Blade Manufacturing Process Research Articles

Application of Laser Cladding Additive Manufacturing Technology in TRT Blade Manufacturing and Repair Process

Application of Laser Cladding Additive Manufacturing Technology in TRT Blade Manufacturing and Repair Process

Vibration damping method of cantilever structure considering redundant constraint of monocrystalline blade casting mold shell

Excessive vibrations of the mold shell during the manufacturing process of monocrystalline blades lead to dendirite and frekle defects in directional solidification. The dynamics of the casting lifting device-mold shell system is analysed theoretically to reveal the influence of key parameters such as excitation force, damping and stiffness on the monocrystalline blade casting. The effect of redundant constraint onto the system is analysed via the developed vibration model. A lifting device-mold shell system test bench is developed, a slide-support arm device is designed to provide redundant constraint. A self-developed high-precision sensor is used to test the vibration signals, and the effectiveness of the damping method is verified. The experimental results show that the redundant constraint can reduce the undesired vibration of mold shell by more than 77 %, which ensures the casting quality of monocrystalline blades. The proposed vibration damping method can provide a reference for the vibration damping of the cantilever machine.

Research on rapid detection of characteristic parameters of aeroengine blade surface based on laser scanning

How to detect and evaluate the profile quality of aeroengine blades and provide technical support for blade manufacturing has become one of the key technical problems in the field of aviation manufacturing quickly and effectively. This paper studies the evaluation criteria of medium surface quality in the processing and manufacturing process of aeroengine blades, optimizes and innovates the fast extraction algorithms of various geometric parameters such as aeroengine blade section line, middle arc, front/rear edge center, front/rear edge radius, blade chord length, and chord angle, and establishes the evaluation criteria of aeroengine blade surface. According to the geometric relationship of blade chord length and front/rear edge radius in the blade section profile, the parameters are solved one by one through an optimization algorithm, combined with non-contact laser scanning measurement, and the blade detection efficiency is improved by more than 40%.

Strategic Quality Control Measures to Reduce Defects in Composite Wind Turbine Blades

Wind turbine blades are made from polymer composites to provide high specific stiffness, strength, and good fatigue performance. However, large composite structures are prone to manufacturing defects such as delamination and adhesive failure, which can lead to crack initiation and propagation under cyclic stresses. National renewable energy laboratory, USA statistics shows 26% fatigue failure modes are created by laminate and adhesive joint manufacturing errors. A range of manufacturing processes are used to construct wind turbine blades. Resin transfer infusion is one of the most frequently used methods in wind turbine blade manufacturing industry. This paper provides assessment on regular defects occurring in resin transfer infusion processes which lead to poor quality in wind turbine blade manufacture. The assessment is based on the existing literature and the know-how generated from manufacturing wind turbine blades. The effect of these defects for the structural failure of composite wind turbine blades is analysed. The final phase of the study provides manufacturing quality control measures which can be implemented to improve the composite wind turbine blade manufacturing process.

Manufacturing methods for assessing the impact of wrinkles in wind turbine blades

Wrinkles are defects prone to occur during the manufacturing process of wind turbine blades. Wrinkles can emerge at various locations of the structure, exhibiting a range of diverse shapes. Different manufacturing steps can lead to different defect types. This work presents different manufacturing methods to embed artificial wrinkle defects in laminates representing a typical defect that can be found in a wind turbine blade. Several methods are tested at coupon scale to design a critical wrinkle defect that can lead to the blade structural knock-down on the mechanical performance during high cycle fatigue operation. Following the selection of the defect types for investigation at the test coupon scale, the corresponding defect types are embedded while manufacturing a 12.6 m wind turbine blade.

Using radar to improve composite manufacturing

The Fraunhofer Institute in Germany describes the development of a new radar technique which can automatically monitor the rotor blade manufacturing process.

Methodology to predict stiffness knock-down in laminates for wind turbine blades with artificial wrinkles

Abstract. This work presents a methodology to evaluate the effect of wrinkle defects in the stiffness response of laminate characteristic of wind turbine blades. The assessment is carried out through numerical models and experimental tests with coupon specimens embedded with artificial wrinkles. Specimens are manufactured with two types of defects, prone to arising along the manufacturing process of wind turbine blades. Image-based numerical models were built to enclose the actual features of the cross-sectional wrinkling of each defect type. Experimental quasi-static tension and compression tests were performed, where extensometers collect the strain distribution about the wrinkle section as around the flat section of the test specimens. Two-dimensional finite element simulations carried out in Abaqus/Standard captured the stiffness behaviour of the two types of wrinkles. The numerical approach is validated against the quasi-static tests retrieving a fair agreement with experimental data. A significant knock-down in the stiffness response was found due to the wrinkle with larger aspect ratio of amplitude / half-wavelength.

