Blade Contour Research Articles

A comparative study of principal component analysis and kernel principal component analysis for photogrammetric shape-based turbine blade damage analysis

Photogrammetry is popular as a non-contact full-field data acquisition technique for machine condition monitoring purposes. Two popular implementations thereof are Digital Image Correlation (DIC) and 3D Point Tracking (3DPT). Since these two approaches require surface preparation in the form of applying speckle patterns or discrete markers, their use is negated in several industrial applications, such as the online condition monitoring and/or assessment of horizontal axis wind turbines. A shape-based photogrammetric approach that focuses on analysing changes in the form of a rotating blade’s boundary contour is a viable alternative that does not require any surface preparation. 3D shapes of a blade at a particular instance can be extracted from a pair of stereoscopic images of the blade. Shape Principal Component Descriptors (SPCDs) determined from applying Principal Component Analysis (PCA) to Fourier coefficients of chain-code shape signatures of the blade contour can be determined. These can be regarded as indicators of the form of the shape, and as the blade rotates, variations in the SPCDs can be investigated to better understand the dynamics of the blades. This paper focuses on the application and performance evaluation of data reduction and classification techniques for a novel shape-based photogrammetry condition monitoring technique. Investigations are conducted to show that applying data reduction methods to raw time domain SPCDs can result in successful classification of differently damaged blades. Post-processing strategies are developed to ensure a more robust shape based condition monitoring tool for analysing turbine blades. Kernel Principal Component Analysis (KPCA) is implemented and it is shown that it out-performs the conventional PCA in terms of classifying different blade damage modes. The feasibility of using multi-domain statistical features as feature vectors to which PCA or KPCA is applied for classification purposes is also investigated. Results indicating how well differently damaged blades can be distinguished are provided, and it is clearly illustrated that multi-domain statistical features are more robust to noise contamination in the signals compared to using the raw SPCDs data.

Micro geometry analysis of WC-Co carbide blades modified with PVD coating subjected to blunting during milling in chipboard

ABSTRACT In this work, a number of geometrical parameters related to the microgeometry of the cutting edge, such as rounding radius r, maximum clearance wear VBmax and a number of others, were determined. Tools for processing wood materials made of WC-Co cemented carbide with a PVD coating based on Ti and Al. were blunted until the wear indicator VBmax reached the value of 0.2 mm. The cutting blades prepared in this way were tested using a contact profilometer. Based on the data obtained in this way, an analysis of the blade contour over a length of 10 mm was carried out in the AutoCad environment. This section included both the blunted part and the part not involved in the cutting process. Correlations obtained using a procedure written in Visual Basic for Applications using elements of statistical data analysis built into the Excel program, between the selected rounding asymmetry coefficients denoted with letter K and the blade wear indicators proposed in the tests were analyzed. Geometric indicators were also determined, taking into account the working conditions of the tool, affecting the process of its blunting, such as e.g. h (uncut chip thicknesses).

An Enhanced U-Net Approach for Segmentation of Aeroengine Hollow Turbine Blade

The hollow turbine blade plays an important role in the propulsion of the aeroengine. However, due to its complex hollow structure and nickel-based superalloys material property, only industrial computed tomography (ICT) could realize its nondestructive detection with sufficient intuitiveness. The ICT detection precision mainly depends on the segmentation accuracy of target ICT images. However, because the hollow turbine blade is made of special superalloys and contains many small unique structures such as film cooling holes, exhaust edges, etc., the ICT image quality of the hollow turbine blades is often deficient, with artifacts, low contrast, and inhomogeneity scattered around the blade contour, making it hard for traditional mathematical model-based methods to acquire satisfying segmentation precision. Therefore, this paper presents a deep learning-based approach, i.e., the enhanced U-net with multiscale inputs, dense blocks, focal loss function, and residual path in the skip connection to realize the high-precision segmentation of the hollow turbine blade. The experimental results show that our proposed enhanced U-net can achieve better segmentation accuracy for practical turbine blades than conventional U-net and traditional mathematical model-based methods.

