Performance Of Blade Research Articles

Evaluation of film cooling effect in multi-row hole configurations on turbine blade leading edge

The present study evaluated the film cooling performance of turbine blade leading edges with multi-row hole configurations. Numerical models were refined to improve simulation accuracy by adjusting the turbulent viscosity coefficient, enhancing the prediction of jet diffusion in stagnation areas. The film cooling effectiveness distribution was analyzed through pressure-sensitive paint (PSP) experiments, and the numerical method was validated. The Sellers formula, a two-dimensional model, was used to evaluate the impact of upstream jets on downstream film cooling, with comparisons to simulations. The results show that the Sellers formula generally predicts well at low blowing ratios, but strong interactions between the mainstream and secondary jets, along with vortex formation between hole rows, undermine its accuracy at high blowing ratios, creating a concentrated high-effectiveness cooling zone. Changes in hole row layout affect the film cooling effectiveness distribution but have minimal impact on area-average predictions by the Sellers formula. Combining experimental data at high blowing ratios with the Sellers formula provides critical insights for designing leading edge multi-row hole film cooling structures. This study emphasizes the importance of understanding vortex structures and jet interactions to optimize film cooling strategies, offering significant value for engineering designs in turbine blades.

Unsteady CFD simulation of a rotor blade under various wind conditions

Wind and gusts can significantly impact the performance of rotors and turbines. The transient behavior of the rotor should be carefully examined to account for these effects. This paper investigates the unsteady aerodynamic characteristics of a rotor blade under different wind conditions, such as direction, speed, and angle. A 3D transient Computational Fluid Dynamics (CFD) simulation using the dynamic mesh technique is performed to analyze the rotor dynamics. The unsteady Reynolds-averaged Navier–Stokes (URANS) equations with the k-ω SST turbulence model are solved. The rotor blade used for this study is the U15XXL Combo KV29 industrial blade, which has not been numerically analyzed before. The results show that wind in the same direction as the rotation reduces the thrust more than lateral or opposite wind. Lateral wind with a speed lower than 5 m/s decreases the blade performance, but higher speeds increase it. Higher lateral wind speeds also cause two peaks in the torque curve, forming a butterfly wing shape in the polar torque plot and multiple extrema in the torque curve with increasing speed. The maximum thrust shifts slightly to the left with increasing lateral wind speed. The lateral angle does not affect the average thrust produced in one blade revolution but only causes a spatial shift. The thrust production decreases as the angle approaches the opposite direction of rotation. The motion amplitude decreases, and the curve becomes smoother as this angle increases. A nearly straight line similar to no side wind is observed at 60 and 90 degrees, which is attributed to the constant effective angle of attack during the rotation cycle.

Evaluation on the performance and wear of blades in a small‐sized high‐density polyethylene shredder

AbstractIn this study, a small‐sized shredder machine equipped with spiral oriented double‐edged rotating and fixed blades was utilized to shred high‐density polyethylene (HDPE) waste. The performance of the shredder machine was determined based on the recycling and shredding efficiency, the percentage of retention, and the wear of its rotating and fixed blades. The wear of the blades was examined using an optical microscope, a scanning electron microscope, an energy dispersive x‐ray, and an x‐ray diffraction. High recycling (~95 %–98 %) and shredding (~66 %–70 %) efficiency, and low percentage of retention (~1.2 %–4.1 %) indicated a reliable performance of the shredder machine. The rotating blade exhibited higher wear at the back end, compared to the front end for the fixed blade. The wear of the blades was due to scratching and edge chipping. Formation of iron oxides during shredding did not cause significant changes in the hardness of the blades. Based on the evaluation, cost‐effective and time saving maintenance of the shredder blades could be achieved by gradual maintenance starting from the blade exhibited high wear.

In-Depth Study on the Application of a Graphene Platelet-reinforced Composite to Wind Turbine Blades.