3D positioning of defects for gas turbine blades based on digital radiographic projective imaging

During the manufacturing and service process of gas turbine blades, various types of defects may be formed and bring huge threat to the safe operation of gas turbine. To confirm whether the gas turbine blades with defects could be in safe service for some period of time, the residual strength and fatigue life of gas turbine blade should be analyzed and predicted based on the 3D spatial position of defect, which significantly determines the degree of effect on the strength of gas turbine blade. Considering the characteristics of shape (free-from surface) and material (high density superalloy), the digital radiographic imaging techniques could be used in the non-destructive testing of gas turbine blades. However, the projective nature of digital radiography (DR) technique results in the unavailability of position in the transmitting direction of X-ray beam and brings difficulty to the 3D characterization of defect. Aiming at this critical issue, based on the exploration of the changing rule for the projection of a point feature relative to the irradiating angle, a new method is presented to obtain the 3D spatial position of defect. Finally, the accuracy of the proposed method is validated using a metrological computed tomography (CT) system. It can be learned that the proposed DR based method could obtain the 3D spatial position of defect with a relative error less than 2%. The 3D spatial position of defect could be used in the following residual strength analysis and fatigue life prediction of gas turbine blade.

The Mechanical Structure Contact Mechanism Analysis Considering Modified Tangential Stiffness with Friction’s Effect

This paper proposes a modified tangential contact stiffness model considering friction’s effect, which is the first key step to establish the dynamic model of the fixture-workpiece system, and this is the foundation of vibration suppression for the manufacturing process of aerospace blades. According to Love’s elastic deformation, the model’s derivation process starts with the potential function in each coordinate axis’s direction respectively. The generalized Hertz contact theory is employed to calculate the contact forces in this model. The symmetrical characteristic of the contact area has simplified the derivation process to obtain the eventual tangential contact stiffness model. A validation experiment focusing on a tangential stiffness measuring is achieved by putting two spherical objects in contact together to get the tangential contact stiffness. Based on the data collected in this experiment, a comparison with a most similar existed model is carried out, and the result shows that the relative error of this modified model are all less than 10%, while the original model’s (the most similar model) relative error exceeding 50% captures more than 3/4 of the 30 data sets randomly selected in each experiment group, and that means the modification of this paper brings great improvement to the contact stiffness model.

Development of high‐fidelity design‐driven wind blade manufacturing process models to investigate labor predictions in wind blade manufacture

AbstractWind turbines have shown significant advancements in efficiency and power output in the last 20 years. However, during the same time period, parallel advances in the manufacturing of wind blades have not happened due to the reluctance of wind blade manufacturers to make significant capital investments into unproven automation technologies. This reluctance is due in part to the lack of access to a robust techno‐economic model that can give feedback on if and how these investments will impact the overall cost to make a blade. In the current research, existing costing methods are reviewed and a new techno‐economic model for estimating the number of man‐hours required to manufacture a wind turbine blade is proposed. A set of standardized input parameters for the proposed model is developed from time studies completed at three wind blade manufacturing facilities. The proposed model uses 77 discrete processing steps. The credibility of the proposed model is validated by its ability the predict the required man‐hours for the manufacture of previously produced blades by the blade manufacturers. Additionally, validation is done against models of publicly available designs. The proposed model delivers more accurate and realistic estimates over prior models reflecting the application of current production techniques and detailed design information.

Vibration Suppression with Use of Input Shaping Control in Machining.

This article discusses the problem of vibrations during machining. The manufacturing process of generator turbine blades is highly complex. Machining using Computerized Numerical Control (CNC) requires low cutting parameters in order to avoid vibration problems. However, even under these conditions, the surface quality and accuracy of the manufactured objects suffer from high levels of vibrations. Hence, the aim of this research is to counteract this phenomenon. Basic issues related to vibration problems will also be also discussed and a short review of currently available solutions for both active and passive vibration monitoring during machining will be presented. The authors developed a method which does not require any additional equipment other than modified CNC code. The proposed method can be applied to any CNC machine, and is especially suitable for lathes. The method seeks to eradicate the phenomenon of vibrations by providing enhanced control through Input Shaping Control (ISC). For this purpose, the authors present a method for modeling the machining process and design an ISC filter; the model is then implemented in the Matlab and Simulink environment. The last part of the article presents the results, together with a discussion, and includes a brief summary.

Towards a fully autonomous robotic system for detection and removal of surface defects in fiber glass panels

Wind blades for turbines are commonly manufactured from fiber glass. A last step in the manufacturing process of such blades is sanding of the surface to remove defects that occur during the process. This paper presents an autonomous robotic system performing sanding operations for surface defect removal in fiber glass panels. The proposed approach uses a collaborative robotic system equipped with a vision system. Surface defects are detected using traditional computer vision algorithms and a path planning strategy is designed that solves multi-goal and coverage path planning problems. The robotic system equipped with a specialized end-effector will autonomously perform sanding of the defected areas using a constant velocity control system. Experimental results are evaluated based on the accuracy of the defect detection and roughness measurements before and after the sanding process has been completed.

