End-plate Design Research Articles

Effects of endplate designs on the performance of Savonius vertical axis wind turbine

In aerodynamic studies, endplates or wingtip devices play a crucial role in enhancing the performance of airfoil blades and minimizing losses. This is particularly important for wind turbines, especially the drag-type Savonius turbine. This paper aims to investigate the effects of different endplate designs. Both experimental works and numerical simulations were conducted on a Savonius rotor with an aspect ratio of 1. A total of eight different endplate geometries and sizes were investigated. The mechanical torque and rotational speed were measured experimentally under various loads with an incoming wind speed of 5.89 m/s. The coefficient of torque (CT) and coefficient of power (CP) were calculated in both the experiments and simulations. The simulation was first validated using data from the literature, and flow characteristics were then scrutinized. The results indicate that the endplates greatly impact the turbine performance, with improvements of up to 299.7 % compared to a turbine without endplates from the experiment. The endplates help prevent flow leakage near the blade edges. In addition to tip losses reducing turbine performance, aerodynamic parasitic drag also contributed to a decrease in CP for the full endplate. The relationship between the aerodynamic parasitic drag with TSR is also reported. By implementing a well-designed endplate, these adverse effects can be mitigated.

Finite Element Modeling of Beam-to-Column Steel Timber Composite Joints with Different Parameters

This study presents a comprehensive three-dimensional finite element modeling and parametric analysis of composite beam-to-column joints in steel–timber composite structures. The investigation encompassed a variety of shear connector configurations, end plate designs, and bolt dimensions, aiming to elucidate their respective influences on the structural performance and behavior of these joints. Through meticulous numerical simulation, this research sought to enhance the understanding of the interactions and load transfer mechanisms within composite connections, thereby contributing to the optimization of design practices in the field of structural engineering. The load–displacement relationship for timber–steel composite joints subjected to monotonic loading was investigated using ABAQUS 6.14 software. This study systematically analyzed the effects of various parameters, including different configurations of shear connectors, end plate thicknesses, and bolt dimensions, on the overall performance of the joints. Through this comprehensive numerical analysis, the research aimed to provide deeper insights into the mechanical behavior and structural integrity of these composite connections under the applied loading conditions. A non-linear finite element model of timber was developed and verified with the results of the experiment in this study. The findings are discussed in detail, highlighting the intricate relationships between the selected parameters and their respective effects on the performance and overall stability of the composite connections. This thorough evaluation aimed to enhance the understanding of how these variables interact within the context of composite joint design and behavior. Finally, design recommendations for composite structures, such as the dimensions of the bolt, end plate thickness, and different sizes of shear connectors are provided.

Experimental investigation into the effects of endplate designs for a Savonius turbine

Abstract Wind energy is experiencing a trend of exponential growth in both literature and industrial employment, emphasizing its current pivotal role in achieving carbon neutrality by replacing fossil fuels. Vertical axis wind turbines (VAWTs) particularly Savonius rotors operate at a lower tip-speed-ratio (TSR) range compared to horizontal axis wind turbines (HAWTs). The Savonius rotor has good starting characteristics, making it suitable to be placed in urban areas with lower wind speeds. Due to its low efficiency, studies on augmentation and optimization have been conducted to improve its blade and deflector designs. Extensive research has established a common consensus that the use of endplates significantly improves the aerodynamic performance of the Savonius rotor. However, limited research has been undertaken to explore the endplate design further. In this study, wind tunnel tests were conducted on different endplate ratios, to investigate the effects of endplate design on the aerodynamic performance of a conventional Savonius turbine. Three different Savonius rotor with no endplate, semi-circular endplate and circular endplate were designed and manufactured. Experiments were conducted in an open-type suction wind tunnel at a constant measured wind velocity of 5.89 m/s. The turbine’s performance for different endplate ratios was evaluated across a TSR range of 0.2 to 1.0. The performance was assessed based on the maximum power generated and its self-starting ability. From the experimental results, the circular endplate ratio of 1.1 shows a significantly high coefficient of power compared to both semi-circular and without endplates. This is due to reduced spanwise spillage and enhanced airflow capture by the rotor. The endplates direct incoming air to the advancing blade and overlap region, resulting in the increased pressure difference between the concave and convex sides of both the advancing and returning blade, thereby improving the power efficiency of the turbine with 1.1D diameter endplate and semi-circular endplate by 296.6% and 6.9% compared to no endplates case.

