Cavitation Wear Research Articles

An improved Eulerian-Lagrangian method combined with ductile material model for cavitation erosion assessment

Abstract Cavitation erosion in hydraulic machinery constitutes a multifaceted, instantaneous physicochemical process resulting in material wear and decreased efficiency. This paper employs an enhanced Eulerian-Lagrangian method to evaluate cavitation erosion. The method captures erosive impact loads released by the non-spherical collapse of near-wall bubbles and integrates them with a one-dimensional ductile material mode, a capability lacking in traditional homogeneous mixture methods. A classic axisymmetric nozzle test case is conducted under four different cavitation numbers (s=0.8, 0.9, 1.09, and 1.6) to validate the reliability of the new approach. Qualitative and quantitative analysis demonstrates that the impact load distribution on the lower and upper walls aligns with experimental measurements. Compared with reference works, the new method accurately predicts the maximum wear position and yields a narrower erosion area closer to the experimental data. Moreover, the relative error of the minimum incubation time at s=0.9 on the lower wall calculated by the new method is 4.67%, and the relative error of the maximum wear rate is 36.6%. This method is pivotal for further studying how various materials respond to cavitation wear. Further analysis reveals that material response patterns are similar under cavitation erosion conditions at s=0.8, 0.9, and 1.09. In contrast, the material surface wear rate is reduced by 46.7%, and the incubation time nearly triples at s=1.6.

Innovation and possibility of various coating materials with microwave hybrid heating

Cavitation wear is causing considerable financial losses for a range of industries, such as chemical, food processing and hydropower plants. Microwave cladding process involves the application of a coating of another material over the surface of a specific material, which offers properties beneficial for high electrical conductivity, low loss tangent and excellent thermal stability. This review article is intended to provide a basic understanding of the properties of various types of microwave cladding materials. This chapter also emphasises on the characterisation of the samples produced through the microwave cladding on various substrate materials. Furthermore, this chapter describes the potential applications of the microwave cladding process in numerous engineering and industrial sectors. Additionally, this chapter also reports the potential future technological advancements in the field of microwave cladding process.

Features of cavitation wear of chrome electrolytic coatings

Cavitation wear is a pervasive phenomenon on water transport. The parts of ship propulsion system as well as the water-cooled surface of cylinder liners of high-speed ship diesels are subjected to cavitation attack. Bright chromium deposits are used to protect the water-cooled surface of liners. Nevertheless, the effect of cracks appearing in the electrolytic chrome coating upon depositing on the cavitation resistance of coating is still an open relevant problem. The goal of the study is to analyze the kinetics and mechanism of the destruction of the bright chrome electrolytic deposit under cavitation attack. The cavitation resistance of chrome electrolytic coatings after grinding and after polishing was studied. The chrome electrolytic coatings were obtained on the plates (90 × 30 × 7 mm in size) made of cast iron SCh21. The chrome was deposited on one side (90 × 30 mm) of the plate placed vertically by flow anodic jet chrome plating in standard electrolyte (kg/m3): chrome anhydride — 250; sulfuric acid — 2.5; trivalent chrome — no more than 5; trivalent iron ions — no more than 10. The electrolyte was prepared using distilled water of a single distillation. The parameters of depositing: electrolyte temperature is 50°C; the current density amounts to 60 A/dm2. Four samples cut from the same plate were used. The coatings on the first two samples were ground using the abrasive paper number 320. The coatings on the second pair of samples were first ground successively on the abrasive paper of different grit: 320, 500, 800, 1000, and 1200, and then polished on the cloth with GOI paste. The cavitation wear tests were carried out on a magnetostrictive vibratory rig in fresh water, the frequency and amplitude of the rig horn vibration was equal to 22 kHz and 28 μm, respectively. The spacing between the chrome-plated sample surface and the horn butt was 0.5 mm. The wear of the samples was evaluated by periodical weighing during testing. The wear of the ground samples turned to be significantly higher, than that of polished samples. The photographs of the surface after different duration of the cavitation attack show that the initial cracks formed on the coating during chrome plating are the centers of cavitation destruction. To reduce the negative impact of initial cracks on the cavitation resistance of the bright chrome electrolytic coatings deposited on the water-cooled surface of the cylinder liners of diesels it is shown expedient to include polishing in the technological process of depositing chrome coatings.