Time-Resolved Particle Image Velocimetry Measurements and Proper Orthogonal Decomposition Analysis of Unsteady Flow in a Centrifugal Impeller Passage

Time-resolved particle image velocimetry (TR-PIV) measurements were conducted to analyze the unsteady flow field developing in a centrifugal pump. The flow structures in the impeller passage under different flow rates were investigated. The overall statistical characteristics of the flow were obtained with the study of relative phase-averaged flow field, phase-averaged turbulent kinetic energy (TKE), and the analysis of frequency. Through the study of the first few proper orthogonal decomposition (POD) modes of the flow field, the coherent flow structures under several flow rates were revealed, consequently, the flow fields were reconstructed by the POD modes. Results show that the main flow structures could be reflected by the first few modes of the flow field: when the fluid follows the blade contour well, the first few modes corresponded to the “jet-wake” structures; when the large-scale flow structures appear in the passage, the 1st and 2nd modes were associated in pairs and corresponded to the stall cells, the 3rd and 4th modes corresponded to the “jet-wake” structures, and the 5th and 6th modes corresponded to the passage vortexes or the “jet-wake” structures (for the extreme part-load conditions). The flow structures that were reflected by the first few modes change as the decrease of flow rate, especially, at the extreme part-load condition, not only the shapes of the flow structures changed, but also the flow direction is reversed. This indicates that the generation mechanism of turbulent kinetic energy in the flow passage changed at the extreme part-load conditions.

Tree species delimitation in tropical forest inventories: Perspectives from a taxonomically challenging case study

Forest conservation and management programs rely on precise knowledge of local tree diversity. Distinguishing tree species is a major concern in tropical forest inventories as morphology alone may not be sufficient for species identifications in those highly diverse environments. Therefore, a multi-evidence approach is desirable to avoid subjective interpretations. We tested the contribution of a low-cost integrative protocol for delimiting sympatric species of the taxonomically challenging genus Myrcia (Myrtaceae) in the central Amazon region. We classified specimens into local species by morphotyping them and then validated our hypotheses using two additional sources of evidence: i) near-infrared spectroscopic data, consisting of 1557 absorbance values obtained from dried leaves; and, ii) morphometric data of leaf blade contours, translated into Fourier descriptors and summarized by principal component analysis (PCA), together with four additional leaf characters. The morphotypes were validated using linear discriminant analyses (LDAs) of the raw NIR spectra, stepwise-selected spectral regions, PCA-reduced spectra, as well as the morphometric data. A taxonomic name was assigned to each validated species based on comparisons with herbarium specimens and/or the technical literature. We delimited 38 species of Myrcia, and our hypotheses were well-supported by the LDAs (81–99% accuracy), evidencing that inexpensive tools can be effectively used to discriminate species in large-scale projects, and that integrative approaches are fundamental in that regard. Although vegetative traits were sufficient for species discrimination, fertile samples were crucial for obtaining taxonomic names for them. Thirteen species delimited by us belong to four species complexes, each treated under single species names in the current systematics of the genus. We therefore argue that species delimitations prior to individual identifications are essential for robust species definition in forest plot research because local species do not necessarily match global circumscriptions. This type of approach may greatly alter how local community structures are viewed and consequently modify the results of downstream analyses of ecological studies. We also emphasize that local species delimitations may contribute to the field of taxonomy by identifying potential inconsistencies in global species definitions.

Description of Aphelenchoides roulingae n. sp. (Tylenchomorpha: Aphelenchoididae) isolated from Xylocopa collaris sauteri collected from Yilan, Taiwan, with some notes on A. xylocopae Kanzaki, 2006

Summary Aphelenchoides roulingae n. sp. is described and illustrated. This new species was isolated from Xylocopa collaris sauteri collected at Fushan, Yilan county, Taiwan. Typologically, the new species is characterised by a three-lined lateral field, conical female tail with various and not pointed termini, male spicule with well-developed and slightly dorsally truncate condylus, blunt triangular-shaped rostrum and unevenly ventrally curved dorsal contour of the spicule blade (calomus-lamina complex). The combination of typological characters of the new species is unique. Aphelenchoides roulingae n. sp. shares the three-lined lateral field and female tail shape with ‘A. helicus’, which was previously transferred to Robustodorus from Aphelenchoides, but can be differentiated from that species by its longer and more slender female tail, narrower female tail tip, and longer female stylet. In addition, the spicule morphology of A. roulingae n. sp. is unique and not similar to that of any other Aphelenchoides species. Phylogenetically, the new species forms a well-supported clade with the other Xylocopa bee-associated species, A. xylocopae, but can be typologically and molecularly distinguished from the species. In addition to the taxonomic description, some typological characters of the genus Aphelenchoides are discussed.