Graphene platelets (GPLs) are gaining popularity across various sectors for enhancing the strength and reducing the weight of structures, thanks to their outstanding mechanical characteristics and low manufacturing cost. Among many engineering structures, wind turbine blades are a prime candidate for the integration of such advanced nanofillers, offering potential improvements in the efficiency of energy generation and reductions in the construction costs of support structures. This study aims to explore the potential of GPLs for use in wind turbine blades by evaluating their impact on material costs as well as mechanical performance. A series of finite element analyses (FEAs) were conducted to examine the variations of mechanical performances-specifically, free vibration, bending, torsional deformation, and weight reductions relative to conventional fiberglass-based blades. Details of computational modeling techniques are presented in this paper. Based on the outcomes of these analyses, the mechanical performances of GPL-reinforced wind turbine blades are reviewed along with a cost-benefit analysis, exemplified through a 5MW-class wind turbine blade. The findings affirm the practicality and benefits of employing GPLs in the design and fabrication of wind turbine blades.

The Unsteady Shock-Boundary Layer Interaction in a Compressor Cascade – Part 3: Mechanisms of Shock Oscillation

Abstract The shock-boundary layer interaction in transonic flows is known to cause strong unsteady flow effects that negatively affect the performance and operability of blade and cascade designs. Despite decades of research on the subject, little is still known about the physical mechanisms that drive the different oscillation frequencies observed with different designs. In the conclusion of this three-part series, the experimental and numerical data obtained with the Transonic Cascade TEAMAero are analyzed together in detail in order to test the main theories of continuous shock oscillation. This analysis exposes a main mechanism of shock oscillation, where pressure waves generated inside the passage of the cascade propagate upstream and interact strongly with the main shock when the latter is also in the passage. The interaction of these features causes a breakdown of the flow that is shown to propagate upstream, inevitably causing strong variations in the inflow angle and therefore on the operating conditions of the cascade. The high frequency content of these pressure waves is also shown to be responsible for weaker high-frequency variations of the shock movement throughout the cycle. Parallels are also drawn with previous experimental campaigns in order to search for a global understanding of the different observations made. Although various parts of the described interaction are not fully understood yet, and the dataset of experimental measurements compiled is still rather small, a good basis is provided on which to further study the underlying mechanisms of unsteady flows in transonic cascades.

A numerical study on the effect of spanwise installation of vortex generators on Francis runner blades

Abstract Hydro turbine operation far off from its best efficiency point introduces vortices and swirl that detaches flow from the blade surface. This break-off of flow accounts to loss in hydrodynamic lift accompanied by pressure fluctuations and vibration that leads to poor performance and mechanical failure of the turbine blades. Vortex generators (VGs) are efficient passive devices deployed to enhance aerodynamic lift of wind turbine blades and aircraft wings and can improve hydrodynamic lift on turbine runner blades as well. This study aims to investigate on the possibility of installation of VGs on the runner blade at leading edge, midspan and trailing edge of the runner blade. The study is carried out on a model Francis turbine developed at Waterpower Laboratory, NTNU. The numerical study is mainly focused on improving performance of the turbine at low speed as well as at the best efficiency speed. The operating head selected for the study is 11.94 m and the speed of the turbine is varied from 233 rpm to 433 rpm at an increment of 25 rpm. The turbine is simulated at different positions of guide vanes and hydraulic performance is calculated and the results of the analysis are compared with reference case without VGs. The results at deep-part load show major improvement in runner efficiency with increment in values up to 4%. The core purpose of the research is to develop effective techniques to operate traditional turbine runner at variable speed with cost-efficient minimal modifications in the geometry of the runner blades.

Numerical studies on the performance of Savonius turbines for hydropower application by varying the frontal cross-sectional area

The Savonius turbine is a drag-based device that utilizes hydrokinetic energy in irrigation channels for small-scale hydropower generation. Since it is a drag-type device, the turbine blade frontal cross-sectional area influences the performance of the turbine blade. In this paper, the influence of taper on the turbine blade bottom, top, and middle sides on the Savonius turbine performance was computed numerically using the sliding mesh technique with a 0.5 m/s water inlet velocity. In this study, the effect of various blades with varying cross-sectional areas has been analyzed numerically using the sliding mesh technique, and the results were compared with the semicircular blade profile. The variation of torque coefficient with respect to rotor blade rotation was plotted, and pressure and velocity variation were analyzed to investigate the performance parameters. The results showed that the top small, middle high, and bottom small blade profiles performed better than the semicircular, inverted taper and top high, middle small, and bottom high blade profiles. It is observed that the maximum torque coefficient at a TSR of 0.7 is 0.35, and the maximum power coefficient at a TSR of 0.9 is 0.253.

