Solid Blade Research Articles

Особый тип каменных топоров эпохи бронзы с реки Коротаиха (бассейн Баренцева моря)

Finds of thrust tools made of rocks and minerals are rare to find in the sites of the European North-East. This can be probably explained through a high mobility of the local hunters-gatherers and through the way such artefacts were left behind. Considering that there is an outstanding set of six axes and three workpieces found at Korotaikha 1979/3 site at the Korotaikha river (the Barentsev Sea basin). There they found not as a treasure; traces of their production were missing. The research aims to verify the assumption that the artefacts constitute a special type thrust tool series. To do so the study analysed the consequence of formation and layout of diverse macrotraces on the thrust tools surface. The study provides their morphography and classic morphometry. It is determined that the Korotaikha 1979/3 axes are made with the same technology. To start with, the shape of the future tool was formed with bifacial knapping. The final staged implied abrasive treatment (polishing) to form a straight sharp blade, level off and dull down sharp bifacial ribs along the longitudinal edges of the work pieces. The process preserved a large part of the surface formed by knapping. Thus, the Korotaikha 1979/3 axes are partly polished tools with a rectangular or nearly triangular form and lens-shaped cross- and longitudinal section. Macrotraces left by knocking upon solid materials, blade corrections and tool wear-out are evident of the axes use and repair. The nature of the work piece bilateral treatment conforms is harmonized with the bifacial knapping that the Korotaikha 1979/3 flint arrowheads and scrapers are made with. Along with homogeneous ceramics and evidence of bronze smelting production these items conform that these materials shall be attributed to records for studying the Korshak culture assigned to the Bronze Age and preliminarily dated back to the 2nd millennium B.C. Based on this data the study defined equivalent tools within sites located in a very short area at the Korotaikha river. However, the study failed to find equivalents outside this microregion. The production peculiarities, geography and attribution of these axes allow to define their special type of thrust tools of the Bronze Age European north-east. This type can be designated as the Korotaikha type axes. The location is found with an abnormal number of good-condition thrust tools left in one place. It may be associated with the functioning of a sanctuary or burial ground at this site.

Evaluating Mechanical Strength in Vertical-Axis Tidal Turbines: A Comparative Study of Internal Blade Structure and Material Selection through CFD Simulation

Due to the density of water, tidal turbine blades are subject to significantly greater stresses than wind turbine blades. Multiple blade failures occurred during prototype testing as a result of loading conditions and protracted exposure to seawater, which created a severe work environment. The structural integrity of tidal turbine blades is essential for long-term reliability and performance. Numerous investigations into structural performance have been conducted. However, previous research has centred on horizontal-axis tidal turbines, while research on small-scale vertical-axis tidal turbines is limited. This paper aims to compare the Vertical-Axis Tidal Turbine (VATT) structural performance of hollow and solid blade structures in an identical NACA profile using three distinct materials. Finite element analysis (FEA) is employed to construct a model and simulate the mechanical characteristics of VATT blades. The use of static analysis simulation is employed in order to evaluate many parameters, including stress distribution and deflection. Parametric studies are conducted to explore the impact of internal blade structure and materials on mechanical strength. The use of computational fluid dynamics (CFD) simulations is employed for the purpose of analyzing the interaction between blades of vertical axis tidal turbines (VATT) and tidal currents, thereby enabling the assessment of structural loading. According to the simulation results, the hollow profile is subject to significant deflections and stresses. Other data indicates that the utilization of stiffeners in porous structures improves material efficiency and results in lighter blades, although further analysis is needed to investigate fatigue life prediction in optimizing structural design.

Effect of leading edge and trailing edge serrations on a rotating Wells turbine

Wells turbine used for wave and wind power generation is known to generate loud noise during its operation. Aerodynamic noise reduction is an important issue in the design of the turbines. Since aerodynamic noise depends highly on behavior of the vortices around the turbine and the flow structure in the wake region, understanding of behavior of the unsteady flow past a rotating turbine plays important role. In this study, we modeled Wells turbine with normal (solid) blades and serrated turbine. To visualize the flow separation and vortex generation near the rotating turbine at its startup, LES simulations were performed by using moving mesh and transient inlet condition. In addition to the detailed flow structure around the turbine, the results show that the axial torque of the turbine increases with respect to the monotonically increasing inlet velocity. It is also found that positive axial torque generated for the normal and trailing edge serrated turbines as the inlet flow velocity increased, but no torque was obtained for the leading edge serrated turbine due to flow separation at the leading edge.

