet wear test was conducted for four different operating parameters such as filler content (0-6wt.%), impact velocity (10-25 m/s), impingement angle (30-75 0) and erodent discharge (160-280 gm), respectively. The slurry erosion rate was a maximum at 0wt.% granite powder reinforcement in uncoated, single layer and multilayer coating samples such as: 0.0203 gm/kg, 0.00981 gm/kg and 0.00756 gm/kg, respectively at impact velocity of 25 m/sec. Taguchi’s orthogonal array (L 16) was applied to study the experimental results of the uncoated and coated alloy composites. A correlation was derived from the results of the Taguchi experimental design and a proposed predictive equation for estimation of slurry erosion rate of these composites. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were conducted to analyze the topography of the eroded surface of uncoated and coated granite powder reinforced aluminum alloy composites.