Comparative Analysis of wear on Hard and Soft Coated Francis Runners: A Case study of Kali Gandaki ‘A’ Hydro Power Station

Abstract Surface coating on Turbine components is a regular practice in hydro power plants to tackle with wear. The Kali Gandaki ‘A’ hydro power station of Nepal having 3x48 MW Francis Turbine units made of CN 13/4 material has been regularly coating its Runners entirely using Tungsten Carbide based alloy through HP-HVOF hard coating process. In 2021 for the first time one of the Runners was partially coated around the blades using elastomeric semi-soft coating material manually via brush application, while the remaining portion of the Runner was hard coated. This study was conducted to compare the wear on the hard and soft coated runners after a similar period of operation under similar circumstances. Both the Runners were found to be heavily worn out at the upper and lower wearing rings, suction side of all blade inlets at the shroud and all blade outlets. The soft coated runner was found to have more erosion and cavitation wear than the hard coated runner. A unique canal-type cavity was found on the hub side wearing ring of the soft coated runner but no such pattern was seen on the hard coated Runner. The sections of the soft coated Runner where the coating was still intact had the parent material fully protected, but the sections with coating completely washed away were found to have deeper and wider cavities showing that the parent material had significantly washed away. The major reason behind the soft coated Runner being more worn out could be the manual application of coating material using hand brush which could have resulted in blade profile being distorted due to which the Runner efficiency might have reduced and thus higher erosion and cavitation occurred. This study could be useful to assess the applicability as well as the benefits and drawbacks of hard and soft coating on Francis Runner.

Optimization and reconstruction of pelton buckets based on statistical techniques, artificial neural networks and CFD modelling

During operation Pelton turbines suffer from erosion and cavitation wear, which decreases the hydraulic efficiency. Welding repair is a cost-effective method for recovering the original bucket geometry but requires templates to ensure proper results. However, those templates may be unavailable for Pelton units with decades of operation. This is the case of one of the 2.8 MW Pelton units at Nima II, a small hydropower plant in Colombia that began operation in 1942. This paper presents the redesign and optimization of the bucket. First, the bucket is rebuilt following both, technical recommendations, and Design of Experiments (DOE) to verify the effects of the basic dimensions on the hydraulic efficiency. Experimental measurements on the eroded turbine validate the two-phase computational fluid dynamics (CFD) modelling to be applied in the optimization process. Second, the best inner surface is found by using a multi-objective optimization based on Artificial Neural Networks trained by the previous DOE and a genetic algorithm. At the end, the CFD results suggest a total hydraulic efficiency recovery of 8 %. Further experimental tests on the optimized runner showed a difference of 0.7 % from the predicted value.

Analysis of the cavitation phenomenon: A case study in the drainage channel of the Aruana neighborhood located in the city of Aracaju-SE

Drainage channels are intended for the drainage of surface water and watercourses. Having a high construction cost, over time they present pathologies requiring inspection and maintenance. Among these pathologies, we can mention the wearing caused by cavitation. Given the above, this research aims to carry out a visual survey, and subsequent analysis, of the occurrences of wearing by cavitation in a drainage channel, in the neighborhood of Aruana, city of Aracaju-SE. First, a visual survey was achieved to assess the situation of the structure; Then, an analysis was performed through the registration of images and a bibliographic survey of the main causes and consequences of this phenomenon. It was possible to verify the occurrence of cavitation wear next to the culverts, on the side walls of the channel, and more intensely, at the junction of the rainwater galleries with the channel. It is concluded that, in many points, the pathology is at an advanced level, requiring urgent intervention; the intervention prevents the evolution of pathologies; the cost of repairs at an advanced stage is high, justifying the importance of periodic maintenance and correction at an early stage; And finally, problems can be avoided or mitigated in the design phase, with the use of better quality materials, and with constant inspections of the structure.

Análisis del efecto de cavitación en una turbina hidráulica de tipo francis en condiciones de operación de la C.H. Chaglla

The performance of a hydropower plant depends on several parameters, i.e., the turbine type used, plant design, turbine classification, plant head, flow rate. All turbines are used for their best operation under the best level of efficiency with optimal values for their nominal head, water flow and turbine speed. However, under these conditions, the cavitation phenomenon occurs in the hydraulic turbine. It is only for the reason that the dynamic attribute of liquid flow becomes unstable with high pressure fluctuations. Cavitation is an unavoidable and unavoidable problem in hydraulic turbines. Cavitation destroys the performance of the turbines. When turbines operate at partial loads rather than their highest efficiency point, they experience cavitation to a greater extent. Francis turbines are designed to be operated in various conditions. The research objective was to analyze the cavitation occurrence in a Francis type turbine and how to minimize it, as a result a report was obtained on damages caused by the bubbles implosion on the surfaces of the turbine, especially in the impeller, at the exit waist edge of the intermediate zone in UG-1, present areas with cavitation wear between blade and blade 1-2. 3-4. 8-9. 11-12. 13-1. According to the inspection, the evolution of the cavitated areas is controlled and a slight detachment of material is observed, which does not compromise the useful life of the impeller. Likewise, for the impeller blades in the UG-2, cavitation wear areas occur between blade and blade 3-4. 9-10. 11-12; It is also controlled and slight material release is observed which does not compromise the useful life of the impeller. Regarding the wear of the blades in the impeller, we can indicate that in the UG2 there is 6.47 % accumulated wear, while in the UG1 there is 5.47 %. In the case of the guide vanes, the wear clearance with the highest incidence is in the UG2 with 0.692 mm of accumulated wear, while in the UG1 with 0.2595 mm.