Numerical Simulation of Fluid-Structure Coupling for a Multi-Blade Vertical-Axis Wind Turbine

The aerodynamic characteristics of the vertical-axis wind turbine with three, four, five, and six blades are studied numerically. A coupling model of fluid flow and solid turbine blade is established to model the interactions between air and wind turbine. The pressure distribution and blade deformation affected by air are obtained and discussed. For the four wind turbines with different numbers of blades, the maximum pressure in the entire machine structure occurs at the variable angle position of the blades in the windward region under the same wind speed. Mainly due to the rapid airflow variation, complex turbulence, and significant influence of the wind field on the blades in this position, this part of the blades is prone to bending or damage. Under identical external wind field conditions, wind turbines with four and six blades exhibit significantly higher equivalent pressures on their surfaces compared to those with five and three blades. The maximum equivalent pressure of six blades can reach 3.161 × 106 Pa. The maximum deformation of the blade basically occurs at the tip and four sides of the blade. The six-blade wind turbines withstand higher and non-uniform surface pressures on their blades, resulting in the largest deformation of up to 11.658 mm. On the other hand, the four-blade wind turbine exhibits the smallest deformation. The above conclusions provide theoretical guidance for the design and optimization of vertical-axis wind turbines.

A comprehensive multi-objective optimization study for the aerodynamic noise mitigation of a small wind turbine

The noise emitted by small wind turbines is one of the main reasons for their poor public perception for use in urban areas. An optimization study was performed to mitigate the aerodynamic noise of a 750 W turbine through altering the geometry of solid and more importantly hollow blades for the first time. A validated in-house code simultaneously minimizes the aerodynamic noise and maximizes the output power. The inertia of the blades is another important design parameter for small turbines as it influences the starting performance. The minimization of starting time was added to the above-mentioned goals and another optimization was done. The outcomes highlight the great significance of two ends of the blade; the tip section has a key role in alleviation of the noise as well as the improvement of the power coefficient while the root part could speed up the starting. Quantitatively, the optimization of solid blades shows that a 1.9 dB reduction in aerodynamic noise is attainable at the expense of a 1.6% loss in the power coefficient. Compared to solid blades, the aerodynamic noise and the starting time were reduced for hollow ones by 1 dB and 30% respectively. The latter is very attractive for use of small turbines in low-wind areas.

Durable solid lubricant wind turbine blade anti-icing coating based on saturated chain polyhydrocarbons

The use of anti-icing coatings and surfaces can be an effective solution to the problem of icing on infrastructure equipment such as wind turbines. Slippery liquid-infused porous surfaces (SLIPS) are receiving increasing attention due to their stability under droplet impact, high humidity tolerance, and low ice adhesion strength. Nevertheless, since SLIPS uses a sacrificial liquid lubricating fluid for deicing, improving the durability and economy of SLIPS is an important challenge at present. The present research aimed to prepare a cross-linked solid lubricant SLIPS using a simple coating method, and compare it with a SLIPS using liquid paraffin as a lubricant to study their wettability, impact resistance, freezing time, and ice adhesion strength. The results showed that the solid lubricant could bond well to the substrate material and that the surface presented hydrophobicity, which effectively repelled water droplets. Furthermore, the coating has good delayed icing properties and high durability in different environments. Compared with the SLIPS, which uses liquid lubricants, the solid lubricant has almost no lubricant loss after 8 h of rainwater impact, and it offers better environmental friendliness. After 15 icing/deicing tests, the ice adhesion strength still reaches a low 44.1 kPa. In addition, the stable performance and low price of the solid lubricant make the coating a good candidate for the development of a practical ice-repellent coating that can be used to solve the problem of ice accumulation on wind turbine blades in humid alpine regions.