Aerothermal Effect of Cavity Welding Beads on a Transonic Squealer Tip

Abstract High-pressure turbine blade tips are critical for gas turbine performance and are sensitive to small geometric variations. For this reason, it is increasingly important for experiments and simulations to consider real geometry features. One commonly absent detail is the presence of welding beads on the cavity of the blade tip, which are an inherent by-product of the blade manufacturing process. This paper therefore investigates how such welds affect the Nusselt number, film cooling effectiveness and aerodynamic performance. Measurements are performed on a linear cascade of high-pressure turbine blades at engine realistic Mach and Reynolds numbers. Two cooled blade tip geometries were tested: a baseline squealer geometry without welding beads, and a case with representative welding beads added to the tip cavity. Combinations of two tip gaps and several coolant mass flow rates were analyzed. Pressure sensitive paint was used to measure the adiabatic film cooling effectiveness on the tip, which is supplemented by heat transfer coefficient measurements obtained via infrared thermography. Drawing from all of this data, it is shown that the weld beads have a generally detrimental impact on thermal performance, but with local variations. Aerodynamic loss measured downstream of the cascade is shown to be largely insensitive to the weld beads.

Leveraging the Advantages of Additive Manufacturing to Produce Advanced Hybrid Composite Structures for Marine Energy Systems

Many marine energy systems designers and developers are beginning to implement composite materials into the load-bearing structures of their devices, but traditional mold-making costs for composite prototyping are disproportionately high and lead times can be long. Furthermore, established molding techniques for marine energy structures generally require many manufacturing steps, such as secondary bonding and tooling. This research explores the possibilities of additively manufactured internal composite molds and how they can be used to reduce costs and lead times through novel design features and processes for marine energy composite structures. In this approach, not only can the composite mold be additively manufactured but it can also serve as part of the final load-bearing structure. We developed a conceptual design and implemented it to produce a reduced-scale additive/composite tidal turbine blade section to fully demonstrate the manufacturing possibilities. The manufacturing was successful and identified several critical features that could expedite the tidal turbine blade manufacturing process, such as single-piece construction, an integrated shear web, and embedded root fasteners. The hands-on manufacturing also helped identify key areas for continued research to allow for efficient, durable, and low-cost additive/composite-manufactured structures for future marine energy systems.

Silica strengthened alumina ceramic cores prepared by 3D printing

Ceramic cores based on alumina and silica are important in the manufacturing of hollow blades. However, obtaining good properties and precision is still challenging. In this research, alumina-based ceramics cores were obtained by 3D printing technology, and the effects of silica contents on the mechanical properties of the as-obtained alumina ceramic cores were evaluated. The results showed significant improvements in flexural strengths of the ceramics from 13.3 MPa to 46.3 MPa at silica contents from 0 wt% to 30 wt% due to formation of mullite phase (Al6Si2O13). By contrast, the flexural strengths declined as silica content further increased due to the generation of massive liquid phase. Also, porous structures and cracks were observed by scanning electron microscopy due to the removal of cured photosensitive resin and the mullitization reaction between alumina and silica, respectively. The manufacturing process of hollow blades required ceramic cores with flexural strengths greater than 20 MPa to resist the strike of metal liquid, as well as open porosity above 20 % to provide space for alkali liquor to dissolve the ceramic cores. As a result, 10 wt% silica was determined as the optimal value to yield ceramics with improved properties in terms of flexural strength (35.6 MPa) and open porosity (47.5 %), thereby satisfy the application requirement for the fabrication of ceramic cores.

Numerical Study of a Novel Concept for Manufacturing Savonius Turbines with Twisted Blades

This work presents a numerical study of the aerodynamic performance and the resulting flow field of two novel Savonius wind turbines with twisted blades. The novelty relies on the blade manufacturing process which is characterized by a ‘twisted cut’ through the central axis of a hollow cylinder (tube), followed by a partial twisted cut in the range of 90°. This approach does not require any expensive fabrication process such as blade molding and/or 3D prints, and, therefore, it can potentially mitigate the production costs. The main goal is to investigate the operational parameters and the overall performance of the presented devices, which are currently being operated in atmospheric conditions. For this purpose, three-dimensional simulations have been performed using the open-source CFD library OpenFOAM in order to solve the governing equations and for characterizing the main phenomena involved in the flow pattern. The Reynolds-averaged Navier–Stokes (RANS) approach together with the k − ω SST model were employed to reproduce the flow turbulence effects. This model is validated using wind tunnel measurements of the power ( C P ) and torque ( C M ) coefficients from a straight blade Savonius turbine. Unsteady simulations of the two turbine prototypes were investigated at different tip speed ratio TSR ( λ ) by varying the rotational speed of the rotor while keeping constant the free stream (rated) velocity V ∞ . The results were compared against the Savonius turbine employed for validating the model. Aerodynamic loads and general wake structure were studied at the optimal operational conditions as well. For the same turbine configurations, the new blade geometry improved the performance by 20–25% (at its optimal TSR), compared to the conventional straight blade Savonius rotor, as well as the reducing torque fluctuation.

