Design Tuning of High Aspect Ratio Shrouded Turbine Blades

2008 ◽  
Author(s):  
Alexander N. Arkhipov ◽  
Andrey V. Pipopulo ◽  
Igor V. Putchkov
Keyword(s):  
Aspect Ratio ◽  
Turbine Blade ◽  
Natural Frequencies ◽  
Frequency Tuning ◽  
Turbine Blades ◽  
Mathematical Optimization ◽  
3D Models ◽  
Design Parameters ◽  
Blade Design ◽  
Cross Sectional

A large height to chord ratio, or aspect ratio, of industrial gas turbine blades, especially for the last rows, requires an increase of the blade natural frequencies above the 2nd Engine Order (EO). Generally this is possible only by utilizing a shrouded blade design. During the design process there are also several other mechanical factors, such as LCF, HCF, creep, shroud coupling, and aero efficiency, which have to be taken into consideration. It is shown that mathematical models of different complexity levels (1D / 3D models) can give comparable results for many important parameters if the boundary conditions for the 1D model are corrected by using the results of 3D model analysis. These parameters include quantities such as shroud contact pressure and coupling forces, the rotor speed at which full coupling is achieved, the first three blade natural frequencies, blade profile untwist moment and angle, and von Mises elastic stresses in critical sections. Thus a combination of 1D and 3D models can achieve a reduction of the time required for design of a shrouded turbine blade. The type of shroud design, the initial shroud clearance, and the contact surface angle are the important parameters for a shrouded turbine blade. The influence of these factors on dynamic response and lifetime prediction is non-linear and not always obvious, so a good blade design usually requires searching for an optimal combination of different design, technological and operational factors. Significant design parameters for blade frequency tuning are the radial distributions of cross-sectional geometrical characteristics and especially the radial distribution of the stagger angle. The latter one allows the designer to bring together or to move apart the first and the second vibration modes. More suitable parameter combinations are determined by the usage of mathematical optimization methods. The method presented and the corresponding techniques were used during design of shrouded blades for a few new turbines, where the length of the blade airfoil has exceeded 800mm.

Optimization of Supersonic Axial Turbine Blades Based on Surrogate Models

2020 ◽  
Author(s):  
Markus Waesker ◽  
Bjoern Buelten ◽  
Norman Kienzle ◽  
Christian Doetsch
Keyword(s):  
Reynolds Number ◽  
Turbine Blade ◽  
Surrogate Model ◽  
Cfd Simulation ◽  
Turbine Blades ◽  
Energy System ◽  
Design Parameters ◽  
Blade Design ◽  
Axial Turbine ◽  
Velocity Coefficient

Abstract Due to the transition of the energy system to more decentralized sector-coupled technologies, the demand on small, highly efficient and compact turbines is steadily growing. Therefore, supersonic impulse turbines have been subject of academic research for many years because of their compact and low-cost conditions. However, specific loss models for this type of turbine are still missing. In this paper, a CFD-simulation-based surrogate model for the velocity coefficient, unique incidence as well as outflow deviation of the blade, is introduced. This surrogate model forms the basis for an exemplary efficiency optimization of the “Colclough cascade”. In a first step, an automatic and robust blade design methodology for constant-channel blades based on the supersonic turbine blade design of Stratford and Sansome is shown. The blade flow is fully described by seven geometrical and three aerodynamic design parameters. After that, an automated numerical flow simulation (CFD) workflow for supersonic turbine blades is developed. The validation of the CFD setup with a published supersonic axial turbine blade (Colclough design) shows a high consistency in the shock waves, separation zones and boundary layers as well as velocity coefficients. A design of experiments (DOE) with latin hypercube sampling and 1300 sample points is calculated. This CFD data forms the basis for a highly accurate surrogate model of supersonic turbine blade flow suitable for Mach numbers between 1.1 and 1.6. The throat-based Reynolds number is varied between 1*104 and 4*105. Additionally, an optimization is introduced, based on the surrogate model for the Reynolds number and Mach number of Colclough and no degree of reaction (equal inlet and outlet static pressure). The velocity coefficient is improved by up to 3 %.