Inspection of blade profile and machining deviation analysis based on sample points optimization and NURBS knot insertion

As the core component of aviation industry, the machining accuracy of blade has great impact on the performance of aeroengine. Blade inspection can get knowledge of machining accuracy and can be used to compensate the machining error. In consideration of measuring time and efficiency, measuring trace planning based on sample points optimization (SPO) is introduced, and NURBS knot insertion (NURBS-KI) method is proposed to reconstruct the blade contour. Then, the designed model and the reconstructed model are compared to analyze the machining error. The reconstruction result shows that the presented method can better restore the blade contour, and NURBS-KI algorithm is proved in this paper to be an effective method to reconstruct blade curve and surface based on small number of measurement points. As illustrated in deviation analysis results, the machining error is within the design tolerance, and the finishing allowance can be removed afterwards.

Research on Partition Segment Grinding Path Method of Aero-Engine Blade Based on Robot Group

In this paper, the contour of aero-engine blade is fitted with spline curve, and the surface of the blade is segmented according to the fitted curve curvature. The mathematical model of continuous precession of blade surface grinding is established, and the algorithm of grinding path is studied. A program capable of simulating the surface grinding path of the blade was developed. 3-D reconstruction of the blade using the blade contour fitting curve was established. The experiments in this paper were performed on a system consisting of two robots, one of which was responsible for the blade space adjustment for its partition segment, and another robot responsible for the path of the grinding. This paper presents the experimental results data, analyzes the data, and selects some experimental condition parameters that can obtain better results.

Model-based displacement estimation of wind turbine blades using strain modal data

For wind turbine rotor blades, the use of strain sensors is preferred over acceleration sensors for the purpose of permanent monitoring. Experimental modal analysis during operation is thus constrained to strain information, yielding strain modal data including strain mode shapes. For follow-up investigations such as aerodynamic load assessment or flutter monitoring it is however advantageous to have this information as displacement mode shapes or as displacements of the blade contour over time. This research applies a generic approach that converts strain mode shapes to displacement mode shapes utilizing an FE shell model as a basis for approximation. The accuracy of the approach is assessed by comparison with experimentally identified high-resolution displacement mode shapes which are acquired with accelerometers and serve as a reference. In the process the conversion procedure is illustrated with the help of strain data that has been obtained using a sensor instrumentation installed for certification testing of the blade. The requirements for successful usage of the employed conversion scheme and its suitability for rotor blade data are discussed.

Effects research on theoretical-modelling based suppression of the contact flutter in blisk belt grinding

Blisk is one of the critical parts of aero-engine whose surface processing quality directly affects the performance of aero-engine. The vibration phenomenon usually happened in the novel open belt grinding, and seriously affects the dimension precision as well as the surface quality of the whole blade profile. In order to figure out that, this paper established a vibration model for the blisk belt grinding. The weak rigidity characteristics of the system were analyzed initially, and the vibratory mechanism was revealed from the view of dynamic analysis. Based on the theoretical model, the stability conditions were proposed by analyzing the influencing of vital factors on processing stability. The experimental validation indicated that the vibration signal waveforms during the process had been successfully reduced by introducing adjustment of grinding parameters. The profile accuracy of the blade contour edge was improved by 9.53 % from the range of −0.0376–0.1145 mm to that of −0.0359–0.1017 mm. After parameter adjustment, the smoothness of the micro-morphology of the blade surface was improved, and the roughness of the blade surface decreased from Ra 0.379–0.573 μm to 0.291–0.368 μm, which fully met the processing requirement of Ra <0.4 μm.

Numerical Simulation of a Bionic Blade on Small-Scale Wind Turbine

This study presents the aerodynamic characteristics of a small-scale horizontal axis wind turbine (HAWT) with bionic blade contours. Taiwan incense cedar was chosen as imitations. On account of the contour of the winged disseminules and the ANSYS FLUENT 14, we designed the bionic blades to process the computations of aerodynamic characteristics of the bionic wind turbine blades. The aerodynamic characteristics and the wind/electricity power transform efficiency of the turbines were examined in a wind tunnel. The wind tunnel experimental outcomes showed that the wind/electricity transformation efficiency of the wind turbine setup could reach to 37%, and it is benefit environment and global energy management.

基于视觉式刀具测量的刀刃轮廓整体拟合

基于视觉式刀具测量的刀刃轮廓整体拟合

Geometric modeling of a closed flat contour with the application of rational cubic curves

