Blade Structure Research Articles

Noise reduction of automobile cooling fan based on bio-inspired design

This study aims to minimize the noise generated by automobile cooling fans. Fan blade structures with ridged surfaces based on bio-inspired principles are 3D printed and used to replace the conventional fan blades. The effect of the bio-inspired ridge structures on the noise reduction of the cooling fan is demonstrated by orthogonal experiments in a semi-anechoic chamber. Experimental results show that with an increase in the rotational speed, the effect of the surface textures on the acoustic performance of the cooling fan becomes more significant. For example, at a fan speed of 1750 r/min, all the bio-inspired blade designs reduce noise compared with the original fan and, in particular, the sound pressure level is reduced by 3.83 dB(A) for the design with a ridge width of 4 mm and a ridge pitch of 15 mm. Through variance analysis of the measured noise, the ridge pitch distance has the most significant impact on noise reduction under low speed conditions whilst, under high speed conditions, the ridge width has the most significant influence. In addition to the experimental studies, computational fluid dynamics (CFD) simulations of the cooling fan are carried out to explain the mechanism of noise reduction for the ridged fan blades. When the fan runs, the horseshoe vortexes generated by the ridge structures disturb the flow of the boundary layer, reduce the influence of the fluid flow on the boundary layer, and delay the transition of the fan blade laminar flow to turbulence. It is also seen that there is a reduction of the intensity of the fan blade trailing edge vortices and the scale of the secondary vortices, thereby achieving the overall aim of noise reduction. This research has significance in the noise reduction design of automobile cooling fans.

Method for modeling the modes of induction heating of turbine blades

In this paper there are offered calculated and experimental methods of simulating the high-speed modes of induction heating and designing the new inductor to provide the preset nonuniform thermal and thermostress state for cooled and uncooled blades of gas-turbine engine by changing the inductor width (specific power of induction heating). The peculiarity of this technique is the possibility of conducting the thermal cyclic tests of gas-turbine-engine parts with remaining the guaranteed minimal constant clearance between inductor and blade surface that reduces the probability of temperature-field distortion in changing the blades and promotes the efficiency enhancement of induction heating. Obtained results were used to conduct the tests of blades of gas-turbine-engine turbine. Carried out tests at this set with using the high-speed modes of induction heating helped to reveal quickly required changes in the blade structure.

A Critical Review of Damage and Failure of Composite Wind Turbine Blade Structures

Advancing beyond the historic feasibility limits deemed by designers, wind turbine rotor blades have eventually surpassed the 100m milestone, making them reside among the largest single components in the world made of fiber composite materials. In the development of wind energy, aerodynamics has been an essential field of research, just as it will still be, the recent two decades witnesses structures becoming more critical due to the ever-increasing size of the rotor blades. The fact is simple: for wind turbines to operate continuously and cost-efficiently, rotor blades must maintain their structural integrity and reliability. This study reviews recent advances in the field of the structural integrity of large scale composite wind turbine blades. A particular focus is placed on damage and failure in such structures from the triad of field observations, laboratory experiments and numerical modeling. This study also identifies the established knowledge, the latest achievements, the topical research fields and the current challenges for future research and development.

Chemical recycling of End-of-Life wind turbine blades by solvolysis/HTL

The focus of this contribution is to highlight the challenges of chemical recycling of End-of-Life glass fiber composite (GFRP) waste from wind turbine blades utilizing solvolysis/HTL (hydrothermal liquefaction) methods based on subcritical water as solvent. A multitude of investigations have been published during the years regarding solvolysis of newly produced composite laminates and known thermoset composition (epoxy, polyester, and vinyl ester). However, a real wind turbine blade is more complex and constitutes of thermosets, thermoplastics, and other materials such as balsa wood. It is a very challenging task to separate these materials from each other within the wind turbine blade structure, so the premise for recycling is a mixed waste stream where little is known about the chemical composition. In the present study, the solvolysis process for GFRPs based on sub/supercritical water at 250-370 °C and 100-170 bar process conditions with catalyst (acid and base) and additives (alcohols and glycols) was studied and optimized. The samples used are representative for End-of-Life wind turbine blades. The aim is therefore to investigate if it is possible to develop a general process that can accept all material constituents in a real wind turbine blade, resulting in recycled glass fibers and a hydrocarbon fraction that can be used as a refinery feedstock.

