Development of a computational tool for turbomachinery Blade Generator

Turbomachinery blade designer is a tool whose main functionality is to design a turbomachine blade. It provides the ability to interactively construct a 2D smooth blade. There are two modalities of designing depending on the control that user wants to have on final geometry: cascade families - thickness profiles are superimposed over the camber line - and manual design - there is a large set of parameters that has to be filled to obtain the pro le. In addition, Turbomachinery blade design performs the ow computation of this blade with MISES. MISES, a quasi 3D CFD (Computational Fluid Dynamics), is a set of different programs that analyse the viscous and boundary layer evolution in a cascade. Along with sample designs which are analysed and several examples, the effect of two geometric parameters are presented in this project.Ingeniería Aeroespacia

Analytics of turbomachine geometry

Abstract: For any type of reaction turbomachine, the blade geometry has the same topology and can be modeled by a single mathematical representation. This canonical representation of a blade has been implemented in the Beltrami workbench (BW) which is fully integrated into the FreeCAD modeler. The result is a geometric representation embedded in FreeCAD that allows the blade to be considered as a parametric object that can be analyzed and modified. Before any complex fluid simulation, analysis of the parametric representation of the blade profile can be useful to detect any deviation from healthy fluid behavior. This analysis can be carried out during the design but in addition, it can be carried out on an existing blade parameterized by a reverse engineering process. One effect of the use in the design of such a tool is to control the angular deviation of the fluid in a progressive manner by avoiding successions of accelerations-decelerations which are not desirable and could cause losses, cavitation, vibes. This can result in a significant gain in performance and reliability.Résumé de la communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023

NURBS-Based Geometry for Integrated Structural Analysis

This grant was initiated in April 1993 and completed in September 1996. The primary goal of the project was to exploit the emerging defacto CAD standard of Non- Uniform Rational B-spline (NURBS) based curve and surface geometry to integrate and streamline the process of turbomachinery structural analysis. We focused our efforts on critical geometric modeling challenges typically posed by the requirements of structural analysts. We developed a suite of software tools that facilitate pre- and post-processing of NURBS-based turbomachinery blade models for finite element structural analyses. We also developed tools to facilitate the modeling of blades in their manufactured (or cold) state based on nominal operating shape and conditions. All of the software developed in the course of this research is written in the C++ language using the Iris Inventor 3D graphical interface tool-kit from Silicon Graphics. In addition to enhanced modularity, improved maintainability, and efficient prototype development, this design facilitates the re-use of code developed for other NASA projects and provides a uniform and professional 'look and feel' for all applications developed by the Iowa State Team

Multi-Objective structural optimization of repairs of blisk blades

Modern manufacturing technologies offer multiple options to extend the service life of expensive jet engine components through repairs. In this context, the repair processes of blade-integrated disks (blisks) are of particular interest, as the complex design makes replacement of this part very costly. However, currently, repairs of blisks are mainly done manually and repair design decisions still rely on the expertise of maintenance technicians. From a scientific perspective, these subjective, experience-based decisions are a major drawback, as today’s computational methods allow for systematic analysis and evaluation of design alternatives. The present doctoral thesis contributes to the decision-making process related to the repair of blisk blades by blending and patching by providing an engineering optimization framework and simulation routines for structural assessment of different repair designs. First, an object-oriented optimization framework is developed that is ideally suited to address engineering optimization problems such as blisk repair optimization. The design of the software architecture is chosen to achieve a high degree of flexibility and modularity. In particular, the framework provides a unified interface for global and local derivative-free optimization algorithms and custom engineering optimization problems. Thereby, optimization of single- as well as multi-objective problems is supported. The broad applicability of the framework in engineering optimization is demonstrated using examples from wind energy research. Furthermore, the optimization framework forms a suitable environment for structural multi-objective optimization of blend and patch repairs. The second part of this thesis is devoted to the application of the optimization framework to blend repairs of a compressor blisk. The geometry of the removed blade part and the resulting blend is parameterized by three geometric design variables. The two objectives of the optimization correspond to two modal criteria, because especially the vibration behavior of blades is affected by this kind of geometric modification. To check if frequency requirements are harmed by the repair the first objective reflects the deviation of the natural frequencies of the repaired blade to the natural frequencies of the nominal blade. The second objective considers resonance conditions by evaluating the proximity of natural frequencies to excitation frequencies. Pareto optimal repair designs are found by solving the derived optimization problem using appropriate structural mechanics models of a blade sector and employing the developed optimization framework. By analyzing the optimal blend shapes for two different damage patterns, it is shown that the characteristics of Pareto frontiers, like the occurrence of discontinuities, are damage-specific. Therefore, it is concluded that design decisions on blend repairs have to be made on a case-by-case basis. The third part of this thesis is concerned with the multi-objective optimization of patch repairs. While blend repairs change the blade geometry, patch repairs restore the original blade contour. In terms of structural integrity, the most significant modification due to patching is hence associated with the welding process to join patch and blade. The remaining residual stresses, affect the strength of the repaired blade, are therefore the most critical aspect of patch repairs. Utilizing the engineering optimization framework and the parametric simulation model, a multi-objective optimization problem is solved considering the length of the weld and the fatigue strength of the repaired blade. In addition to fatigue strength properties, the weld length is selected as an optimization goal, since the manufacturing effort of the high-tech repair is of practical importance. Pareto optimal repair designs are presented for a damage pattern at the leading edge. The optimization results are further complemented by subsequent thermal and mechanical simulations of the welding and heat treatment process. Different patch geometries are classified from the Pareto optimal solutions. Depending on the preferences in terms of weld length and the High-Cycle Fatigue strength of different load cases, short or long patches are to be used. In addition, the results show that some potential patch designs are not optimal in any case, and therefore can be completely excluded. Finally, the benefits of the unified interface of the engineering optimization framework are emphasized. Different optimization settings of a patch repair optimization are presented and compared utilizing the hypervolume metric. Concluding remarks on the potential of computational methods for improved repair design and an outlook on future maintenance of blisks complete this work.DFG/SFB 871/119 193 472./E