The article describes the method of geometric modeling of a closed planar contour using rational cubic curves. When modeling, the task was to make a contour from the minimum number of curve segments not more than third order. An approximation is made for the turbine blade profile. To do this, a flat closed contour of the blade is divided into two parts. The upper and lower parts of the approximating contour at the inflection points of the blade profile have common tangents. The upper part of the contour bounded by inflection points consists of two segments of rational third-order curves having the same curvature at a common point. The first segment of the cubic curve passes through three points of the given contour of the turbine blade, and at these points has tangents common with this contour. Moving the singular point of the first cubic curve within certain limits allows you to change its shape, as well as draw a segment of the curve through an additional point of the given contour and guarantees the absence of a singular point, break and inflection points within the of segment. After constructing the first segment of the cubic curve, the radius of curvature at the endpoint of the segment is determined. The segment of the second cubic curve, like the segment of the first curve, has three common points and tangents in them with a given contour of the turbine blade. Moving the singular point of the second cubic curve within the arc of the previously defined curve provides the specified curvature at the junction with the segment of the first cubic curve, and also guarantees the absence of a singular point, break points, and inflection points within the of segment. The lower part of the turbine blade profile is approximated by a segment of a second-order curve that passes through three points of the blade profile, and at the end points shares common tangents with the contour. The equations of the curves are determined in parametric form in the projective plane, and then written in the affine plane in vector-parametric form. The proposed method can be used both for modeling closed planar contours and for modeling planar contours of the second order of smoothness, the segments of which are rational curves of the third order.

Analysis of quadcopter propeller vibration based on laser vibrometer

An unbalanced propeller can affect a quadcopter’s performance due to vibration, also decreasing its thrust’s yield. Analyses were conducted to determine the correlation between vibration in the dynamic movement of a balanced and an imbalanced propeller using a laser vibrometer (portable digital vibrometer) PDV-100, to determine the correlation between propeller rotational speed and its vibration, as well as to determine the propeller’s maximum rotational speed to avoid over-vibration. The vibration analysis was conducted on a carbon fiber 2-blade propeller by comparing the results of vibration tests with the propeller blade contour. The vibration response of the propeller has been analyzed at three points, respectively the hub, the center, and the tip of the blade, to determine the point having the largest value of the vibration on the propeller running at a maximum rotation speed of 7000 rpm. The same analysis was made on two propellers: the first one of type 1340 with a diameter of 13 inches and the second one of type 1447 with a diameter of 14 inches. The vibration was reduced by propeller’s static balancing, thus increasing the propeller stability. The result showed that an imbalanced propeller generated a decrease in the rotational speed and higher vibration values compared to the balanced propeller. The vibration values showed a linear dependency to the rotor speed; the higher the speed, the bigger the vibration. The limit of rotational speed for the balanced model of the 1340 type propeller was 5000 rpm whilst the corresponding value for the 1447 type propeller was 4500 rpm. Finally, the result was used to optimize the propeller’s overall performance.

Modelling of Vane and Rotor Blade Rows in Simulations of Gas Turbine Performance

Abstract A method of modelling of nozzle and rotor blade rows of gas turbine dedicated to simulations of gas turbine performance is proposed. The method is applicable especially in early design stage when many of geometric parameters are yet subject to change. The method is based on analytical formulas derived from considerations of flow theory and from cascade experiments. It involves determination of parameters of gas flow on the mean radius of blade rows. The blade row gas exit angle, determined in turbine design point is a basis for determination of details of blade contour behind the throat position. Throat area is then fixed based on required maximum mass flow in critical conditions. Blade leading edge radius is determined based on flow inlet angle to the blade row in the design point. The accuracy of analytical formulas applied for definition of blade contour details for assumed gas exit angle was verified by comparing the results of analytical formulas with CFD simulations for an airfoil cascade. Losses of enthalpy due to non-isentropic gas flow are evaluated using the analytical model of Craig and Cox, based on cascade experiments. Effects of blade cooling flows on losses of total pressure of the gas are determined based on analytical formulas applicable to film cooling with cooling streams blowing from discrete point along blade surface, including leading and trailing edges. The losses of total pressure due to film cooling of blades are incorporated into the Craig and Cox model as additional factor modifying gas flow velocities.

A study on the control strategies of a series–parallel hybrid platform for blade polishing

Blades are key components of turbines, aircraft engines, and high-speed ship propulsion systems, such that their manufacturing quality has a considerable influence on a machine’s performance. This paper presented a series–parallel hybrid platform that employed abrasive belt as the tool and integrated the measuring equipment to achieve in-situ measurement for blade polishing. It studied the control strategies for solving the processing parameters aiming to the characteristics of the alternate measurement and processing in the process of polishing. According to singularity analysis of the parallel mechanism, the platform structure parameters were appropriately optimized to avoid the singular position. Then, based on the in-situ measuring data of the blade contour, a method was proposed for calculating the normal vector of machining points, while the platform kinematics were studied, and the total machining allowance was determined by comparing the actual and ideal contour profiles of the blade. Finally, a testing experiment was performed to validate the proposed method of the normal vector calculation, and blade polishing experiment was conducted on the developed platform, which proved the effectiveness and feasibility of the platform.