Influence of Geometric Design Parameters Onto Vibratory Response and HCF Safety for Turbine Blades With Friction Damper

2018 ◽  
Author(s):  
Matthias Hüls ◽  
Lars Panning-von Scheidt ◽  
Jörg Wallaschek
Keyword(s):  
Aspect Ratio ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Design Parameters ◽  
System Response ◽  
Blade Design ◽  
Cycle Fatigue ◽  
Resonance Amplitude ◽  
Damped System ◽  
Vibratory Response

Among the major concerns for high aspect-ratio turbine blades are forced and self-excited (flutter) vibrations which can cause failure by high-cycle fatigue. The introduction of friction damping in turbine blades, such as by coupling of adjacent blades via under platform dampers, can lead to a significant reduction of resonance amplitudes at critical operational conditions. In this paper, the influence of basic geometric blade design parameters onto the damped system response will be investigated to link design parameters with functional parameters like damper normal load, frequently used in nonlinear dynamic analysis. The shape of a simplified large aspect-ratio turbine blade is parameterized along with the under platform damper configuration. The airfoil is explicitly included into the parameterization in order to account for changes in blade mode shapes. For evaluation of the damped system response under a typical excitation, a reduced order model for non-linear friction damping is included into an automated 3D FEA tool-chain. Based on a design of experiments approach, the design space will be sampled and a surrogate model is trained on the received dataset. Subsequently, the mean and interaction effects of the true geometric blade design parameters onto the resonance amplitude and safety against high-cycle fatigue will be outlined for a critical first bending type vibrational motion. Design parameters were mainly found to influence the resonance amplitude by their effect onto the tip-to-platform deflection ratio. The HCF safety was affected by those design parameters with large sensitivity onto static and resonant vibratory stress levels. Applying an evolutionary optimization algorithm, it is shown that the optimum blade design with respect to minimum vibratory response at a particular node can differ significantly from a blade designed toward maximum HCF safety.

Prescribed-Curvature-Distribution Airfoils for the Preliminary Geometric Design of Axial-Turbomachinery Cascades

1992 ◽  
Author(s):  
Theodosios Korakianitis
Keyword(s):  
Turbine Blade ◽  
High Performance ◽  
Direct Method ◽  
Thickness Distribution ◽  
Turbine Blades ◽  
Leading Edge ◽  
Design Parameters ◽  
Blade Design ◽  
Curvature Distribution ◽  
Stagger Angle

Blade surfaces with continuous curvature and continuous slope of curvature minimize the possibility of flow separation, lead to improved blade designs, and reduce the direct and inverse blade-design iterations for the selection of isolated airfoils and gas-turbine-blade cascades. A method for generating two-dimensional blade shapes is presented. The geometry near the trailing edge is specified by an analytic polynomial, the main portion of the blade surface is mapped using as input a prescribed surface-curvature distribution, and the leading edge is specified as a thickness distribution added to a construction line. This procedure is similar for the suction and pressure surfaces, and by specification it constructs continuous slope-of-curvature surfaces that result in smooth surface-Mach-number and surface-pressure distributions. The method can be used to generate subsonic or supersonic airfoils for compressors and turbines, or isolated airfoils. The resulting geometric shapes can be used as inputs to various blade-design sequences. It is shown that, with other cascade-design parameters being equal, increasing the stagger angle of turbine blades results in more-front-loaded and thinner blades, and that there is an optimum stagger angle resulting in minimum wake thickness. The subsonic axial-turbine blade rows included for discussion in this paper have been designed by iterative modifications of the blade geometry to obtain a desirable velocity distribution. The blade-design method can be used to improve the aerodynamic and heat transfer performance of turbine cascades, and it can result in high-performance airfoils, even if using the direct method exclusively, in very few iterations.

Prescribed-Curvature-Distribution Airfoils for the Preliminary Geometric Design of Axial-Turbomachinery Cascades

1993 ◽  
Vol 115 (2) ◽  
pp. 325-333 ◽  
Author(s):  
T. Korakianitis
Keyword(s):  
Turbine Blade ◽  
High Performance ◽  
Direct Method ◽  
Thickness Distribution ◽  
Turbine Blades ◽  
Leading Edge ◽  
Design Parameters ◽  
Blade Design ◽  
Curvature Distribution ◽  
Stagger Angle

Blade surfaces with continuous curvature and continuous slope of curvature minimize the possibility of flow separation, lead to improved blade designs, and reduce the direct and inverse blade-design iterations for the selection of isolated airfoils and gas-turbine-blade cascades. A method for generating two-dimensional blade shapes is presented. The geometry near the trailing edge is specified by an analytic polynomial, the main portion of the blade surface is mapped using as input a prescribed surface-curvature distribution, and the leading edge is specified as a thickness distribution added to a construction line. This procedure is similar for the suction and pressure surfaces, and by specification it constructs continuous slope-of-curvature surfaces that result in smooth surface-Mach-number and surface-pressure distributions. The method can be used to generate subsonic or supersonic airfoils for compressors and turbines, or isolated airfoils. The resulting geometric shapes can be used as inputs to various blade-design sequences. It is shown that, with other cascade-design parameters being equal, increasing the stagger angle of turbine blades results in more front-loaded and thinner blades, and that there is an optimum stagger angle resulting in minimum wake thickness. The subsonic axial-turbine blade rows included for discussion in this paper have been designed by iterative modifications of the blade geometry to obtain a desirable velocity distribution. The blade-design method can be used to improve the aerodynamic and heat transfer performance of turbine cascades, and it can result in high-performance airfoils, even if using the direct method exclusively, in very few iterations.