Influence of Herringbone Grooves Inspired by Bird Feathers on Aerodynamics of Compressor Cascade under Different Reynolds Number Conditions

Nowadays, high aerodynamic load has made blade separation an issue for compact axial compressors under high-altitude low-Reynolds-number conditions. In this study, herringbone grooves inspired by bird feathers were applied to suppress the suction side separation and reduce loss. To study the effect of bio-inspired herringbone grooves on the aerodynamic performance of compressor cascades, a high subsonic compressor cascade was taken as the research object. Under the conditions of different Reynolds numbers, the effects of herringbone grooves of different depths on the flow separation were numerically studied. The research results show that at a high-Reynolds-number condition (Re = 5.6 × 105), the sawtooth-shaped wake induced by herringbone grooves increases the turbulent mixing loss near the suction surface, and the blade performance deteriorates. At a low-Reynolds-number condition (Re = 1.3 × 105), the span-wise secondary flow and micro-vortex structure induced by the herringbone grooves effectively suppress the laminar separation on the suction surface of the blade, and there is an optimal depth for the herringbone grooves that reduces the profile loss by 8.33% and increases the static pressure ratio by 0.55%. The selection principle of the optimal groove depth with the Re is discussed based on the research results under six low-Reynolds-number conditions.

An insight into the creep failure mechanism of sliver defect in the second-generation nickel-based single crystal superalloy CMSX-4

Sliver defects are common casting imperfections in the preparation of single crystal blades, significantly impacting the high-temperature mechanical performance of blades and potentially leading to blade failure. A detailed study was conducted on the microstructure of sliver in the second-generation nickel-based single crystal superalloy CMSX-4, focusing on its influence on creep performance at 980 °C/250 MPa. Results indicate a substantial impact of sliver on the creep performance of single crystal superalloys, with a 26.37 % reduction in creep rupture time for samples with sliver compared to those without. Fracture analysis reveals that sliver primarily contributes to performance deterioration by promoting the extension of grain boundary microcracks through grain boundary sliding during the creep process, accelerating sample fracture. Utilizing crystal plasticity theory, a successful fit was achieved for the creep rupture life of samples with sliver, allowing the prediction of fracture life for samples with different orientations of slivers. Predictive results suggest that, for CMSX-4 alloy, the orientation of the sliver should be restricted to within 8°.

Exploratory Study on the Application of Graphene Platelet-Reinforced Composite to Wind Turbine Blade.

With the growth of the wind energy market and the increase in the size of wind turbines, the demand for advanced composite materials with high strength and low density for wind turbine blades has become imperative. Graphene platelets (GPLs) stand out as highly premising reinforcements due to their exceptional physical properties, resulting in their widespread adoption in the composite industry in recent years. The present study aims to analyze the applicability of a graphene-platelet-reinforced composite (GPLRC) to wind turbine blades in terms of structural performance. A finite element blade model is constructed by referring to the National Renewable Energy Laboratory (NREL) 5 MW wind turbine, and its reliability is verified through a convergence test. The performance of the wind turbine blade is quantitatively examined in terms of the deflection and stress, natural frequencies, and twist angle. The applicability of the GPL-reinforced wind blade is explored through a comparison with wind blades manufactured with glass fiber and carbon nanotubes (CNTs). The comparison indicates that the performance of a wind blade can be remarkably improved by reinforcing with GPLs instead of traditional fillers, and the weight of not only the wind blade itself but also the wind turbine system can be remarkably reduced. The present results can be useful in the development of next-generation high-strength lightweight wind turbine blades.

Investigation on drag reduction on rotating blade surfaces with microtextures.