Research on deposition toolpath planning and laser head Z-axis rising height setting for directed energy deposition

In this study, the biggest goal was using laser directed energy deposition (L-DED) process to fabricate a solid blade part. In the process of CAD modeling, a blade model was built by sweeping a blade cross-section and twisting 10° simultaneously, which made it to have overhanging and tilting features. So, to select an appropriate deposition toolpath was the most important thing. The deposition toolpath in this study was decomposed into contour and field toolpaths. First of all, a cuboid part model of which the geometry was simpler was created to test toolpath planning approaches. The results recommended to use “Fixed rising height per layer with proper laser head rising height (Z-offset setting)” or “Spiral” approaches to plan contour toolpaths. For field toolpaths, “Reciprocating zigzag” planning approach was suggested and it needed to adjust the cladding angle to fit the cross-section of the parts. According to the test results of cuboid part fabrications, the contour of the target blade part was successfully manufactured with a 50% Z-offset setting and the spiral toolpath. The solid blade fabrication was also finished with a fixed rising height per layer with a 50% Z-offset setting and 45° reciprocating zigzag toolpath. In addition, the relationship between the Z-offset setting and the dilution was investigated through experiments. A conjecture that a height shrinkage of an old layer caused by thermal deformation is equal to the single-layer deposition dilution was proposed. Based on this conjecture, users can improve L-DED deposition results by setting the Z-offset as “the product of single-track height and the degree of shrinkage of an old layer height.” By combining the predictive value of dilution surface fitting model with the conjecture, it can be easier to get better LDED deposition quality.

Effect of uniformly varying width leading-edge slots on the aerodynamic performance of wind turbine blade

According to the Betz limit, the maximum wind power that can be extracted from wind is limited to 59 %. Practically it stands at a 30–40 % level. Therefore, current research targets to increase the aerodynamic performance of wind turbines by introducing uniformly varying width (UVW) leading-edge slots. In present work, a UVW narrow channel is deployed using NACA (National Advisory Committee for Aeronautics) 4412 aerofoil, which starts from the leading-edge region and goes away to the pressure side of the aerofoil after a slight bending. NACA 4412 aerofoil is chosen as it has the highest lift to drag ratio. Six wind turbine blades of different dimensions (Gradually increasing Wi/Wo ratio) are proposed. Six proposed wind turbine blades are designed and analysed using CFD (computational fluid dynamics) with 0° to 16° at a 2° increment. Wind speed is taken at 7 m/s as per Indian conditions. Out of six proposed blade designs, NACA 4412 aerofoil (Wi/Wo = 2) gives 12 % spike lift to drag ration than the uniform slotted one. Again NACA 4412 aerofoil (Wi/Wo = 2) performs at its peak at angle of attack (AOA) 6°. It is observed that interaction of fluid separation zone and slot inlet results in a down grade of the aerodynamic performance of wind turbine blade. A scaled-down (one-fifth) model of the superior blade (made up of wood) and Solid blade have been made for the wind tunnel test and comparison. The computational results were compared from a series of wind tunnel tests.

Vibration-Based Fatigue Analysis of Octet-Truss Lattice Infill Blades for Utilization in Turbine Rotors.

Vibration fatigue characteristics are critical for rotating machinery components such as turbine rotor blades. Lattice structures are gaining popularity in engineering applications due to their unique ability to reduce weight and improve the mechanical properties. This study is an experimental investigation of octet-truss lattice structure utilization in turbine rotor blades for weight reduction and to improve vibration fatigue characteristics. One completely solid and three lattice infilled blades with variable strut thickness were manufactured via additive manufacturing. Both free and forced experimental vibration analyses were performed on the blades to investigate their modal and vibration fatigue characteristics. The blades were subjected to random vibration using a vibration shaker. The response was measured using a triaxial accelerometer in terms of vibration acceleration time histories in the X, Y, and Z directions. Results indicate a weight reduction of up to 24.91% and enhancement in the first natural frequency of up to 5.29% were achieved using lattice infilled blades. The fatigue life of the blades was investigated using three frequency domain approaches, namely, Lalanne, Dirlik and narrow band. The fatigue life results indicate that the 0.25 mm lattice blade exhibits the highest fatigue life, while the solid blade exhibits the lowest fatigue life of all four blades. The fatigue life of the 0.25 mm lattice blade was 1822-, 1802-, and 1819- fold higher compared to that of the solid blade, using the Lalanne, Dirlik, and narrow-band approaches, respectively. These results can serve as the first step towards the utilization of lattice structures in turbine blades, with thermal analysis as the next step. Therefore, apart from being light weight, the octet-truss lattice infilled blades exhibited superior vibration fatigue characteristics to vibration loads, thereby making them a potential replacement for solid blades in turbine rotors.