Studies on Determination of Natural Frequencies of Industrial Turbine Blades

1995 ◽  
Author(s):  
Mahesh M. Bhat ◽  
V. Ramamurti ◽  
C. Sujatha
Keyword(s):  
Steam Turbine ◽  
Dynamic Behavior ◽  
Turbine Blade ◽  
Natural Frequencies ◽  
Complex Structure ◽  
Turbine Blades ◽  
Blade Root ◽  
Steam Turbine Blade ◽  
Manufacturing Tolerances

Abstract Steam turbine blade is a very complex structure. It has geometric complexities like variation of twist, taper, width and thickness along its length. Most of the time these variations are not uniform. Apart from these geometric complexities, the blades are coupled by means of lacing wire, lacing rod or shroud. Blades are attached to a flexible disc which contributes to the dynamic behavior of the blade. Root fixity also plays an important role in this behavior. There is a considerable variation in the frequencies of blades of newly assembled turbine and frequencies after some hours of running. Again because of manufacturing tolerances there can be some variation in the blade to blade frequencies. Determination of natural frequencies of the blade is therefore a very critical job. Problems associated with typical industrial turbine bladed discs of a 235 MW steam turbine are highlighted in this paper.

Accelerated 3D Aerodynamic Optimization of Gas Turbine Blades

2014 ◽  
Author(s):  
Philipp Amtsfeld ◽  
Michael Lockan ◽  
Dieter Bestle ◽  
Marcus Meyer
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Optimization Process ◽  
Design Parameters ◽  
Blade Design ◽  
Aerodynamic Optimization ◽  
Multi Stage ◽  
Design Variables ◽  
Real Flow ◽  
Blade Model

State-of-the-art aerodynamic blade design processes mainly consist of two phases: optimal design of 2D blade sections and then stacking them optimally along a three-dimensional stacking line. Such a quasi-3D approach, however, misses the potential of finding optimal blade designs especially in the presence of strong 3D flow effects. Therefore, in this paper a blade optimization process is demonstrated which uses an integral 3D blade model and 3D CFD analysis to account for three-dimensional flow features. Special emphasis is put on shortening design iterations and reducing design costs in order to obtain a rapid automatic optimization process for fully 3D aerodynamic turbine blade design which can be applied in an early design phase already. The three-dimensional parametric blade model is determined by up to 80 design variables. At first, the most important design parameters are chosen based on a non-linear sensitivity analysis. The objective of the subsequent optimization process is to maximize isentropic efficiency while fulfilling a minimal set of constraints. The CFD model contains both important geometric features like tip gaps and fillets, and cooling and leakage flows to sufficiently represent real flow conditions. Two acceleration strategies are used to cut down the turn-around time from weeks to days. Firstly, the aerodynamic multi-stage design evaluation is significantly accelerated with a GPU-based RANS solver running on a multi-GPU workstation. Secondly, a response surface method is used to reduce the number of expensive function evaluations during the optimization process. The feasibility is demonstrated by an application to a blade which is a part of a research rig similar to the high pressure turbine of a small civil jet engine. The proposed approach enables an automatic aerodynamic design of this 3D blade on a single workstation within few days.

Identification of Replica Modes in Integrally Bladed Rotor

2011 ◽  
Vol 110-116 ◽  
pp. 2348-2353
Author(s):  
Rana Noman Mubarak ◽  
Jen Yuan Chang
Keyword(s):  
Natural Frequencies ◽  
Low Frequency ◽  
Free Vibrations ◽  
Forced Response ◽  
Design Parameters ◽  
Blade Design ◽  
Blade Angle ◽  
Blade Thickness ◽  
Symmetric Rotor ◽  
Bladed Rotor

Effects on structure designs on free vibrations of integrated bladed rotor (IBR) have been conducted in this research through finite element simulations. Migration of natural frequencies is characterized through parameter studies considering changes of blade angle and blade thickness on an underlying uniform axis-symmetric rotor. Recurring coupled repeated doublet modes, defined as replica modes, has been observed in this study by characterizing blade’s vibrations in-phase or out-of-phase to disk’s vibrations. Veering and cluster of replica modes’ natural frequencies are observed with respect to the blade design parameters. Fourier content for low frequency replica component is found to be sensitive and tunable to blade angle design, which has implications on forced response of spinning IBR in engineering applications.