Enhancing Axial Flow Fan Performance in Air-Cooled Condensers: Tip Vortex Manipulators and Comparative Analysis of Numerical Simulation and Experimental Testing

Abstract Direct dry-cooled power plants typically operate numerous large-diameter axial flow fans in air-cooled condensers (ACCs) to facilitate the condensation of steam in the plant's thermodynamic cycle. Enhanced fan efficiency may, at scale, lead to significant parasitic power reductions and subsequent increases in plant power output. The performance of these fans may be increased by adding blade-tip modifications, which act to control blade-tip leakage flow. Previous studies have shown that manipulating the tip leakage vortex (TLV) increases the blade-to-air momentum transfer and stabilizes the air flow structures as it traverses the fan blade. This paper takes a step toward the development of improved tip vortex manipulators for an ACC fan. Three-dimensional computational fluid dynamics (CFD) simulations, and experimental testing of the modified and unmodified fan within an ISO test facility are performed. The results are then utilized to assess the accuracy of the simulation model, visualize the manipulated flow structures at the blade tip, and ultimately quantify the effect of the endplate designs on fan performance. Excellent correlation between numerical and test results for the unmodified fan is observed, and the benefit of blade-tip modification on fan performance is again confirmed experimentally. The simulation model, however, fails to predict improvements in fan performance under modification, and simulated tip leakage flows are investigated for clarification. It is hypothesized that deflection of tip endplates under operation account for differences between simulation and experiment, and that fluid–structure interaction analyses could potentially resolve discrepancies.

Scale Effect of a Kappel Tip-Rake Propeller

In this paper, the scale effect of Kappel tip-rake propellers with different end plate designs was studied using computational fluid dynamics. Given the base size of the mesh and the appropriate numerical model for the determined simulation, the open-water performance of three Kappel propellers with different bending degrees of the end plate at different scales was calculated. Comparing the scale effect of these propellers, the scale effect of the torque coefficient of a Kappel propeller is more intense than that of the conventional propeller. In addition, the scale effect of the torque coefficient is strong when the bending degree of the end plate increases, dwarfing the scale effect on the thrust coefficient. Following the research on the scale effect of the wake field for the Kappel propeller, the laws that reveal the influence of the scale on the wake field were summarized; that is, the high-speed zone in the wake relatively expands with the increase of the scale in company with a trend of tip cross flow. The research reveals the basic variation trend and rule of the open-water performance and wake distribution for the Kappel propeller under different scales within the Reynolds number range of 4.665×105−8.666×107 considering γ transition, as well as the characteristic differences between the Kappel propellers with different end plate designs, which will be of great significance to its optimization design and application to marine vehicles of different scales.

Study on the Optimal Cross-Sectional Shapes of the PEMFC Endplates by Using a Moment of Inertia and 3D FEM Models

The deflection of the endplate under the clamping force has a vital effect on fuel cell performance. An optimal cross-sectional shape with a high moment of inertia of the endplate is significant to maximize the bending stiffness of the fuel cell stack. Five cross-sectional shapes (rectangular, round, parabolic, rectangular + round, and rectangular + parabolic) of the typical endplates are proposed. An analytical study on the moments of inertia of the endplates is introduced and analyzed. The maximum moments of inertia of the cross-sections are obtained and displayed in a matrix in thickness and length. The statistical results show that the “rectangular + parabolic” cross-section has the advantage of wide dimensional size while maintaining a high moment of inertia. Finally, the analytical studies are validated by a finite element method (FEM) and the corresponding trends are highly agreed upon. The maximum moment of inertia of the parabolic endplate is 85.71% higher than the rectangular endplate with a thickness of 80 mm, and the corresponding contact pressure variance is 6.15% less than the rectangular endplate. The presented analytical study is significant and effective to optimize the cross-sectional shape of the endplate and provide an endplate design direction for a large fuel cell stack.