Dynamic Response of a Composite Fan Blade Excited Instantaneously by Multiple MFC Actuators

The vibration characteristics of a composite fan blade are much more complex than those of a solid titanium fan blade due to the anisotropic material properties and complex excitations coming from unsteady flow and mechanically induced vibration. In this study, the dynamic response measurement of a wide-chord composite fan blade was carried out to study the vibration characteristics using multiple macro fiber composite (MFC) actuators, which can generate complex excitation forces with different frequencies and peak values at different locations. The measured mode shapes and natural frequencies were compared with the finite element simulation results. Based on these results, the responses of the blade under the instantaneous excitation of three MFC actuators with different combinations of several natural frequencies were measured and compared. The results show that the responses of the blade excited by different combinations of MFC actuators with different frequencies were significantly different from those excited by a single MFC actuator. The superposition of different mode shapes may cause the change of the vibration stress state, which indicates that the high cycle fatigue location of the blade under complex excitations may change to an unexpected location. The results will be helpful in understanding the vibration characteristics of the composite blades under complex excitations, and the MFC actuator could be a potential tool in vibration active control.

NUMERICAL INVESTIGATION OF THE IMPELLER BLADES, MANUFACTURED BY METAL 3D PRINTING TECHNOLOGY WITH INTERNAL STRUCTURES

This paper presents the results of FEM (Finite Element Method), CFD (Computational Fluid Dynamics) and modal analyses of model semi-axial pump. Two sets of impeller blades were printed by metal 3D printing technology with internal honeycomb structures. The set of solid blades, manufactured by CNC machining for a comparison, was also included. 3D printed blades were designed with internal structures in order to save material, and with respect to mechanical and dynamic properties. Saved material can change the starting moment, modulate modal properties or decrease strength properties. The 3D printed blades can be produced very quickly and with accurate blade surface finish. One of the reasons of this approach can be the use of 3D printed blades as spare parts for industrial applications or for model pump research. This paper contains short introduction to blade design with internal honeycomb structures and their one-way FSI analyses (Fluid Structure Interaction). The final results of best design are presented and discussed.

Experimental and Numerical Vibration Analysis of Octet-Truss-Lattice-Based Gas Turbine Blades

This paper aims to investigate the utilization of octet truss lattice structures in gas turbine blades to achieve weight reduction and improvement in vibration characteristics, which are desired for turbine blades to improve the efficiency and load capacity of turbines. A solid blade model using NACA 23012 airfoil was designed as reference. Three lattice-based blades were designed and manufactured via additive manufacturing by replacing the internal volume of solid blades with octet truss unit cells of variable strut thickness. Experimental and numerical vibration analyses were performed on the blades to establish their suitability for potential use in turbine blades. A maximum weight reduction of 24.91% was achieved. The natural frequencies of lattice blades were higher than those of solid blades. A stress reduction up to 38.6% and deformation reduction of up to 21.5% compared with solid blades were also observed. Both experimental and numerical results showed good agreement with a maximum difference of 3.94% in natural frequencies. Therefore, apart from being lightweight, octet-truss-lattice-based blades have excellent vibration characteristics and low stress levels, thereby making these blades ideal for enhancing the efficiency and durability of gas turbines.

Parametric study on the flutter sensitivity of a wide-chord hollow fan blade

In recent years, the hollow fan blades have been widely used to meet the demand for light weight and good performance of the aero-engine. However, the relationship between the hollow structure and the aeroelastic stability has not been studied yet in the open literature. In this paper, it has been investigated for an H-shaped hollow fan blade. Before studying the flutter behavior, the methods of parametric modeling and auto-generation of Finite Element Model (FEM) are presented. The influence of the feature parameters on the vibration frequency and mode shape (as the input of flutter calculation) of the first three modes are analyzed by the Orthogonal Experimental Design (OED) method. The results show that the parameters have a more remarkable impact on the first torsional mode and thus it is concerned in the flutter sensitivity analysis. Compared with the solid blade, the minimum aerodynamic damping of the hollow blade decreases, indicating that the hollow structure makes the aeroelastic stability worse. For the parameters describing the hollow section, the rib number N has the greatest influence on the minimum aerodynamic damping, followed by the wall thickness W5. For the parameters in the height of hollow segment, the aerodynamic damping increases with the increase of parameters M1 and M2. This means that reducing the height of the hollow segment is helpful to improve the aeroelastic stability. Compared with the impact of parameters in hollow section, the variation of aerodynamic damping caused by the height of the hollow segment is small.

