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Author: Seyyed Arash Mousavi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"This research work presents an adjoint approach to optimize the aero-thermalproperties of gas turbine blades. The flow solver is a Reynolds-Averaged Navier-Stokes code applicable to structured grids. The flow governing equations are discretizedusing a second-order finite-volume scheme and for artificial dissipation, theJameson-Schmidt-Turkel (JST) scheme is applied in order to accurately capture theflow discontinuities. The code uses a five-stage modified Runge-Kutta explicit temporaldiscretisation and utilizes the multigrid method, residual smoothing and thelocal time stepping for convergence acceleration.A loosely coupled conjugate heat transfer (CHT) method is applied to considerthe effect of the internal convective cooling and obtain the fluid-solid interface temperatureat the blade surface. A finite-element solver is developed to solve the energyequation in the solid domain and the governing equation is solved by implementingthe weak-Galerkin finite-element discretization scheme where an unstructured lineartriangular mesh is adopted for the solution domain. The temperature at the solid andfluid interface is computed through an iterative exchange of the boundary conditionsacross the interface using the Flux Forward Temperature Back (FFTB) method. Forexternally cooled blades, a source term injection model is implemented to model theeffect of external cooling on the blade surface heat transfer.The optimization procedure is gradient-based and the blade shape optimizationis accomplished through SNOPT, a sequential-quadratic programming package thatis capable of automatically handling the linear and/or non-linear flow and geometric constraints. To efficiently calculate the gradients, a continuous adjoint method isemployed and in order to be consistent with the flow boundary condition, a characteristicbased approach is utilized in developing the adjoint boundary conditions.The flow solver is validated for several benchmark turbomachinery cascades.The optimization procedure is applied to several inviscid and viscous turbine andcompressor blades to enhance the aerodynamic and/or thermal performance. Thedeveloped optimization algorithm is demonstrated to be efficient in terms of computationaltime and accuracy for the optimization of two-dimensional turbomachinerycases where it provides promising results in reducing the desired objective functionswhile respecting the imposed flow and geometric constraints." --
Author: Seyyed Arash Mousavi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"This research work presents an adjoint approach to optimize the aero-thermalproperties of gas turbine blades. The flow solver is a Reynolds-Averaged Navier-Stokes code applicable to structured grids. The flow governing equations are discretizedusing a second-order finite-volume scheme and for artificial dissipation, theJameson-Schmidt-Turkel (JST) scheme is applied in order to accurately capture theflow discontinuities. The code uses a five-stage modified Runge-Kutta explicit temporaldiscretisation and utilizes the multigrid method, residual smoothing and thelocal time stepping for convergence acceleration.A loosely coupled conjugate heat transfer (CHT) method is applied to considerthe effect of the internal convective cooling and obtain the fluid-solid interface temperatureat the blade surface. A finite-element solver is developed to solve the energyequation in the solid domain and the governing equation is solved by implementingthe weak-Galerkin finite-element discretization scheme where an unstructured lineartriangular mesh is adopted for the solution domain. The temperature at the solid andfluid interface is computed through an iterative exchange of the boundary conditionsacross the interface using the Flux Forward Temperature Back (FFTB) method. Forexternally cooled blades, a source term injection model is implemented to model theeffect of external cooling on the blade surface heat transfer.The optimization procedure is gradient-based and the blade shape optimizationis accomplished through SNOPT, a sequential-quadratic programming package thatis capable of automatically handling the linear and/or non-linear flow and geometric constraints. To efficiently calculate the gradients, a continuous adjoint method isemployed and in order to be consistent with the flow boundary condition, a characteristicbased approach is utilized in developing the adjoint boundary conditions.The flow solver is validated for several benchmark turbomachinery cascades.The optimization procedure is applied to several inviscid and viscous turbine andcompressor blades to enhance the aerodynamic and/or thermal performance. Thedeveloped optimization algorithm is demonstrated to be efficient in terms of computationaltime and accuracy for the optimization of two-dimensional turbomachinerycases where it provides promising results in reducing the desired objective functionswhile respecting the imposed flow and geometric constraints." --
Author: Slawomir Koziel
Publisher: Springer
ISBN: 3319275178
Category : Mathematics
Languages : en
Pages : 405
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Book Description
This edited volume is devoted to the now-ubiquitous use of computational models across most disciplines of engineering and science, led by a trio of world-renowned researchers in the field. Focused on recent advances of modeling and optimization techniques aimed at handling computationally-expensive engineering problems involving simulation models, this book will be an invaluable resource for specialists (engineers, researchers, graduate students) working in areas as diverse as electrical engineering, mechanical and structural engineering, civil engineering, industrial engineering, hydrodynamics, aerospace engineering, microwave and antenna engineering, ocean science and climate modeling, and the automotive industry, where design processes are heavily based on CPU-heavy computer simulations. Various techniques, such as knowledge-based optimization, adjoint sensitivity techniques, and fast replacement models (to name just a few) are explored in-depth along with an array of the latest techniques to optimize the efficiency of the simulation-driven design process. High-fidelity simulation models allow for accurate evaluations of the devices and systems, which is critical in the design process, especially to avoid costly prototyping stages. Despite this and other advantages, the use of simulation tools in the design process is quite challenging due to associated high computational cost. The steady increase of available computational resources does not always translate into the shortening of the design cycle because of the growing demand for higher accuracy and necessity to simulate larger and more complex systems. For this reason, automated simulation-driven design—while highly desirable—is difficult when using conventional numerical optimization routines which normally require a large number of system simulations, each one already expensive.