Design and Braking Performance Analysis of Hydrodynamic Retarders with Vertical Blade Structure

Design and Braking Performance Analysis of Hydrodynamic Retarders with Vertical Blade Structure

Direct Numerical Simulation of Interaction between Transient Flow and Blade Structure in a Modern Low-Pressure Turbine

A feature of a modern aeronautical Low-Pressure Turbine (LPT) is the high blade loadings with complex, transient and separated flow regimes. Most existing research have focused only on analysing the transient flow and flow separation in such turbines. The aerodynamics of a modern LPT, however, can be significantly influenced by the interaction between the unsteady flow field and the blade structure motion in a complex non-linear fashion which could lead to aeroelastic instabilities such as flutter. Therefore, the understanding of the mechanism of the interaction between the flow field unsteadiness and the blade structure in a modern LPT is essential to examine the vibration stress levels to ensure the blade mechanical integrity. The novelty of this paper, first and foremost, is using a high-fidelity direct numerical simulation method to explore the mechanism of flutter and forced response in a modern LPT, T106A turbine, and to study the effects of various sources of unsteadiness on the aeroelastic instabilities of the blade. Secondly, this paper investigates and identifies the adequate working ranges of the harmonic balance method, which has been widely used for the aeromechanical analysis of turbomachines, on predicting the behaviour of the highly unsteady flow due to fluid-structure interaction in an LPT. Another emphasis of this paper is the determination of the capability of the Unsteady Reynolds Averaged Navier–Stokes (URANS) model for the aeroelasticity analysis of an LPT involving the highly unsteady flow. This paper will bridge a key gap in the knowledge of aeroelasticity modelling and analysis of modern LPTs.

Особливості адаптації окремих видів роду Oenothera L. до посушливо-спекотних умов Правобережного Степового Придніпров'я

Наведено особливості анатомічної адаптації листків двох видів роду Oenothera L. за умов вирощування у Правобережному степовому Придніпров'ї. Здійснено огляд наукових інформаційних вітчизняних і закордонних джерел щодо декоративних якостей представників роду Oenothera, походження, поширення, гібридизації, лікувальних властивостей та переваг використання у ландшафтному дизайні. З'ясовано, що у фітодизайні України їх використовують мало, а в декоративному садівництві м. Кривий Ріг цих видів немає через нестачу інформації щодо їх пластичності у посушливих спекотних умовах Правобережного степового Придніпров'я (ПСП). Для визначення адаптаційного потенціалу видів Oenothera досліджено анатомо-морфологічну структуру листків деяких представників за умов вирощування у ПСП. Матеріалом дослідження слугували рослини O. missuriensis та O. tetragona колекційного фонду квітниково-декоративних трав'яних рослин Криворізького ботанічного саду НАН України, інтродукованих впродовж 20 років. Встановлено особливості анатомо-морфологічної будови листкової пластинки досліджуваних видів. Виявлено специфіку кількісно-якісних адаптаційних пристосувань у структурі листка за умов вирощування в посушливо-спекотних умовах ПСП. З'ясовано, що рослини O. missouriensis та O. tetragona добре адаптовані до зростання в умовах інтенсивної інсоляції, про що свідчить наявність ксероморфних рис в анатомічній будові обох видів, таких як: кутикула та опушення, рафіди оксалату кальцію, диференційований мезофіл, розміщення продихів з адаксільної та абаксіальної сторін. Виявлено, що за умов дефіциту вологи та високих температур у рослин O. missouriensis та O. tetragona сформувалися ксероморфні ознаки, а саме: відбулося значне збільшення шару кутикули, товщини обох епідермісів, зменшилися розміри продихів та їх кількість, ущільнилося розміщення клітин мезофілу, що значно підвищує рівень їх посухостійкості. Кількісна і якісна мінливість елементів структури листкової пластики свідчить про достатній рівень адаптації та пластичність видів в умовах регіону досліджень, що дає підстави рекомендувати їх для застосування у декоративному садівництві в посушливих умовах ПСП.

Structural analysis of an offshore vertical axis wind turbine composite blade experiencing an extreme wind load

The vertical axis wind turbine (VAWT) configuration has many advantages for an offshore wind turbine installation. The VAWT is omnidirectional and its rotating mechanical components can be placed close to sea level. In this paper, the structural analysis of a VAWT blade structure subject to a critical load case was investigated with two methods, an analytical model and a finite element (FE) model. It was shown that the utilisation of a composite blade topology can resist the induced flapwise loading and the material strains were contained within their allowable limits. The analytical approach was demonstrated to be a quick and accurate technique to compute the composite blade strain distribution when compared to the FE model results.