The effect of recoater geometry and speed on granular convection and size segregation in powder bed fusion

In metal additive manufacturing (AM), powder bed fusion technologies such as selective laser melting and binder jetting rely on the spreading of fine metal powder to build up the layers of a part. This work studies the complex interaction between metal powder particles and the recoater. We apply the Discrete Element Method (DEM) to a calibrated cohesive Ti-6Al-4V powder model, matching the particle properties to experimental measurements of size, shape and inter-particle forces. We simulate powder bed fusion recoating at varying speeds and layer thicknesses with two different recoater geometries: a toothed rake and a solid blade. Our results demonstrate that the recoating mechanism induces significant granular convection, with the recoater velocity and geometry strongly influencing the degree of particle circulation and size segregation. Notably a toothed rake recoater improved particle circulation – while the solid blade recoater increases size segregation within the heap. Furthermore the recoater was found to filter fine and coarse particles, allowing smaller particles to flow underneath the recoater, and larger particles through its teeth. Our results demonstrate the key mechanisms which drive granular convection during recoating and how the fine details of recoater geometry impacts surface layer roughness and final part quality.

Energy harvesting efficiency analysis of counter-rotating horizontal-axis tidal turbines

ABSTRACT In this paper, a new design scheme for counter-rotating horizontal-axis tidal turbines (CRHATTs) is introduced using blade element momentum (BEM) theory. The coordinated working performance between rotor and generator of the CRHATT are analysed by experimental and CFD methods. The effects of the key parameters on the energy harvesting efficiency of the CRHATT are studied in detail. The study indicates the existence of the optimal rotor solidity (σ) combination and blade installation angle (γ) combination for dual rotors to reduce the power coefficient (C p ) deviation of the dual rotors. The distance between dual rotors (L) is suggested to be set as about 0.225D, which can maximise the C p of the CRHATT. Finally, the hydrodynamic performance of the flow field is carried out to verify the reliability of the CRHATT design. The results presented in this paper may serve as a reference in the design of CRHATTs in practical engineering.

Numerical study on swirl cooling flow, heat transfer and stress characteristics based on fluid-structure coupling method under different swirl chamber heights and Reynolds numbers

In this study, a three-dimensional swirl cooling model coupled with high temperature mainstream cascade channel and blade leading edge solid region is established to simulate the flow, heat transfer and stress characteristics. The fluid-structure coupling model is utilized to analyze the interaction of external mainstream, solid blades and swirl cooling air. Six different swirl chamber heights are selected to explore the optimal height which is the most beneficial to gas turbine blade operation. Finally, influences of coolant chamber inlet Reynolds number on swirl cooling performance are discussed in detail. Results show that the temperature distribution of blade solid region is highly related to swirl cooling effect. Compared with aerodynamic load, the thermal load behaves more significant effects for blade stress conditions. As the swirl chamber height increases, the swirl cooling heat transfer performance gradually decreases, and the flow resistance also gradually decreases. The comprehensive heat transfer factor is introduced to evaluate the swirl cooling overall performance. When swirl chamber height is 19 mm, it has higher heat transfer capacity and lower flow resistance, and the comprehensive heat transfer factor is the highest. The Reynolds number has a strong influence on heat transfer performance. In order to avoid high aerodynamic losses, the Reynolds number should be selected appropriately.

Numerical Assesment of a Small-Scale and Very Low Tip Speed Ratio Wind Turbine

The aim of this paper is to study by CFD the performance and to characterize the velocity fields in the wake of an horizontal axis wind turbine. The design of this wind turbine is far from classical as it has been designed to work at very low angular velocity to promote torque. The 8 blades are not isolated but form a high solidity blade cascade. The numerical simulation compares well to experimental data regarding the power coefficients. The analysis of the wake does show that high tangential velocities, close to the order of magnitude that was used as a design requirement, are generated and form a stable rotating wake. This rotating kinetic energy in the wake may be used to rotate a second rotor in a counter-rotating arrangment.