Author: Temesgen Teklemariam Mengistu
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 0
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Book Description
Aerodynamic shape optimization of gas turbine blades is a very challenging task, given e.g. the flow complexity, the stringent performance requirements, the structural and manufacturing constraints, etc ... This work addresses the challenge by automating the optimization process through the development, implementation and integration of state-of-the-art shape parametrization, numerical optimization methods, Computational Fluid Dynamics (CFD) algorithms and computer architectures. The resulting scheme is successfully applied to single and multi-point aerodynamic shape optimization of several cascades involving two-dimensional transonic and subsonic, viscous and inviscid flow in compressor and turbine cascades. The optimization objective is to achieve a better aerodynamic performance, subject to aerodynamic and structural constraints, over the full operating range of gas turbine cascades by varying the blade profile. That profile is parameterized using a Non-Uniform Rational B-Splines (NURBS) representation, which is flexible accurate and capable of representing the blade profiles with a relatively small number of control points for a given tolerance. The NURBS parameters are then used as design variables in the optimization process. The optimization objective is determined from simulating the flow using an in-house CFD code that solves the two-dimensional Reynolds-Averaged Navier-Stokes (or Euler) equations using a cell-vertex finite volume method on an unstructured triangular mesh and turbulence is modeled using the Baldwin-Lomax model. To save computing time significantly, Artificial Neural Network (ANN) is used to build a low fidelity model that approximates the optimization objective and constraints. Moreover, to reduce the computing wall-clock time, the optimization scheme was parallelized on an SGI ALTIX 3700 machine using Message Passing Interface (MPI), resulting in a parallelization efficiency of almost 100%. Different numerical optimization methods (genetic algorithm, simulated annealing and sequential quadratic programming) were developed, tested and implemented for the different parts of this work. The present choice of objective function and optimization methodology results in a significant improvement in performance for all the cascades that were optimized, without violating the design constraints. The use of ANN results in a ten-fold speed-up of the design process and the scheme parallelization allows for further reduction of the wall-clock time.
Author: Chaitanya D Ghodke
Publisher: SAE International
ISBN: 0768095026
Category : Technology & Engineering
Languages : en
Pages : 238
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Book Description
Gas turbines play an extremely important role in fulfilling a variety of power needs and are mainly used for power generation and propulsion applications. The performance and efficiency of gas turbine engines are to a large extent dependent on turbine rotor inlet temperatures: typically, the hotter the better. In gas turbines, the combustion temperature and the fuel efficiency are limited by the heat transfer properties of the turbine blades. However, in pushing the limits of hot gas temperatures while preventing the melting of blade components in high-pressure turbines, the use of effective cooling technologies is critical. Increasing the turbine inlet temperature also increases heat transferred to the turbine blade, and it is possible that the operating temperature could reach far above permissible metal temperature. In such cases, insufficient cooling of turbine blades results in excessive thermal stress on the blades causing premature blade failure. This may bring hazards to the engine's safe operation. Gas Turbine Blade Cooling, edited by Dr. Chaitanya D. Ghodke, offers 10 handpicked SAE International's technical papers, which identify key aspects of turbine blade cooling and help readers understand how this process can improve the performance of turbine hardware.
Author: Ernst Rudolf Georg Eckert
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 44
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Book Description
Summary: Transpiration and film cooling promise to be effective methods of cooling gas-turbine blades; consequently, analytical and experimental investigations are being conducted to obtain a better understanding of these processes. This report serves as an introduction to these cooling methods, explains the physical processes, and surveys the information available for predicting blade temperatures and heat-transfer rates. In addition, the difficulties encountered in obtaining a uniform blade temperature are discussed, and the possibilities of correcting these difficulties are indicated. Air is the only coolant considered in the application of these cooling methods.
Author: Erich Pollman
Publisher:
ISBN:
Category : Blades
Languages : en
Pages : 600
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Book Description
The present treatise reports on theoretical investigations and test-stand measurements which were carried out in the BMW Flugmotoren GMbH in developing the hollow blade for exhaust gas turbines. As an introduction the temperature variation and the stress on a turbine blade for a gas temperature of 900 degrees and circumferential velocities of 600 meters per second are discussed. The assumptions onthe heat transfer coefficients at the blade profile are supported by tests on an electrically heated blade model. The temperature distribution in the cross section of a blade Is thoroughly investigated and the temperature field determined for a special case. A method for calculation of the thermal stresses in turbine blades for a given temperature distribution is indicated. The effect of the heat radiation on the blade temperature also is dealt with. Test-stand experiments on turbine blades are evaluated, particularly with respect to temperature distribution in the cross section; maximum and minimum temperature in the cross section are ascertained. Finally, the application of the hollow blade for a stationary gas turbine is investigated. Starting from a setup for 550 C gas temperature the improvement of the thermal efficiency and the fuel consumption are considered as well as the increase of the useful power by use of high temperatures. The power required for blade cooling is taken into account.