Francis Type Turbine Runner Design and Comparison with Model Test Results

Cavitation wear and hydraulic efficiency decrease in hydroelectric power plants have frequently been the subject of various research and studies. A hydroelectric power plant built on the Kızılırmak River in Türkiye started operating in 1960 and has not been subjected to any large-scale rehabilitation work other than general maintenance until today. The power plant has 4 Francis-type turbines, each with a power of 32 MW. Due to cavitation wear of turbine runners over the years, performance loss, vibration, and noise problems have arisen. Moreover, the maximum turbine hydraulic efficiency, which was 92% in 1960, the year the power plant was commissioned, decreased to 87.9% according to the efficiency measurements carried out at the power plant in 2020. In this study, Computational Fluid Dynamics (CFD) analyses were accomplished with Reynolds averaged Navier Stokes (RANS) calculations for the redesign of the Francis-type turbine runner and finally checked by a model test according to IEC 60193. It was observed that the model test and CFD results were close to each other, especially at the best efficiency point. The maximum turbine hydraulic efficiency, which was calculated as 94.95% as a result of CFD analysis at the nominal head, was calculated as 95.19% by the model test. The x-blade shape created in the redesigned turbine runner blades ensured homogeneous pressure distribution and increased the hydraulic efficiency significantly.

Studies of the Solid Particle Erosion Resistance of 30 L Steel with Different Types of Surface Modification

Earlier studies have shown that 30 L steel, used for the manufacture of hydraulic machinery equipment elements, has greater resistance to cavitation wear than 20 GL steel. This paper presents the results of experimental studies of the solid particle erosion resistance of 30 L structural steel samples with different surface modifications based on nitriding and boriding processes. The characteristics of the modified near-surface layers were determined. The results of the solid particle erosion resistance tests carried out according to the ASTM G76-13 standard are presented. The research results demonstrated that boriding processes worsen the solid particle erosion resistance of 30 L steel at flow impact angles of 30° and 90°. All the considered variants of surface nitriding at an impact angle of 90° do not worsen the solid particle erosion resistance of 30 L steel samples, while at an impact angle of 30°, they increase the solid particle erosion resistance by at least 10–20%.

CAVITATION EROSION RESISTANCE OF VACUUM-ARC COATINGS BASED ON TiN

This review presents an examination of various studies investigating the impact of deposition process conditions and structural characteristics of TiN-based vacuum-arc coatings on their ability to withstand cavitation erosion in water. The structural and phase composition of TiN coatings is influenced by two key technological parameters: the nitrogen pressure in the vacuum chamber and the substrate bias potential. However, it has been observed that vacuum-arc alloy coatings such as TiSiN and TiAlYN exhibit notably lower resistance to cavitation erosion. Additionally, research on multilayer Ti-TiN coatings with varying numbers and thickness ratios of layers has not shown an improvement in resistance to cavitation wear when compared to single-layer coatings deposited under optimal conditions. On the other hand, single-phase stoichiometric TiN coatings deposited at a higher nitrogen pressure of 2 Pa and a bias potential of up to -300 V have demonstrated remarkable resistance to cavitation wear. These coatings could be effectively utilized to protect the titanium alloy Ti-6Al-4V against cavitation damage.

Destruction mechanisms of epoxybased composite filled with metal powder under cavitation attack