Investigation on tip clearance control for the high-pressure rotor of an uncooled vaneless counter-rotating turbine

In order to develop a tip clearance control system for an uncooled vaneless counter-rotating turbine, tip clearance variation of its high pressure rotor blade at off-design conditions is analyzed. Aero-thermal interaction simulation is performed to predict the temperature and deformation of the solid blade. At operating conditions with rotating speeds greater than 60% design value and expansion ratios greater than 85% design value, the blade tip clearance height at leading edge remains unchanged when the expansion ratio decreases, meanwhile that at trailing edge decreased obviously. However, the tip clearance height variations at the leading edge and trailing edge are almost the same in a conventional subsonic turbine at such conditions. The cause is that the flow in the high-pressure rotor is choked at these conditions. The choked flow results in that the fluid and solid blade temperatures upstream of the throat are not affected by the back pressure and only those downstream of the throat increases with the back pressure. Consequently, the blade height at leading edge keeps constant, and that at trailing edge varies because of thermal expansion. To avoid the rubbing of the blade and case, the blade height at trailing edge is diminished by 30%. As a result, the blade tip clearance height at low speed operating conditions increases in axial direction. Such a design leads to a stronger tip leakage flow. More flow losses might be generated. Therefore, a casing cooling method is proposed to control the blade tip clearance height at leading edge and trailing edge respectively. The deformations of the casing with different mass flow rate of cooling air at design and off-design conditions are calculated. It shows that the blade tip clearance heights at leading edge and at trailing edge of the rotor can be well controlled with appropriate amount of cooling air.

PENGARUH PUTARAN TURBIN ANGIN SUMBU HORIZONTAL KOMBINASI PEMBERAT BOLA PEJAL

Along with the increase in population is directly proportional to the need for energy sources both to support people's lives and the increase in the industrial sector in Indonesia. One of the most widely used sources of electricity is wind. Wind turbines are very sensitive to the wind speed they receive, as a result of fluctuations in wind speed that affect wind rotation speed. For this reason, the author has the idea to combine a wind turbine with a solid object turbine, it is hoped that the combination can produce more consistent rotation. The tool used is a wind turbine combined with solid blade ball weights 8, 9 and 10 and ballast of 10 gr, 20 gr and 30 gr for each blade and wind speeds of 3.3 m / s, 3.6 m / s and 3.9. m / s with the experimental research method, the experiment was carried out 3 times in each tool for ± 2 minutes which was expected to produce a combination of the variables studied in the form of a turbine with the maximum rotational speed and the most consistent rotation. From these experiments, it was found that a turbine with 10 blades, a weight of 10 gr at a wind speed of 3.9 m / s had the fastest rotation, namely 116.43 rpm while a 9 blade turbine with a weight of 30 gr at all three wind speeds was the turbine with the most consistent rotation, namely the difference between the top and bottom rotation is 2.53 rpm.

Effect Of Leading-edge Geometry Parameters On The Performance Of Miniature Cryogenic Expansion Turbine

The numerical simulation included solid blades with four different leading-edge thicknesses and four different leading-edge geometries. One of the geometries was square, one was ellipse A(ellipse ratio is 1), one was ellipse B(ellipse ratio is 2), and the other was ellipse C(ellipse ratio is 3). The four thicknesses were 0.7mm, 0.6mm, 0.5mm, 0.4mm. The results show increased efficiency loss for increased leading-edge thickness for square geometry. For ellipse geometries, there was no significant difference when the leading-edge thickness changed at the positive incidence range. For the same leading-edge thickness(0.7mm), square leading-edge caused more loss than ellipse leading-edge. For square geometry, the optimal incidence angle was about -8 degree(0.7mm). For ellipse geometries, the optimal incidence angle was about -30 degree(0.7mm). And with the decrease of leading-edge thickness, the square’s optimal incidence angle was toward to zero degree, the ellipse’s optimal incidence angle was toward to larger negative angle.