To enhance the aerodynamic performance of aero engine blades, simulations and experiments regarding microtextures to reduce the flow loss on the blade surfaces were carried out. First, based on the axisymmetric characteristics of the impeller, a new simulation method was proposed to determine the aerodynamic parameters of the blade model through the comparison of flow field characteristics and simulation results. Second, the placement position and geometrical parameters (height, width, and spacing) of microtextures with lower energy loss were determined by our simulation of microtextures on the blade surface, and the drag reduction mechanism was analyzed. Triangular ribs with a height of 0.2 mm, a width of 0.3 mm, and a spacing of 0.2 mm exhibited the best drag reduction, reducing the energy loss coefficient and drag by 1.45% and 1.31% for a single blade, respectively. Finally, the blades with the optimal microtexture parameters were tested in the wind tunnel. The experimental results showed that the microtexture decreased energy loss by 3.7% for a single blade under 57° angle of attack and 136.24 m/s, which was favorable regarding the drag reduction performance of the impeller with 45 blades.

A simulation based analysis for enhancement of performances of turbine blades in turbo jet engines with thermal barrier coatings (TBCs)

The enhancement of turbine blade performance within turbo jet engines is crucial for prolonged engine life. Amidst various cooling strategies for turbine blades, thermal barrier coatings (TBCs) emerge as a highly effective method. Just as the choice of material for the turbine blade holds importance, so too do the materials comprising TBCs. The current research work aims to pursue finite element-based analyses of turbine blades with TBCs, an almost real complex-shaped geometric model comprising the blade body with a rabbet is essential, the stress generated during TGO growth which is crucial for analysis, to select the substrate from both a thermo-structural and cost perspective. In this research endeavor, TBCs were structured with a substrate, a bond coat (NiCoCrAlY), and a top coat of lanthanum cerate (La2Ce2O7) ceramic layers. A thermally grown oxide (TGO), namely α-Al2O3, forms between the bond coat and the top coat due to the elevated temperatures experienced. Two distinct substrates, Inconel 625 and Titanium-T6 alloy, were meticulously chosen as turbine blade materials. Commencing with NACA 4412 airfoil data, the turbine blade was meticulously designed using CATIA, followed by simulations conducted on ANSYS software through a static thermal structural model. The simulation aimed to determine the optimal top coat/thermally grown oxide (TC/TGO) and TGO/bond coat (TGO/BC) layer thicknesses to achieve minimal equivalent stress and total deformation in the turbine blade. The simulated results revealed that a combination of 400 µm TC/10 µm TGO and 10 µm TGO/100 µm BC provided the lowest equivalent stress and total deformation, thereby offering valuable insights for the current research.

A Preconditioner-Based Data-Driven Polynomial Expansion Method: Application to Compressor Blade With Leading Edge Uncertainty

Abstract In engineering practice, the amount of measured data is often scarce and limited, posing a challenge in uncertainty quantification (UQ) and propagation. Data-driven polynomial chaos (DDPC) is an effective way to tackle this challenge. However, the DDPC method faces problems from the lack of robustness and convergence difficulty. In this paper, a preconditioner-based data-driven polynomial chaos (PDDPC) method is developed to deal with UQ problems with scarce measured data. Two numerical experiments are used to validate the computational robustness, convergence property, and application potential in case of scarce data. Then, the PDDPC is first applied to evaluate the uncertain impacts of real leading edge (LE) errors on the aerodynamic performance of a two-dimensional compressor blade. Results show that the overall performance of compressor blade is degraded and there is a large performance dispersion at off-design incidence conditions. The actual blade performance has a high probability of deviating from the nominal performance. Under the influence of uncertain LE geometry, the probability distributions of the total pressure loss coefficient and static pressure ratio have obvious skewness characteristics. Compared with the PDDPC method, the UQ results obtained by the fitted Gaussian and Beta probability distributions seriously underestimate the performance dispersion of compressor blade. The mechanism analysis illustrates that the large flow variation around the leading edge is the main reason for the overall performance degradation and the fluctuations of the entire flow field.