The samples of epoxy compound with a powder filler and without it are tested on cavitation wear. The powder of aluminum bronze BrAZhNMts9–4–4–1 is used as a filler. The powder is obtained by filing the rod of the bronze. The composition of the epoxy compound is 100 parts of the resin K‑153 plus 12 parts of the hardener (polyethylene epolyamine). The distribution of the bronze particles in the epoxy compound follows the law close to the exponential one, the average particle size is equal to approximately 27 μm, and the volume fraction of the bronze powder in the compound is about 9,5 percent. The tests are conducted using the ultrasonic magnetostrictve vibrator UZDN‑2T in fresh water of room temperature, the frequency and amplitude of the vibrator horn end equal to 22 kHz and 28 µm respectively. The distance between the horn end and the sample surface is 0,5 mm. During the experiments the wear of the samples is evaluated by their weighting on analytical scales with step-type indication of 0,1 mg, measuring the surface roughness and the microhardness of the bronze particles in the composite is carried out as well. It has been shown that the addition of the bronze particles into the epoxy compound not only changes the kinetics of cavitation wear of the polymer but also decreases its cavitation resistance. The decrease in cavitation resistance caused by bronze particles addition is attributed to the fact, that the boundary between a metal particle and epoxy matrix is a «weak» spot, and the destruction of polymer begins from this boundary area under cavitation attack.

Selected technical ceramics as nanoreinforcement for polyvinyl butyral/epoxy polymer composites

In this study, various technical ceramics in the form of nanostructures, known for their exceptional mechanical properties and thermal resistance, were analysed as potential reinforcement of a polymer matrix system. A combined, hybrid composite matrix was considered, consisting of epoxy resin and polyvinyl butyral. The following nanostructures were incorporated into the polymer matrix by ultrasonication and solvent-casting technique: B4C, TiB2, CNT and INT-WS2. Polymer composites were prepared by solvent-casting of neat hybrid polymer matrix and polymer matrix reinforcing with each chosen individual nanostructure from a temporary solvent – ethanol. The characterisation of the obtained polymer composite samples encompassed Fourier transform infrared spectroscopy analysis, differential scanning calorimetry, tensile test, hardness measurement and examination of resistance to cavitation wear.

Evaluation of the incubation period of polymers in cavitation wear by the method of profilometry

The possibility of using profilometry for determining the duration of the incubation period of polymeric materials upon their testing for cavitation wear is considered. Six polymeric materials were tested for cavitation wear: plexiglass, fluoroplastic, low-pressure polyethylene, caprolon, Thordon SXL polymer, and epoxy compound. All the polymers were tested in fresh water kept at 20 ± 3°C, using an ultrasonic magnetostrictive vibrator, the vibration frequency and amplitude of the device horn butt were 22 kHz and 28 μm, respectively. The distance between horn butt and the butt-end surface of the cylindrical polymer sample was set at 0.50 mm. The samples were periodically weighed during testing, the roughness of their worn surface was evaluated, and sample mass loss and arithmetical mean deviation of the assessed profile of its surface were plotted as a function of the test duration. Like the cavitation wear of metals, the cavitation wear of polymers is also characterized by the presence of an incubation period, during which the separation of the wear particles from the sample surface does not take place yet. It is shown, that determination of the incubation period from the dependence of the mass loss vs test duration distinguishes is rather laborious, and, moreover, is accompanied by large errors due to water absorption. The use of profilometry was proposed to shorten the time and increase the accuracy of the determination of the incubation period of the cavitation wear of polymers. The arithmetical mean deviation of the profile of the surface under study is measures periodically during testing for cavitation wear. The duration of the incubation period is determined using the dependence of the arithmetic mean deviation of the wear surface profile on the duration of the cavitation impact by the abscissa of the point, in which the monotony and(or) smoothness of the dependence (plot) is violated.

Common Failures in Hydraulic Kaplan Turbine Blades and Practical Solutions.

Kaplan turbines, as one of the well-known hydraulic turbines, are generally utilized worldwide for low-head and high-flow conditions. Any failure in each of the turbine components can result in long-term downtime and high repair costs. In a particular case, if other parts are damaged due to the impact of the broken blades (e.g., the main shaft of the turbine), the whole power plant may be shut down. On the other hand, further research on the primary causes of failures in turbines can help improve the present failure evaluation methodologies in power plants. Hence, the main objective of this paper is to present the major causes of Kaplan turbine failures to prevent excessive damage to the equipment and provide practical solutions for them. In general, turbines are mainly subjected to both Internal Object Damage (IOD) and Foreign Object Damage (FOD). Accordingly, this paper presents a state-of-the-art review of Kaplan turbine failures related to material and physical defects, deficiencies in design, deficits in manufacturing and assembly processes, corrosion failures, fatigue failure, cavitation wear, types of cavitation in hydro turbines, hydro-abrasive problems, and hydro-erosion problems. Eventually, the authors have attempted to discuss practical hints (e.g., nanostructured coatings) to prevent damages and improve the performance of Kaplan turbines.

