Part Of Blade Research Articles

Multi-Objective Optimization Design of Dynamic Performance of Hydrofoil with Gurney Flap

The horizontal axis tidal turbine, as a crucial device for capturing tidal energy, has gained significant attention because it has better energy efficiency performance. Enhancing the performance of foils, a vital part of tidal turbine blades, can significantly improve tidal turbine performance. Among numerous methods to enhance the foil performance, the Gurney flap has gained significant attention due to its avoidance of complex structural design. Currently, there is limited research on optimizing the design of Gurney flaps while considering the dynamic performance of foils. In this study, the S809 foil with a blade cross-section was selected as the research subject, a multi-objective optimization design platform was created by integrating a multi-objective optimization algorithm with Computational Fluid Dy-namics (CFD) numerical simulation techniques. The objective of this platform is to enhance the dynamic performance of the hydrofoil by optimizing the geometric structure of the Gurney flap. The improvement of dynamic lift and the size of the dynamic stall hysteresis loop are used as objective variables in this study to evaluate the hydrofoil’s dynamic performance. The optimal Latin hypercube design method is used in the optimization process to choose sample locations, and the Kriging approximation model is used to determine the relationship between the design variables and the objective variables. Meanwhile, the Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) is used to create a multi-objective optimization platform for solving the optimization problem, and the optimized results are validated using CFD. Comparative validation results show that quantifying the dynamic performance during hydrofoil pitching oscillation and using the optimal Latin hypercube design method and Kriging approximation model for optimizing the Gurney flap structure is rational and accurate. This study explores the mechanism of the Gurney flap through in-depth CFD numerical simulations and finds that the Gurney flap affects the flow characteristics at the hydrofoil’s trailing edge, thereby influencing the performance. It increases the pressure difference between the pressure and suction surfaces, thus enhancing the hydrofoil’s lift. Finally, this article provides three recommended parameters to improve the dynamic performance of the hydrofoil. This research can serve as a reference for the application of Gurney flaps in tidal turbine blade design.

Initial Study of the Onsite Measurement of Flow Sensors on Turbine Blades (SOTB).

This paper presents a new framework using MEMS flow sensors on turbine blades (SOTB) to investigate unsteady flow features of a rotating wind turbine. Self-heating flow sensors were implemented by the U18 complementary metal-oxide semiconductor (CMOS) MEMS foundry provided by Taiwan Semiconductor Research Institute (TSRI). Flow sensor chips with a size of 1.5 mm × 1.5 mm were parylene-coated, output via a wireless data acquisition system (WDAQ), and mounted at the root, middle and tip of a 1.2 m diameter semi-rigid turbine blade of a 400 W horizontal axis wind turbine (HAWT). The instantaneous angles of attack (AOAs) of the SOTB were found to be 46~62°, much higher than the general stall AOA of 15°, but were accurate considering the normal detection of the flow sensors. The computational fluid dynamics (CFD) simulation of the HAWT was also compared with the SOTB output. The onsite measurement herein revealed that the 3D secondary flow increment, mostly obvious near the middle part of the turbine blades, degraded both the sensor and the turbine performance and initially justified the onsite measurement application.

Fatigue Damage Assessment of Turbine Runner Blades Considering Sediment Wear

The wear phenomenon that occurs on the blades during operation has a significant impact on the fatigue life of the blades. To address the issue of fatigue life assessment for turbine runner blades subjected to increased dynamic stress due to sediment wear, taking a specific high-head hydropower unit’s mixed-flow turbine as the research subject, a hydraulic model of the turbine was established. The wear zones of the runner blades are determined based on the distribution of the flow field’s velocity and the sediment volume fraction. According to the wear rate formula for runner blade material, the amount of wear on the blades is determined, and the dynamic stress data for the dangerous areas of the blades under different degrees of wear are calculated using a unidirectional fluid–structure coupling method. The load spectrum of the time–stress history data for the dangerous area at different levels of wear was compiled using the rain-flow counting statistical method. The operating time ratios for the flood season and the non-flood season are combined. Based on the fatigue cumulative damage theory, the total fatigue damage at the maximum stress part of the runner blade was calculated for different stages of wear, providing a reference for the life calculation of mixed-flow hydraulic turbines.