Development of thermal residual stresses during manufacture of wind turbine blades

Thermal residual stresses have a major impact on the bond line fatigue of wind turbine blades, which can initiate tunneling cracks in the adhesive layer of the bond lines early in the operational life of the blade. This work investigates the simulation accuracy for predicting thermal residual stresses within a thick bond line. The trailing-edge bond line strip of a 34 m blade was modeled with classical laminated plate theory (CLT) on the one hand and with finite element (FE) plate models of different fidelities on the other. For the model benchmark, the thermal residual stresses were on the basis of a thermal simulation. These develop during the cooling after a typical curing cycle of a wind turbine blade manufacturing process. It was found that the analytical model on the basis of CLT was in good agreement with the plate models of higher fidelity. Additionally, a full 3D FE blade model was used to calculate the shape distortion and the thermal residual stresses. It was found that the analytical model, which did not take into account effects stemming from the whole blade structure, underestimated the full 3D FE model.

Improving the quality of the manufacturing process of turbine blades of the gas turbine engine

This paper describes the results of research and development work, which lead to an increase in the quality of the technological process of manufacturing the working turbine blades of a gas turbine engine. The mathematical description of the four-zone process of directional crystallization made it possible to select the most optimal thermophysical parameters of the casting process that affect the macrostructure of casting the blades. Digital modeling of casting technology, taking into account the proposed mathematical models, as well as the boundary, contact and initial conditions of the process, made it possible to most reliably describe the temperature front distribution in the crystallization zone at discrete points for any moment in any section. The temperature-time optimization of the technological process for casting turbine blades made it possible to select the optimal temperature conditions for the respective areas of the foundry plant, which ultimately allowed a 20% reduction in rejects associated with the mismatch of the macrostructure of castings the blades to the standard.

Detection of Three-Dimensional Parameter of Defects for Gas Turbine Blades Based on Two-Dimensional Digital Radiographic Projective Imaging

During the manufacturing and service process of turbine blades, various types of defects may be formed and bring huge threat to the safe operation of gas turbine. However, if qualifying the turbine blade only by the existence of defects, it will lead to the unavoidable large waste. Preferably, it should determine whether the turbine blades with defects could be in safe service for some period of time. Therefore, the residual strength and fatigue life should be analyzed and predicted based on the three-dimensional feature of defect, such as size, location. Considering the characteristics of shape (free-from surface) and material (high density superalloy), the radiographic imaging based techniques could be used in the non-destructive testing of turbine blades. For one thing, although the industrial computed tomography can obtain the three-dimensional feature of defects, the low efficiency and high cost may limit its practical application. For another, the projective nature of digital radiographic imaging technique results in the unavailability of geometric parameter in the transmitting direction and brings difficulty to the three-dimensional characterization of defect. Aiming at this critical issue, a new method based on the determination of mapping relationship between the thickness of material and the gray value of image is presented in this paper. By acquiring the thickness of two defects in a gas turbine blade, the three-dimensional geometric parameter (volume) can be calculated. Finally, the accuracy of the proposed method is verified using a test specimen. In comparison with the industrial CT, the proposed method could have relative high efficiency and low cost in the application of the three-dimensional quantitative characterization of defects for gas turbine blades.

Research on Machining Fixture Layout Optimization for Near-Net-Shaped Jet Engine Blade

The design of machining fixture layout optimization for near-net-shaped jet engine blade is a major problem in the blade processing and manufacturing process. In this paper, the mathematical model of machining fixture layout optimization is established, and the influence of the clamping point position on the machining deformation of the blade-fixture system is analysed. Firstly, the mathematical model of machining fixture layout optimization is established according to the process requirements and clamping characteristics. Secondly, the positioning clamp points of machining fixture is optimized by the combination of finite element analysis (FEA) and genetic algorithm under the optimization target of the minimum value of the maximum deformation of the blade. Finally, cutting experiments are carried out to verify the reliability of the optimal layout fixtures, and the feasibility of the algorithm is verified by comparing with the minimum value obtained by the traditional Monte Carlo statistical method.