Investigation into the Aerodynamic Performance of a Vertical Axis Wind Turbine with Endplate Design

For the past decade, research on vertical axis wind turbines (VAWTs) has garnered immense interest due to their omnidirectional characteristic, especially the lift-type VAWT. The H-rotor Darrieus VAWT operates based on the lift generated by aerofoil blades and typically possesses higher efficiency than the drag-type Savonius VAWT. However, the open-ended blades generate tip loss effects that reduce the power output. Wingtip devices such as winglets and endplates are commonly used in aerofoil design to increase performance by reducing tip losses. In this study, a CFD simulation is conducted using the sliding mesh method and the k-ω SST turbulence model on a two-bladed NACA0018 VAWT. The aerodynamic performance of a VAWT with offset, symmetric V, asymmetric and triangular endplates are presented and compared against the baseline turbine. The simulation was first validated with the wind tunnel experimental data published in the literature. The simulation showed that the endplates reduced the swirling vortex and improved the pressure distribution along the blade span, especially at the blade tip. The relationship between TSR regimes and the tip loss effect is also reported in the paper. Increasing VAWT performance by using endplates to minimise tip loss is a simple yet effective solution. However, the improvement of the power coefficient is not remarkable as the power degradation only involves a small section of the blades.

Numerical Investigation of the Power Performance of the Vertical-Axis Wind Turbine with Endplates

An H-rotor vertical axis wind turbine (VAWTs) can operate independently in any wind direction, making it aerodynamically efficient and suitable to harness wind energy in low wind speed areas. The aerodynamic efficiency of VAWTs is highly dependent on the blade geometry, especially the blade tip. Tip vortices produced at the blade tips can negatively affect the VAWT’s aerodynamic efficiency. Adding endplates to the blade tips can minimize the effects of tip vortices on VAWTs. In this paper, several endplate designs are used to evaluate the effectiveness in improving the power coefficient, Cp of a VAWT at three different tip speed ratios (TSRs) using three-dimensional computational fluid dynamics (3D CFD) simulation. The power coefficients of VAWTs with endplates are compared with the baseline model with the same geometrical parameters where the baseline VAWT model is based on the experimental model from the literature. Since the focus of this study is on the blade tip design, a simplified 3D VAWT model is used where the supporting shaft and arms of the VAWT are excluded to reduce the needed computational capacity. Among the various endplate designs used in this study, the semi-circular inward endplate (ED3) with a diameter equivalent to 1.2 blade chord length showed the best improvement in the Cp which is by 7.45%, and 5.79% for at the TSRs of 2.19 and 2.58, respectively. The pressure difference on both sides of the blade was also examined. The results revealed that the endplate can prevent the flow from bypassing the blade tip, hence, preventing the occurrence of tip vortices while improving the aerodynamic efficiency near the blade tip, ultimately, improving the overall Cp of a VAWT.

Endplate Design and Topology Optimization of Fuel Cell Stack Clamped with Bolts

The endplate plays an important role in the performance and durability of fuel cell stacks, and also to mass power density. Aiming at a lightweight endplate and uniform deflection of the endplate, the purpose of this study is to model the endplate including the supply, discharge ports and the distribution manifolds. The stress and displacement distribution of the endplate are also analyzed by numerical simulation. After that, the three optimized topologies aiming to minimize compliance, uniform stress distribution and two objectives coupling are discussed, and the intake endplate and blind endplate are individually reconstructed. The mass of optimized intake endplate is reduced by 35%, and the mass of optimized blind endplate is reduced by 46% for the goal of attaining a lightweight endplate, while maintaining the uniformity of the stress distribution of the first cell next to the endplate. Considering these factors, optimized endplates are obtained, which are valuable to fuel cell stack design.