Design and performance analysis of soft pneumatic manipulator‐based linear cutter and stem holder for sweet pepper harvesting

AbstractEfficient automation of stem‐cutting processes in agricultural practices is crucial but little‐studied for improving productivity and reducing labor‐intensive tasks. To address this need, we present a customized stem cutter and stem holder designed explicitly for sweet pepper harvesting. The stem cutter comprises a fixed plate and a moving plate with a blade, which moves in a single plane at an upward angle of 30° toward the fixed plate. The movement of the blade is facilitated by a soft bellows pneumatic actuator constructed using silicon rubber material. By applying air pressure from a DC air pump, the actuator extends forward, causing the blade part to make contact with the fixed plate and effectively cut the stem. The stem holder holds the stem securely before cutting. It contains two inflatable manipulators made of soft materials that expand inwards when air‐filled, ensuring that the stem is securely held and readily collected after harvest. Both simulation and experimental results are presented, in which the average cutting time was 2.356 s. We believe that these innovations represent an efficient method for automating the stem‐cutting process in sweet pepper cultivation and thus significantly contribute to the field of agricultural robotics.

Erysiphe corylacearum as a New Pathogen of Hazelnut in the Czech Republic

In July 2021, leaves and shoot tops of the common hazel (Corylus avellana L.), with a whitish coating, were found in the Czech Republic (southern Moravia region). The infected hazel bushes were found along a road in a deciduous forest and in an urban garden. In most European countries, Phyllactinia guttata is found on the abaxial surface of the leaves in the form of a continuous whitish to light grey mycelium, possibly with large black chasmothecia. In our case, the mycelium was present on both sides of the leaves, but the symptoms and the incidence were much stronger on the adaxial side. The first symptoms usually appeared on the adaxial side of the leaves as small white radially expanding patches of mycelium. In the final stage, the spots merged and covered a substantial part of the leaf blade (50–85 % on the adaxial side, 5–25 % on the abaxial side). When the abaxial side of the leaves was infected, chlorotic spots were evident on the adaxial side. The spots of powdery mildew were small (3–15 mm), whitish, rounded to irregular, effuse eventually becoming confluent, and occurred primarily on the adaxial side of the leaves. Conidiophores (30–53×4–6 µm) grew on the amphigenic mycelium, were erect, consisted of 1–3 cells, i.e. cylindrical foot cell and followed 1–2 cells, from which hyaline ellipsoid to doliform-limoniform conidia (17–34 ×15–21) (n = 50) were individually detached. Single or in groups dark brown chasmothecia (77–116 µm in diameter) had up to hyaline 8–15 aseptate straight appendages (50–102 µm) with multiple (3–5×) dichotomously branched apexes and recurved tips. Chasmothecia contained 3–6 asci (42–62 × 34–55 µm) with 4–8 obovoid to broadly ellipsoidal hyaline ascospores (14–22 × 75 µm). Based on morphological characters, the powdery mildew was identified as Erysiphe corylacearum (2). Morphological identification was confirmed by molecular analysis of samples. DNA was extracted from symptomatic leaves tissue using the DNeasy Plant Mini Kit, (Quiagen, Hilden, Germany) and the rDNA internal transcribed spacer region of 2 isolates was amplified using primers PMITS1 and PMITS2 (Cunnington et al. 2003) and sequenced. BLAST analysis of our 720bp fragments (both identical and represented by GenBank accession no. OR432526) showed 100% sequence identity to ITS rDNA sequences of E. corylacearum other countries of Central Europe for example from Austria (MW031866), Italy (MW045428), Hungary (OQ411007), Germany (OP554268) or Slovakia (MT176105). Pathogenicity was verified on two-year-old plants of Corylus avellana. Healthy leaves were artificially infected by dusting conidia from infected leaves. Inoculated plants were incubated under controlled conditions (21–23 °C, 70–80 % relative humidity). Characteristic symptoms of powdery mildew appeared on the adaxial side of the leaves 9–12 days after inoculation. Control plants treated with distilled water remained symptomless. Powdery mildew isolated from inoculated leaves was morphologically identical to isolates from naturally infected leaves. The first record of E. corylacearum in Europe on cultivated hazelnut species was reported by Sezer et al. (2017) in Turkey in 2013. Within a few years, the E. corylacearum spread and was recorded on various species of Corylus in other European countries (for example Mezzalama et al., 2020; Rosati et al., 2021; Beenken et al., 2022; Boneva et al., 2023), East Asia (Arzanlou et al., 2018) and the USA (Meparishvili 2019). To our knowledge, this is the first report of Erysiphe corylacearum in the Czech Republic.

