Blade Geometry Research Articles

A Parametric Blade Design Method for High-Speed Axial Compressor

The blade geometry design method is an important tool to design high performance axial compressors, expected to have large design space while limiting the quantity of design variables to a suitable level for usability. However, the large design space tends to increase the quantity of the design variables. To solve this problem, this paper utilizes the normalization and subsection techniques to develop a geometry design method featuring flexibility and local adjustability with limited design variables for usability. Firstly, the blade geometry parameters are defined by using the normalization technique. Then, the normalized camber angle f1(x) and thickness f2(x) functions are proposed with subsection techniques used to improve the design flexibility. The setting of adjustable coefficients acquires the local adjustability of blade geometry. Considering the usability, most of the design parameters have clear, intuitive meanings to make the method easy to use. To test this developed geometry design method, it is applied in the design of a transonic, two flow-path axial fan component for an aero engine. Numerical simulations indicate that the designed transonic axial fan system achieves good efficiency above 0.90 for the entire main-flow characteristic and above 0.865 for the bypass flow characteristic, while possessing a sufficiently stable operation range. This indicates that the developed design method has a large design space for containing the good performance compressor blade of different inflow Mach numbers, which is a useful platform for axial-flow compressor blade design.

Precision blade deflection measurement system using wireless inertial sensor nodes

AbstractStructural health monitoring on wind turbine blades is a great enhancement for operational safety and failure avoidance. Blade deflection is a key parameter, which is a function of blade geometry and material properties. The absolute blade deflection is affected by wind load, gravitational, and centrifugal forces and must exceed neither material stress limits nor tower clearance. In this paper, we introduce a novel method for real time reconstruction of blade movement using inertial measurement units (IMUs) located at defined positions along the blade. An algorithm is introduced that combines IMU measurements and a priori information of the fundamental blade mode shapes to accurately reconstruct the blade movement. A low‐power wireless sensor node for blade deflection monitoring is presented. The autonomous sensor node is equipped with an IMU together with a low‐power wireless transceiver and powered by a compact translational electromagnetic energy harvester. Sufficient energy is harvested each rotor revolution for continuous measurement data streaming within the wind turbine's operating range. A data stream of six‐axis IMU measurements enables real time, three‐dimensional reconstruction of the entire blade movement in the back end positioned in the tower. The reconstruction of blade tip deflection is possible even under high wind turbulences with a minimum accuracy of 0.22 m for an onshore 5 MW and 0.58 m for an offshore 15‐MW reference turbine. The complete system has been tested thoroughly under conditions similiar to a real wind turbine. Realistic stimulation of the reconstruction algorithm is performed by means of OpenFAST simulations.

An in vitro assessment of light intensity provided during direct laryngeal visualization by videolaryngoscopes with Macintosh geometry blades.

Adequate illumination of the larynx is needed during laryngoscopy to facilitate tracheal intubation. The International Organization for Standardization (ISO) has established a minimum light intensity for direct laryngoscopy (DL) of over 500 lux for at least ten minutes, but no such standard exists for Macintosh geometry videolaryngoscope (Mac-VL) blades, which allow for both direct or indirect (videoscopic) viewing of the larynx. Using in situ bench and in vitro testing in a human cadaver, we determined illumination and luminance values delivered by various Mac-VLs and compared these with published minimum lighting benchmarks as well as a reference direct laryngoscope. We tested six Mac-VLs (i-view™, McGRATH™ MAC, GlideScope® Spectrum™ [single-use] DVM S4, GlideScope® Titanium [reusable] Mac T4, C-MAC® S [single-use] Macintosh #4, C-MAC® [reusable] Macintosh #4) together with one direct laryngoscope (Heine LED). Each laryngoscope was assessed with three measurements, as follows: part 1: illuminance (lux) was measured in situ using a purpose-designed benchtop light intensity measurement apparatus; part 2: luminance (light reflected back to the eye) was measured (in candela m-2 [cd·m-2]) during videolaryngoscopy (VL) and DL in a human cadaver using a spot meter pointed at the interarytenoid notch; part 3: illuminance (lux) was measured during VL and DL in a human cadaver using a light meter surgically implanted just proximal to the vocal cords. Illuminance and luminance varied significantly among the Mac-VLs. Mean (standard devitation) illuminance among the six tested Mac-VLs ranged from 117 (11) to 2,626 (42) lux in the measurement apparatus and from 228 (11) to 2,900 (374) lux by the surgically implanted light meter in the cadaver. All values were less than the reference Heine direct laryngoscope and some fell below the published ISO standard of 500 lux for DL. Luminance testing by spot meter had a similarly wide range, varying from 3.78 (0.60) to 49.1 (10.4) cd·m-2, with some Mac-VLs delivering less luminance than the reference Heine direct laryngoscope. Our results indicate that illuminance and luminance provided by Mac-VLs used for direct laryngeal viewing varies substantially between devices, with some falling below standards previously suggested as the minimum required for DL. While this may have no implications for the quality of image visible on a device's video monitor, the clinician should be aware that when Mac-VLs are used for direct viewing of the larynx, lighting may not be optimal. This might adversely affect ease or success of tracheal intubation.