A Review of Machine Learning Methods in Turbine Cooling Optimization

In the current design work, turbine performance requirements are getting higher and higher, and turbine blade design needs multiple rounds of iterative optimization. Three-dimensional turbine optimization involves multiple parameters, and 3D simulation takes a long time. Machine learning methods can make full use of historically accumulated data to train high-precision data models, which can greatly reduce turbine blade performance evaluation time and improve optimization efficiency. Based on the data model, the advanced intelligent combinatorial optimization technology can effectively reduce the number of iterations, find the better model faster, and improve the optimization calculation efficiency. Based on the different cooling parts of turbine blades and machine learning, this research explores the potential of implementing different machine learning algorithms in the field of turbine cooling design.

An Experimental Performance Assessment of a Passively Controlled Wind Turbine Blade Concept: Part A—Isotropic Materials

This paper is the first part of a two-part series, which presents preliminary findings on a novel flexible curved wind turbine blade designed for passive control, comparing its aerodynamic performance and behavior against a conventional straight blade. Characterized by its ability to twist around its longitudinal axis under bending loads, the flexible curved blade is engineered to self-regulate in response to varying wind speeds, optimizing power output and enhancing operational safety. This design utilizes inherent elasticity and specific geometric configurations to develop torsional loads, resulting in continuous adjustment of the blade’s pitch angle via twist–bend deformation. The study focuses on a comparative analysis conducted in a wind tunnel, testing both a small-scale model of the conventional blade and the flexible curved blade of equivalent diameter. Results indicate that the flexible curved blade concept successfully moderates its rotational speed and power output at higher wind speeds and demonstrates the capability to start generating power at lower wind speeds and stabilize power effectively, aligning with sustainability goals by potentially reducing reliance on active control systems. Despite promising outcomes, passive control mechanisms did not activate at the designed wind speeds, revealing a misalignment between expected and actual performance and underscoring the need for further refinements in blade design and control settings. Additionally, the power coefficient (Cp) versus tip speed ratio (TSR) comparison showed that flexible curved blades operate within a lower TSR range and exhibit controlled capping of power under high wind conditions, marked by a distinctive ‘hook-like’ feature in Cp behavior. This study confirms the feasibility of designing and manufacturing passively controlled wind turbine blades tailored to specific performance criteria and underscores the potential of such technology. Future work, to be detailed in a subsequent paper, will explore further optimizations and the use of Glass Fiber-Reinforced Polymer (GFPR) composite materials to enhance blade flexibility and performance.

Assessment of the effect of thermal barrier coating blockage on film cooling effectiveness: An experimental study of full-coverage turbine vane

The improved performance of turbine blades leads to increased temperature loads, thereby necessitating higher design standards for heat protection. Thermal barrier coating (TBCs) and film cooling are the predominant technologies employed for blade cooling. However, the application of thermal barrier coatings through spraying inevitably modifies the structure of film holes, resulting in deviations from the original design in film cooling. In this study, numerical calculations are used to examine the impact of TBCs blockage on coolant mixing and flow mechanisms in the film holes at typical locations on the vane surface. Additionally, models with actual engine vane dimensions were developed, and the full-coverage film cooling effectiveness (.) vanes with and without TBCs were measured using Pressure-sensitive paint (PSP). The results indicate that the impact of TBCs blockage on the cooling characteristics of cylindrical holes is more pronounced than that of laid-back fan-shaped holes. The TBCs blockage leads to a redistribution of coolant, causing a greater tendency for the coolant to flow out from the hole rows on the suction surface in the tested vane. This results in higher η on the suction surface for the vane with TBCs compared to the vane without TBCs, with a maximum increase of approximately 16.7%. For the other regions of the vane, TBCs spraying significantly reduced η at the leading edge of the vane (with a maximum reduction of approximately 52%) and slightly reduced η at the pressure surface for other regions of the vane (with a maximum reduction of approximately 7%). The application of TBCs reduces the uniformity of film coverage on vane surfaces, with a maximum reduction of approximately 22.5%.