Investigation of radial force in a high-speed miniature pump

A high-speed miniature pump design is put forth for utilization in the aerospace sector, where the pump’s reliability holds critical importance under microgravity operational conditions. This study focuses on a dynamic bearing-equipped miniature centrifugal pump, chosen for its suitability in investigating radial forces. The prototype of the miniature pump is manufactured and tested by experiments at the rotational speed of 10,000r/min. A good agreement is observed between the numerical predictions and the experimental results. The radial force acting on different blade part has been analyzed for several flow rate conditions using the steady state CFD calculation. It has been found that the radial force exerted on the blade trailing edge exit is the main cause of the total radial force for the impeller. Moreover, using the unsteady CFD simulation, the evolution process of the radial force changing for both the direction and the magnitude with respect to the annular position due to the shaft rotation is discussed in details. The pressure pulsation is also monitored in impeller and volute casing. The results show that the amplitude of the unsteady radial force has a strong relationship with the time it takes for the blade trailing edge exit passing the volute tongue region, while the direction of the radial force hardly changes. The findings of this study contribute to facilitating the broader implementation of the high-speed miniature pump across diverse sectors of society.

Modern Technological Processes of Shaping in the Treatment of the Flowing Part of GTE Blades

Modern Technological Processes of Shaping in the Treatment of the Flowing Part of GTE Blades

PSXII-13 The Design of Equipment That Combines a High-Pressure Jet and a Translational Scraper to Improve the Manure Treatment Efficiency of Pig Barn Cleaning Machine

Abstract Livestock farming generates a significant amount of manure, which must be effectively managed to prevent environmental pollution and ensure the health and well-being of animals. The cleaning machine is a commonly used tool for removing manure from pig barns: however, it often leaves behind residual waste that is difficult to remove. To address this issue, a new equipment design that combines a high-pressure jet and a translational scraper has been proposed. This design aims to improve the efficiency of manure treatment by weakening the adhesion and removing stubborn waste particles, making it easier for the cleaning machine to collect the manure. The high-pressure jet provides a powerful stream of water that can dislodge even the most stubborn waste particles. For high-pressure washing, a DC 10V/10A standard water pump and a 70L water tank are included. The translational scraper, on the other hand, can move left and right across the surface of the slatted floor, effectively scraping away any remaining waste. For this work, an actuator was installed to move the blade part and the hook type work part. These two components work together to improve the efficiency of manure treatment and reduce the amount of waste left behind. By improving the efficiency of manure treatment, this new equipment design can help to reduce environmental pollution and improve the overall health and well-being of pigs. In addition, it can also reduce labor costs and improve the profitability of pig farming operations. In conclusion, the design of equipment that combines a high-pressure jet and a translational scraper has the potential to significantly improve the manure treatment efficiency of a pig barn cleaning machine. This new design can help to address the challenges associated with manure management in pig farming and promote a more sustainable and efficient approach to livestock farming. This achievement was made by the support of the Ministry of Agriculture, Food and Rural Affairs, R&D project(421044043HD030)

Numerical study of airfoil used for helicopter rotor tip to investigate the enhancement in the aerodynamic characteristics using active flow control at forward flight conditions