Spectral/hp element simulation of flow past a Formula One front wing: Validation against experiments

Emerging commercial and academic tools are regularly being applied to the design of road and race cars, but there currently are no well-established benchmark cases to study the aerodynamics of race car wings in ground effect. In this paper we propose a new test case, with a relatively complex geometry, supported by the availability of CAD model and experimental results. We refer to the test case as the Imperial Front Wing, originally based on the front wing and endplate design of the McLaren 17D race car. A comparison of different resolutions of a high fidelity spectral/hp element simulation using under-resolved DNS/implicit LES approach with fourth and fifth polynomial order is presented. The results demonstrate good correlation to both the wall-bounded streaklines obtained by oil flow visualization and experimental PIV results, correctly predicting key characteristics of the time-averaged flow structures, namely intensity, contours and locations. This study highlights the resolution requirements in capturing salient flow features arising from this type of challenging geometry, providing an interesting test case for both traditional and emerging high-fidelity simulations.

Effect of Tip Vortex Reduction on Air-Cooled Condenser Axial Flow Fan Performance: An Experimental Investigation

AbstractLarge diameter axial flow fans are used in air-cooled condenser (ACC) systems of modern power stations. Efficiency improvements on these fans can significantly reduce the ACC power consumption and increase the net sent-out power to the grid. This study targets fan performance enhancement through blade tip vortex reduction. Experimental investigations are performed on a representative ACC scale fan, where tests consider the effects of tip clearance and two new tip endplate designs on fan performance. Test results confirm the findings of previous studies, showing the negative effect of increasing tip clearance on performance. Despite testing limitations, results from tests incorporating endplates show that fan static pressure coefficient and efficiency increase over large ranges of flow coefficient compared to the datum fan. These outcomes agree with observations from literature and warrants further exploration. Future work is recommended to provide confirmation on the presented trends.

Design of a Tip Appendage for the Control of Tip Leakage Vortices in Axial Flow Fans

Abstract This article reports on numerical investigations of passive control techniques used for the performance enhancement of a large diameter axial flow cooling fan through modification of the blade tip geometry. Using open-source software, a novel meshing strategy is developed to carry out both steady and unsteady numerical computations of a periodic section of an axial flow fan. Analyzing the flow near the blade tip with a reduction in tip clearance, two predominant flow phenomena are identified. These two flow phenomena are further investigated with the aim of controlling them through implementation of a tip appendage design. Both introduced end-plate designs indicate effective control of each relevant flow phenomena. The constant thickness (CT) end-plate design is found to increase all fan performance characteristics at lower than design point (DP) flowrates, while increasing the fan’s peak efficiency plateau toward the rotor stall margin. However, none of the CT end-plate designs are able to improve the fan’s performance characteristics at its DP. The introduction of a novel trailing-edge (TE) end-plate design is found to increase all fan performance characteristics across the entire evaluated stable operating range, with an indicated increase of 37.3 percent in total-to-static pressure rise and a 2.9 percentage point increase in total-to-static efficiency at the fan’s DP flowrate. The aerodynamic performance results attest to the associated benefits of the investigated passive control techniques.

Numerical investigation on the sensitivity of endplate design and gas diffusion material models in quantifying localized interface and bulk electrical resistance

A localized non-intuitive relationship between electrical interface contact resistance and bulk properties such as bulk electrical resistance and permeability in the fuel cell gas diffusion layer (GDL) is reported. A numerical method is adopted to investigate contact pressure and hence the interface contact resistance at the interfaces of bipolar plate (BPP)|GDL and GDL|Polymer electrolyte membrane (PEM). The results are observed to be sensitive to GDL material models as well as endplate designs. This means, endplates designed to improve the electrical contact resistance or contact pressure at the BPP|GDL interface may not necessarily assure an improvement in bulk properties, in fact, it is observed in this study that these properties are inversely related. Further, a differential deformation in GDL along with consolidation effect is predicted with compressible version of hyperelastic material model. More importantly, it is revealed that the selection of material models plays a significant role in the deformation behaviour of the GDLs irrespective of the clamping design adopted.