Numerical investigation on dimpled tube effects on internal cooling performance of turbine blades

This research examines how modified surfaces may improve the internal cooling performance of advanced turbine blades. A few correlations are established for three different dimpled tubes to estimate their heat transfer coefficient. To save computational expenses, these correlations are used in a reduced conjugate heat transfer (RCHT) scheme. Using a numerical simulation with the k- ω SST turbulence model, the formulation is validated by comparison with numerical and experimental data for a smooth tube. The scheme is applied to the advanced C3X turbine blades to asses the merit of the new design. The research finds that dimples in the cooling passage may reduce the temperature on the blade surface up to 130 K and increase the heat flux on the blade surface up to 50 %. Teardrop dimples offered the best performance in enhancing heat transfer. Additionally, they reduced the average temperature on the midspan of the C3X blade by up to 19.8 %. The study demonstrates the advantages of employing modified surfaces to improve blade internal cooling performance. It also confirms the validity of the RCHT assumption, which can simplify simulation in comparable test cases.

Design, Analysis, and Wind Tunnel Evaluation of Novel Fabric-Covered Rotor Blades in Wind Energy Generation

This paper investigates the performance of a novel fabric-covered rotor blade. The study aims to address the need for cost-effective wind turbine blades by exploring the potential of textile-based materials. The research includes a comprehensive wind tunnel experiment to evaluate the aerodynamic response of the fabric-covered blade, compared to a traditional hard-shell blade. The experimental data are systematically processed and corrected for wind tunnel effects, providing valuable insights into the aerodynamic behavior of the novel blade. The results show that the fabric-covered blade, constructed from PTFE-coated fiberglass fabric, exhibits promising aerodynamic characteristics, with potential applications in reducing manufacturing expenses and enhancing power generation. The study concludes by proposing a novel control strategy leveraging the natural deformation of blades at high wind speeds, suggesting potential applications in limiting power output at high wind speeds. Overall, these findings contribute to the ongoing efforts in developing innovative and cost-efficient solutions for wind energy generation.

Study on the Influence of Protuberance Amplitude on the Performance of Vertical Axis Wind Turbines

Abstract The performance of vertical axis wind turbine (VAWT) is mainly affected by the dynamic stall process of the blade. Inspired by the anti-stall performance of the humpback whale flipper, leading edge protuberances (LEPs) are applied to 2-blade VAWT. Based on computational fluid dynamics simulation method, the effects of LEPs amplitude on VAWT performance are investigated when blade tip speed ratio is 2.19. The results show that the larger the amplitude of the LEP, the lower the average power coefficient. When the number of protuberances is 3, the average power coefficient of the VAWT with a protuberance amplitude of 6.625mm is 1.8% higher than prototype blade. Considering the impact of increasing the chord length of biomimetic blades, the average tangential force coefficient of all biomimetic VAWTs decreases. The peak section performance of the bionic blade decreases significantly while the trough section performance increases significantly. The difference between the peak section and trough section of the LEPS plays an important role in improving the performance. This study provides a reference for the application of bionic protuberances in VAWTs.

Effect of Blade Thickening Law on the Internal Flow Field and Hydraulic Performance of Double Suction Pumps for Yellow River Pumping

Abstract The thickness of the blades is a fundamental parameter of the impeller and has a substantial impact on the performance of the pump. With the other geometric parameters of a centrifugal pump fixed, six kinds of impellers with different blade thickness were designed. Numerical simulations of the pumps were performed with Fluent under six different operating conditions based on the RNG k-epsilon equation and the SIMPLE algorithm. The hydraulic performance of the pump and its external characteristics were analysed based on the internal flow field to understand the relationship between blade thickness and performance. The results have showed that the hydraulic performance of the pump increases with the backward movement of the maximum thickness of the blade; Under the same sand concentration, the efficiency increases slightly with the increase of blade thickness within a certain range;With the increase of blade thickness, the turbulent kinetic energy loss of the pump under design operating conditions increases continuously; The thickening rules of schemes A1 and B can improve the hydraulic performance of the pump and the transport capacity of the sediment laden two-phase flow. That is, on the premise of meeting the structural strength of the blades, selecting a reasonable blade thickness can ensure that the double suction pump has good hydraulic performance.