Erratum to: Morphometric analysis of Passiflora leaves: the relationship between landmarks of the vasculature and elliptical Fourier descriptors of the blade.

BackgroundLeaf shape among Passiflora species is spectacularly diverse. Underlying this diversity in leaf shape are profound changes in the patterning of the primary vasculature and laminar outgrowth. Each of these aspects of leaf morphology—vasculature and blade—provides different insights into leaf patterning.ResultsHere, we morphometrically analyze >3300 leaves from 40 different Passiflora species collected sequentially across the vine. Each leaf is measured in two different ways: using 1) 15 homologous Procrustes-adjusted landmarks of the vasculature, sinuses, and lobes; and 2) Elliptical Fourier Descriptors (EFDs), which quantify the outline of the leaf. The ability of landmarks, EFDs, and both datasets together are compared to determine their relative ability to predict species and node position within the vine. Pairwise correlation of x and y landmark coordinates and EFD harmonic coefficients reveals close associations between traits and insights into the relationship between vasculature and blade patterning.ConclusionsLandmarks, more reflective of the vasculature, and EFDs, more reflective of the blade contour, describe both similar and distinct features of leaf morphology. Landmarks and EFDs vary in ability to predict species identity and node position in the vine and exhibit a correlational structure (both within landmark or EFD traits and between the two data types) revealing constraints between vascular and blade patterning underlying natural variation in leaf morphology among Passiflora species.

Morphometric analysis of Passiflora leaves: the relationship between landmarks of the vasculature and elliptical Fourier descriptors of the blade.

Background: Leaf shape among Passiflora species is spectacularly diverse. Underlying this diversity in leaf shape are profound changes in the patterning of the primary vasculature and laminar outgrowth. Each of these aspects of leaf morphology—vasculature and blade—provides different insights into leaf patterning. Results: Here, we morphometrically analyze >3300 leaves from 40 different Passiflora species collected sequentially across the vine. Each leaf is measured in two different ways: using 1) 15 homologous Procrustes-adjusted landmarks of the vasculature, sinuses, and lobes; and 2) Elliptical Fourier Descriptors (EFDs), which quantify the outline of the leaf. The ability of landmarks, EFDs, and both datasets together are compared to determine their relative ability to predict species and node position within the vine. Pairwise correlation of x and y landmark coordinates and EFD harmonic coefficients reveals close associations between traits and insights into the relationship between vasculature and blade patterning. Conclusions: Landmarks, more reflective of the vasculature, and EFDs, more reflective of the blade contour, describe both similar and distinct features of leaf morphology. Landmarks and EFDs vary in ability to predict species identity and node position in the vine and exhibit a correlational structure (both within landmark or EFD traits and between the two data types) revealing constraints between vascular and blade patterning underlying natural variation in leaf morphology among Passiflora species.

NUMERICAL SIMULATON OF AXIAL FLOW FAN USING GAMBIT AND FLUENT

The main objective of this paper consists of the computation of the aerodynamic performances of symmetrical blade contours of fully reversible axial fans by Numerical (CFD) methods, developing by a public literature survey, methodology for the design of reversible axial fans and analysis of the designed fan with CFD methods. The aerodynamic shows of the blade cascades are evaluated using FLUENT 6.0 software for different boundary conditions, strengths and angles called Angle of Attack(AoA) cascade also performing for varying speeds. The consequences of these computations are embedded into the industrialized methodology. Which is designed with the developed methodology, is done with Numerical methods.

Comparison study of fabrication of ceramic rotor using various manufacturing methods

An alumina ceramic turbine rotor with both large volume (90mm in diameter and 20mm in height) and sub-millimeter geometry (0.42mm at the blade tip with curvature) was successfully prepared by using various manufacturing approaches. Polyjetting and computer numerical control (CNC) machining were respectively adopted to fabricate an integral sacrificial polymeric mold and a separable aluminum mold for the tailored gelcasting process, whereas selective laser sintering (SLS) was used to directly fabricate the turbine rotor by laser sintering the alumina and epoxy powders followed by liquid phase sintering in furnace. A series of experimental studies on these three rotor-forming routes were performed throughout the process. For the green rotor, the alumina slurry preparation, specific drying strategy and microstructure of the green part were presented and compared. For the sintered rotor, comparisons in terms of surface roughness, microstructure, mechanical properties and blade contour deformation were conducted. Finally, the most suitable method to fabricate the complex-shaped alumina rotor with the best performances was suggested.