Progressive structural scaling of a 20 MW two-bladed offshore wind turbine rotor blade examined by finite element analyses

Two-bladed turbines offer a promising opportunity for rotor cost savings, especially considering the ongoing growth trend in rotor size. An increased chord and airfoil thickness of a two-bladed turbine’s blade results in potential structural improvements caused by a rapidly growing second moment of area. Compared to a three-bladed turbine’s blade, the blade structure would theoretically require less material, while withstanding 50% higher flapwise loads. An analytical method of progressive structural scaling for three-dimensional rotor blade structures, based on equal material stresses, is introduced to calculate the modified structural thickness properties of the two-bladed turbine’s blade. It simplifies the airfoil-shaped structure to a thin-walled rectangle, utilizes a fixed initial flapwise load factor, and scales the edgewise loads proportionally to the required blade mass. To evaluate the validity of this analytical approach, a progressively scaled and an iterated 20 MW two-bladed turbine’s blade are examined with finite element analyses for static loads. The outcomes are then compared to corresponding analyses of a three-bladed turbine’s reference blade. Overall, the static stress comparisons at different blade positions show good agreement with the analytical results. Nevertheless, the buckling analyses performed reveal stability issues, which subsequently will lead to a readjustment of the blade mass.

An optimization and test method for ducted fans based on CFD

Some unmanned aircrafts with ducted fan systems are characterized by high efficiency, structural safety and good stability. As a major part of such aircrafts, the ducted fan plays an important role in performance. However, changes in the fan blade structure will influence the fan action. First, from a manufacturing point of view, materials and gate positions were selected. The injection molding process parameters were optimized based on an orthogonal testing analysis method, and this optimization process reduced the warpage by 36.4%. Then, the flow fields of the ducted fans in the theoretical and deformed models were compared and analyzed with SolidWorks computational fluid dynamics (CFD). Finally, the wind velocity values at different distances from the nozzle outlet of the ducted fan were obtained using a wind speed measurement experiment system. The results from the model comparisons showed that fan blade deformation reduced the wind speed by approximately 5%.

Structural Analysis of a Small Wind Turbine Blade Subjected to Gyroscopic Load

A study was conducted to investigate the structural response of a composite constructed small wind turbine blade subjected to gyroscopic load using finite element analysis. An Aerogenesis 5 kW small wind turbine blade was used as a case study. As part of this study, a high-fidelity finite element model of the 2.5 m long composite blade was built, and the accuracy of its predictions validated against experimental data. The blade model was loaded using a comprehensive method for applying gyroscopic load to finite element models of small-scale blades. The predicted results show gyroscopic loading causes the blade to deflect in both the flap-wise and lead-lag directions and induce reasonably high strains in the composite blade structure. The direction of the gyroscopic loading is a function of the direction of turbine yaw as well as the blade position as it rotates, therefore gyroscopic loading can both exacerbate and reduce the effects of aerodynamic loading acting on the blade.

Utilizing the Natural Composition of Brown Seaweed for the Preparation of Hybrid Ink for 3D Printing of Hydrogels

This study aims to utilize the natural composition of brown seaweed by deriving alginate and cellulose concurrently from the stipe (stem-like) and blade (leaf-like) structures of the seaweed; further, this is followed by fibrillation for the direct and resource-efficient preparation of alginate/cellulose nanofiber (CNF) hybrid inks for three-dimensional (3D) printing of hydrogels. The efficiency of the fibrillation process was evaluated, and the obtained gels were further studied with regard to their rheological behavior. As a proof of concept, the inks were 3D printed into discs, followed by cross-linking with CaCl2 to form biomimetic hydrogels. It was shown that the nanofibrillation process from both seaweed structures is very energy-efficient, with an energy demand lower than 1.5 kW h/kg, and with CNF dimensions below 15 nm. The inks displayed excellent shear-thinning behavior and cytocompatibility and were successfully printed into 3D discs that, after cross-linking, exhibited an interconnected network structure with favorable mechanical properties, and a cell viability of 71%. The designed 3D biomimetic hydrogels offers an environmentally benign, cost-efficient, and biocompatible material platform with a favorable structure for the development of biomedical devices, such as 3D bio printing of soft tissues.