Comparative Analysis of Circular and Square End Plates for a Highly Pressurized Proton Exchange Membrane Water Electrolysis Stack

End plates are located at both ends of a proton exchange membrane water electrolysis (PEMWE) stack. If the end plates are thin, clamping pressure is not uniform and the performance of PEMWE can deteriorate from leakage and high electrical contact resistance caused by the deformation of the thin end plates. In this study, end plates were designed to reduce the weight while clamping the stack uniformly by finite element analysis (FEA). The weights of the circular and square end plates were reduced compared to conventional end plates by 22.9% and 23.3%, respectively. The stress and strain distribution of square and circular end plates are analyzed using topology optimization. This analysis can improve the performance of the PEMWE by using new end plate designs verified by dummy cell stack simulation to maintain uniform pressure.

Numerical performance of blind-bolted demountable square CFST K-joints

A demountable connection is an effective solution to separate and reuse steel or composite components after their first-stage design life, and could therefore benefit the environment by reducing material consumption and saving natural resources. Blind bolts and through-bolts are usually served as connectors in such demountable connections to replace traditional welding works. This paper puts forward a novel design on demountable square concrete-filled steel tubular (CFST) K-joints fabricated with concrete filled chord, hollow braces, flush endplate, blind bolts and through-wall bolts. Advanced finite element analysis models of the novel joints were established using verified modelling techniques. Among the investigated flush endplate designs and bolt arrangements, it is found that the design with through-bolt anchored beneath the tensile brace and a continuous flush endplate has advantages in material efficiency, joint strength and limiting endplate-chord separation, and is therefore chosen as the prototype design. Analysis on the failure modes shows that brace buckling failure prevents premature failure of the other members and ensures the safety as well as reusability of the main composite chord. Furthermore, discussions on the strength prediction based on numerical analysis and parametric study on key factors such as flush endplate thickness and brace-chord width ratio are given.

Seismic behavior of concrete shear walls with bolted end-plate DfD connections

An experimental study was carried out to investigate the seismic behavior of newly developed concrete shear walls with the bolted end-plate design for deconstruction (DfD) connections, with the aim of applying reused structural components to mid-rise buildings. This DfD connection was characterized by pre-buried end-plates and welding shear studs. The proper design was proposed to facilitate the application for future deconstruction and reconstruction. Four concrete shear walls with different aspect ratios were designed and tested according to a cyclic loading test to evaluate the seismic behavior. The principle of reuse and recycle were firstly both applied to concrete structures in the domain of this research. It can be found that the existence of the proposed DfD connection changed the cracking pattern and failure modes of the concrete shear wall. The interface between the DfD connection and the concrete wall turned to be the weak part of the whole structure. Moreover, the proposed DfD connection had a limited effect on the load bearing and transferring mode for the slender shear wall, while significantly changed the load resistance of the squat shear wall. The disassembly and assembly for the proposed shear wall with DfD connections were calibrated during the test process, proving that deconstruction and reconstruction purpose for this shear wall can be achieved.

P53. Spike versus keel: does endplate design of lumbar artificial discs affect radiographic outcomes?

BACKGROUND CONTEXT Lumbar total disc replacements (TDR) come in a variety of designs. The two primary device endplate designs for anchoring the device in the disc space use multiple spikes or have a keel. To date, the possible impact device design and endplate anchoring type on device motion have not been investigated. PURPOSE The purpose of the study was to determine if different endplate designs for lumbar TDR devices impact long term radiographic outcomes in patients, and whether the outcomes are the same for L4-5 and L5-S1 level procedures. STUDY DESIGN/SETTING The study was based on post-hoc analyses of prospectively collected data. PATIENT SAMPLE The study included 282 patients who received single-level TDR at L4-5 or L5-S1 to treat degenerative disc disease unresponsive to at least 6 month of nonoperative care. All patients fulfilled the same selection criteria as described in the FDA IDE trial protocol. OUTCOME MEASURES Measures included segmental range of motion (ROM) of the operated level measured on flexion/extension radiographs, adjacent segment degeneration (ASD), and heterotopic ossification (HO). All radiographic measurements were conducted by a centralized lab specializing in image assessments. METHODS Patients were grouped based on device and endplate design: mobile core device (MCD) with either spike (n=115) or keel endplate (n=102), and constrained core device (CCD) with keel endplate (n=65). Assessments were conducted prior to surgery and at predefined points after surgery. This study was based on the 2- and 5-year follow-up points. RESULTS ROM was maintained or improved from baseline values for both spike and keel MCD at 2 years (7.8o (p 0o) was significantly greater with keel MCD compared to keel CCD at L5-S1 (77% vs. 48%, p CONCLUSIONS This study found that radiographic outcomes are impacted by the device and endplate design of lumbar TDRs. Radiographic outcomes were generally better at L4-5 than L5-S1 for all device and device endplate designs. However, at L5-S1 motion was preserved in a greater proportion of patients with keel MCD. Furthermore, ASD had a greater propensity to develop or worsen with keel CCD at L5-S1 where motion was significantly lower at follow-up compared with baseline. FDA DEVICE/DRUG STATUS activL (Approved for this indication), ProDisc-L (Approved for this indication)