Метод оптимизации многоступенчатых компрессоров

The paper presents an algorithm for seeking an optimal blade configuration for multistage axial-flow compressors. The primary tool behind the algorithm is 3D CFD simulation, augmented by commercial optimisation software. The core of the algorithm involves feeding an initial data vector to the parametric simulation module so as to form a "new" blade geometry, which is then transferred to 3D computational software. The results obtained are further processed in a program that implements the algorithm for seeking the optimum and forms a new input data vector to achieve the set goal. We present a method of parametrically simulation the blade shape, implemented in a software package, making it possible to describe the shape of the compressor blade profiles using a minimum number of variables and to automatically change the shape in the optimisation cycle. The algorithm developed allows the main parameters of compressor operation (efficiency, pressure ratio, air flow rate, etc.) to be improved by correcting the profile shape and relative position of the blades. The algorithm takes into account various possible constraints. We used the method developed to solve practical problems of optimising multistage axial compressors of gas turbine engines for various purposes, with the number of compressor stages ranging from 3 to 15. As a result, the efficiency, pressure ratio and stability margin of gas turbine engines were increased

Influence of the angle and perimeter of contact of the blades in a horizontal axis aerator on the transfer of dissolved oxygen

Dissolved oxygen (DO) is a fundamental parameter in water bodies that can be supplied using horizontal axis mechanical agitators. However, blade geometry and operating conditions can influence the process cost. In this work, it is studied the effect of the perimeter and angle of impact of the blades on the water in a prototype of horizontal axis mechanical aeration, starting from the DO transfer analysis. Measurements were made on anoxic water samples using two types of blades with the same area, varying their perimeter and angle of impact. Other parameters that influence the DO transfer process were controlled in this work. The results show the increase in the perimeter, and blade impact angle with the water body, which generates a reduction in the standard aeration efficiency (SAE) up to 30 % in the process. In that way, it is obtained the best results for the prototype Type II blades with a KLa value of 3.69 h-1, and a SAE of 0.47 kgO2∙kW-1h-1 when using an impact angle of 13.5 °. In general, the geometry of the blades is a fundamental design parameter, which influences the transfer of dissolved oxygen in the water. The results of this study can contribute to improving the efficiency of these mechanical systems, reducing the energy consumption associated with oxygenation processes.

Study of √2 Conjecture in the Construction of Drag Induced Wind Turbine Blade Morphology

