Aerodynamic Inverse Design of Multistage Turbomachinery Blading PDF Download
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Author: Benedikt Roidl
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Languages : en
Pages : 0
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A recently developed inverse method for single blade rows is extended to 2-D and quasi 3-D multi-stage application. In that method, the pressure distribution on the blade surfaces or alternatively, the blade loading and their thickness distribution are specified and the blade shape is sought using a virtual wall movement. The blade walls move with a virtual velocity distribution that is derived from the difference between the current and the target pressure distribution on the blade surfaces. The scheme is fully consistent with the viscous flow assumption and it is implemented into the time accurate solution of the Reynolds-Averaged Navier-Stokes equations that are expressed in an arbitrary Lagrangian-Eulerian (ALE) form to account for mesh movement. A cell-vertex finite volume method of the Jameson type is used to discretize the equations in space; time accurate integration is obtained using dual time stepping. An algebraic Baldwin-Lomax turbulence model is used for turbulence closure. In order to extend the present method to multistage applications a mixing plane approach using flux averaged flow conditions is employed to couple the vane (stator) and blade (rotor) regions and non-reflecting boundary conditions are implemented at the interface between the two regions to account for short distances between blade leading and trailing edges and the corresponding inlet and exit boundaries. The method is validated on two different cases. Finally three different stages are redesigned: The E/TU-3 single stage turbine, the E/TU-4 2.5 stage turbine and the E/CO-5 2.5 stage compressor. For all cases presented in this thesis the blade pressure distributions and pressure loadings, respectively were selected as design variables, and, by modifying the original profile, it was possible to improve the aerodynamic performance.
Author: Benedikt Roidl
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Languages : en
Pages : 0
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Book Description
A recently developed inverse method for single blade rows is extended to 2-D and quasi 3-D multi-stage application. In that method, the pressure distribution on the blade surfaces or alternatively, the blade loading and their thickness distribution are specified and the blade shape is sought using a virtual wall movement. The blade walls move with a virtual velocity distribution that is derived from the difference between the current and the target pressure distribution on the blade surfaces. The scheme is fully consistent with the viscous flow assumption and it is implemented into the time accurate solution of the Reynolds-Averaged Navier-Stokes equations that are expressed in an arbitrary Lagrangian-Eulerian (ALE) form to account for mesh movement. A cell-vertex finite volume method of the Jameson type is used to discretize the equations in space; time accurate integration is obtained using dual time stepping. An algebraic Baldwin-Lomax turbulence model is used for turbulence closure. In order to extend the present method to multistage applications a mixing plane approach using flux averaged flow conditions is employed to couple the vane (stator) and blade (rotor) regions and non-reflecting boundary conditions are implemented at the interface between the two regions to account for short distances between blade leading and trailing edges and the corresponding inlet and exit boundaries. The method is validated on two different cases. Finally three different stages are redesigned: The E/TU-3 single stage turbine, the E/TU-4 2.5 stage turbine and the E/CO-5 2.5 stage compressor. For all cases presented in this thesis the blade pressure distributions and pressure loadings, respectively were selected as design variables, and, by modifying the original profile, it was possible to improve the aerodynamic performance.
Author: Kasra Daneshkhah
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Languages : en
Pages : 0
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An inverse blade design method, applicable to 2D and 3D flow in turbomachinery blading is developed and is implemented for the design of 2D cascades in compressible viscous flow. The prescribed design quantities are either the pressure distributions on the blade suction and pressure surfaces or the blade pressure loading and its thickness distribution. The design scheme is based on a wall movement approach where the blade walls are modified based on a virtual velocity distribution that would make the current and target momentum fluxes balance on the blade suction and pressure surfaces. The virtual velocity is used to drive the blade geometry towards a steady state shape corresponding to the prescribed quantities. The design method is implemented in a consistent manner into the unsteady Reynolds Averaged Navier-Stokes (RANS) equations, where an arbitrary Lagrangian-Eulerian (ALE) formulation is used and the boundaries of the computational domain can move and deform in any prescribed time-varying fashion to accommodate the blade movement. A cell vertex finite volume method is used for discretizing the governing equations in space and, at each physical time level, integration in pseudotime is performed using an explicit Runge-Kutta scheme, where local time stepping and residual smoothing are used for convergence acceleration. For design calculations, which are inherently unsteady due to blade movement, the time accuracy of the solution is achieved by means of a dual time stepping scheme. An algebraic Baldwin-Lomax model is used for turbulence closure. The flow analysis method is applied to several test cases for steady state internal flow in linear cascades and the results are compared to numerical and experimental data available in the literature. The inverse design method is first validated for three different configurations, namely a parabolic cascade, a subsonic compressor cascade and a transonic impulse turbine cascade, where different choices of the prescribed design variables are used. The usefulness, robustness, accuracy, and flexibility of this inverse method are then demonstrated on the design of an ONERA transonic compressor cascade, a NACA transonic compressor cascade, a highly cambered DFVLR subsonic turbine cascade, and a VKI transonic turbine cascade geometries, which are typical of gas turbine blades used in modern gas turbine engines.
Author: Majīd Aḥmadī
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ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 0
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An aerodynamic inverse design method for turbomachinery cascades is presented and is implemented in a finite volume method. In this design method, the mass-averaged swirl schedule and the blade thickness distribution are prescribed. The design method then provides the blade shape that would accomplish this loading by imposing the appropriate pressure jump across the blades and satisfying the blade boundary condition, the latter implies that the flow is tangent to the blade surfaces. This inverse design method is implemented using a cell-vertex finite volume method which solves the Euler equations on unstructured triangular meshes. A five-stage Runge-Kutta pseudo-time integration scheme is used to march the solution to steady state. Non-linear artificial viscosity is added to eliminate pressure-velocity decoupling and to capture shocks. Convergence is accelerated using local time stepping and implicit residual smoothing. The boundary conditions at inflow and outflow are based on the method of characteristics. The finite volume discretization method is validated against some standard cases of internal flow as well as linear cascades. The inverse design method is first validated for three different cascades namely, a parabolic cascade, a compressor cascade and a turbine inlet guide vane. It is then used to obtain a shock-free design of an impulse transonic cascade and of the ONERA transonic compressor cascade. A parametric study has shown that the blade profile is rather sensitive to the prescribed loading distributions and that, in most cases, a smooth loading distribution results in a shock-free cascade design.
Author: Temesgen Teklemariam Mengistu
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Category : Aerodynamics
Languages : en
Pages : 0
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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:
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Category :
Languages : en
Pages :
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Author: Massachusetts Institute of Technology. Gas Turbine Laboratory
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Category :
Languages : en
Pages : 65
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Author: Yi-Lung Yang
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Category :
Languages : en
Pages :
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Author: Y. L. Lang
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Category :
Languages : en
Pages : 0
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Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Orlando, FL, Jun 2 - Jun 5, 1997.
Author: Yi-Lung Yang
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Category :
Languages : en
Pages :
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Author: John J. Adamczyk
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Languages : en
Pages : 0
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Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Indianapolis, Indiana, June 7-June 10, 1999.