Helicopter forward flight is the most important state of flight due to time spent in this mode during the complete helicopter trip. In this study, a main rotor blade tip airfoil was simulated to obtain the effect of applying active flow control on the tip part of the rotor blade. A blowing excitation jet is applied to the leading edge of the airfoil just before the separation point with small momentum and high frequency to enhance the near wall boundary layer characteristic. This jet is used with different amplitude, frequency and excitation location from a leading edge to study the effect of this parameter. A numerical model is used to solve two different angles of attack and all results are compared with NACA report that used the same helicopter hub and airfoil. Results show good agreement with the experimental results and the chosen excitation parameter gives good enhancement to the performance of the airfoil used in the tip part of the helicopter blade in this mode of flight. Performance represented in lift and drag and lift to drag ratio shows improvement, reaching about 10% increase in lift and 30% decrease in drag, which means more than 50% change in lift to drag ratio. Furthermore, this study gives a good estimation of the best excitation location that is required for real application on the helicopter blade to improve of forward flight performance.

Using conditional generative adversarial networks for the prediction of stresses in an adhesive composite

AbstractFiber reinforced adhesives are an integral part of wind energy turbine blades and play an important role in evaluation of structural integrity of the blades. Digitization of manufacturing processes and demand for fast and efficient stress analysis argues for the application of deep learning. As a step forward in using deep learning to predict structural properties in composite, the work would explore the applicability of deep learning methods to 2D fiber reinforced composite. In this work, a composite adhesive used in wind energy turbine blades is used as an illustrative example. The composite adhesive when viewed using a CT scan machine shows a heterogeneous structure with two phases, a softer matrix phase and a much stiff fiber phase. For this purpose, several CT scan images of the fiber adhesive composite are used. The images on subsequent FEA analysis serves as the training data for the deep learning framework. Once trained, the neural network would be able to predict the stress distributions in the structure. We apply conditional adversarial networks as general purpose solutions to problems focused on stress prediction, which could be thought of as an image‐to‐image translation from the microstructure domain to the stress domain. These networks in addition to learning the mapping from input image to output image also learn a loss function to train for this mapping. This makes the method more generic because otherwise different loss formulations for different problems have to be formulated.

THEORETICAL STUDIES OF DRILLING FROZEN SOILS WITH A SCREW DRILL

Link for citation: Martyuchenko I.G., Zenin M.I., Kolesnikov A.Yu., Boikov E.V. Theoretical studies of drilling frozen soils with a screw drill. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 9, рр. 194-202. In Rus. The relevance of the study is caused by the need to create a new drilling tool to drill frozen soil in difficult conditions. This line of research is important and relevant for ensuring the formation of wells on frozen sands, since the screw drilling tool performs the deformation of frozen soil separation, which makes it possible to drill hard-to-drill soils, namely frozen sands. The main aim: to study the interaction of the destructive part of the helical drill with frozen soil and determine the rational values of the geometric parameters of the helical blade when achieving the lowest value of the force of soil separation and the highest value of the productivity of drilling. Objects: interaction of the destructive part of the helical blade of a helical drill with frozen soil. Methods: plotting dependencies of factors showing the energy intensity of drilling, on the angle of rotation of the radius of the helical blade, at which it increments, and on the pitch of the helical blade in the second section of the destructive part of the helical drill; analysis of the obtained results of theoretical studies of the force of soil separation and the efficiency of drilling from the geometric parameters of the helical blade of a drilling tool on frozen soils. Results. The authors have studied the influence of the geometrical parameters of the helical drill on well formation, obtained the dependences of the efforts and constructed the graphs for soil separation, as well as the dependence of the productivity of drilling on the angle of rotation of the radius of the helical blade, at which it increments, and on the pitch of the helical blade in the second section of the destructive part of the helical drill. Based on the results of theoretical studies, an analysis of the obtained dependencies was carried out and the area of rational values of the geometric parameters of the helical blade of a helical drill on frozen soils was found.