In wind engineering, the morphology of the turbine blade system governs the effectiveness in harvesting wind energy. The flow field response is the result of the turbine blade shape interaction with flow. Hence, mathematically interpreting the shape of the blade will help to understand the principals and properties of the utilized geometry for the blade construction. In this study, semicircle geometry of Savonius wind turbine blade is mathematically analyzed in order to understand its fundamental building block. We provide discussion on √2 conjecture found in the construction of circles, Fibonacci and Pythagoras spiral in relations to √2, √2 + 1 and √2 + 2. It is found that √2 conjecture can be utilized in determining the geometrical properties of circle and spiral. We also performed thorough assessment of the proposed conjecture to prove its robustness and reliability. The proposed conjecture is adapted to construct the blade morphology of drag induced wind turbine. CFD analysis is carried out to investigate the aerodynamic properties namely moment coefficient (Cm) of the constructed wind turbine shape via the proposed conjecture. Results shows that the proposed shape constructed based on the conjecture has improved Cm by 7.2 % at λ = 0.59 and 4 % at λ = 0.94 compared to conventional SWT

Aerodynamic design and acoustic effect study of key geometric parameters of a sirocco fan

A sirocco fan (forward-curved centrifugal fan), including impeller blades and volute, is designed, and the empirical value ranges of several significant design parameters are discussed and summarized fromthe perspective of both aerodynamics and practical structure. Unsteady-flow numerical simulation and radiated sound-field calculation by indirect boundary element method are combined to evaluate its aerodynamic and acoustic performances. Both the discrete noise source from the rotating impeller and broadband noise source from the volute are considered. Obvious flow separation occurs in the flow passage of impeller blades due to large angle of attack, and the tongue region is the major noise source area due to the small impeller-tongue gap. Therefore, parametric studies for blade installation angle and impeller-tongue gap are performed. Analyses of flow- and sound-field indicate that appropriate reduction of blade geometry incidence angle weakens the flow separation, thereby improving both the aerodynamic and acoustic performances, and reasonable increase of the impeller-tongue gap has a remarkable noise reduction effect for the major noise source area near the volute tongue. The optimized sirocco fan meets the requirement of the industrial project, i.e., the far-field A-weighted sound power level lower than 64.0 dB(A), and achieves larger volume flow rate and total pressure rise. The results also imply that fast steady-flow numerical simulation result is indicative of the acoustic performance to some extent if the acoustic evaluation is urgent. Furthermore, optimization of the key structural parameters in the stage of design is preferable in practical engineering, instead of taking follow-up noise reduction measures.

Numerical analysis of an elasto-flexible membrane blade using steady-state fluid–structure interaction simulations

A steady-state fluid–structure interaction analysis on an elasto-flexible membrane blade is presented. The membrane blade geometry is designed based on the NASA-Ames Phase VI model. Form-finding is used to compute the pre-stressed membrane’s initial equilibrium shape directly on the Computer-Aided Design model using isogeometric analysis. To study the effects and potential advantages of such a membrane blade concept, a co-simulation framework is used to couple fluid and structure solvers. The resulting pressure, thrust, and torque coefficient distributions are presented and compared to the reference configuration. The membrane’s deflection increases the blade’s camber, which results in a change in the thrust and torque radial distributions. The larger decrease of the axial momentum at the wake of the flexible configuration indicates that it has a larger capacity to extract energy from the flow than its rigid counterpart.

Design and Analysis of Horizontal Axis Wind Turbine (HAWT) Blades Using CFD

Abstract: Within the current years wind power is extensively taken into consideration and applied as one of the most promising renewable electricity assets. In the recent studies have a look at, aerodynamic analysis of horizontal axis turbine is achieved with the aid of using cfd. Blades which can be often possible for industrial grade wind turbines embody a directly span-wise profile in conjunction with airfoil fashioned go sections. Wind tunnel test is applied in order to check aerodynamic efficiency wind turbine blade. The goal of this study is to design a wind turbine. The layout manner includes the choice of the sun machine for max efficiency and wind turbine kind and the determination of the blade airfoil, pitch attitude distribution along the radius, and chord duration distribution along the radius. The pitch angle and chord period distributions are optimized primarily based on conservation of angular momentum and principle of aerodynamic forces on an airfoil. Blade element momentum (BEM) principle is first derived then used to conduct a parametric observe to be able to determine if the optimized values of blade pitch and chord period create the maximum green blade geometry. This work includes a discussion of the most important parameters in wind turbine blade layout to maximize efficiency. Keywords: Wind Turbine, HAWT, BEM Theory, Parametric Study, Maximization of efficiency etc.