Application of repair composites as wear-resistant coatings

This article is devoted to reconditioning of working surfaces of equipment exposed to abrasive, corrosive, and cavitation wears. Importance of implementation of rational reconditioning methods at enterprises is discussed. The reasons and properties of wear types are listed, peculiar attention is paid to cavitation wear and its consequences. Classification of faults and reconditioning methods of worn working surfaces are described, it is proposed to use composite materials on polymer basis with various fillers; composite materials with ceramic fillers are more preferred as the most wear resistant ones and providing restoration of numerous wears of process equipment and pipelines. The article presents physicomechanical properties of compounds with ceramic fillers. In order to solve the formulated problems, practical proposals are given with regard to application of composite materials available at Russian market. The most suitable materials are determined on the basis of quality/price ratio. Examples of performed activities are given, economic efficiency of reconditioning using composite materials is highlighted. Major advantages of the proposed technology are described.

Plasma Coatings for Protection Against Hydroabrasive and Cavitation Wear

The results of research work on the application of coatings designed to protect the working surfaces of machine parts and mechanisms operating under conditions of hydroabrasive and cavitation wear are presented. Coatings were produced by supersonic atmospheric plasma spraying of powder materials using air as a plasma gas. The experimental list of materials was chosen taking into account the experience of the authors in protecting the details of the propulsion and steering complex of river vessels using coatings applied by subsonic thermal plasma flows.

Study of operating mode of axial and centrifugal pumps with hydroabrasive wear of parts in flow section of pumping units

To date, a significant amount of work has been done to study the processes of cavitation and hydroabrasive wear in laboratory conditions. Using existing equations for assessing hydroabrasive or cavitation wear leads to certain inaccuracies since the action mechanism underlying them does not correspond to the actual operating conditions of hydraulic machines. Very little has been studied about the issues associated with joint and intense cavitation-abrasive wear, which always occur in fullscale hydraulic machines operating on natural watercourses with high turbidity. So far, the wear of the working bodies of centrifugal and axial pumps has been poorly studied, depending on the mode of their operation, and a methodology has not been developed for selecting operating modes, taking into account the wear of their parts. In this paper, the wear of parts of axial and centrifugal pumps in laboratory conditions is studied, and the dependences of wear on the characteristic dimensions and duration of their operation are given. The results of micrometering of the working parts of the pumps showed that the blades of the impellers along the length and width wear out unevenly both in size and shape. In axial and centrifugal pumps, the most intense wear occurs at the outlet sections of the impeller blades and their sealing elements. When pumping muddy water for 2000 hours, the sealing gaps of type D pumps with a head of 75–80 m are 2.8– 3.1 mm. With an increase in the end clearance of the impeller of an axial pump from the impact of a slotted cavitation-abrasive flow, the pressure value and the local concentration of solid particles in the flow play a leading role.

Reducing vibration of pumping units of reclamation systems

The article presents the results of scientific research on the operation of pumping equipment at reclamation pumping stations. In pumping stations, more and more attention is being paid to measures to maintain the reliability and efficiency of pumping units and reduce the negative impact of factors of various origins. One of the most significant factors affecting the service life of the equipment is the increased vibration of the pumping unit. According to the analysis of failures of pumping equipment at pumping stations in Uzbekistan for 2010-2021, more than 40% of the pump stops occurred due to increased vibration. The most common cause of vibration of pumping equipment is waterjet and cavitation wear of the impeller, destruction of seals, wear, and temperature rise of the bearing. The greatest vibration occurs when the equipment is operated in heavy and non-optimal modes. As a result of the generalization of the research results, active methods and means of reducing the vibration of pumping units were identified.

Parametric Studies of Effect of Cavitation Jet Modes on Wear Rate of Surface of Structural Materials

In this study the kinetic curves of cavitation wear of cast steels 20 GL and 30 L used for production of critical elements of hydraulic machines were obtained. The typical predominance of growth rate of cavitation mark diameter over its depth was found on the surfaces of the investigated cast steels. The revealed phenomenon made it possible to offer a formula for estimating the volume removal of the examined cast steels in order to expand the scope of the method according to ASTM G134-17. This method uses profilometry and microscopy and allows to determine cavitation resistance both for homogeneous and heterogeneous materials, including materials after modification of their surface (with different types of coatings and hardenings).

Development and analysis of coatings cavitation erosion model by controlling changes in the acoustic properties of liquid media in limited volumes with resonant dimensions

The article considers the influence of the extent of cavitation wear of materials and their coatings on the acoustic properties of the sounded liquid media in a limited volume. The model of an liquid media bounded by a volume with resonant dimensions is considered based on an electromechanical analogy system. The parameters and characteristics of the sounded liquid media most sensitive to changes in the dimensions of the volumes confining them as a result of their cavitation erosion are determined.