Articulating Axial-Flow Turbomachinery Rotor Blade For Enabling Variable Speed Gas Turbine Engine

Current technology gas turbine engines are generally optimized to operate at nearly a fixed speed with fixed blade geometries for the design operating condition. When the operating condition of the engine changes, the flow incidence angles may not be optimum with the blade geometries resulting in reduced off-design performance. But, if we have the capability of articulating the pitch angle of axial-flow compressor/turbine blades in coordination with adjustable stator vanes, it can improve performance by maintaining flow incidence angles within the optimum range for given blade geometries at all operating conditions. Maintaining flow incidence angles within the optimum range can prevent the likelihood of flow separation in the blade passage and also reduce the thermal stresses developed due to aerothermal loads for variable speed gas turbine applications. This paper discusses a recent invention of adaptable articulating axial-flow compressor or turbine rotor blade that can significantly impact developing a high efficiency variable speed gas turbine for rotorcraft or ground vehicles that may need to operate optimally at different torque/speed conditions during various maneuvers. U.S. Army Research Laboratory has partnered with University of California San Diego and Iowa State University Collaborators to conduct high fidelity stator-rotor interaction analysis for evaluating the aerodynamic efficiency benefits of an articulating axial flow turbine blade concept. In addition, a design study for articulating turbine or compressor rotor blade using smart material based actuators using Shape Memory Alloy (SMA) has been carried out. Highly coupled fluid-structure interaction computational study of articulating turbine rotor and stator blades, together with a design concept of articulating axial-flow turbomachinery rotor blade using a smart material such as SMA is presented

AUTOMATED OPTIMIZATION OF CENTRIFUGAL COMPRESSORS “ECKARDT ROTOR O”

Centrifugal compressors play an important role in many industries. Improving the efficiency of centrifugal compressors and extending their range has been an important subject for both engineers and researchers working in the turbomachinery field. This paper discusses the optimization of Eckardt O impeller through changing its blade angles distribution to increase its efficiency. the optimization process is performed using an automated procedure performed within ANSYS workbench. The geometry is parameterized using ANSYS design modeler, the mesh is generated using ANSYS Turbogrid and steady flow CFD results are obtained using ANSYS CFX. Optimization by genetic algorithm is done using a surrogate model generated through a sample of designs selected through Design of experiments “DOE” sampling. The performance of the optimized and the original designs are compared both qualitatively and quantitatively, the optimized design efficiency successfully increased from 87.994 % to 88.481% based on CFD results

CFD Applications in Energy Engineering Research and Simulation: An Introduction to Published Reviews

Computational Fluid Dynamics (CFD) has been firmly established as a fundamental discipline to advancing research on energy engineering. The major progresses achieved during the last two decades both on software modelling capabilities and hardware computing power have resulted in considerable and widespread CFD interest among scientist and engineers. Numerical modelling and simulation developments are increasingly contributing to the current state of the art in many energy engineering aspects, such as power generation, combustion, wind energy, concentrated solar power, hydro power, gas and steam turbines, fuel cells, and many others. This review intends to provide an overview of the CFD applications in energy and thermal engineering, as a presentation and background for the Special Issue “CFD Applications in Energy Engineering Research and Simulation” published by Processes in 2020. A brief introduction to the most significant reviews that have been published on the particular topics is provided. The objective is to provide an overview of the CFD applications in energy and thermal engineering, highlighting the review papers published on the different topics, so that readers can refer to the different review papers for a thorough revision of the state of the art and contributions into the particular field of interest

A Comparative Analysis of Two Competing Mid-size Oxy-fuel Combustion Cycles

Conceptual turbine and compressor designs have been established for the semi-closed oxy-fuel combustion combined cycle and the Graz cycle. Real gas effects are addressed by extending cycle and conceptual design tools with a fluid thermodynamic and transport property database. Maximum compressor efficiencies are established by determining optimal values for stage loading, degree of reaction and number of compressor stages. Turbine designs are established based on estimates on achievable blade root stress levels and state of the art design parameters. The work indicates that a twin shaft geared compressor is needed to keep stage numbers to a feasible level. The Graz cycle is expected to be able to deliver around 3% net efficiency benefit over the semi-closed oxy-fuel combustion combined cycle at the expense of a more complex realization of the cycle