On the issue of the oretical substantiation and development of a cutting working body for harvesting industrial hemp

The interaction of a knife with a stalk of industrial hemp in the process of unsupported cut is described. An analytical dependence of the critical cutting force on the physicomechanical properties of the stem and blade geometry is obtained. The factors influencing the shape of the cutting tooth are analyzed. The profiles of cutting segments have been developed taking into account the peculiarities of the structure of the industrial hemp stem.

Field reconstruction and off-design performance prediction of turbomachinery in energy systems based on deep learning techniques

Obtaining the off-design characteristics of core components such as turbines and compressors is the basis of off-design analysis for energy systems. However, the characteristics are difficult to accurately acquire in the initial design stage of turbomachinery. Based on deep learning techniques, an accurate and rapid field reconstruction and off-design aerodynamic performance prediction method is proposed. First, a Generative Adversarial Network with the added Bezier layer is employed to establish a database of turbine blade profiles. Then, a Dual Convolutional Neural Network (Dual-CNN) is established to reconstruct the pressure and temperature fields as well as predict the off-design performances of different profiles and working conditions. Based on the above two kinds of neural networks, a turbine in a solar-based supercritical carbon dioxide Brayton cycle is taken as an example. The field reconstruction and off-design performance prediction are conducted on the basis of the established rotor blade profile database. The accuracy of field reconstruction is guaranteed. The off-design performance prediction of the established Dual-CNN indicates that the example blade profile is suitable for operation with larger mass flow rate. Compared with the traditional method, Dual-CNN can reduce the off-design analysis time of one blade geometry from 38.4 h to 7.68s.

Techniques for adaptive metamodelling of propeller arrays far-field noise

The fast development of Urban-Air-Mobility as well as the constant growth of the air transport have made the acoustic pollution abatement a crucial requirement for the aviation industries in order to comply with the increasingly demanding constraints for the community acceptance. The aeroacoustic characterization of arrays of electrically-powered propellers is one of the most challenging issues. The vast majority of the UAM concepts under development adopt propulsion systems based on multiple propellers, for which reliable and cost-efficient aeroacoustic models are still lacking. The present paper proposes the development of surrogate models for the description of acoustic emission of multi-propeller configurations. The numerical investigation focuses on surrogate models able to take into account the effects of the propeller blade geometry (e.g., chord and twist distributions) and global propeller-array geometric parameters (e.g., propellers clearance) on acoustic performances of the whole system. An innovative Artificial Neural Network adaptive metamodelling technique is applied on a numerical database obtained through a boundary integral formulation for the solution of incompressible potential flows around lifting/thrusting bodies, followed by the application of the Farassat 1A boundary integral formulation for the noise field evaluation.

Computational Fluid Dynamics Study of a Modified Savonius Rotor Blade by Universal Consideration of Blade Shape Factor Concept

This work aims to investigate computationally the performance of Savonius vertical axis wind turbine having a new design feature for its blade geometry. The proposed design is based on a universal consideration of blade shape factor concept for the Savonius rotor blade. A blade shape factor ranges from zero to infinity, or vice versa, is considered in a single blade of the modified Savonius rotor. This means that each point in the two-dimensional blade profile of the suggested blade design has a single value of blade shape factor that is defined based on the dimensions of conventional semi-circular blade. The computational results of the proposed blade shape design, having blade shape factor varying from infinity to zero, showed an improvement in turbine performance as compared to conventional blade shape design. Moreover, increasing the operating range of Savonius wind turbine is expected.