Wind Turbine Blade Design and Analysis With Tubercle Technology

2012 ◽  
Author(s):  
Sourabh Kumar ◽  
R. S. Amano
Keyword(s):  
Wind Turbine ◽  
Flow Pattern ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Cad Model ◽  
Blade Design ◽  
Cfd Analysis ◽  
Straight Blade ◽  
Turbine Blade Design ◽  
Insight Into

The objective of this project is to construct a CAD model for tubercle wind turbine. Once the model is developed a complete CFD analysis of the flow pattern around the wind turbine will be carried out. The main objective of the study is to analyze and compare the performance of the tubercle wind turbine with the usual wind turbine. The power developed by both the turbine blades can be compared to support the use of tubercle. The tubercles are very effective for increasing the lift without stalling. The main objective of this project is to study the aerodynamic advantages of tubercle turbine blade. The effort will be to compare the obtained results with the straight blade of the same airfoil. This will provide insight into the advantages of using the tubercle blade. This technology being new the study is done numerically to study the overall effect of the tubercle.

A Study of Optimization of Blade Section Shape for a Steam Turbine

2005 ◽  
Author(s):  
Kyung-Nam Chung ◽  
Yang-Ik Kim ◽  
Ju-Heon Sung ◽  
In-Ho Chung ◽  
Sang-Hoon Shin
Keyword(s):  
Turbine Blade ◽  
Optimization Design ◽  
Design Method ◽  
Turbine Blades ◽  
Design Parameters ◽  
Surface Model ◽  
Impulse Turbine ◽  
Object Function ◽  
Section Shape ◽  
Blade Section

In this study, an optimization design method is established for a rotor blade of a Curtis turbine. Bezier curve is generally used to define the profile of turbine blades. However, this curve is not proper to a supersonic impulse turbine. Section shape of a supersonic turbine blade is composed of straight lines and circular arcs. That is, it has several constraints to define the section shape. Thus, in this study, a blade design method is developed by using B-spline curve in which local control is possible. The turbine blade section has been changed by varying three design parameters of exit blade angle, stagger angle and maximum camber. Then flow analyses have been carried out for the sections. Lift-drag ratio of the blade section is used as the object function, and it is maximized in the optimization. Second-order response surface model is employed to express the object function as a function of design parameters. Central composite design method is used to reduce the number of design points. Then, an evolution strategy is employed to obtain the optimized section of the Curtis turbine blade.

scholarly journals PSO-BP Neural Network-Based Strain Prediction of Wind Turbine Blades

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1889 ◽  
Author(s):  
Xin Liu ◽  
Zheng Liu ◽  
Zhongwei Liang ◽  
Shun-Peng Zhu ◽  
José A. F. O. Correia ◽  
...  
Keyword(s):  
Neural Network ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Full Scale ◽  
Wind Turbine Blade ◽  
Blade Design ◽  
Wind Turbine Blades ◽  
Static Testing ◽  
Bpnn Model

The full-scale static testing of wind turbine blades is an effective means to verify the accuracy and rationality of the blade design, and it is an indispensable part in the blade certification process. In the full-scale static experiments, the strain of the wind turbine blade is related to the applied loads, loading positions, stiffness, deflection, and other factors. At present, researches focus on the analysis of blade failure causes, blade load-bearing capacity, and parameter measurement methods in addition to the correlation analysis between the strain and the applied loads primarily. However, they neglect the loading positions and blade displacements. The correlation among the strain and applied loads, loading positions, displacements, etc. is nonlinear; besides that, the number of design variables is numerous, and thus the calculation and prediction of the blade strain are quite complicated and difficult using traditional numerical methods. Moreover, in full-scale static testing, the number of measuring points and strain gauges are limited, so the test data have insufficient significance to the calibration of the blade design. This paper has performed a study on the new strain prediction method by introducing intelligent algorithms. Back propagation neural network (BPNN) improved by Particle Swarm Optimization (PSO) has significant advantages in dealing with non-linear fitting and multi-input parameters. Models based on BPNN improved by PSO (PSO-BPNN) have better robustness and accuracy. Based on the advantages of the neural network in dealing with complex problems, a strain-predictive PSO-BPNN model for full-scale static experiment of a certain wind turbine blade was established. In addition, the strain values for the unmeasured points were predicted. The accuracy of the PSO-BPNN prediction model was verified by comparing with the BPNN model and the simulation test. Both the applicability and usability of strain-predictive neural network models were verified by comparing the prediction results with simulation outcomes. The comparison results show that PSO-BPNN can be utilized to predict the strain of unmeasured points of wind turbine blades during static testing, and this provides more data for characteristic structural parameters calculation.

Sign in / Sign up

Export Citation Format

Share Document