Study of PEM Fuel Cell End Plate Design by Structural Analysis Based on Contact Pressure

A fuel cell stack is configured to power any load ranging from watts to megawatt by varying cells connected in series. During stack assembly, major emphasis must be placed on application of adequate external pressure for reducing the ohmic losses, the purpose of which is to achieve proper contact between the cell components and minimize the contact resistance. Present work aims to study the influence of geometry of the cell, bolt configuration, gasket thickness mismatch, and material properties of different components of average and distribution contact pressure. The geometries are evaluated for end plate designs with a view to understand the pressure distribution and contact resistance in each case. Among different designs, extruded hexagon is found to perform well with an average contact pressure of 0.13 MPa and contact resistance of 28 Ω-cm2. Greater gasket thickness requires higher forces to be applied before the GDL makes contact with BPP. The effect of gasket thickness mismatch is evaluated for different values to identify its appropriate value. The pressure is applied using bolts and position and number of bolts is determined for homogeneous contact pressure on the active area. This study provides a framework for future end plate design of fuel cells.

Numerical study on air turbines with enhanced techniques for OWC wave energy conversion

In recent years, the oscillating water column (OWC) wave energy converter, which can capture wave energy from the ocean, has been widely applied all over the world. As the essential part of the OWC system, the impulse and Wells turbines are capable of converting the low pressure pneumatic energy into the mechanical shaft power. As an enhanced technique, the design of endplate or ring attached to the blade tip is investigated numerically in this paper. 3D numerical models based on a CFD-software FLUENT 12.0 are established and validated by the corresponding experimental results from the reports of Setoguchi et al. (2004) and Takao et al. (2001). Then the flow fields and non-dimensional evaluating coefficients are calculated and analyzed under steady conditions. Results show that the efficiency of impulse turbine with ring can reach up to 0.49 when ϕ=1, which is 4% higher than that in the cases for the endplate-type and the original one. And the ring-type Wells turbine with fixed guide vanes shows the best performance with the maximal efficiency of 0.55, which is 22% higher than that of the original one. In addition, the quasi-steady analysis is used to calculate the mean efficiency and output-work of a wave cycle under sinusoidal flow condition. Taking all together, this study provides support for structural optimization of impulse turbine and Wells turbine in the future.

Modelling and analysis of the JET EP2 neutral beam full energy ion dump curved end plate

This paper describes enhanced modelling of the power loading on the current JET full energy ion dump (FEID) curved end plate, and the new end plate design with improvements to the power handling capabilities and additional features to improve fatigue life. Monte-Carlo simulations of each of the nine residual ion components which are intercepted by the plate shows a peak power density of 20MW/m2 and compares well with recently installed fast thermocouple measurements. Analytical calculations and simulations with the Charged Particle Optics (CPO) code are used to investigate the potential for movement of the residual ion focus due to space charge effects. Cooling performance is significantly enhanced by improved water channel flow which is both modelled and confirmed by experiment. Fatigue life, calculated from ANSYS modelling is improved using a slot arrangement to relieve stresses created from focussed heat load distribution.