Numerical Fluid-Structure Interaction Analysis for a Flexible Marine Propeller Using Co-Simulation Method

Carbon fibre composite has exceptionally high strength, low density and corrosion resistance in the marine environment compared to conventional materials. These characteristics make it a favourable alternative material to be considered for manufacturing marine screw propellers. Despite these advantages, the flexibility of the material leads to a significant change in blade geometry due to loads acting on blades which alter hydrodynamic performance. A two-way coupled fluid-structure interaction analysis is required to accurately capture its hydrodynamic performance due to the reduced stiffness and material anisotropy. The present study focuses on numerical investigation for the hydro-elastic based performance analysis of a composite marine propeller in open water condition. The procedure involves the coupling of Reynolds-Averaged Navier-Stokes Equation based computational fluid dynamics solver with the finite element method solver using co-simulation technique. The open water characteristics, including thrust coefficient, torque coefficient and open water efficiency, are discussed as a function of advance ratio. This paper presents a comparison of the hydrodynamic performance and structural responses between a carbon fibre composite propeller and a conventional steel propeller which are geometrically identical. The results for the composite propeller show a significant improvement in hydrodynamic performance compared to the metallic propeller while remaining structurally safe throughout the tested range.

Surrogate-Based Optimization of Horizontal Axis Hydrokinetic Turbine Rotor Blades

A design method was developed for automated, systematic design of hydrokinetic turbine rotor blades. The method coupled a Computational Fluid Dynamics (CFD) solver to estimate the power output of a given turbine with a surrogate-based constrained optimization method. This allowed the characterization of the design space while minimizing the number of analyzed blade geometries and the associated computational effort. An initial blade geometry developed using a lifting line optimization method was selected as the base geometry to generate a turbine blade family by multiplying a series of geometric parameters with corresponding linear functions. A performance database was constructed for the turbine blade family with the CFD solver and used to build the surrogate function. The linear functions were then incorporated into a constrained nonlinear optimization algorithm to solve for the blade geometry with the highest efficiency. A constraint on the minimum pressure on the blade could be set to prevent cavitation inception.

Structural and Aerodynamic Characteristics Analysis of a Small V-shaped Vertical Axis Wind Turbine Rotor

ABSTRACT A detailed comprehensive study of a proposed V-shaped turbine rotor is performed in order to examine its structural and aerodynamic characteristics. The structural analysis section of this work determined the most structurally sound blade geometry from 3 different blade geometries. Using the chosen blade profile, 8 rotor models are developed and are tested numerically. These rotor models are of different configurations, focusing on an inclination angle of 45 and 60 degrees, blade twist angle of 0 and 5 degrees and number of blades. Four rotor models are taken from the initial tests for further study, 3B45D which is a three-bladed rotor with a 45 degree inclination angle, 5B45D which is a five-bladed rotor with a 45 degree inclination angle, 5B45D (5deg) which is a five-bladed rotor with a 45 degree inclination angle and a 5 degree blade twist angle, and 5B60D which is a five-bladed rotor with a 60 degree inclination angle. From the structural study, blade design 2 held the best structural characteristics. The design showed an excellent Von-Mises at 8.8 MPa for static structural and 22.2 MPa for fatigue stress response which is well below the yield strength of ABS Plastic. Both experimental and numerical data have relatively good agreement that is within 15% difference. Overall, maximum power coefficient achieved in this study is about 0.259 numerically and 0.213 experimentally. The best performance is seen by the 3B45D rotor in both static and dynamic study considering experimental and numerical corroboration of results.

Wake characteristics of a freely rotating bioinspired swept rotor blade.

Rotor blades can be found in many engineering applications, mainly associated with converting energy from fluids to work (or electricity). Rotor blade geometry is a key factor in the mechanical efficiency of the energy conversion process. For example, wind turbines' performance directly depends on the blade geometry and the wake flow formed behind them. We suggest to use a bioinspired blade based on the common swift wing. Common swift (Apus apus) is known to be a long-distance flyer, able to stay aloft for long periods of time by maintaining high lift and low drag. We study the near-wake flow characteristics of a freely rotating rotor with swept blades and its aerodynamic loads. These are compared with a straight-bladed rotor. The experiments were conducted in a water flume using particle image velocimetry (PIV) technique. Both blades were studied for four different flow speeds with freestream Reynolds numbers ranging from 23 000 to 41 000. Our results show that the near wake developed behind the swept-back blade was significantly different from the straight blade configuration. The near wake developed behind the swept-back blade exhibited relatively lower momentum loss and suppressed turbulent activity (mixing and production) compared with the straight blade. Comparing the aerodynamic characteristics, though the swept-back blade generated relatively less lift than the straight blade, the drag was relatively low. Thus, the swept-back blade produced two to three times higher lift-to-drag ratio than the straight blade. Based on these observations, we suggest that, with improved design optimizations, using the swept-back configuration in rotor blades (specifically used in wind turbines) can improve mechanical efficiency and reduce the energy loss during the conversion process.