Utilization of The Saga Plant Abrus Precatorius L. in Indonesian Folk Medicine

Saga or known by the Latin name Abrus precatorius L. belongs to the Fabaceae family and is a leguminosae plant that grows in tropical and subtropical regions and has also been widely used for traditional medicinal practices. Saga is believed to be a plant that has natural properties and is important as a source of ingredients for making medicines to treat various diseases. Many pharmacological studies have been carried out which state that saga has various biological activities that can be act as anti-diabetic, anti-fertility, anti-germ, anti-cancer, and so on. Parts of the saga plant in the form of leaves, roots and seeds can be used for natural medicine which has been carried out by many traditional people for generations. Part of the leaf blade contains triterpene compounds, alkaloids, glycosides, and glycyrrhizin. It is known that the saga plant also has an abrin compound which has a very dangerous toxic effect when consumed by humans. The review of this article aims to gather useful information regarding the saga plant so that it can be better utilized and empowered for the benefit of human beings.

Designing Vortex Generators for Tidal Turbine Blades

Increasing tidal turbine performance through innovation is crucial if the cost of tidal energy is to become competitive compared to other sources of energy. The present investigation deals with the application of Vortex Generators (VGs) on tidal turbines in view of increasing their performance. The more mature wind energy industry uses passive VGs either as a retrofit or in the blade design process to reduce separation at the inboard part of wind turbine blades. Tidal turbine blades also experience flow separation and here we examine whether passive vane VGs can be used to reduce or suppress that separated flow.
 Vortex generators (VGs) in various forms have been used and studied for flow separation control on wings since the 1940s [1]. Their working principle is relatively simple: they generate streamwise vortices that energise the boundary layer on the surface they are attached to, by bringing high momentum fluid closer to the surface [2]. This mechanism has been described by various researchers [3–6], while a number of studies have provided optimization guidelines under a variety of flow conditions [7–13].
 In the present investigation, a VG configuration is selected following a thorough wind tunnel campaign. It is found that sizing parameters for the tidal turbine profile are very similar to the wind turbine relevant literature [13,14]. The best performing vane VG configuration had a height of 0.007c, which corresponded to half the local boundary layer height (0.5δ) for operational Reynolds numbers. The results are also used to validate a Reynolds Averaged Navier Stokes (RANS) VG modelling approach using the BAY model [15]. The validated method is used to simulate the flow past a tidal turbine in both model size (1:8) and full scale, see Figure 1. The results show that VGs do suppress flow separation in both cases. However, and importantly, it is revealed that the significance of rotational effects is such that when deciding VG placement locations, only the full size blade should be considered. In the interest of brevity, the performance increase caused by a standard VG configuration is show in Figure 2, where a power coefficient improvement of 1.05% is predicted at λ=3. Figure 3 shows the effect on the normal and tangential forces on the blade. In the final paper and presentation, the results for different VG locations will be included and analysed in detail.

Helicopter performance enhancement by alleviating retreating blade stall using active flow control

In this study, a model was created numerically to study the effect of active flow control on helicopter blade to improve the retreating blade stall. Active flow control is applied to helicopter blades to improve retreating blade stall along with the overall helicopter performance. The novel aspect of this study is using active control in a helicopter with a complex aerodynamic environment and using it in all significant flight modes. This has the advantage of practical application since active control can be used constantly without having to turn it off. The flow control is established by using blowing jets at the leading edge of the airfoil that is used at the tip part of the main rotor blade. 2D and 3D computational fluid dynamics (CFD) Turbulent-unsteady models are developed to investigate the effect of applying blowing jets on different helicopter modes of flight (hover and forward flight). Different excitation parameters and turbulence models are compared to get the maximum possible enhancement of the aerodynamic characteristic of the flow both in 2D and 3D. The results are validated against a NASA helicopter main rotor hub with known geometry and available performance parameters. Both models illustrated a good agreement with the published benchmark problem. The results revealed that the active control blowing jets can enhance the stall characteristics and aerodynamic performance of helicopter blades. The method delays the flow separation and increase the blade lift by about 10% in addition to a 40% increase in the lift to drag ratio. Thus, we can conclude that the present active control technique can enhance the helicopter in forward flight by delaying the retreating blade stall. This research offers insightful information on the usage of blowing jets for rotor flow control.

Jasmonates, gibberellins, and powdery mildew modify cell cycle progression and evoke differential spatiotemporal responses along the barley leaf.