Flow structure and convective heat transfer in a bladed structure under wind conditions

Bladed receivers have been proposed as an alternative to conventional external receivers for high-temperature concentrating solar power systems. Instead of flat banks of tubes arranged on the receiver surface, the tube-banks are oriented into the form of blades protruding from the back-wall of the receiver. This modified arrangement improves light-trapping, without the size and cost implications of a large cavity receiver, and also acts to trap hot air between the blades, hence reducing convective transfer per-tube-area. The present paper investigates the convective heat transfer from a scaled model of a bladed receiver and its correlation with the flow behavior between the blades. Wind tunnel measurements were undertaken to investigate the effects of the wind speed, the blade length and the receiver orientation on the convective heat transfer. It was observed that increasing the pitch angle from 26° to 70°, measured downwards from the vertical in a headwind configuration, leads to a significant reduction in the convective heat transfer coefficient of up to 60%, for the investigated blade lengths. To identify the effect of flow structure on the rate of the convective heat transfer at low Richardson umbers, a second experimental study with isothermal conditions was conducted in a water channel matching the Reynolds number of the wind tunnel experiment. The mean velocity fields and the associate streamline topologies within an open cavity with different pitch angles and blade length to spacing ratios (RBS) were also investigated through Particle Image Velocimetry (PIV) measurements. The streamlines revealed that the shear layer at a pitch angle of 70° for the receiver with the longest blade,RBS = 3, bridges the cavity opening without a strong interaction with the counter-rotating vortices inside the cavity, which resulted in an enlargement of the stagnation zone close to the cavity back-wall. This stagnation zone was identified to be the cause of the convective heat transfer reduction observed in the earlier wind tunnel experiments. It was also found that the Reynolds number has a strong impact on the heat transfer rate, as increasing the wind speed from 3 m/s to 6 m/s enhanced the heat transfer coefficient by up to 50%. As the corresponding Reynolds number in the water channel increased from 1.4 × 104 to 2.8 × 104, PIV data showed that the shear layer was drawn into the cavity and consequently, the velocity magnitude near the back-wall of the cavity reached up to 90% of the freestream velocity. The results provide a good understanding of flow behavior in the vicinity of the blades and its impacts on the convective heat transfer from the receiver.

Optimization of belt grinding stepover for biomimetic micro-riblets surface on titanium alloy blades

As an important component of aero-engine, the surface integrity of aero-engine blade directly affects the performance of the engine. The bionic ribbed surface of drag reduction inspired from shark skin has been widely used in various parts and achieved good drag reduction effect. However, in the actual processing process, there are situations where the ribbed surface cannot be processed due to the large stepover, while the ribbed surface processed can be damaged due to the small stepover, which ultimately affects the surface quality and surface integrity. Combining the particularity of the structure of the aero-engine blade and the micro-characteristics of the bionic ribbed surface, the relationship between the stepover and the micro-characteristics of belt grinding is established. Experimental detection found that the optimization effectively avoids the situation where the ribbed surface is largely damaged and the ribbed surface will not be processed in some locations. The surface roughness after the optimization is also relatively reduced. The morphology of the optimized surface is consistent, the surface roughness is improved by more than 3%, and the length of the overlapped part of the section is reduced from 0.32 to about 0.12 mm.

Modeling of shrinkage characteristics during investment casting for typical structures of hollow turbine blades

To study the coupling mechanism of shrinkage distribution and complex structures in the precision casting process of hollow turbine blades, the blade structure was simplified to a hollow thin-walled structure with resistance and non-resistance. Four different structures of casting and a casting system were designed. Based on the combination of numerical simulation and experimental measurement, the shrinkage distribution and shrinkage model of castings were established. The results show that the simulated and measured shrinkages have the same trend. Then, the structural parameters affecting shrinkage, including wall thickness, outer diameter, and unobstructed structure, were discussed. A mapping model based on a backpropagation (BP) neural network reflecting the relationship between structural parameters and shrinkage rate was constructed. According to the BP neural-network-based mapping model, the average deviations between the predicted and measured values of the transitional and normal sections are 5.8% and 2.4%, respectively, which improves the accuracy compared with existing research, indicating that the shrinkage model has a good performance in predicting shrinkage of the typical structure in hollow thin-walled castings.

Cooling structure design of gas turbine blade by using multi-level highly efficient design platform

In this paper, the internal cooling structure of a second-stage rotor blade is designed by using a multi-level highly efficient design platform. The design process is divided into schematic design and detailed design in sequence. The calculations of pipe-network and heat conduction are presented to preliminary evaluate the cooling structures derived from the schematic design stage. The flow field and heat transfer characteristics of the revised cooling structures are analyzed in the detailed design by using the three-dimensional conjugated heat transfer calculation method. Topological structure, mass flow rate, pressure distribution, heat transfer coefficient and temperature distribution of the cooling channels are presented. It is found that the schematic design results based on one-dimensional to three-dimensional solution method are in good agreement with the detailed design results. Meanwile, the introduction of the schematic design is helpful to shorten the cooling design cycle and reduce the dependence of the design experience. In this work, a five-pass serpentine passage with single cooling air inlet in the cooling system may lead to low flow rate at the trailing edge, which is prone to cause hot gas back-flow and local high heat load. The cooling system with a right-angle channel and a three-pass serpentine channel helps to distribute the flow reasonably and reduce the thermal gradient on the blade surface. The optimal cooling structure meet the requirements well. Compared with the uncooled blade, the average temperature of the blade decrease over 530 K with limited cooling air.