Localization of wind turbine noise using a microphone array in wind tunnel measurements

AbstractAn experimental investigation on scaled wind turbine models in a wind tunnel with a microphone array is presented. Our study focuses on the localization and quantification of aerodynamic noise sources on rotating wind turbine blades with the aim of identifying the contributing factors that have an impact on the source spectra. Therefore, wind tunnel measurements were conducted for three different blade geometries (NACA 4412 shape, Clark‐Y shape, and sickle shape), five pitch angles between −2° and +8° and five wind velocities between 5 and 13 mŝ−1. For the localization of rotating sound sources with a microphone array, a rotating beamforming method based on the acoustic ray method is used. The Clean‐SC deconvolution method was used to improve the resolution of the acoustic sources, and integrated spectra were calculated for the individual blades. The sound sources were localized at the wind turbine blades and assigned to the leading edge and trailing edge subregions. The results show a high dependency on the sound source distribution and the source strength with regard to the observed one‐third octave bands, wind velocity, and blade geometry. Hence, the localization of rotating sound sources with a microphone array is a suitable method for the development of wind turbine blades that emit less noise.

Engagement of the Median Glossoepiglottic Fold and Laryngeal View During Emergency Department Intubation

When using a standard geometry laryngoscope, experts recommend engaging the hyoepiglottic ligament-a ligament deep to the vallecula not visible to the intubator. The median glossoepiglottic fold (hereafter termed midline vallecular fold) is a superficial mucosal structure, visible to the intubator, that lies in the midline of the vallecula. We aimed to determine whether engaging the midline vallecular fold with a standard geometry blade tip during orotracheal intubation improved laryngeal visualization. We reviewed laryngoscopic videos from intubations by emergency physicians using standard geometry video laryngoscopes over a 2-year period. Two reviewers watched each video and recorded whether the blade tip engaged the midline vallecular fold (obscured the fold with the blade tip) and the best modified Cormack-Lehane grade and percent of glottic opening obtained. We compared laryngeal views in the presence and absence of fold engagement. We analyzed 183 discrete laryngoscopic episodes, including 113 instances in which the midline vallecular fold was engaged and 70 instances in which the fold was not engaged. The proportion with a Cormack-Lehane grade 1 or 2a was higher with fold engagement (96%) than without (87%) (absolute difference 9% [95% confidence interval (CI) 1 to 18%]). Ordinal logistic regression demonstrated that midline vallecular fold engagement was associated with a more favorable Cormack-Lehane grade (odds ratio 2.1 [95% CI 1.1 to 4.2]). The median percent of glottic opening score was 95% (interquartile range 90 to 100%) with fold engagement and 95% (65 to 100%) without engagement (median difference 0% [95% CI 0 to 5%]). Engaging the midline vallecular fold with the laryngoscope blade tip during orotracheal intubation when using a standard geometry blade was associated with improved laryngeal visualization.

Wind Blade Twist Correction for Enhanced Annual Energy Production of Wind Turbines

Blade geometry is an important design parameter that influences global wind turbine energy harvesting performances. The geometric characteristics of the blade profile are obtained by determining the distribution of the chord and twist angle for each blade section. In order to maximize the wind energy production, implying a maximum lift-to-drag ratio for each wind speed, this distribution should be optimized. This paper presents a methodology to numerically determine the change in the twist angle by introducing a range of pitch angles for the maximum power coefficient case. The obtained pitch values were distributed from the root to the tip of blade. The results prove that the power coefficient increases for wind speeds greater than the rated point, which improves the yearly production of energy by 5% compared to the reference case.