Barley (Hordeum vulgare) is an important cereal crop, and its development, defence, and stress responses are modulated by different hormones including jasmonates (JAs) and the antagonistic gibberellins (GAs). Barley productivity is severely affected by the foliar biotrophic fungal pathogen Blumeria hordei. In this study, primary leaves were used to examine the molecular processes regulating responses to methyl-jasmonate (MeJA) and GA to B. hordei infection along the leaf axis. Flow cytometry, microscopy, and spatiotemporal expression patterns of genes associated with JA, GA, defence, and the cell cycle provided insights on cell cycle progression and on the gradient of susceptibility to B. hordei observed along the leaf. Notably, the combination of B. hordei with MeJA or GA pre-treatment had a different effect on the expression patterns of the analysed genes compared to individual treatments. MeJA reduced susceptibility to B. hordei in the proximal part of the leaf blade. Overall, distinctive spatiotemporal gene expression patterns correlated with different degrees of cell proliferation, growth capacity, responses to hormones, and B. hordei infection along the leaf. Our results highlight the need to further investigate differential spatial and temporal responses to pathogens at the organ, tissue, and cell levels in order to devise effective disease control strategies in crops.

Solidification microstructure characteristics and their formation mechanism of K447A nickel-based superalloy for dual-performance blisk

In this paper, the effects of cooling rate after casting and stirring process on γ’ phase, γ / γ’ eutectic phase, MC type carbide morphology and grain structure of K447A alloy turbine blisk were studied systematically. The quantitative relationships between cooling rate, stirring process and γ’ phase, γ / γ’ eutectic phase, MC type carbide and grain size were described in detail. The results show that with the increase of cooling rate, the distribution region of γ / γ ‘eutectic phase from the center of blisk to blade decreases gradually and MC type carbide changes from skeleton to block due to the shorter formation time of eutectic and carbide in the later stage of solidification. Besides, with the decrease of cooling rate, the size of γ’ phase increases under the influence of interfacial strain energy and elastic strain energy, and the morphology of γ’ phase gradually evolves from cuboid to concave cuboid, octet and dendritic. At the same time, due to the synergistic effect of cooling rate and stirring process, the blade part is columnar grain and the central part of the blisk is equiaxed grains. In this paper, the evolution mechanism of γ ‘phase, γ / γ’ eutectic phase, MC type carbide and grain size with cooling rate and stirring process was proposed. The research results would play a key supporting role in precise control during solidification for microstructures and properties of dual-performance superalloy blisk.

Geometric morphometrics and phylogenetic analysis of Delphinium taxa from south of Russia

The leaf blade’s shape of 665 samples of 18 taxa from the genus Delphinium was analyzed using geometric morphometrics method. Within the subgenus Delphinastrum, D. elatum and, to a lesser extent, D. uralense were relatively well separated by canonical analysis, while D. litwinowii, D. pubiflorum, D. duhmbergii, and D. subcuneatumwere not actually separated. Within the subgenus Oligophyllon, D. caucasicum was well separated by this method. The scatter clouds of D. freynii + D. puniceum + D. sergii on the one hand, and D. fedorovii + D. gelmetzicum on the other hand, also separated. D. arcuatum, D. bracteosum, D. crispulum, D. flexuosum, and D. mariae did not separate from each other. The nature of such separation of species groups observed in the space of canonical variables and their relative proximity to each other can be associated with the habitat similarity of their populations driven by ecological or geographical conditions, as well as the influence of hybridization processes in the zone of secondary contact of species. The differences in leaf blade’s shape are mainly related to the width of the segments, the lengths of the central segment of the middle lobe and the undissected part of the leaf blade, the degree of its dissection, the shape of the base and the distance between the lower lobes. Based on the results of DNA sequencing of the intergenic transcribed spacer ITS2, the taxonomic independence of D. puniceum, D. macropogon, D. mariae, D. samurense, and D. pubiflorum is beyond any doubt. The synonymy of D. freynii and D. sergii is supported, with the priority name of D. schmalhausenii. D. cuneatum, D. subcuneatum, D. duhmbergii, and D. litwinowii should be considered as synonyms with the priority name of D. cuneatum. The taxonomic status of D. dictyocarpum, D. elatum, and D. uralense needs further clarification. This is probably related to their easy hybridization with D. cuneatum in sympatric populations within the overlapping areas. Delphinium arcuatum, D. bracteosum, D. caucasicum, D. crispulum, D. elisabethae, D. fedorovii, D. flexuosum, D. gelmetzicum, and D. speciosum are poorly separated, which can also be associated with hybridization processes. They need to be studied in more detail.