Author: James Reuther
Publisher:
ISBN:
Category : Control theory
Languages : en
Pages : 37
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Book Description
Abstract: "An aerodynamic shape optimization method that treats the design of complex aircraft configurations subject to high fidelity computational fluid dynamics (CFD), geometric constraints and multiple design points is described. The design process will be greatly accelerated through the use of both control theory and distributed memory computer architectures. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by prevous design methods [5, 4, 24, 18]. The resulting problem is implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on a higher order CFD method. In order to facilitate the integration of these high fidelity CFD approaches into future multi-disciplinary optimization (MDO) applications, new methods must be developed which are capable of simultaneously addressing complex geometries, multiple objective functions, and geometric design constraints. In our earlier studies [8, 9, 10, 11, 19, 15, 20, 21, 22, 23, 1], we coupled the adjoint based design formulations with unconstrained optimization algorithms and showed that the approach was effective for the aerodynamic design of airfoils, wings, wing-bodies, and complex aircraft configurations. In many of the results presented in these earlier works, geometric constraints were satisfied either by a projection into feasible space or by posing the design space parametrization such that it automatically satisfied constraints. Furthermore, with the exception of reference [9] where the second author initially explored the use of multipoint design in conjunction with adjoint formulations, our earlier works have focused on single point design efforts. Here we demonstrate that the same methodology may be extended to treat complete configuration designs subject to multiple design points and geometric constraints. Examples are presented for both transonic and supersonic configurations ranging from wing alone designs to complex configurations designs involving wing, fuselage, nacelles and pylons."
Author: Jack B. Esgar
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 44
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Book Description
An analysis has been made to determine the effect of chord size on the weight and cooling characteristics of shell-supported, air-cooled gas-turbine blades. In uncooled turbines with solid blades, the general practice has been to design turbines with high aspect ratio (small blade chord) to achieve substantial turbine weight reduction. With air-cooled blades, this study shows that turbine blade weight is affected to a much smaller degree by the size of the blade chord.
Author: Narasimha R. Nagaiah
Publisher:
ISBN:
Category :
Languages : en
Pages : 165
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Book Description
This test application is quite relevant as gas turbine engines serve a critical role in the design of the next-generation power generation facilities around the world. Furthermore, turbine blades require better cooling techniques to increase their cooling effectiveness to cope with the increase in engine operating temperatures extending the useful life of the blades. The performance of the proposed framework is evaluated via a computational study, where a set of common, real-world design objectives and a set of design variables that directly influence the set of objectives are considered. Specifically, three objectives are considered in this study: (1) cooling channel heat transfer coefficient, which measures the rate of heat transfer and the goal is to maximize this value; (2) cooling channel air pressure drop, where the goal is to minimize this value; and (3) cooling channel geometry, specifically the cooling channel cavity area, where the goal is to maximize this value. These objectives, which are conflicting, directly influence the cooling effectiveness of a gas turbine blade and the material usage in its design. The computational results show the proposed optimization framework is able to generate, evaluate and identify thousands of competitive tradeoff designs in a fraction of the time that it would take designers using the traditional simulation tools and experimental methods commonly used for mechanical component design generation. This is a significant step beyond the current research and applications of design optimization to gas turbine blades, specifically, and to mechanical components, in general.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 7
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Book Description
The gas turbine has the potential for power production at the highest possible efficiency. The challenge is to ensure that gas turbines operate at the optimum efficiency so as to use the least fuel and produce minimum emissions. A key component to meeting this challenge is the turbine. Turbine performance, both aerodynamics and heat transfer, is one of the barrier advanced gas turbine development technologies. This is a result of the complex, highly three-dimensional and unsteady flow phenomena in the turbine. Improved turbine aerodynamic performance has been achieved with three-dimensional highly-loaded airfoil designs, accomplished utilizing Euler or Navier-Stokes Computational Fluid Dynamics (CFD) codes. These design codes consider steady flow through isolated blade rows. Thus they do not account for unsteady flow effects. However, unsteady flow effects have a significant impact on performance. Also, CFD codes predict the complete flow field. The experimental verification of these codes has traditionally been accomplished with point data - not corresponding plane field measurements. Thus, although advanced CFD predictions of the highly complex and three-dimensional turbine flow fields are available, corresponding data are not. To improve the design capability for high temperature turbines, a detailed understanding of the highly unsteady and three-dimensional flow through multi-stage turbines is necessary. Thus, unique data are required which quantify the unsteady three-dimensional flow through multi-stage turbine blade rows, including the effect of the film coolant flow. Also, as design CFD codes do not account for unsteady flow effects, the next logical challenge and the current thrust in CFD code development is multiple-stage analyses that account for the interactions between neighboring blade rows. Again, to verify and or direct the development of these advanced codes, complete three-dimensional unsteady flow field data are needed.