Microstructural and mechanical aspects of micrometric and nanometric Ni + 10% Cr7C3 composite microwave clads

In this paper, we present the development of micrometric and nanometric Ni + 10% Cr7C3 composite clad on ASTM A743 grade CA6NM hydroturbine steel through microwave irradiation. The microstructure of micrometric clad exhibited blade and rod-like structure of carbides embedded in [Formula: see text](Ni, Fe) solid solution, while nanometric clad leads to the evolution of petal-like structure of carbides. The developed nanometric clad shows uniform microstructural features with a low level of carbide decomposition. As a result, the average nanohardness and fracture toughness of nanometric clad improved by 38.11% and 8%, respectively, compared to the micrometric clad. Clads have porosity of the order of 1.1% and 0.81% for micrometric and nanometric clad, respectively.

Mechanical Performances of Lightweight Sandwich Structures Produced by Material Extrusion-Based Additive Manufacturing.

Material Extrusion-Based Additive Manufacturing Process (ME-AMP) via Fused Filament Fabrication (FFF) offers a higher geometric flexibility than conventional technologies to fabricate thermoplastic lightweight sandwich structures. This study used polylactic acid/polyhydroxyalkanoate (PLA/PHA) biodegradable material and a 3D printer to manufacture lightweight sandwich structures with honeycomb, diamond-celled and corrugated core shapes as a single part. In this paper, compression, three-point bending and tensile tests were performed to evaluate the performance of lightweight sandwich structures with different core topologies. In addition, the main failure modes of the sandwich structures subjected to mechanical tests were evaluated. The main failure modes that were observed from mechanical tests of the sandwich structure were the following: face yielding, face wrinkling, core/skin debonding. Elasto-plastic finite element analysis allowed predicting the global behavior of the structure and stressing distribution in the elements of lightweight sandwich structures. The comparison between the results of bending experiments and finite element analyses indicated acceptable similarity in terms of failure behavior and force reactions. Finally, the three honeycomb, diamond-celled and corrugated core typologies were used in the leading edge of the wing and were impact tested and the results created favorable premises for using such structures on aircraft models and helicopter blade structures.

Gain‐improved VHF broadband whip antenna loaded with radiation blades

In this study, a new type of horizontal radiation blade structure is proposed and applied to the very high frequency (VHF) broadband whip antenna. The influence of the radius, length, number of branches of horizontal radiation blade and its distribution on the whip body on the electrical performance of the whip antenna is analysed separately to design a more suitable structure, and then an algorithm optimization of single loading and broadband matching network is carried out for further impedance matching. The simulation and measured results both show that compared with the existing broadband whip antenna, the gain and efficiency of the proposed antenna are significantly improved while maintaining a good voltage standing wave ratio (VSWR) over the frequency band of 30–300 MHz, all the VSWR are −3.5 dB, with an average value of 2.2 dB; and all the efficiency are >15%, with an average value of 47.7%; the pattern deviation in higher frequency is also suppressed to some extent. The proposed antenna has small size, wider bandwidth and higher radiation performance, which is suitable for vehicle-borne and ship-borne VHF communication.

Aerodynamic performance prediction of NREL phase VI blade adopting biplane airfoil

Abstract The NREL Phase VI wind turbine is taken as an example to study the changes in aerodynamics performance and 3D flow structures due to the adoption of the biplane airfoil in the inboard region of the blade. The NREL Phase VI blade is taken as the baseline blade, and the biplane blades are designed by replacing the original inboard region with biplane airfoil. The flows around the blades are simulated by solving the Reynolds averaged Navier–Stokes equations with the Spalart–Allmaras model. Results show that evident performance improvement of biplane blades compared with baseline blade. The rotor flap moment to shaft torque ratios of the biplane blade drop, which proves its applicability in large blades. Detailed analysis of sectional loads along the blades further reveals that the increment in shaft torque of the biplane blades mainly comes from the inboard region, and the gap and stagger of the biplane airfoil have pronounced effects on the performance and flow structures of biplane blades. The biplane blades show a good capacity in suppressing flow separation and radial flow. In addition, the transition section from the biplane airfoil to monoplane airfoil must be carefully designed using 3D simulation approaches to reduce its negative effect.