Effect of double crack on fatigue crack growth life of 3D printing compressor impeller

A compressor impeller with pressure ratio less than 3 is taken as the research object. The 3D printing residual stress was introduced into damage tolerance assessment of blades, and the effect of double crack on Fatigue Crack Growth Life (FCGL) was investigated. The impeller was printed by selective laser melting technology and then heat treated. Finite element method was applied to numerically simulate 3D printing process, heat treatment process and actual working process of impeller, and mechanical quantities such as stress and deformation were completely analyzed. Numerical simulation results agreed well with the experimentally observed crack location in the middle of the blade. Forman–Newman–de Koning model and linear elastic fracture mechanics theory were applied to give the growth law of impeller under single and double crack conditions. The result shows that crack initiation locations of impeller during printing and operating are respectively middle part and root part of blade. The stress intensity factor at the initial crack tips of single and double cracks exhibits a quadratic relationship with rotational speed when only external load is considered. The crack growth paths of single crack in middle and root are radial and axial respectively, and the FCGL of single crack in root is lower than that of single crack in middle. With the increase of rotational speed, the critical crack length decreases linearly and the cycles decreases nonlinearly in both single and double crack conditions. The FCGL of double crack is between two single cracks at low speed and lower than two single cracks at high speed. The critical crack length of double crack is lower than that of corresponding single crack. At 60000rpm, the dominant crack changes from middle crack to root crack.

3D numerical simulation of the Darrieus vertical axis wind turbine with J-type and straight blades under various operating conditions including self-starting mode

A comprehensive three-dimensional numerical analysis is applied in this study to evaluate the competence of the J-type blades in the vertical axis wind turbines under wide range of operating conditions including various wind speeds, tip speed ratios and wind turbulence intensities. It is found that the vortices which are encapsulated in the concave part of the J-type blades escape from the tips of the blades and become stronger than those originated from the straight blades. Such strong wakes behind the J-type blades are responsible for larger negative effects on generating the torque at high tip speed ratios. Neither of the wind speed, nor the wind turbulence intensity have significant effects on performance of the J-type blade turbines. Of particular interest is to discover the behavior of the J-type blade under self-starting conditions which is a major shortcoming with Darrieus turbines. The results show that replacing the straight blades with the J-type blades causes the generated torque to increase by 26.9% and 37.6% at the wind speeds of 10 m/s and 5 m/s, respectively. Better performance of the J-type blades under self-starting conditions, makes them a promising candidate, especially at low wind speed regions such as urban areas.

Wear characteristics of a centrifugal pump transporting solid–liquid mixture: An experimental and numerical study

The present study aims to reveal wear characteristics of an impeller pump transporting the mixture of liquid and solid particles. An experimental work is conducted to detect patterns of wear of the pump components. The computational fluid dynamics (CFD) technique and the discrete element method (DEM) are jointly used to simulate the two-phase flow and wear of the pump components. After a 30-hour wear experiment, the inlet edge of the long blades exhibits wavy profiles, and the outlet part of the long blades is worn through. Regarding the volute, only the volute tongue is severely worn. At a particle diameter of 2.0 mm and a solid mass fraction of 10 %, the ratio of the average wear depth of the long blades to that of the volute reaches 64.5. Wear of the blade inlet edge depends on the normal cumulative contact energy, while the tangential cumulative contact energy contributes significantly to wear of the outlet part of the long blades. As the particle diameter increases from 1.0 mm to 3.0 mm, the average depth of wear of the long blades decreases monotonically by nearly 45 %, but the maximum depth of wear increases by about 34 %. The solid mass fraction serves as a key factor influencing wear of the pump components, especially when particles of large size are transported.